[PATCH 5.15 528/917] x86: Fix __get_wchan() for !STACKTRACE

Greg Kroah-Hartman
2021-11-15T23:47:35Z

From: Peter Zijlstra <peterz@infradead.org>

[ Upstream commit 5d1ceb3969b6b2e47e2df6d17790a7c5a20fcbb4 ]

Use asm/unwind.h to implement wchan, since we cannot always rely on
STACKTRACE=y.

Fixes: bc9bbb81730e ("x86: Fix get_wchan() to support the ORC unwinder")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lkml.kernel.org/r/20211022152104.137058575@infradead.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/x86/kernel/process.c | 17 ++++++++++++++---
1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 266962547b58c..2fe1810e922a9 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -43,6 +43,7 @@
#include <asm/io_bitmap.h>
#include <asm/proto.h>
#include <asm/frame.h>
+#include <asm/unwind.h>

#include "process.h"

@@ -945,10 +946,20 @@ unsigned long arch_randomize_brk(struct mm_struct *mm)
*/
unsigned long __get_wchan(struct task_struct *p)
{
- unsigned long entry = 0;
+ struct unwind_state state;
+ unsigned long addr = 0;

- stack_trace_save_tsk(p, &entry, 1, 0);
- return entry;
+ for (unwind_start(&state, p, NULL, NULL); !unwind_done(&state);
+ unwind_next_frame(&state)) {
+ addr = unwind_get_return_address(&state);
+ if (!addr)
+ break;
+ if (in_sched_functions(addr))
+ continue;
+ break;
+ }
+
+ return addr;
}

long do_arch_prctl_common(struct task_struct *task, int option,
--
2.33.0