From: Chen Zhongjin chenzhongjin@huawei.com
[ Upstream commit 230db82413c091bc16acee72650f48d419cebe49 ]
When a console stack dump is initiated with CONFIG_GCOV_PROFILE_ALL enabled, show_trace_log_lvl() gets out of sync with the ORC unwinder, causing the stack trace to show all text addresses as unreliable:
# echo l > /proc/sysrq-trigger [ 477.521031] sysrq: Show backtrace of all active CPUs [ 477.523813] NMI backtrace for cpu 0 [ 477.524492] CPU: 0 PID: 1021 Comm: bash Not tainted 6.0.0 #65 [ 477.525295] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.0-1.fc36 04/01/2014 [ 477.526439] Call Trace: [ 477.526854] <TASK> [ 477.527216] ? dump_stack_lvl+0xc7/0x114 [ 477.527801] ? dump_stack+0x13/0x1f [ 477.528331] ? nmi_cpu_backtrace.cold+0xb5/0x10d [ 477.528998] ? lapic_can_unplug_cpu+0xa0/0xa0 [ 477.529641] ? nmi_trigger_cpumask_backtrace+0x16a/0x1f0 [ 477.530393] ? arch_trigger_cpumask_backtrace+0x1d/0x30 [ 477.531136] ? sysrq_handle_showallcpus+0x1b/0x30 [ 477.531818] ? __handle_sysrq.cold+0x4e/0x1ae [ 477.532451] ? write_sysrq_trigger+0x63/0x80 [ 477.533080] ? proc_reg_write+0x92/0x110 [ 477.533663] ? vfs_write+0x174/0x530 [ 477.534265] ? handle_mm_fault+0x16f/0x500 [ 477.534940] ? ksys_write+0x7b/0x170 [ 477.535543] ? __x64_sys_write+0x1d/0x30 [ 477.536191] ? do_syscall_64+0x6b/0x100 [ 477.536809] ? entry_SYSCALL_64_after_hwframe+0x63/0xcd [ 477.537609] </TASK>
This happens when the compiled code for show_stack() has a single word on the stack, and doesn't use a tail call to show_stack_log_lvl(). (CONFIG_GCOV_PROFILE_ALL=y is the only known case of this.) Then the __unwind_start() skip logic hits an off-by-one bug and fails to unwind all the way to the intended starting frame.
Fix it by reverting the following commit:
f1d9a2abff66 ("x86/unwind/orc: Don't skip the first frame for inactive tasks")
The original justification for that commit no longer exists. That original issue was later fixed in a different way, with the following commit:
f2ac57a4c49d ("x86/unwind/orc: Fix inactive tasks with stack pointer in %sp on GCC 10 compiled kernels")
Fixes: f1d9a2abff66 ("x86/unwind/orc: Don't skip the first frame for inactive tasks") Signed-off-by: Chen Zhongjin chenzhongjin@huawei.com [jpoimboe: rewrite commit log] Signed-off-by: Josh Poimboeuf jpoimboe@kernel.org Signed-off-by: Peter Zijlstra peterz@infradead.org Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/kernel/unwind_orc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c index e64c5b78fbfd..350f40f9a0bf 100644 --- a/arch/x86/kernel/unwind_orc.c +++ b/arch/x86/kernel/unwind_orc.c @@ -579,7 +579,7 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task, /* Otherwise, skip ahead to the user-specified starting frame: */ while (!unwind_done(state) && (!on_stack(&state->stack_info, first_frame, sizeof(long)) || - state->sp < (unsigned long)first_frame)) + state->sp <= (unsigned long)first_frame)) unwind_next_frame(state);
return;