From c3062ede9927053754ba27b280afe00b9b31b37a Mon Sep 17 00:00:00 2001 From: Benjamin Gray Date: Tue, 25 Jul 2023 10:58:41 +1000 Subject: [PATCH] selftests/powerpc/ptrace: Declare test temporary variables as volatile While the target is volatile, the temporary variables used to access the target cast away the volatile. This is undefined behaviour, and a compiler may optimise away/reorder these accesses, breaking the test. This was observed with GCC 13.1.1, but it can be difficult to reproduce because of the dependency on compiler behaviour. Signed-off-by: Benjamin Gray Signed-off-by: Michael Ellerman Link: https://msgid.link/20230725005841.28854-5-bgray@linux.ibm.com --- .../selftests/powerpc/ptrace/ptrace-hwbreak.c | 24 +++++++++++----------- 1 file changed, 12 insertions(+), 12 deletions(-) diff --git a/tools/testing/selftests/powerpc/ptrace/ptrace-hwbreak.c b/tools/testing/selftests/powerpc/ptrace/ptrace-hwbreak.c index a162392..75d30d6 100644 --- a/tools/testing/selftests/powerpc/ptrace/ptrace-hwbreak.c +++ b/tools/testing/selftests/powerpc/ptrace/ptrace-hwbreak.c @@ -64,26 +64,26 @@ static bool dawr_present(struct ppc_debug_info *dbginfo) static void write_var(int len) { - __u8 *pcvar; - __u16 *psvar; - __u32 *pivar; - __u64 *plvar; + volatile __u8 *pcvar; + volatile __u16 *psvar; + volatile __u32 *pivar; + volatile __u64 *plvar; switch (len) { case 1: - pcvar = (__u8 *)&glvar; + pcvar = (volatile __u8 *)&glvar; *pcvar = 0xff; break; case 2: - psvar = (__u16 *)&glvar; + psvar = (volatile __u16 *)&glvar; *psvar = 0xffff; break; case 4: - pivar = (__u32 *)&glvar; + pivar = (volatile __u32 *)&glvar; *pivar = 0xffffffff; break; case 8: - plvar = (__u64 *)&glvar; + plvar = (volatile __u64 *)&glvar; *plvar = 0xffffffffffffffffLL; break; } @@ -98,16 +98,16 @@ static void read_var(int len) switch (len) { case 1: - cvar = (__u8)glvar; + cvar = (volatile __u8)glvar; break; case 2: - svar = (__u16)glvar; + svar = (volatile __u16)glvar; break; case 4: - ivar = (__u32)glvar; + ivar = (volatile __u32)glvar; break; case 8: - lvar = (__u64)glvar; + lvar = (volatile __u64)glvar; break; } } -- 2.7.4