Commit 0738d395 authored Mar 26, 2026 by Vasily Gorbik

s390/entry: Scrub r12 register on kernel entry



Before commit f33f2d4c ("s390/bp: remove TIF_ISOLATE_BP"),
all entry handlers loaded r12 with the current task pointer
(lg %r12,__LC_CURRENT) for use by the BPENTER/BPEXIT macros. That
commit removed TIF_ISOLATE_BP, dropping both the branch prediction
macros and the r12 load, but did not add r12 to the register clearing
sequence.

Add the missing xgr %r12,%r12 to make the register scrub consistent
across all entry points.

Fixes: f33f2d4c ("s390/bp: remove TIF_ISOLATE_BP")
Cc: stable@kernel.org
Reviewed-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

parent 48b8814e

arch/s390/kernel/entry.S

+3 −0

Original line number	Diff line number	Diff line
		@@ -271,6 +271,7 @@ SYM_CODE_START(system_call)
		xgr %r9,%r9
		xgr %r10,%r10
		xgr %r11,%r11
		xgr %r12,%r12
		la %r2,STACK_FRAME_OVERHEAD(%r15) # pointer to pt_regs
		mvc __PT_R8(64,%r2),__LC_SAVE_AREA(%r13)
		MBEAR %r2,%r13
		@@ -407,6 +408,7 @@ SYM_CODE_START(\name)
		xgr %r6,%r6
		xgr %r7,%r7
		xgr %r10,%r10
		xgr %r12,%r12
		xc __PT_FLAGS(8,%r11),__PT_FLAGS(%r11)
		mvc __PT_R8(64,%r11),__LC_SAVE_AREA(%r13)
		MBEAR %r11,%r13
		@@ -496,6 +498,7 @@ SYM_CODE_START(mcck_int_handler)
		xgr %r6,%r6
		xgr %r7,%r7
		xgr %r10,%r10
		xgr %r12,%r12
		stmg %r8,%r9,__PT_PSW(%r11)
		xc __PT_FLAGS(8,%r11),__PT_FLAGS(%r11)
		xc __SF_BACKCHAIN(8,%r15),__SF_BACKCHAIN(%r15)