symbol-elf.c

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// SPDX-License-Identifier: GPL-2.0
#include <fcntl.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <inttypes.h>

#include "symbol.h"
#include "demangle-java.h"
#include "demangle-rust.h"
#include "machine.h"
#include "vdso.h"
#include "debug.h"
#include "sane_ctype.h"
#include <symbol/kallsyms.h>

#ifndef EM_AARCH64
#define EM_AARCH64  183  /* ARM 64 bit */
#endif

typedef Elf64_Nhdr GElf_Nhdr;

#ifdef HAVE_CPLUS_DEMANGLE_SUPPORT
extern char *cplus_demangle(const char *, int);

static inline char *bfd_demangle(void __maybe_unused *v, const char *c, int i)
{
    return cplus_demangle(c, i);
}
#else
#ifdef NO_DEMANGLE
static inline char *bfd_demangle(void __maybe_unused *v,
                 const char __maybe_unused *c,
                 int __maybe_unused i)
{
    return NULL;
}
#else
#define PACKAGE 'perf'
#include <bfd.h>
#endif
#endif

#ifndef HAVE_ELF_GETPHDRNUM_SUPPORT
static int elf_getphdrnum(Elf *elf, size_t *dst)
{
    GElf_Ehdr gehdr;
    GElf_Ehdr *ehdr;

    ehdr = gelf_getehdr(elf, &gehdr);
    if (!ehdr)
        return -1;

    *dst = ehdr->e_phnum;

    return 0;
}
#endif

#ifndef HAVE_ELF_GETSHDRSTRNDX_SUPPORT
static int elf_getshdrstrndx(Elf *elf __maybe_unused, size_t *dst __maybe_unused)
{
    pr_err("%s: update your libelf to > 0.140, this one lacks elf_getshdrstrndx().\n", __func__);
    return -1;
}
#endif

#ifndef NT_GNU_BUILD_ID
#define NT_GNU_BUILD_ID 3
#endif

#define elf_symtab__for_each_symbol(syms, nr_syms, idx, sym) \
    for (idx = 0, gelf_getsym(syms, idx, &sym);\
         idx < nr_syms; \
         idx++, gelf_getsym(syms, idx, &sym))

static inline uint8_t elf_sym__type(const GElf_Sym *sym)
{
    return GELF_ST_TYPE(sym->st_info);
}

#ifndef STT_GNU_IFUNC
#define STT_GNU_IFUNC 10
#endif

static inline int elf_sym__is_function(const GElf_Sym *sym)
{
    return (elf_sym__type(sym) == STT_FUNC ||
        elf_sym__type(sym) == STT_GNU_IFUNC) &&
           sym->st_name != 0 &&
           sym->st_shndx != SHN_UNDEF;
}

static inline bool elf_sym__is_object(const GElf_Sym *sym)
{
    return elf_sym__type(sym) == STT_OBJECT &&
        sym->st_name != 0 &&
        sym->st_shndx != SHN_UNDEF;
}

static inline int elf_sym__is_label(const GElf_Sym *sym)
{
    return elf_sym__type(sym) == STT_NOTYPE &&
        sym->st_name != 0 &&
        sym->st_shndx != SHN_UNDEF &&
        sym->st_shndx != SHN_ABS;
}

static bool elf_sym__filter(GElf_Sym *sym)
{
    return elf_sym__is_function(sym) || elf_sym__is_object(sym);
}

static inline const char *elf_sym__name(const GElf_Sym *sym,
                    const Elf_Data *symstrs)
{
    return symstrs->d_buf + sym->st_name;
}

static inline const char *elf_sec__name(const GElf_Shdr *shdr,
                    const Elf_Data *secstrs)
{
    return secstrs->d_buf + shdr->sh_name;
}

static inline int elf_sec__is_text(const GElf_Shdr *shdr,
                    const Elf_Data *secstrs)
{
    return strstr(elf_sec__name(shdr, secstrs), "text") != NULL;
}

static inline bool elf_sec__is_data(const GElf_Shdr *shdr,
                    const Elf_Data *secstrs)
{
    return strstr(elf_sec__name(shdr, secstrs), "data") != NULL;
}

static bool elf_sec__filter(GElf_Shdr *shdr, Elf_Data *secstrs)
{
    return elf_sec__is_text(shdr, secstrs) || 
           elf_sec__is_data(shdr, secstrs);
}

static size_t elf_addr_to_index(Elf *elf, GElf_Addr addr)
{
    Elf_Scn *sec = NULL;
    GElf_Shdr shdr;
    size_t cnt = 1;

    while ((sec = elf_nextscn(elf, sec)) != NULL) {
        gelf_getshdr(sec, &shdr);

        if ((addr >= shdr.sh_addr) &&
            (addr < (shdr.sh_addr + shdr.sh_size)))
            return cnt;

        ++cnt;
    }

    return -1;
}

Elf_Scn *elf_section_by_name(Elf *elf, GElf_Ehdr *ep,
                 GElf_Shdr *shp, const char *name, size_t *idx)
{
    Elf_Scn *sec = NULL;
    size_t cnt = 1;

    /* Elf is corrupted/truncated, avoid calling elf_strptr. */
    if (!elf_rawdata(elf_getscn(elf, ep->e_shstrndx), NULL))
        return NULL;

    while ((sec = elf_nextscn(elf, sec)) != NULL) {
        char *str;

        gelf_getshdr(sec, shp);
        str = elf_strptr(elf, ep->e_shstrndx, shp->sh_name);
        if (str && !strcmp(name, str)) {
            if (idx)
                *idx = cnt;
            return sec;
        }
        ++cnt;
    }

    return NULL;
}

static bool want_demangle(bool is_kernel_sym)
{
    return is_kernel_sym ? symbol_conf.demangle_kernel : symbol_conf.demangle;
}

static char *demangle_sym(struct dso *dso, int kmodule, const char *elf_name)
{
    int demangle_flags = verbose > 0 ? (DMGL_PARAMS | DMGL_ANSI) : DMGL_NO_OPTS;
    char *demangled = NULL;

    /*
     * We need to figure out if the object was created from C++ sources
     * DWARF DW_compile_unit has this, but we don't always have access
     * to it...
     */
    if (!want_demangle(dso->kernel || kmodule))
        return demangled;

    demangled = bfd_demangle(NULL, elf_name, demangle_flags);
    if (demangled == NULL)
        demangled = java_demangle_sym(elf_name, JAVA_DEMANGLE_NORET);
    else if (rust_is_mangled(demangled))
        /*
            * Input to Rust demangling is the BFD-demangled
            * name which it Rust-demangles in place.
            */
        rust_demangle_sym(demangled);

    return demangled;
}

#define elf_section__for_each_rel(reldata, pos, pos_mem, idx, nr_entries) \
    for (idx = 0, pos = gelf_getrel(reldata, 0, &pos_mem); \
         idx < nr_entries; \
         ++idx, pos = gelf_getrel(reldata, idx, &pos_mem))

#define elf_section__for_each_rela(reldata, pos, pos_mem, idx, nr_entries) \
    for (idx = 0, pos = gelf_getrela(reldata, 0, &pos_mem); \
         idx < nr_entries; \
         ++idx, pos = gelf_getrela(reldata, idx, &pos_mem))

/*
 * We need to check if we have a .dynsym, so that we can handle the
 * .plt, synthesizing its symbols, that aren't on the symtabs (be it
 * .dynsym or .symtab).
 * And always look at the original dso, not at debuginfo packages, that
 * have the PLT data stripped out (shdr_rel_plt.sh_type == SHT_NOBITS).
 */
int dso__synthesize_plt_symbols(struct dso *dso, struct symsrc *ss)
{
    uint32_t nr_rel_entries, idx;
    GElf_Sym sym;
    u64 plt_offset, plt_header_size, plt_entry_size;
    GElf_Shdr shdr_plt;
    struct symbol *f;
    GElf_Shdr shdr_rel_plt, shdr_dynsym;
    Elf_Data *reldata, *syms, *symstrs;
    Elf_Scn *scn_plt_rel, *scn_symstrs, *scn_dynsym;
    size_t dynsym_idx;
    GElf_Ehdr ehdr;
    char sympltname[1024];
    Elf *elf;
    int nr = 0, symidx, err = 0;

    if (!ss->dynsym)
        return 0;

    elf = ss->elf;
    ehdr = ss->ehdr;

    scn_dynsym = ss->dynsym;
    shdr_dynsym = ss->dynshdr;
    dynsym_idx = ss->dynsym_idx;

    if (scn_dynsym == NULL)
        goto out_elf_end;

    scn_plt_rel = elf_section_by_name(elf, &ehdr, &shdr_rel_plt,
                      ".rela.plt", NULL);
    if (scn_plt_rel == NULL) {
        scn_plt_rel = elf_section_by_name(elf, &ehdr, &shdr_rel_plt,
                          ".rel.plt", NULL);
        if (scn_plt_rel == NULL)
            goto out_elf_end;
    }

    err = -1;

    if (shdr_rel_plt.sh_link != dynsym_idx)
        goto out_elf_end;

    if (elf_section_by_name(elf, &ehdr, &shdr_plt, ".plt", NULL) == NULL)
        goto out_elf_end;

    /*
     * Fetch the relocation section to find the idxes to the GOT
     * and the symbols in the .dynsym they refer to.
     */
    reldata = elf_getdata(scn_plt_rel, NULL);
    if (reldata == NULL)
        goto out_elf_end;

    syms = elf_getdata(scn_dynsym, NULL);
    if (syms == NULL)
        goto out_elf_end;

    scn_symstrs = elf_getscn(elf, shdr_dynsym.sh_link);
    if (scn_symstrs == NULL)
        goto out_elf_end;

    symstrs = elf_getdata(scn_symstrs, NULL);
    if (symstrs == NULL)
        goto out_elf_end;

    if (symstrs->d_size == 0)
        goto out_elf_end;

    nr_rel_entries = shdr_rel_plt.sh_size / shdr_rel_plt.sh_entsize;
    plt_offset = shdr_plt.sh_offset;
    switch (ehdr.e_machine) {
        case EM_ARM:
            plt_header_size = 20;
            plt_entry_size = 12;
            break;

        case EM_AARCH64:
            plt_header_size = 32;
            plt_entry_size = 16;
            break;

        default: /* FIXME: s390/alpha/mips/parisc/poperpc/sh/sparc/xtensa need to be checked */
            plt_header_size = shdr_plt.sh_entsize;
            plt_entry_size = shdr_plt.sh_entsize;
            break;
    }
    plt_offset += plt_header_size;

    if (shdr_rel_plt.sh_type == SHT_RELA) {
        GElf_Rela pos_mem, *pos;

        elf_section__for_each_rela(reldata, pos, pos_mem, idx,
                       nr_rel_entries) {
            const char *elf_name = NULL;
            char *demangled = NULL;
            symidx = GELF_R_SYM(pos->r_info);
            gelf_getsym(syms, symidx, &sym);

            elf_name = elf_sym__name(&sym, symstrs);
            demangled = demangle_sym(dso, 0, elf_name);
            if (demangled != NULL)
                elf_name = demangled;
            snprintf(sympltname, sizeof(sympltname),
                 "%s@plt", elf_name);
            free(demangled);

            f = symbol__new(plt_offset, plt_entry_size,
                    STB_GLOBAL, STT_FUNC, sympltname);
            if (!f)
                goto out_elf_end;

            plt_offset += plt_entry_size;
            symbols__insert(&dso->symbols, f);
            ++nr;
        }
    } else if (shdr_rel_plt.sh_type == SHT_REL) {
        GElf_Rel pos_mem, *pos;
        elf_section__for_each_rel(reldata, pos, pos_mem, idx,
                      nr_rel_entries) {
            const char *elf_name = NULL;
            char *demangled = NULL;
            symidx = GELF_R_SYM(pos->r_info);
            gelf_getsym(syms, symidx, &sym);

            elf_name = elf_sym__name(&sym, symstrs);
            demangled = demangle_sym(dso, 0, elf_name);
            if (demangled != NULL)
                elf_name = demangled;
            snprintf(sympltname, sizeof(sympltname),
                 "%s@plt", elf_name);
            free(demangled);

            f = symbol__new(plt_offset, plt_entry_size,
                    STB_GLOBAL, STT_FUNC, sympltname);
            if (!f)
                goto out_elf_end;

            plt_offset += plt_entry_size;
            symbols__insert(&dso->symbols, f);
            ++nr;
        }
    }

    err = 0;
out_elf_end:
    if (err == 0)
        return nr;
    pr_debug("%s: problems reading %s PLT info.\n",
         __func__, dso->long_name);
    return 0;
}

char *dso__demangle_sym(struct dso *dso, int kmodule, const char *elf_name)
{
    return demangle_sym(dso, kmodule, elf_name);
}

/*
 * Align offset to 4 bytes as needed for note name and descriptor data.
 */
#define NOTE_ALIGN(n) (((n) + 3) & -4U)

static int elf_read_build_id(Elf *elf, void *bf, size_t size)
{
    int err = -1;
    GElf_Ehdr ehdr;
    GElf_Shdr shdr;
    Elf_Data *data;
    Elf_Scn *sec;
    Elf_Kind ek;
    void *ptr;

    if (size < BUILD_ID_SIZE)
        goto out;

    ek = elf_kind(elf);
    if (ek != ELF_K_ELF)
        goto out;

    if (gelf_getehdr(elf, &ehdr) == NULL) {
        pr_err("%s: cannot get elf header.\n", __func__);
        goto out;
    }

    /*
     * Check following sections for notes:
     *   '.note.gnu.build-id'
     *   '.notes'
     *   '.note' (VDSO specific)
     */
    do {
        sec = elf_section_by_name(elf, &ehdr, &shdr,
                      ".note.gnu.build-id", NULL);
        if (sec)
            break;

        sec = elf_section_by_name(elf, &ehdr, &shdr,
                      ".notes", NULL);
        if (sec)
            break;

        sec = elf_section_by_name(elf, &ehdr, &shdr,
                      ".note", NULL);
        if (sec)
            break;

        return err;

    } while (0);

    data = elf_getdata(sec, NULL);
    if (data == NULL)
        goto out;

    ptr = data->d_buf;
    while (ptr < (data->d_buf + data->d_size)) {
        GElf_Nhdr *nhdr = ptr;
        size_t namesz = NOTE_ALIGN(nhdr->n_namesz),
               descsz = NOTE_ALIGN(nhdr->n_descsz);
        const char *name;

        ptr += sizeof(*nhdr);
        name = ptr;
        ptr += namesz;
        if (nhdr->n_type == NT_GNU_BUILD_ID &&
            nhdr->n_namesz == sizeof("GNU")) {
            if (memcmp(name, "GNU", sizeof("GNU")) == 0) {
                size_t sz = min(size, descsz);
                memcpy(bf, ptr, sz);
                memset(bf + sz, 0, size - sz);
                err = descsz;
                break;
            }
        }
        ptr += descsz;
    }

out:
    return err;
}

int filename__read_build_id(const char *filename, void *bf, size_t size)
{
    int fd, err = -1;
    Elf *elf;

    if (size < BUILD_ID_SIZE)
        goto out;

    fd = open(filename, O_RDONLY);
    if (fd < 0)
        goto out;

    elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
    if (elf == NULL) {
        pr_debug2("%s: cannot read %s ELF file.\n", __func__, filename);
        goto out_close;
    }

    err = elf_read_build_id(elf, bf, size);

    elf_end(elf);
out_close:
    close(fd);
out:
    return err;
}

int sysfs__read_build_id(const char *filename, void *build_id, size_t size)
{
    int fd, err = -1;

    if (size < BUILD_ID_SIZE)
        goto out;

    fd = open(filename, O_RDONLY);
    if (fd < 0)
        goto out;

    while (1) {
        char bf[BUFSIZ];
        GElf_Nhdr nhdr;
        size_t namesz, descsz;

        if (read(fd, &nhdr, sizeof(nhdr)) != sizeof(nhdr))
            break;

        namesz = NOTE_ALIGN(nhdr.n_namesz);
        descsz = NOTE_ALIGN(nhdr.n_descsz);
        if (nhdr.n_type == NT_GNU_BUILD_ID &&
            nhdr.n_namesz == sizeof("GNU")) {
            if (read(fd, bf, namesz) != (ssize_t)namesz)
                break;
            if (memcmp(bf, "GNU", sizeof("GNU")) == 0) {
                size_t sz = min(descsz, size);
                if (read(fd, build_id, sz) == (ssize_t)sz) {
                    memset(build_id + sz, 0, size - sz);
                    err = 0;
                    break;
                }
            } else if (read(fd, bf, descsz) != (ssize_t)descsz)
                break;
        } else {
            int n = namesz + descsz;

            if (n > (int)sizeof(bf)) {
                n = sizeof(bf);
                pr_debug("%s: truncating reading of build id in sysfs file %s: n_namesz=%u, n_descsz=%u.\n",
                     __func__, filename, nhdr.n_namesz, nhdr.n_descsz);
            }
            if (read(fd, bf, n) != n)
                break;
        }
    }
    close(fd);
out:
    return err;
}

int filename__read_debuglink(const char *filename, char *debuglink,
                 size_t size)
{
    int fd, err = -1;
    Elf *elf;
    GElf_Ehdr ehdr;
    GElf_Shdr shdr;
    Elf_Data *data;
    Elf_Scn *sec;
    Elf_Kind ek;

    fd = open(filename, O_RDONLY);
    if (fd < 0)
        goto out;

    elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
    if (elf == NULL) {
        pr_debug2("%s: cannot read %s ELF file.\n", __func__, filename);
        goto out_close;
    }

    ek = elf_kind(elf);
    if (ek != ELF_K_ELF)
        goto out_elf_end;

    if (gelf_getehdr(elf, &ehdr) == NULL) {
        pr_err("%s: cannot get elf header.\n", __func__);
        goto out_elf_end;
    }

    sec = elf_section_by_name(elf, &ehdr, &shdr,
                  ".gnu_debuglink", NULL);
    if (sec == NULL)
        goto out_elf_end;

    data = elf_getdata(sec, NULL);
    if (data == NULL)
        goto out_elf_end;

    /* the start of this section is a zero-terminated string */
    strncpy(debuglink, data->d_buf, size);

    err = 0;

out_elf_end:
    elf_end(elf);
out_close:
    close(fd);
out:
    return err;
}

static int dso__swap_init(struct dso *dso, unsigned char eidata)
{
    static unsigned int const endian = 1;

    dso->needs_swap = DSO_SWAP__NO;

    switch (eidata) {
    case ELFDATA2LSB:
        /* We are big endian, DSO is little endian. */
        if (*(unsigned char const *)&endian != 1)
            dso->needs_swap = DSO_SWAP__YES;
        break;

    case ELFDATA2MSB:
        /* We are little endian, DSO is big endian. */
        if (*(unsigned char const *)&endian != 0)
            dso->needs_swap = DSO_SWAP__YES;
        break;

    default:
        pr_err("unrecognized DSO data encoding %d\n", eidata);
        return -EINVAL;
    }

    return 0;
}

bool symsrc__possibly_runtime(struct symsrc *ss)
{
    return ss->dynsym || ss->opdsec;
}

bool symsrc__has_symtab(struct symsrc *ss)
{
    return ss->symtab != NULL;
}

void symsrc__destroy(struct symsrc *ss)
{
    zfree(&ss->name);
    elf_end(ss->elf);
    close(ss->fd);
}

bool __weak elf__needs_adjust_symbols(GElf_Ehdr ehdr)
{
    return ehdr.e_type == ET_EXEC || ehdr.e_type == ET_REL;
}

int symsrc__init(struct symsrc *ss, struct dso *dso, const char *name,
         enum dso_binary_type type)
{
    int err = -1;
    GElf_Ehdr ehdr;
    Elf *elf;
    int fd;

    if (dso__needs_decompress(dso)) {
        fd = dso__decompress_kmodule_fd(dso, name);
        if (fd < 0)
            return -1;

        type = dso->symtab_type;
    } else {
        fd = open(name, O_RDONLY);
        if (fd < 0) {
            dso->load_errno = errno;
            return -1;
        }
    }

    elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
    if (elf == NULL) {
        pr_debug("%s: cannot read %s ELF file.\n", __func__, name);
        dso->load_errno = DSO_LOAD_ERRNO__INVALID_ELF;
        goto out_close;
    }

    if (gelf_getehdr(elf, &ehdr) == NULL) {
        dso->load_errno = DSO_LOAD_ERRNO__INVALID_ELF;
        pr_debug("%s: cannot get elf header.\n", __func__);
        goto out_elf_end;
    }

    if (dso__swap_init(dso, ehdr.e_ident[EI_DATA])) {
        dso->load_errno = DSO_LOAD_ERRNO__INTERNAL_ERROR;
        goto out_elf_end;
    }

    /* Always reject images with a mismatched build-id: */
    if (dso->has_build_id && !symbol_conf.ignore_vmlinux_buildid) {
        u8 build_id[BUILD_ID_SIZE];

        if (elf_read_build_id(elf, build_id, BUILD_ID_SIZE) < 0) {
            dso->load_errno = DSO_LOAD_ERRNO__CANNOT_READ_BUILDID;
            goto out_elf_end;
        }

        if (!dso__build_id_equal(dso, build_id)) {
            pr_debug("%s: build id mismatch for %s.\n", __func__, name);
            dso->load_errno = DSO_LOAD_ERRNO__MISMATCHING_BUILDID;
            goto out_elf_end;
        }
    }

    ss->is_64_bit = (gelf_getclass(elf) == ELFCLASS64);

    ss->symtab = elf_section_by_name(elf, &ehdr, &ss->symshdr, ".symtab",
            NULL);
    if (ss->symshdr.sh_type != SHT_SYMTAB)
        ss->symtab = NULL;

    ss->dynsym_idx = 0;
    ss->dynsym = elf_section_by_name(elf, &ehdr, &ss->dynshdr, ".dynsym",
            &ss->dynsym_idx);
    if (ss->dynshdr.sh_type != SHT_DYNSYM)
        ss->dynsym = NULL;

    ss->opdidx = 0;
    ss->opdsec = elf_section_by_name(elf, &ehdr, &ss->opdshdr, ".opd",
            &ss->opdidx);
    if (ss->opdshdr.sh_type != SHT_PROGBITS)
        ss->opdsec = NULL;

    if (dso->kernel == DSO_TYPE_USER)
        ss->adjust_symbols = true;
    else
        ss->adjust_symbols = elf__needs_adjust_symbols(ehdr);

    ss->name   = strdup(name);
    if (!ss->name) {
        dso->load_errno = errno;
        goto out_elf_end;
    }

    ss->elf    = elf;
    ss->fd     = fd;
    ss->ehdr   = ehdr;
    ss->type   = type;

    return 0;

out_elf_end:
    elf_end(elf);
out_close:
    close(fd);
    return err;
}

static bool ref_reloc_sym_not_found(struct kmap *kmap)
{
    return kmap && kmap->ref_reloc_sym && kmap->ref_reloc_sym->name &&
           !kmap->ref_reloc_sym->unrelocated_addr;
}

static u64 ref_reloc(struct kmap *kmap)
{
    if (kmap && kmap->ref_reloc_sym &&
        kmap->ref_reloc_sym->unrelocated_addr)
        return kmap->ref_reloc_sym->addr -
               kmap->ref_reloc_sym->unrelocated_addr;
    return 0;
}

void __weak arch__sym_update(struct symbol *s __maybe_unused,
        GElf_Sym *sym __maybe_unused) { }

static int dso__process_kernel_symbol(struct dso *dso, struct map *map,
                      GElf_Sym *sym, GElf_Shdr *shdr,
                      struct map_groups *kmaps, struct kmap *kmap,
                      struct dso **curr_dsop, struct map **curr_mapp,
                      const char *section_name,
                      bool adjust_kernel_syms, bool kmodule, bool *remap_kernel)
{
    struct dso *curr_dso = *curr_dsop;
    struct map *curr_map;
    char dso_name[PATH_MAX];

    /* Adjust symbol to map to file offset */
    if (adjust_kernel_syms)
        sym->st_value -= shdr->sh_addr - shdr->sh_offset;

    if (strcmp(section_name, (curr_dso->short_name + dso->short_name_len)) == 0)
        return 0;

    if (strcmp(section_name, ".text") == 0) {
        /*
         * The initial kernel mapping is based on
         * kallsyms and identity maps.  Overwrite it to
         * map to the kernel dso.
         */
        if (*remap_kernel && dso->kernel) {
            *remap_kernel = false;
            map->start = shdr->sh_addr + ref_reloc(kmap);
            map->end = map->start + shdr->sh_size;
            map->pgoff = shdr->sh_offset;
            map->map_ip = map__map_ip;
            map->unmap_ip = map__unmap_ip;
            /* Ensure maps are correctly ordered */
            if (kmaps) {
                map__get(map);
                map_groups__remove(kmaps, map);
                map_groups__insert(kmaps, map);
                map__put(map);
            }
        }

        /*
         * The initial module mapping is based on
         * /proc/modules mapped to offset zero.
         * Overwrite it to map to the module dso.
         */
        if (*remap_kernel && kmodule) {
            *remap_kernel = false;
            map->pgoff = shdr->sh_offset;
        }

        *curr_mapp = map;
        *curr_dsop = dso;
        return 0;
    }

    if (!kmap)
        return 0;

    snprintf(dso_name, sizeof(dso_name), "%s%s", dso->short_name, section_name);

    curr_map = map_groups__find_by_name(kmaps, dso_name);
    if (curr_map == NULL) {
        u64 start = sym->st_value;

        if (kmodule)
            start += map->start + shdr->sh_offset;

        curr_dso = dso__new(dso_name);
        if (curr_dso == NULL)
            return -1;
        curr_dso->kernel = dso->kernel;
        curr_dso->long_name = dso->long_name;
        curr_dso->long_name_len = dso->long_name_len;
        curr_map = map__new2(start, curr_dso);
        dso__put(curr_dso);
        if (curr_map == NULL)
            return -1;

        if (adjust_kernel_syms) {
            curr_map->start  = shdr->sh_addr + ref_reloc(kmap);
            curr_map->end    = curr_map->start + shdr->sh_size;
            curr_map->pgoff  = shdr->sh_offset;
        } else {
            curr_map->map_ip = curr_map->unmap_ip = identity__map_ip;
        }
        curr_dso->symtab_type = dso->symtab_type;
        map_groups__insert(kmaps, curr_map);
        /*
         * Add it before we drop the referece to curr_map, i.e. while
         * we still are sure to have a reference to this DSO via
         * *curr_map->dso.
         */
        dsos__add(&map->groups->machine->dsos, curr_dso);
        /* kmaps already got it */
        map__put(curr_map);
        dso__set_loaded(curr_dso);
        *curr_mapp = curr_map;
        *curr_dsop = curr_dso;
    } else
        *curr_dsop = curr_map->dso;

    return 0;
}

int dso__load_sym(struct dso *dso, struct map *map, struct symsrc *syms_ss,
          struct symsrc *runtime_ss, int kmodule)
{
    struct kmap *kmap = dso->kernel ? map__kmap(map) : NULL;
    struct map_groups *kmaps = kmap ? map__kmaps(map) : NULL;
    struct map *curr_map = map;
    struct dso *curr_dso = dso;
    Elf_Data *symstrs, *secstrs;
    uint32_t nr_syms;
    int err = -1;
    uint32_t idx;
    GElf_Ehdr ehdr;
    GElf_Shdr shdr;
    GElf_Shdr tshdr;
    Elf_Data *syms, *opddata = NULL;
    GElf_Sym sym;
    Elf_Scn *sec, *sec_strndx;
    Elf *elf;
    int nr = 0;
    bool remap_kernel = false, adjust_kernel_syms = false;

    if (kmap && !kmaps)
        return -1;

    dso->symtab_type = syms_ss->type;
    dso->is_64_bit = syms_ss->is_64_bit;
    dso->rel = syms_ss->ehdr.e_type == ET_REL;

    /*
     * Modules may already have symbols from kallsyms, but those symbols
     * have the wrong values for the dso maps, so remove them.
     */
    if (kmodule && syms_ss->symtab)
        symbols__delete(&dso->symbols);

    if (!syms_ss->symtab) {
        /*
         * If the vmlinux is stripped, fail so we will fall back
         * to using kallsyms. The vmlinux runtime symbols aren't
         * of much use.
         */
        if (dso->kernel)
            goto out_elf_end;

        syms_ss->symtab  = syms_ss->dynsym;
        syms_ss->symshdr = syms_ss->dynshdr;
    }

    elf = syms_ss->elf;
    ehdr = syms_ss->ehdr;
    sec = syms_ss->symtab;
    shdr = syms_ss->symshdr;

    if (elf_section_by_name(runtime_ss->elf, &runtime_ss->ehdr, &tshdr,
                ".text", NULL))
        dso->text_offset = tshdr.sh_addr - tshdr.sh_offset;

    if (runtime_ss->opdsec)
        opddata = elf_rawdata(runtime_ss->opdsec, NULL);

    syms = elf_getdata(sec, NULL);
    if (syms == NULL)
        goto out_elf_end;

    sec = elf_getscn(elf, shdr.sh_link);
    if (sec == NULL)
        goto out_elf_end;

    symstrs = elf_getdata(sec, NULL);
    if (symstrs == NULL)
        goto out_elf_end;

    sec_strndx = elf_getscn(runtime_ss->elf, runtime_ss->ehdr.e_shstrndx);
    if (sec_strndx == NULL)
        goto out_elf_end;

    secstrs = elf_getdata(sec_strndx, NULL);
    if (secstrs == NULL)
        goto out_elf_end;

    nr_syms = shdr.sh_size / shdr.sh_entsize;

    memset(&sym, 0, sizeof(sym));

    /*
     * The kernel relocation symbol is needed in advance in order to adjust
     * kernel maps correctly.
     */
    if (ref_reloc_sym_not_found(kmap)) {
        elf_symtab__for_each_symbol(syms, nr_syms, idx, sym) {
            const char *elf_name = elf_sym__name(&sym, symstrs);

            if (strcmp(elf_name, kmap->ref_reloc_sym->name))
                continue;
            kmap->ref_reloc_sym->unrelocated_addr = sym.st_value;
            map->reloc = kmap->ref_reloc_sym->addr -
                     kmap->ref_reloc_sym->unrelocated_addr;
            break;
        }
    }

    /*
     * Handle any relocation of vdso necessary because older kernels
     * attempted to prelink vdso to its virtual address.
     */
    if (dso__is_vdso(dso))
        map->reloc = map->start - dso->text_offset;

    dso->adjust_symbols = runtime_ss->adjust_symbols || ref_reloc(kmap);
    /*
     * Initial kernel and module mappings do not map to the dso.
     * Flag the fixups.
     */
    if (dso->kernel || kmodule) {
        remap_kernel = true;
        adjust_kernel_syms = dso->adjust_symbols;
    }
    elf_symtab__for_each_symbol(syms, nr_syms, idx, sym) {
        struct symbol *f;
        const char *elf_name = elf_sym__name(&sym, symstrs);
        char *demangled = NULL;
        int is_label = elf_sym__is_label(&sym);
        const char *section_name;
        bool used_opd = false;

        if (!is_label && !elf_sym__filter(&sym))
            continue;

        /* Reject ARM ELF "mapping symbols": these aren't unique and
         * don't identify functions, so will confuse the profile
         * output: */
        if (ehdr.e_machine == EM_ARM || ehdr.e_machine == EM_AARCH64) {
            if (elf_name[0] == '$' && strchr("adtx", elf_name[1])
                && (elf_name[2] == '\0' || elf_name[2] == '.'))
                continue;
        }

        if (runtime_ss->opdsec && sym.st_shndx == runtime_ss->opdidx) {
            u32 offset = sym.st_value - syms_ss->opdshdr.sh_addr;
            u64 *opd = opddata->d_buf + offset;
            sym.st_value = DSO__SWAP(dso, u64, *opd);
            sym.st_shndx = elf_addr_to_index(runtime_ss->elf,
                    sym.st_value);
            used_opd = true;
        }
        /*
         * When loading symbols in a data mapping, ABS symbols (which
         * has a value of SHN_ABS in its st_shndx) failed at
         * elf_getscn().  And it marks the loading as a failure so
         * already loaded symbols cannot be fixed up.
         *
         * I'm not sure what should be done. Just ignore them for now.
         * - Namhyung Kim
         */
        if (sym.st_shndx == SHN_ABS)
            continue;

        sec = elf_getscn(runtime_ss->elf, sym.st_shndx);
        if (!sec)
            goto out_elf_end;

        gelf_getshdr(sec, &shdr);

        if (is_label && !elf_sec__filter(&shdr, secstrs))
            continue;

        section_name = elf_sec__name(&shdr, secstrs);

        /* On ARM, symbols for thumb functions have 1 added to
         * the symbol address as a flag - remove it */
        if ((ehdr.e_machine == EM_ARM) &&
            (GELF_ST_TYPE(sym.st_info) == STT_FUNC) &&
            (sym.st_value & 1))
            --sym.st_value;

        if (dso->kernel || kmodule) {
            if (dso__process_kernel_symbol(dso, map, &sym, &shdr, kmaps, kmap, &curr_dso, &curr_map,
                               section_name, adjust_kernel_syms, kmodule, &remap_kernel))
                goto out_elf_end;
        } else if ((used_opd && runtime_ss->adjust_symbols) ||
               (!used_opd && syms_ss->adjust_symbols)) {
            pr_debug4("%s: adjusting symbol: st_value: %#" PRIx64 " "
                  "sh_addr: %#" PRIx64 " sh_offset: %#" PRIx64 "\n", __func__,
                  (u64)sym.st_value, (u64)shdr.sh_addr,
                  (u64)shdr.sh_offset);
            sym.st_value -= shdr.sh_addr - shdr.sh_offset;
        }

        demangled = demangle_sym(dso, kmodule, elf_name);
        if (demangled != NULL)
            elf_name = demangled;

        f = symbol__new(sym.st_value, sym.st_size,
                GELF_ST_BIND(sym.st_info),
                GELF_ST_TYPE(sym.st_info), elf_name);
        free(demangled);
        if (!f)
            goto out_elf_end;

        arch__sym_update(f, &sym);

        __symbols__insert(&curr_dso->symbols, f, dso->kernel);
        nr++;
    }

    /*
     * For misannotated, zeroed, ASM function sizes.
     */
    if (nr > 0) {
        symbols__fixup_end(&dso->symbols);
        symbols__fixup_duplicate(&dso->symbols);
        if (kmap) {
            /*
             * We need to fixup this here too because we create new
             * maps here, for things like vsyscall sections.
             */
            map_groups__fixup_end(kmaps);
        }
    }
    err = nr;
out_elf_end:
    return err;
}

static int elf_read_maps(Elf *elf, bool exe, mapfn_t mapfn, void *data)
{
    GElf_Phdr phdr;
    size_t i, phdrnum;
    int err;
    u64 sz;

    if (elf_getphdrnum(elf, &phdrnum))
        return -1;

    for (i = 0; i < phdrnum; i++) {
        if (gelf_getphdr(elf, i, &phdr) == NULL)
            return -1;
        if (phdr.p_type != PT_LOAD)
            continue;
        if (exe) {
            if (!(phdr.p_flags & PF_X))
                continue;
        } else {
            if (!(phdr.p_flags & PF_R))
                continue;
        }
        sz = min(phdr.p_memsz, phdr.p_filesz);
        if (!sz)
            continue;
        err = mapfn(phdr.p_vaddr, sz, phdr.p_offset, data);
        if (err)
            return err;
    }
    return 0;
}

int file__read_maps(int fd, bool exe, mapfn_t mapfn, void *data,
            bool *is_64_bit)
{
    int err;
    Elf *elf;

    elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
    if (elf == NULL)
        return -1;

    if (is_64_bit)
        *is_64_bit = (gelf_getclass(elf) == ELFCLASS64);

    err = elf_read_maps(elf, exe, mapfn, data);

    elf_end(elf);
    return err;
}

enum dso_type dso__type_fd(int fd)
{
    enum dso_type dso_type = DSO__TYPE_UNKNOWN;
    GElf_Ehdr ehdr;
    Elf_Kind ek;
    Elf *elf;

    elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
    if (elf == NULL)
        goto out;

    ek = elf_kind(elf);
    if (ek != ELF_K_ELF)
        goto out_end;

    if (gelf_getclass(elf) == ELFCLASS64) {
        dso_type = DSO__TYPE_64BIT;
        goto out_end;
    }

    if (gelf_getehdr(elf, &ehdr) == NULL)
        goto out_end;

    if (ehdr.e_machine == EM_X86_64)
        dso_type = DSO__TYPE_X32BIT;
    else
        dso_type = DSO__TYPE_32BIT;
out_end:
    elf_end(elf);
out:
    return dso_type;
}

static int copy_bytes(int from, off_t from_offs, int to, off_t to_offs, u64 len)
{
    ssize_t r;
    size_t n;
    int err = -1;
    char *buf = malloc(page_size);

    if (buf == NULL)
        return -1;

    if (lseek(to, to_offs, SEEK_SET) != to_offs)
        goto out;

    if (lseek(from, from_offs, SEEK_SET) != from_offs)
        goto out;

    while (len) {
        n = page_size;
        if (len < n)
            n = len;
        /* Use read because mmap won't work on proc files */
        r = read(from, buf, n);
        if (r < 0)
            goto out;
        if (!r)
            break;
        n = r;
        r = write(to, buf, n);
        if (r < 0)
            goto out;
        if ((size_t)r != n)
            goto out;
        len -= n;
    }

    err = 0;
out:
    free(buf);
    return err;
}

struct kcore {
    int fd;
    int elfclass;
    Elf *elf;
    GElf_Ehdr ehdr;
};

static int kcore__open(struct kcore *kcore, const char *filename)
{
    GElf_Ehdr *ehdr;

    kcore->fd = open(filename, O_RDONLY);
    if (kcore->fd == -1)
        return -1;

    kcore->elf = elf_begin(kcore->fd, ELF_C_READ, NULL);
    if (!kcore->elf)
        goto out_close;

    kcore->elfclass = gelf_getclass(kcore->elf);
    if (kcore->elfclass == ELFCLASSNONE)
        goto out_end;

    ehdr = gelf_getehdr(kcore->elf, &kcore->ehdr);
    if (!ehdr)
        goto out_end;

    return 0;

out_end:
    elf_end(kcore->elf);
out_close:
    close(kcore->fd);
    return -1;
}

static int kcore__init(struct kcore *kcore, char *filename, int elfclass,
               bool temp)
{
    kcore->elfclass = elfclass;

    if (temp)
        kcore->fd = mkstemp(filename);
    else
        kcore->fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0400);
    if (kcore->fd == -1)
        return -1;

    kcore->elf = elf_begin(kcore->fd, ELF_C_WRITE, NULL);
    if (!kcore->elf)
        goto out_close;

    if (!gelf_newehdr(kcore->elf, elfclass))
        goto out_end;

    memset(&kcore->ehdr, 0, sizeof(GElf_Ehdr));

    return 0;

out_end:
    elf_end(kcore->elf);
out_close:
    close(kcore->fd);
    unlink(filename);
    return -1;
}

static void kcore__close(struct kcore *kcore)
{
    elf_end(kcore->elf);
    close(kcore->fd);
}

static int kcore__copy_hdr(struct kcore *from, struct kcore *to, size_t count)
{
    GElf_Ehdr *ehdr = &to->ehdr;
    GElf_Ehdr *kehdr = &from->ehdr;

    memcpy(ehdr->e_ident, kehdr->e_ident, EI_NIDENT);
    ehdr->e_type      = kehdr->e_type;
    ehdr->e_machine   = kehdr->e_machine;
    ehdr->e_version   = kehdr->e_version;
    ehdr->e_entry     = 0;
    ehdr->e_shoff     = 0;
    ehdr->e_flags     = kehdr->e_flags;
    ehdr->e_phnum     = count;
    ehdr->e_shentsize = 0;
    ehdr->e_shnum     = 0;
    ehdr->e_shstrndx  = 0;

    if (from->elfclass == ELFCLASS32) {
        ehdr->e_phoff     = sizeof(Elf32_Ehdr);
        ehdr->e_ehsize    = sizeof(Elf32_Ehdr);
        ehdr->e_phentsize = sizeof(Elf32_Phdr);
    } else {
        ehdr->e_phoff     = sizeof(Elf64_Ehdr);
        ehdr->e_ehsize    = sizeof(Elf64_Ehdr);
        ehdr->e_phentsize = sizeof(Elf64_Phdr);
    }

    if (!gelf_update_ehdr(to->elf, ehdr))
        return -1;

    if (!gelf_newphdr(to->elf, count))
        return -1;

    return 0;
}

static int kcore__add_phdr(struct kcore *kcore, int idx, off_t offset,
               u64 addr, u64 len)
{
    GElf_Phdr phdr = {
        .p_type     = PT_LOAD,
        .p_flags    = PF_R | PF_W | PF_X,
        .p_offset   = offset,
        .p_vaddr    = addr,
        .p_paddr    = 0,
        .p_filesz   = len,
        .p_memsz    = len,
        .p_align    = page_size,
    };

    if (!gelf_update_phdr(kcore->elf, idx, &phdr))
        return -1;

    return 0;
}

static off_t kcore__write(struct kcore *kcore)
{
    return elf_update(kcore->elf, ELF_C_WRITE);
}

struct phdr_data {
    off_t offset;
    off_t rel;
    u64 addr;
    u64 len;
    struct list_head node;
    struct phdr_data *remaps;
};

struct sym_data {
    u64 addr;
    struct list_head node;
};

struct kcore_copy_info {
    u64 stext;
    u64 etext;
    u64 first_symbol;
    u64 last_symbol;
    u64 first_module;
    u64 last_module_symbol;
    size_t phnum;
    struct list_head phdrs;
    struct list_head syms;
};

#define kcore_copy__for_each_phdr(k, p) \
    list_for_each_entry((p), &(k)->phdrs, node)

static struct phdr_data *phdr_data__new(u64 addr, u64 len, off_t offset)
{
    struct phdr_data *p = zalloc(sizeof(*p));

    if (p) {
        p->addr   = addr;
        p->len    = len;
        p->offset = offset;
    }

    return p;
}

static struct phdr_data *kcore_copy_info__addnew(struct kcore_copy_info *kci,
                         u64 addr, u64 len,
                         off_t offset)
{
    struct phdr_data *p = phdr_data__new(addr, len, offset);

    if (p)
        list_add_tail(&p->node, &kci->phdrs);

    return p;
}

static void kcore_copy__free_phdrs(struct kcore_copy_info *kci)
{
    struct phdr_data *p, *tmp;

    list_for_each_entry_safe(p, tmp, &kci->phdrs, node) {
        list_del(&p->node);
        free(p);
    }
}

static struct sym_data *kcore_copy__new_sym(struct kcore_copy_info *kci,
                        u64 addr)
{
    struct sym_data *s = zalloc(sizeof(*s));

    if (s) {
        s->addr = addr;
        list_add_tail(&s->node, &kci->syms);
    }

    return s;
}

static void kcore_copy__free_syms(struct kcore_copy_info *kci)
{
    struct sym_data *s, *tmp;

    list_for_each_entry_safe(s, tmp, &kci->syms, node) {
        list_del(&s->node);
        free(s);
    }
}

static int kcore_copy__process_kallsyms(void *arg, const char *name, char type,
                    u64 start)
{
    struct kcore_copy_info *kci = arg;

    if (!kallsyms__is_function(type))
        return 0;

    if (strchr(name, '[')) {
        if (start > kci->last_module_symbol)
            kci->last_module_symbol = start;
        return 0;
    }

    if (!kci->first_symbol || start < kci->first_symbol)
        kci->first_symbol = start;

    if (!kci->last_symbol || start > kci->last_symbol)
        kci->last_symbol = start;

    if (!strcmp(name, "_stext")) {
        kci->stext = start;
        return 0;
    }

    if (!strcmp(name, "_etext")) {
        kci->etext = start;
        return 0;
    }

    if (is_entry_trampoline(name) && !kcore_copy__new_sym(kci, start))
        return -1;

    return 0;
}

static int kcore_copy__parse_kallsyms(struct kcore_copy_info *kci,
                      const char *dir)
{
    char kallsyms_filename[PATH_MAX];

    scnprintf(kallsyms_filename, PATH_MAX, "%s/kallsyms", dir);

    if (symbol__restricted_filename(kallsyms_filename, "/proc/kallsyms"))
        return -1;

    if (kallsyms__parse(kallsyms_filename, kci,
                kcore_copy__process_kallsyms) < 0)
        return -1;

    return 0;
}

static int kcore_copy__process_modules(void *arg,
                       const char *name __maybe_unused,
                       u64 start, u64 size __maybe_unused)
{
    struct kcore_copy_info *kci = arg;

    if (!kci->first_module || start < kci->first_module)
        kci->first_module = start;

    return 0;
}

static int kcore_copy__parse_modules(struct kcore_copy_info *kci,
                     const char *dir)
{
    char modules_filename[PATH_MAX];

    scnprintf(modules_filename, PATH_MAX, "%s/modules", dir);

    if (symbol__restricted_filename(modules_filename, "/proc/modules"))
        return -1;

    if (modules__parse(modules_filename, kci,
               kcore_copy__process_modules) < 0)
        return -1;

    return 0;
}

static int kcore_copy__map(struct kcore_copy_info *kci, u64 start, u64 end,
               u64 pgoff, u64 s, u64 e)
{
    u64 len, offset;

    if (s < start || s >= end)
        return 0;

    offset = (s - start) + pgoff;
    len = e < end ? e - s : end - s;

    return kcore_copy_info__addnew(kci, s, len, offset) ? 0 : -1;
}

static int kcore_copy__read_map(u64 start, u64 len, u64 pgoff, void *data)
{
    struct kcore_copy_info *kci = data;
    u64 end = start + len;
    struct sym_data *sdat;

    if (kcore_copy__map(kci, start, end, pgoff, kci->stext, kci->etext))
        return -1;

    if (kcore_copy__map(kci, start, end, pgoff, kci->first_module,
                kci->last_module_symbol))
        return -1;

    list_for_each_entry(sdat, &kci->syms, node) {
        u64 s = round_down(sdat->addr, page_size);

        if (kcore_copy__map(kci, start, end, pgoff, s, s + len))
            return -1;
    }

    return 0;
}

static int kcore_copy__read_maps(struct kcore_copy_info *kci, Elf *elf)
{
    if (elf_read_maps(elf, true, kcore_copy__read_map, kci) < 0)
        return -1;

    return 0;
}

static void kcore_copy__find_remaps(struct kcore_copy_info *kci)
{
    struct phdr_data *p, *k = NULL;
    u64 kend;

    if (!kci->stext)
        return;

    /* Find phdr that corresponds to the kernel map (contains stext) */
    kcore_copy__for_each_phdr(kci, p) {
        u64 pend = p->addr + p->len - 1;

        if (p->addr <= kci->stext && pend >= kci->stext) {
            k = p;
            break;
        }
    }

    if (!k)
        return;

    kend = k->offset + k->len;

    /* Find phdrs that remap the kernel */
    kcore_copy__for_each_phdr(kci, p) {
        u64 pend = p->offset + p->len;

        if (p == k)
            continue;

        if (p->offset >= k->offset && pend <= kend)
            p->remaps = k;
    }
}

static void kcore_copy__layout(struct kcore_copy_info *kci)
{
    struct phdr_data *p;
    off_t rel = 0;

    kcore_copy__find_remaps(kci);

    kcore_copy__for_each_phdr(kci, p) {
        if (!p->remaps) {
            p->rel = rel;
            rel += p->len;
        }
        kci->phnum += 1;
    }

    kcore_copy__for_each_phdr(kci, p) {
        struct phdr_data *k = p->remaps;

        if (k)
            p->rel = p->offset - k->offset + k->rel;
    }
}

static int kcore_copy__calc_maps(struct kcore_copy_info *kci, const char *dir,
                 Elf *elf)
{
    if (kcore_copy__parse_kallsyms(kci, dir))
        return -1;

    if (kcore_copy__parse_modules(kci, dir))
        return -1;

    if (kci->stext)
        kci->stext = round_down(kci->stext, page_size);
    else
        kci->stext = round_down(kci->first_symbol, page_size);

    if (kci->etext) {
        kci->etext = round_up(kci->etext, page_size);
    } else if (kci->last_symbol) {
        kci->etext = round_up(kci->last_symbol, page_size);
        kci->etext += page_size;
    }

    kci->first_module = round_down(kci->first_module, page_size);

    if (kci->last_module_symbol) {
        kci->last_module_symbol = round_up(kci->last_module_symbol,
                           page_size);
        kci->last_module_symbol += page_size;
    }

    if (!kci->stext || !kci->etext)
        return -1;

    if (kci->first_module && !kci->last_module_symbol)
        return -1;

    if (kcore_copy__read_maps(kci, elf))
        return -1;

    kcore_copy__layout(kci);

    return 0;
}

static int kcore_copy__copy_file(const char *from_dir, const char *to_dir,
                 const char *name)
{
    char from_filename[PATH_MAX];
    char to_filename[PATH_MAX];

    scnprintf(from_filename, PATH_MAX, "%s/%s", from_dir, name);
    scnprintf(to_filename, PATH_MAX, "%s/%s", to_dir, name);

    return copyfile_mode(from_filename, to_filename, 0400);
}

static int kcore_copy__unlink(const char *dir, const char *name)
{
    char filename[PATH_MAX];

    scnprintf(filename, PATH_MAX, "%s/%s", dir, name);

    return unlink(filename);
}

static int kcore_copy__compare_fds(int from, int to)
{
    char *buf_from;
    char *buf_to;
    ssize_t ret;
    size_t len;
    int err = -1;

    buf_from = malloc(page_size);
    buf_to = malloc(page_size);
    if (!buf_from || !buf_to)
        goto out;

    while (1) {
        /* Use read because mmap won't work on proc files */
        ret = read(from, buf_from, page_size);
        if (ret < 0)
            goto out;

        if (!ret)
            break;

        len = ret;

        if (readn(to, buf_to, len) != (int)len)
            goto out;

        if (memcmp(buf_from, buf_to, len))
            goto out;
    }

    err = 0;
out:
    free(buf_to);
    free(buf_from);
    return err;
}

static int kcore_copy__compare_files(const char *from_filename,
                     const char *to_filename)
{
    int from, to, err = -1;

    from = open(from_filename, O_RDONLY);
    if (from < 0)
        return -1;

    to = open(to_filename, O_RDONLY);
    if (to < 0)
        goto out_close_from;

    err = kcore_copy__compare_fds(from, to);

    close(to);
out_close_from:
    close(from);
    return err;
}

static int kcore_copy__compare_file(const char *from_dir, const char *to_dir,
                    const char *name)
{
    char from_filename[PATH_MAX];
    char to_filename[PATH_MAX];

    scnprintf(from_filename, PATH_MAX, "%s/%s", from_dir, name);
    scnprintf(to_filename, PATH_MAX, "%s/%s", to_dir, name);

    return kcore_copy__compare_files(from_filename, to_filename);
}

int kcore_copy(const char *from_dir, const char *to_dir)
{
    struct kcore kcore;
    struct kcore extract;
    int idx = 0, err = -1;
    off_t offset, sz;
    struct kcore_copy_info kci = { .stext = 0, };
    char kcore_filename[PATH_MAX];
    char extract_filename[PATH_MAX];
    struct phdr_data *p;

    INIT_LIST_HEAD(&kci.phdrs);
    INIT_LIST_HEAD(&kci.syms);

    if (kcore_copy__copy_file(from_dir, to_dir, "kallsyms"))
        return -1;

    if (kcore_copy__copy_file(from_dir, to_dir, "modules"))
        goto out_unlink_kallsyms;

    scnprintf(kcore_filename, PATH_MAX, "%s/kcore", from_dir);
    scnprintf(extract_filename, PATH_MAX, "%s/kcore", to_dir);

    if (kcore__open(&kcore, kcore_filename))
        goto out_unlink_modules;

    if (kcore_copy__calc_maps(&kci, from_dir, kcore.elf))
        goto out_kcore_close;

    if (kcore__init(&extract, extract_filename, kcore.elfclass, false))
        goto out_kcore_close;

    if (kcore__copy_hdr(&kcore, &extract, kci.phnum))
        goto out_extract_close;

    offset = gelf_fsize(extract.elf, ELF_T_EHDR, 1, EV_CURRENT) +
         gelf_fsize(extract.elf, ELF_T_PHDR, kci.phnum, EV_CURRENT);
    offset = round_up(offset, page_size);

    kcore_copy__for_each_phdr(&kci, p) {
        off_t offs = p->rel + offset;

        if (kcore__add_phdr(&extract, idx++, offs, p->addr, p->len))
            goto out_extract_close;
    }

    sz = kcore__write(&extract);
    if (sz < 0 || sz > offset)
        goto out_extract_close;

    kcore_copy__for_each_phdr(&kci, p) {
        off_t offs = p->rel + offset;

        if (p->remaps)
            continue;
        if (copy_bytes(kcore.fd, p->offset, extract.fd, offs, p->len))
            goto out_extract_close;
    }

    if (kcore_copy__compare_file(from_dir, to_dir, "modules"))
        goto out_extract_close;

    if (kcore_copy__compare_file(from_dir, to_dir, "kallsyms"))
        goto out_extract_close;

    err = 0;

out_extract_close:
    kcore__close(&extract);
    if (err)
        unlink(extract_filename);
out_kcore_close:
    kcore__close(&kcore);
out_unlink_modules:
    if (err)
        kcore_copy__unlink(to_dir, "modules");
out_unlink_kallsyms:
    if (err)
        kcore_copy__unlink(to_dir, "kallsyms");

    kcore_copy__free_phdrs(&kci);
    kcore_copy__free_syms(&kci);

    return err;
}

int kcore_extract__create(struct kcore_extract *kce)
{
    struct kcore kcore;
    struct kcore extract;
    size_t count = 1;
    int idx = 0, err = -1;
    off_t offset = page_size, sz;

    if (kcore__open(&kcore, kce->kcore_filename))
        return -1;

    strcpy(kce->extract_filename, PERF_KCORE_EXTRACT);
    if (kcore__init(&extract, kce->extract_filename, kcore.elfclass, true))
        goto out_kcore_close;

    if (kcore__copy_hdr(&kcore, &extract, count))
        goto out_extract_close;

    if (kcore__add_phdr(&extract, idx, offset, kce->addr, kce->len))
        goto out_extract_close;

    sz = kcore__write(&extract);
    if (sz < 0 || sz > offset)
        goto out_extract_close;

    if (copy_bytes(kcore.fd, kce->offs, extract.fd, offset, kce->len))
        goto out_extract_close;

    err = 0;

out_extract_close:
    kcore__close(&extract);
    if (err)
        unlink(kce->extract_filename);
out_kcore_close:
    kcore__close(&kcore);

    return err;
}

void kcore_extract__delete(struct kcore_extract *kce)
{
    unlink(kce->extract_filename);
}

#ifdef HAVE_GELF_GETNOTE_SUPPORT

static int populate_sdt_note(Elf **elf, const char *data, size_t len,
                 struct list_head *sdt_notes)
{
    const char *provider, *name, *args;
    struct sdt_note *tmp = NULL;
    GElf_Ehdr ehdr;
    GElf_Addr base_off = 0;
    GElf_Shdr shdr;
    int ret = -EINVAL;

    union {
        Elf64_Addr a64[NR_ADDR];
        Elf32_Addr a32[NR_ADDR];
    } buf;

    Elf_Data dst = {
        .d_buf = &buf, .d_type = ELF_T_ADDR, .d_version = EV_CURRENT,
        .d_size = gelf_fsize((*elf), ELF_T_ADDR, NR_ADDR, EV_CURRENT),
        .d_off = 0, .d_align = 0
    };
    Elf_Data src = {
        .d_buf = (void *) data, .d_type = ELF_T_ADDR,
        .d_version = EV_CURRENT, .d_size = dst.d_size, .d_off = 0,
        .d_align = 0
    };

    tmp = (struct sdt_note *)calloc(1, sizeof(struct sdt_note));
    if (!tmp) {
        ret = -ENOMEM;
        goto out_err;
    }

    INIT_LIST_HEAD(&tmp->note_list);

    if (len < dst.d_size + 3)
        goto out_free_note;

    /* Translation from file representation to memory representation */
    if (gelf_xlatetom(*elf, &dst, &src,
              elf_getident(*elf, NULL)[EI_DATA]) == NULL) {
        pr_err("gelf_xlatetom : %s\n", elf_errmsg(-1));
        goto out_free_note;
    }

    /* Populate the fields of sdt_note */
    provider = data + dst.d_size;

    name = (const char *)memchr(provider, '\0', data + len - provider);
    if (name++ == NULL)
        goto out_free_note;

    tmp->provider = strdup(provider);
    if (!tmp->provider) {
        ret = -ENOMEM;
        goto out_free_note;
    }
    tmp->name = strdup(name);
    if (!tmp->name) {
        ret = -ENOMEM;
        goto out_free_prov;
    }

    args = memchr(name, '\0', data + len - name);

    /*
     * There is no argument if:
     * - We reached the end of the note;
     * - There is not enough room to hold a potential string;
     * - The argument string is empty or just contains ':'.
     */
    if (args == NULL || data + len - args < 2 ||
        args[1] == ':' || args[1] == '\0')
        tmp->args = NULL;
    else {
        tmp->args = strdup(++args);
        if (!tmp->args) {
            ret = -ENOMEM;
            goto out_free_name;
        }
    }

    if (gelf_getclass(*elf) == ELFCLASS32) {
        memcpy(&tmp->addr, &buf, 3 * sizeof(Elf32_Addr));
        tmp->bit32 = true;
    } else {
        memcpy(&tmp->addr, &buf, 3 * sizeof(Elf64_Addr));
        tmp->bit32 = false;
    }

    if (!gelf_getehdr(*elf, &ehdr)) {
        pr_debug("%s : cannot get elf header.\n", __func__);
        ret = -EBADF;
        goto out_free_args;
    }

    /* Adjust the prelink effect :
     * Find out the .stapsdt.base section.
     * This scn will help us to handle prelinking (if present).
     * Compare the retrieved file offset of the base section with the
     * base address in the description of the SDT note. If its different,
     * then accordingly, adjust the note location.
     */
    if (elf_section_by_name(*elf, &ehdr, &shdr, SDT_BASE_SCN, NULL)) {
        base_off = shdr.sh_offset;
        if (base_off) {
            if (tmp->bit32)
                tmp->addr.a32[0] = tmp->addr.a32[0] + base_off -
                    tmp->addr.a32[1];
            else
                tmp->addr.a64[0] = tmp->addr.a64[0] + base_off -
                    tmp->addr.a64[1];
        }
    }

    list_add_tail(&tmp->note_list, sdt_notes);
    return 0;

out_free_args:
    free(tmp->args);
out_free_name:
    free(tmp->name);
out_free_prov:
    free(tmp->provider);
out_free_note:
    free(tmp);
out_err:
    return ret;
}

static int construct_sdt_notes_list(Elf *elf, struct list_head *sdt_notes)
{
    GElf_Ehdr ehdr;
    Elf_Scn *scn = NULL;
    Elf_Data *data;
    GElf_Shdr shdr;
    size_t shstrndx, next;
    GElf_Nhdr nhdr;
    size_t name_off, desc_off, offset;
    int ret = 0;

    if (gelf_getehdr(elf, &ehdr) == NULL) {
        ret = -EBADF;
        goto out_ret;
    }
    if (elf_getshdrstrndx(elf, &shstrndx) != 0) {
        ret = -EBADF;
        goto out_ret;
    }

    /* Look for the required section */
    scn = elf_section_by_name(elf, &ehdr, &shdr, SDT_NOTE_SCN, NULL);
    if (!scn) {
        ret = -ENOENT;
        goto out_ret;
    }

    if ((shdr.sh_type != SHT_NOTE) || (shdr.sh_flags & SHF_ALLOC)) {
        ret = -ENOENT;
        goto out_ret;
    }

    data = elf_getdata(scn, NULL);

    /* Get the SDT notes */
    for (offset = 0; (next = gelf_getnote(data, offset, &nhdr, &name_off,
                          &desc_off)) > 0; offset = next) {
        if (nhdr.n_namesz == sizeof(SDT_NOTE_NAME) &&
            !memcmp(data->d_buf + name_off, SDT_NOTE_NAME,
                sizeof(SDT_NOTE_NAME))) {
            /* Check the type of the note */
            if (nhdr.n_type != SDT_NOTE_TYPE)
                goto out_ret;

            ret = populate_sdt_note(&elf, ((data->d_buf) + desc_off),
                        nhdr.n_descsz, sdt_notes);
            if (ret < 0)
                goto out_ret;
        }
    }
    if (list_empty(sdt_notes))
        ret = -ENOENT;

out_ret:
    return ret;
}

int get_sdt_note_list(struct list_head *head, const char *target)
{
    Elf *elf;
    int fd, ret;

    fd = open(target, O_RDONLY);
    if (fd < 0)
        return -EBADF;

    elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
    if (!elf) {
        ret = -EBADF;
        goto out_close;
    }
    ret = construct_sdt_notes_list(elf, head);
    elf_end(elf);
out_close:
    close(fd);
    return ret;
}

int cleanup_sdt_note_list(struct list_head *sdt_notes)
{
    struct sdt_note *tmp, *pos;
    int nr_free = 0;

    list_for_each_entry_safe(pos, tmp, sdt_notes, note_list) {
        list_del(&pos->note_list);
        free(pos->name);
        free(pos->provider);
        free(pos);
        nr_free++;
    }
    return nr_free;
}

int sdt_notes__get_count(struct list_head *start)
{
    struct sdt_note *sdt_ptr;
    int count = 0;

    list_for_each_entry(sdt_ptr, start, note_list)
        count++;
    return count;
}
#endif

void symbol__elf_init(void)
{
    elf_version(EV_CURRENT);
}