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/*
*
* Copyright (c) 2016 Samsung Electronics Co., Ltd.
*
* Licensed under the Apache License, Version 2.0 (the License);
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* Author: Adrian Szyndela <adrian.s@samsung.com>
*/
/**
* @file crash-stack-libelf-helpers.c
* @brief unwinding call stacks, functions for accessing libelf for other
* purposes than unwinding
*/
#include "crash-stack.h"
#include <string.h>
#include <sys/ptrace.h>
#include <errno.h>
bool _crash_stack_libelf_read_value(Dwfl *dwfl, Elf *core, pid_t pid,
Dwarf_Addr a, void *v, size_t size,
Mappings *mappings)
{
Dwfl_Module *module = 0;
Elf_Data *data = NULL;
int segment = dwfl_addrsegment(dwfl, a, &module);
if (module != NULL) {
Dwarf_Addr start;
dwfl_module_info(module, NULL, &start, NULL, NULL, NULL, NULL, NULL);
GElf_Addr bias;
Elf *elf = dwfl_module_getelf(module, &bias);
data = elf_getdata_rawchunk(elf, a-start, size, ELF_T_BYTE);
}
if (NULL == data && segment != -1) {
// get data from segment
GElf_Phdr mem;
GElf_Phdr *phdr = gelf_getphdr(core, segment, &mem);
Dwarf_Addr offset_in_segment = a - phdr->p_vaddr;
if (offset_in_segment < phdr->p_filesz) {
Dwarf_Addr offset_in_file = phdr->p_offset + offset_in_segment;
data = elf_getdata_rawchunk(core, offset_in_file, size, ELF_T_BYTE);
}
}
if (NULL == data && module != NULL) {
const char *name = dwfl_module_info(module, NULL, NULL, NULL, NULL, NULL, NULL, NULL);
if (name != NULL && name[0] == '[') {
int i;
// get module from mappings
for (i = 0; i < mappings->elems; i++) {
if (mappings->tab[i].m_start <= a && a < mappings->tab[i].m_end) {
// compute offset relative to the start of the mapping
long offset = a - mappings->tab[i].m_start;
// read from the file, but also account file offset
data = elf_getdata_rawchunk(mappings->tab[i].m_elf,
offset + mappings->tab[i].m_offset, size, ELF_T_BYTE);
break;
}
}
}
}
if (data != NULL) {
memcpy(v, data->d_buf, size);
return true;
}
/* Still no data, but we have a process - read memory with ptrace */
/* FIXME need to know if we are still in the mapped area */
/* Bigger issue is that dwfl does not have modules */
if (pid > 1) {
long val = ptrace(PTRACE_PEEKDATA, pid, a, NULL);
if (-1 == val && errno)
return false;
memcpy(v, &val, size);
return true;
}
return false;
}
Dwarf_Addr _crash_stack_libelf_get_prologue_pc(Dwfl *dwfl, Dwarf_Addr current_pc, Mappings *mappings)
{
Dwarf_Addr result = 0;
Dwfl_Module *module = dwfl_addrmodule(dwfl, current_pc);
if (module) {
GElf_Sym sym;
dwfl_module_addrsym(module, current_pc, &sym, NULL);
result = sym.st_value;
}
if (0 == result) {
int i;
for (i=0; i < mappings->elems; i++) {
if (mappings->tab[i].m_start <= current_pc && current_pc < mappings->tab[i].m_end) {
/* go through symbols to find the nearest */
Elf_Scn *scn = NULL;
Elf *elf = mappings->tab[i].m_elf;
while ((scn = elf_nextscn(elf, scn)) != NULL) {
GElf_Shdr shdr_mem;
GElf_Shdr *shdr = gelf_getshdr(scn, &shdr_mem);
if (shdr != NULL && (shdr->sh_type == SHT_SYMTAB || shdr->sh_type == SHT_DYNSYM)) {
Elf_Data *sdata = elf_getdata(scn, NULL);
unsigned int nsyms = sdata->d_size / (gelf_getclass(elf) == ELFCLASS32 ?
sizeof(Elf32_Sym) :
sizeof(Elf64_Sym));
unsigned int cnt;
uintptr_t address_offset = current_pc;
if (shdr->sh_type == SHT_DYNSYM)
address_offset -= mappings->tab[i].m_start;
for (cnt = 0; cnt < nsyms; ++cnt) {
GElf_Sym sym_mem;
Elf32_Word xndx;
GElf_Sym *sym = gelf_getsymshndx(sdata, NULL, cnt, &sym_mem, &xndx);
if (sym != NULL && sym->st_shndx != SHN_UNDEF) {
if (sym->st_value <= address_offset && address_offset < sym->st_value + sym->st_size) {
return sym->st_value;
}
}
}
}
}
}
}
}
return result;
}
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