sym-handling.c

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/*
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License, version 2, as
 * published by the Free Software Foundation.
 *
 * Copyright (C) 2015 Naveen N. Rao, IBM Corporation
 */

#include "debug.h"
#include "symbol.h"
#include "map.h"
#include "probe-event.h"
#include "probe-file.h"

#ifdef HAVE_LIBELF_SUPPORT
bool elf__needs_adjust_symbols(GElf_Ehdr ehdr)
{
    return ehdr.e_type == ET_EXEC ||
           ehdr.e_type == ET_REL ||
           ehdr.e_type == ET_DYN;
}

#endif

#if !defined(_CALL_ELF) || _CALL_ELF != 2
int arch__choose_best_symbol(struct symbol *syma,
                 struct symbol *symb __maybe_unused)
{
    char *sym = syma->name;

    /* Skip over any initial dot */
    if (*sym == '.')
        sym++;

    /* Avoid "SyS" kernel syscall aliases */
    if (strlen(sym) >= 3 && !strncmp(sym, "SyS", 3))
        return SYMBOL_B;
    if (strlen(sym) >= 10 && !strncmp(sym, "compat_SyS", 10))
        return SYMBOL_B;

    return SYMBOL_A;
}

/* Allow matching against dot variants */
int arch__compare_symbol_names(const char *namea, const char *nameb)
{
    /* Skip over initial dot */
    if (*namea == '.')
        namea++;
    if (*nameb == '.')
        nameb++;

    return strcmp(namea, nameb);
}

int arch__compare_symbol_names_n(const char *namea, const char *nameb,
                 unsigned int n)
{
    /* Skip over initial dot */
    if (*namea == '.')
        namea++;
    if (*nameb == '.')
        nameb++;

    return strncmp(namea, nameb, n);
}

const char *arch__normalize_symbol_name(const char *name)
{
    /* Skip over initial dot */
    if (name && *name == '.')
        name++;
    return name;
}
#endif

#if defined(_CALL_ELF) && _CALL_ELF == 2

#ifdef HAVE_LIBELF_SUPPORT
void arch__sym_update(struct symbol *s, GElf_Sym *sym)
{
    s->arch_sym = sym->st_other;
}
#endif

#define PPC64LE_LEP_OFFSET  8

void arch__fix_tev_from_maps(struct perf_probe_event *pev,
                 struct probe_trace_event *tev, struct map *map,
                 struct symbol *sym)
{
    int lep_offset;

    /*
     * When probing at a function entry point, we normally always want the
     * LEP since that catches calls to the function through both the GEP and
     * the LEP. Hence, we would like to probe at an offset of 8 bytes if
     * the user only specified the function entry.
     *
     * However, if the user specifies an offset, we fall back to using the
     * GEP since all userspace applications (objdump/readelf) show function
     * disassembly with offsets from the GEP.
     */
    if (pev->point.offset || !map || !sym)
        return;

    /* For kretprobes, add an offset only if the kernel supports it */
    if (!pev->uprobes && pev->point.retprobe) {
#ifdef HAVE_LIBELF_SUPPORT
        if (!kretprobe_offset_is_supported())
#endif
            return;
    }

    lep_offset = PPC64_LOCAL_ENTRY_OFFSET(sym->arch_sym);

    if (map->dso->symtab_type == DSO_BINARY_TYPE__KALLSYMS)
        tev->point.offset += PPC64LE_LEP_OFFSET;
    else if (lep_offset) {
        if (pev->uprobes)
            tev->point.address += lep_offset;
        else
            tev->point.offset += lep_offset;
    }
}

#ifdef HAVE_LIBELF_SUPPORT
void arch__post_process_probe_trace_events(struct perf_probe_event *pev,
                       int ntevs)
{
    struct probe_trace_event *tev;
    struct map *map;
    struct symbol *sym = NULL;
    struct rb_node *tmp;
    int i = 0;

    map = get_target_map(pev->target, pev->nsi, pev->uprobes);
    if (!map || map__load(map) < 0)
        return;

    for (i = 0; i < ntevs; i++) {
        tev = &pev->tevs[i];
        map__for_each_symbol(map, sym, tmp) {
            if (map->unmap_ip(map, sym->start) == tev->point.address)
                arch__fix_tev_from_maps(pev, tev, map, sym);
        }
    }
}
#endif /* HAVE_LIBELF_SUPPORT */

#endif