tcheck() is used to check the current transaction state (active, suspended, doomed) via the "tcheck" instruction, which writes its result into CR field 0. The inline asm declared a GPR output operand for this result but never actually moved the CR into it.
Every caller (tcheck_doomed(), tcheck_active(), tcheck_suspended(), tcheck_transactional()) has effectively been testing bits of an unrelated, arbitrary register value since this helper was introduced. The "& 4" mask discards the TDOOMED and TS_lsb (suspended) bits before they ever reach the callers, so tcheck_doomed() and tcheck_suspended() can never return true, and tcheck_transactional() degrades to being equivalent to tcheck_active(). Fix tcheck() to actually move CR into the output register with mfcr, and widen the mask from "& 4" to "& 0xf" so the full CR0 nibble (TDOOMED | TS_msb | TS_lsb | reserved) is preserved for the callers. This bug has been present since tcheck() was introduced. Link: https://bugs.launchpad.net/bugs/2107442 Fixes: 8e03bd4e70b6 ("selftests/powerpc: Add TM tcheck helpers in C") Signed-off-by: Thibault Ferrante <[email protected]> --- tools/testing/selftests/powerpc/tm/tm.h | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/tools/testing/selftests/powerpc/tm/tm.h b/tools/testing/selftests/powerpc/tm/tm.h index c03c6e778876..6024ce4ba6ff 100644 --- a/tools/testing/selftests/powerpc/tm/tm.h +++ b/tools/testing/selftests/powerpc/tm/tm.h @@ -105,8 +105,12 @@ static inline bool failure_is_nesting(void) static inline int tcheck(void) { long cr; - asm volatile ("tcheck 0" : "=r"(cr) : : "cr0"); - return (cr >> 28) & 4; + asm volatile("tcheck 0;" + "mfcr %0;" + : "=r"(cr) + : + : "cr0"); + return (cr >> 28) & 0xf; } static inline bool tcheck_doomed(void) -- 2.55.0
