2023-11-21 22:05:39

by Ilya Leoshkevich

Subject: [PATCH v2 26/33] s390/ftrace: Unpoison ftrace_regs in kprobe_ftrace_handler()

s390 uses assembly code to initialize ftrace_regs and call
kprobe_ftrace_handler(). Therefore, from the KMSAN's point of view,
ftrace_regs is poisoned on kprobe_ftrace_handler() entry. This causes
KMSAN warnings when running the ftrace testsuite.

Fix by trusting the assembly code and always unpoisoning ftrace_regs in
kprobe_ftrace_handler().

Signed-off-by: Ilya Leoshkevich <[email protected]>
---
arch/s390/kernel/ftrace.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/arch/s390/kernel/ftrace.c b/arch/s390/kernel/ftrace.c
index c46381ea04ec..3bad34eaa51e 100644
--- a/arch/s390/kernel/ftrace.c
+++ b/arch/s390/kernel/ftrace.c
@@ -300,6 +300,7 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
if (bit < 0)
return;

+ kmsan_unpoison_memory(fregs, sizeof(*fregs));
regs = ftrace_get_regs(fregs);
p = get_kprobe((kprobe_opcode_t *)ip);
if (!regs || unlikely(!p) || kprobe_disabled(p))
--
2.41.0

2023-12-08 14:19:03

by Alexander Potapenko

Subject: Re: [PATCH v2 26/33] s390/ftrace: Unpoison ftrace_regs in kprobe_ftrace_handler()

On Tue, Nov 21, 2023 at 11:02 PM Ilya Leoshkevich <[email protected]> wrote:
>
> s390 uses assembly code to initialize ftrace_regs and call
> kprobe_ftrace_handler(). Therefore, from the KMSAN's point of view,
> ftrace_regs is poisoned on kprobe_ftrace_handler() entry. This causes
> KMSAN warnings when running the ftrace testsuite.
>
> Fix by trusting the assembly code and always unpoisoning ftrace_regs in
> kprobe_ftrace_handler().
>
> Signed-off-by: Ilya Leoshkevich <[email protected]>
Reviewed-by: Alexander Potapenko <[email protected]>