selftests/powerpc/tm: Fix tcheck() reading uninitialised CR value

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 <thibault.ferrante@canonical.com>
Reported-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
Tested-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
Closes: https://lore.kernel.org/all/364996ce-aba2-4213-8d20-7dd481b43fe6@linux.ibm.com/
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20260907215420.1258678-1-thibault.ferrante@canonical.com

0 files changed, 0 insertions, 0 deletions