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Eh_elf: make local unwinding work

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Remote unwinding yet to be tested
This commit is contained in:
Théophile Bastian 2018-06-05 18:22:23 +02:00
parent 1068aa2368
commit 07e6a1a96f
2 changed files with 46 additions and 11 deletions
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54
src/eh_elf/eh_elf.c
View file

@ -46,25 +46,57 @@ static uintptr_t fetchw_here(uintptr_t addr) {
return out;
}
dwarf_loc_t of_eh_elf_loc(uintptr_t eh_elf_loc) {
if(eh_elf_loc + 1 == 0) // Undefined
return DWARF_NULL_LOC;
return DWARF_LOC(eh_elf_loc, DWARF_LOC_TYPE_VAL);
}
int eh_elf_step_cursor(struct cursor *cursor) {
uintptr_t ip = cursor->dwarf.ip;
// Check for the end of the call chain
if(DWARF_IS_NULL_LOC(cursor->dwarf.loc[UNW_TDEP_IP]))
return 0;
if(!DWARF_IS_NULL_LOC(cursor->dwarf.loc[UNW_TDEP_BP])) {
uintptr_t bp;
dwarf_get(&cursor->dwarf,
cursor->dwarf.loc[UNW_TDEP_BP], &bp);
if(bp == 0)
return 0;
}
// Retrieve memory map entry
mmap_entry_t* mmap_entry = mmap_get_entry(ip);
if(mmap_entry == NULL)
return -1;
Debug(5, "In memory map entry %lx-%lx (%s) - off %lx, ip %lx%s\n",
mmap_entry->beg_ip,
mmap_entry->end_ip,
mmap_entry->object_name,
mmap_entry->offset,
ip - mmap_entry->offset,
mmap_entry->eh_elf == NULL ? " [MISSING EH_ELF]" : "");
// Retrieve a pointer to the eh_elf function
_fde_func_with_deref_t fde_func =
(_fde_func_t) (dlsym(mmap_entry->eh_elf, "_eh_elf"));
(_fde_func_with_deref_t) (dlsym(mmap_entry->eh_elf, "_eh_elf"));
if(fde_func == NULL)
return -2;
// Setup an eh_elf context
unwind_context_t eh_elf_context;
eh_elf_context.rip = ip;
eh_elf_context.rsp = cursor->dwarf.loc[UNW_TDEP_SP].val;
eh_elf_context.rbp = cursor->dwarf.loc[UNW_TDEP_BP].val;
dwarf_get(&cursor->dwarf,
cursor->dwarf.loc[UNW_TDEP_SP], &eh_elf_context.rsp);
dwarf_get(&cursor->dwarf,
cursor->dwarf.loc[UNW_TDEP_BP], &eh_elf_context.rbp);
Debug(4, "BEFORE eh_elf_context: rip=0x%lx, rsp=0x%lx, rbp=0x%lx\n",
eh_elf_context.rip,
eh_elf_context.rsp,
eh_elf_context.rbp);
// Set _fetch_state before passing fetchw_here
_fetch_state.addr_space = cursor->dwarf.as;
@ -76,24 +108,26 @@ int eh_elf_step_cursor(struct cursor *cursor) {
ip - mmap_entry->offset,
fetchw_here);
// Check for the end of the call chain
if(eh_elf_context.rbp == 0 || eh_elf_context.rip + 1 == 0)
return 0;
// Push back the data into libunwind's structures
for (int i = 0; i < DWARF_NUM_PRESERVED_REGS; ++i)
cursor->dwarf.loc[i] = DWARF_NULL_LOC;
cursor->dwarf.loc[UNW_TDEP_BP].val = eh_elf_context.rbp;
cursor->dwarf.loc[UNW_TDEP_SP].val = eh_elf_context.rsp;
cursor->dwarf.loc[UNW_TDEP_IP].val = eh_elf_context.rip;
cursor->dwarf.loc[UNW_TDEP_BP] = of_eh_elf_loc(eh_elf_context.rbp);
cursor->dwarf.loc[UNW_TDEP_SP] = of_eh_elf_loc(eh_elf_context.rsp);
cursor->dwarf.loc[UNW_TDEP_IP] = of_eh_elf_loc(eh_elf_context.rip);
cursor->dwarf.use_prev_instr = 1;
Debug(4, "AFTER eh_elf_context: rip=0x%lx, rsp=0x%lx, rbp=0x%lx\n",
eh_elf_context.rip,
eh_elf_context.rsp,
eh_elf_context.rbp);
cursor->frame_info.frame_type = UNW_X86_64_FRAME_GUESSED;
cursor->frame_info.cfa_reg_rsp = 0;
cursor->frame_info.cfa_reg_offset = 16;
cursor->frame_info.rbp_cfa_offset = -16;
cursor->dwarf.cfa += 16;
cursor->dwarf.ip = eh_elf_context.rip;
return 1;
}

3
src/x86_64/Gstep.c
View file

@ -68,12 +68,13 @@ unw_step (unw_cursor_t *cursor)
c, c->dwarf.ip, c->dwarf.cfa);
// Try eh_elf based unwinding...
ret = eh_elf_step_cursor(&c);
ret = eh_elf_step_cursor(c);
if(ret < 0) {
Debug(2, "eh_elf unwinding failed (%d), falling back\n", ret);
}
else {
Debug (2, "returning %d\n", ret);
return ret;
}