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-rw-r--r--src/symbolize.cc27
1 files changed, 24 insertions, 3 deletions
diff --git a/src/symbolize.cc b/src/symbolize.cc
index b18796e..f83c309 100644
--- a/src/symbolize.cc
+++ b/src/symbolize.cc
@@ -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;
}