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Merge pull request #115 from pcc/fix1

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symbolize: Calculate a module's zero VA using program headers.
This commit is contained in:
Fumitoshi Ukai 2016-07-14 10:44:18 +09:00 committed by GitHub
commit f174cba02c
1 changed files with 24 additions and 3 deletions
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27
src/symbolize.cc
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@ -327,7 +327,7 @@ FindSymbol(uint64_t pc, const int fd, char *out, int out_size,
// false.
static bool GetSymbolFromObjectFile(const int fd, uint64_t pc,
char *out, int out_size,
uint64_t map_start_address) {
uint64_t map_base_address) {
// Read the ELF header.
ElfW(Ehdr) elf_header;
if (!ReadFromOffsetExact(fd, &elf_header, sizeof(elf_header), 0)) {
@ -336,7 +336,28 @@ static bool GetSymbolFromObjectFile(const int fd, uint64_t pc,
uint64_t symbol_offset = 0;
if (elf_header.e_type == ET_DYN) { // DSO needs offset adjustment.
symbol_offset = map_start_address;
ElfW(Phdr) phdr;
// We need to find the PT_LOAD segment corresponding to the read-execute
// file mapping in order to correctly perform the offset adjustment.
for (unsigned i = 0; i != elf_header.e_phnum; ++i) {
if (!ReadFromOffsetExact(fd, &phdr, sizeof(phdr),
elf_header.e_phoff + i * sizeof(phdr)))
return false;
if (phdr.p_type == PT_LOAD &&
(phdr.p_flags & (PF_R | PF_X)) == (PF_R | PF_X)) {
// Find the mapped address corresponding to virtual address zero. We do
// this by first adding p_offset. This gives us the mapped address of
// the start of the segment, or in other words the mapped address
// corresponding to the virtual address of the segment. (Note that this
// is distinct from the start address, as p_offset is not guaranteed to
// be page aligned.) We then subtract p_vaddr, which takes us to virtual
// address zero.
symbol_offset = map_base_address + phdr.p_offset - phdr.p_vaddr;
break;
}
}
if (symbol_offset == 0)
return false;
}
ElfW(Shdr) symtab, strtab;
@ -782,7 +803,7 @@ static ATTRIBUTE_NOINLINE bool SymbolizeAndDemangle(void *pc, char *out,
}
}
if (!GetSymbolFromObjectFile(wrapped_object_fd.get(), pc0,
out, out_size, start_address)) {
out, out_size, base_address)) {
return false;
}