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libdrgn: orc_info: don't assume ORC section alignment

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ORC sections do seem to be aligned as we expected in vmlinux, but not in
kernel modules (the kernel's module loader takes care of aligning it
properly regardless of the ELF section alignment). This causes stack
tracing to fail when the stack trace contains a frame in a kernel module
without DWARF, e.g., vmx_do_nmi_irqoff in arch/x86/kvm/vmx/vmenter.S.

Fix it by going back to copying instead of assuming alignment.

Fixes: 0bb503c6a0 ("libdrgn: orc_info: check ORC section alignment instead of copying")
Signed-off-by: Omar Sandoval <osandov@osandov.com>
This commit is contained in:
Omar Sandoval 2023-08-21 14:34:55 -07:00
parent 2b1b445315
commit 32c0ce9f0d
1 changed files with 9 additions and 15 deletions
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24
libdrgn/orc_info.c
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@ -4,7 +4,6 @@
#include <byteswap.h>
#include <gelf.h>
#include <limits.h>
#include <stdalign.h>
#include <stdlib.h>
#include <string.h>
@ -22,12 +21,13 @@ void drgn_module_orc_info_deinit(struct drgn_module *module)
free(module->orc.pc_offsets);
}
// Getters for "raw" ORC information, i.e., before it is byte swapped or
// normalized to the latest version.
// Getters for "raw" ORC information, i.e., before it is aligned, byte swapped,
// and normalized to the latest version.
static inline uint64_t drgn_raw_orc_pc(struct drgn_module *module,
unsigned int i)
{
int32_t offset = module->orc.pc_offsets[i];
int32_t offset;
memcpy(&offset, &module->orc.pc_offsets[i], sizeof(offset));
if (drgn_elf_file_bswap(module->debug_file))
offset = bswap_32(offset);
return module->orc.pc_base + UINT64_C(4) * i + offset;
@ -36,7 +36,8 @@ static inline uint64_t drgn_raw_orc_pc(struct drgn_module *module,
static bool
drgn_raw_orc_entry_is_terminator(struct drgn_module *module, unsigned int i)
{
uint16_t flags = module->orc.entries[i].flags;
uint16_t flags;
memcpy(&flags, &module->orc.entries[i].flags, sizeof(flags));
if (drgn_elf_file_bswap(module->debug_file))
flags = bswap_16(flags);
if (module->orc.version >= 3) {
@ -310,14 +311,6 @@ static struct drgn_error *drgn_read_orc_sections(struct drgn_module *module)
return drgn_error_create(DRGN_ERROR_OTHER,
".orc_unwind_ip and/or .orc_unwind has invalid size");
}
if ((uintptr_t)orc_unwind_ip->d_buf % alignof(int32_t)) {
return drgn_error_create(DRGN_ERROR_OTHER,
".orc_unwind_ip is not sufficiently aligned");
}
if ((uintptr_t)orc_unwind->d_buf % alignof(struct drgn_orc_entry)) {
return drgn_error_create(DRGN_ERROR_OTHER,
".orc_unwind is not sufficiently aligned");
}
module->orc.pc_offsets = orc_unwind_ip->d_buf;
module->orc.entries = orc_unwind->d_buf;
@ -380,8 +373,9 @@ static struct drgn_error *drgn_debug_info_parse_orc(struct drgn_module *module)
const int version = module->orc.version;
for (unsigned int i = 0; i < num_entries; i++) {
unsigned int index = indices[i];
int32_t offset = orig_offsets[index];
entries[i] = orig_entries[index];
int32_t offset;
memcpy(&offset, &orig_offsets[index], sizeof(offset));
memcpy(&entries[i], &orig_entries[index], sizeof(entries[i]));
if (bswap) {
offset = bswap_32(offset);
entries[i].sp_offset = bswap_16(entries[i].sp_offset);