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/* $OpenBSD: ksyms.c,v 1.1 2020/01/21 16:24:55 mpi Exp $ */
/*
* Copyright (c) 2016 Martin Pieuchot <mpi@openbsd.org>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <assert.h>
#include <err.h>
#include <fcntl.h>
#include <gelf.h>
#include <paths.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include "btrace.h"
int kfd = -1;
Elf *kelf;
Elf_Scn *ksymtab;
size_t kstrtabndx, knsymb;
int kelf_parse(void);
int
kelf_open(void)
{
int error;
assert(kfd == -1);
if (elf_version(EV_CURRENT) == EV_NONE)
errx(1, "elf_version: %s", elf_errmsg(-1));
kfd = open(_PATH_KSYMS, O_RDONLY);
if (kfd == -1) {
warn("open");
return 1;
}
if ((kelf = elf_begin(kfd, ELF_C_READ, NULL)) == NULL) {
warnx("elf_begin: %s", elf_errmsg(-1));
error = 1;
goto bad;
}
if (elf_kind(kelf) != ELF_K_ELF) {
error = 1;
goto bad;
}
error = kelf_parse();
if (error)
goto bad;
return 0;
bad:
kelf_close();
return error;
}
void
kelf_close(void)
{
elf_end(kelf);
kelf = NULL;
close(kfd);
kfd = -1;
}
int
kelf_snprintsym(char *str, size_t size, unsigned long pc)
{
GElf_Sym sym;
Elf_Data *data = NULL;
Elf_Addr offset, bestoff = 0;
size_t i, bestidx = 0;
char *name;
int cnt;
data = elf_rawdata(ksymtab, data);
if (data == NULL)
goto fallback;
for (i = 0; i < knsymb; i++) {
if (gelf_getsym(data, i, &sym) == NULL)
continue;
if (GELF_ST_TYPE(sym.st_info) != STT_FUNC)
continue;
if (pc >= sym.st_value) {
if (pc < (sym.st_value + sym.st_size))
break;
/* Workaround for symbols w/o size, usually asm ones. */
if (sym.st_size == 0 && sym.st_value > bestoff) {
bestidx = i;
bestoff = sym.st_value;
}
}
}
if (i == knsymb) {
if (bestidx == 0 || gelf_getsym(data, bestidx, &sym) == NULL)
goto fallback;
}
name = elf_strptr(kelf, kstrtabndx, sym.st_name);
if (name != NULL)
cnt = snprintf(str, size, "%s", name);
else
cnt = snprintf(str, size, "0x%llx", sym.st_value);
offset = pc - sym.st_value;
if (offset != 0)
cnt += snprintf(str + cnt, size - cnt, "+0x%llx\n", offset);
else
cnt += snprintf(str + cnt, size - cnt, "\n");
return cnt;
fallback:
return snprintf(str, size, "0x%lx\n", pc);
}
int
kelf_parse(void)
{
GElf_Shdr shdr;
Elf_Scn *scn, *scnctf;
char *name;
size_t shstrndx;
if (elf_getshdrstrndx(kelf, &shstrndx) != 0) {
warnx("elf_getshdrstrndx: %s", elf_errmsg(-1));
return 1;
}
scn = scnctf = NULL;
while ((scn = elf_nextscn(kelf, scn)) != NULL) {
if (gelf_getshdr(scn, &shdr) != &shdr) {
warnx("elf_getshdr: %s", elf_errmsg(-1));
return 1;
}
if ((name = elf_strptr(kelf, shstrndx, shdr.sh_name)) == NULL) {
warnx("elf_strptr: %s", elf_errmsg(-1));
return 1;
}
if (strcmp(name, ELF_SYMTAB) == 0 &&
shdr.sh_type == SHT_SYMTAB && shdr.sh_entsize != 0) {
ksymtab = scn;
knsymb = shdr.sh_size / shdr.sh_entsize;
}
if (strcmp(name, ELF_STRTAB) == 0 &&
shdr.sh_type == SHT_STRTAB) {
kstrtabndx = elf_ndxscn(scn);
}
}
if (ksymtab == NULL)
warnx("symbol table not found");
return 0;
}
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