[Crash-utility] [PATCH] x86_64: Fix "bt" command to use correct ORC register values on Linux 7.1 and later
From: Kazuhito Hagio <k-hagio-ab(a)nec.com>
Kernel commit 1735858caa4b ("objtool/x86: Reorder ORC register numbering")
changed the ORC register numbering. Without the patch, crash can interpret ORC
entry incorrectly and the "bt" command may generate broken backtraces on Linux
7.1 and later kernels like this:
crash> bt 1
PID: 1 TASK: ffff8ab0009cd100 CPU: 2 COMMAND: "systemd"
#0 [ffffd2218003b9c8] __schedule at ffffffffaa9d862b
#1 [ffffd2218003ba20] schedule at ffffffffaa9d8993
#2 [ffffd2218003ba30] schedule_hrtimeout_range_clock at ffffffffaa9df77b
#3 [ffffd2218003bab0] ep_poll at ffffffffaa1231e4
#4 [ffffd2218003bb50] do_epoll_wait at ffffffffaa123272
#5 [ffffd2218003bb88] __x64_sys_epoll_wait at ffffffffaa123b1f
#6 [ffffd2218003bbd8] do_syscall_64 at ffffffffaa9cca6c
#7 [ffffd2218003bc58] __memcg_slab_free_hook at ffffffffaa079da3
#8 [ffffd2218003bcf0] __memcg_slab_free_hook at ffffffffaa079da3
#9 [ffffd2218003bd50] __x64_sys_gettid at ffffffffa9ce1656
#10 [ffffd2218003bd58] do_syscall_64 at ffffffffaa9ccaa4
#11 [ffffd2218003bdc0] update_cfs_rq_load_avg at ffffffffa9d1bf59
#12 [ffffd2218003be00] __update_blocked_fair at ffffffffa9d214b8
#13 [ffffd2218003be70] sched_clock at ffffffffa9c460dc
#14 [ffffd2218003be78] sched_clock_cpu at ffffffffa9d4aeab
#15 [ffffd2218003be98] irqtime_account_irq at ffffffffa9d3af0d
#16 [ffffd2218003bec0] handle_softirqs at ffffffffa9cce5ac
#17 [ffffd2218003bf40] entry_SYSCALL_64_after_hwframe at ffffffffa9a0012b
Fix this by making ORC_REG_SP and ORC_REG_PREV_SP depend on kernel version, as
no other way was found.
Signed-off-by: Kazuhito Hagio <k-hagio-ab(a)nec.com>
---
Hi,
I could not find another way except for using kernel version, is there any idea?
defs.h | 6 ++++--
x86_64.c | 11 +++++++++++
2 files changed, 15 insertions(+), 2 deletions(-)
diff --git a/defs.h b/defs.h
index 6373ee1831af..e4bd77a518aa 100644
--- a/defs.h
+++ b/defs.h
@@ -6649,6 +6649,8 @@ struct ORC_data {
orc_entry orc_entry_data;
int has_signal;
int has_end;
+ int reg_sp;
+ int reg_prev_sp;
};
#define ORC_TYPE_CALL ((machdep->flags & ORC_6_4) ? 2 : 0)
@@ -6659,11 +6661,11 @@ struct ORC_data {
#define UNWIND_HINT_TYPE_RESTORE 4
#define ORC_REG_UNDEFINED 0
-#define ORC_REG_PREV_SP 1
+#define ORC_REG_PREV_SP (machdep->machspec->orc.reg_prev_sp)
#define ORC_REG_DX 2
#define ORC_REG_DI 3
#define ORC_REG_BP 4
-#define ORC_REG_SP 5
+#define ORC_REG_SP (machdep->machspec->orc.reg_sp)
#define ORC_REG_R10 6
#define ORC_REG_R13 7
#define ORC_REG_BP_INDIRECT 8
diff --git a/x86_64.c b/x86_64.c
index b2cddbf8ba3d..ec3c0e87fa06 100644
--- a/x86_64.c
+++ b/x86_64.c
@@ -999,6 +999,8 @@ x86_64_dump_machdep_table(ulong arg)
fprintf(fp, " module_ORC: %s\n", ms->orc.module_ORC ?
"TRUE" : "FALSE");
fprintf(fp, " has_signal: %s\n", ms->orc.has_signal ?
"TRUE" : "FALSE");
fprintf(fp, " has_end: %s\n", ms->orc.has_end ?
"TRUE" : "FALSE");
+ fprintf(fp, " reg_sp: %d\n", ms->orc.reg_sp);
+ fprintf(fp, " reg_prev_sp: %d\n", ms->orc.reg_prev_sp);
fprintf(fp, " lookup_num_blocks: %d\n",
ms->orc.lookup_num_blocks);
fprintf(fp, " __start_orc_unwind_ip: %lx\n",
ms->orc.__start_orc_unwind_ip);
fprintf(fp, " __stop_orc_unwind_ip: %lx\n",
ms->orc.__stop_orc_unwind_ip);
@@ -6720,6 +6722,15 @@ x86_64_ORC_init(void)
if (orc->has_signal && !orc->has_end)
machdep->flags |= ORC_6_4;
+ /* See kernel commit 1735858caa4b */
+ if (THIS_KERNEL_VERSION >= LINUX(7,1,0)) {
+ ORC_REG_SP = 3;
+ ORC_REG_PREV_SP = 8;
+ } else {
+ ORC_REG_SP = 5;
+ ORC_REG_PREV_SP = 1;
+ }
+
machdep->flags |= ORC;
}
--
2.31.1