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s390/stack: fix possible register corruption with stack switch helper

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commit 67147e96a332b56c7206238162771d82467f86c0 upstream.

The CALL_ON_STACK macro is used to call a C function from inline
assembly, and therefore must consider the C ABI, which says that only
registers 6-13, and 15 are non-volatile (restored by the called
function).

The inline assembly incorrectly marks all registers used to pass
parameters to the called function as read-only input operands, instead
of operands that are read and written to. This might result in
register corruption depending on usage, compiler, and compile options.

Fix this by marking all operands used to pass parameters as read/write
operands. To keep the code simple even register 6, if used, is marked
as read-write operand.

Fixes: ff340d2472 ("s390: add stack switch helper")
Cc: <stable@kernel.org> # 4.20
Reviewed-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Heiko Carstens 2021-06-18 16:58:47 +02:00 committed by Sasha Levin
parent ab5bef9780
commit 5fd0c2cf7b
1 changed files with 11 additions and 7 deletions
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18
arch/s390/include/asm/stacktrace.h
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@ -90,12 +90,16 @@ struct stack_frame {
CALL_ARGS_4(arg1, arg2, arg3, arg4); \
register unsigned long r4 asm("6") = (unsigned long)(arg5)
#define CALL_FMT_0 "=&d" (r2) :
#define CALL_FMT_1 "+&d" (r2) :
#define CALL_FMT_2 CALL_FMT_1 "d" (r3),
#define CALL_FMT_3 CALL_FMT_2 "d" (r4),
#define CALL_FMT_4 CALL_FMT_3 "d" (r5),
#define CALL_FMT_5 CALL_FMT_4 "d" (r6),
/*
* To keep this simple mark register 2-6 as being changed (volatile)
* by the called function, even though register 6 is saved/nonvolatile.
*/
#define CALL_FMT_0 "=&d" (r2)
#define CALL_FMT_1 "+&d" (r2)
#define CALL_FMT_2 CALL_FMT_1, "+&d" (r3)
#define CALL_FMT_3 CALL_FMT_2, "+&d" (r4)
#define CALL_FMT_4 CALL_FMT_3, "+&d" (r5)
#define CALL_FMT_5 CALL_FMT_4, "+&d" (r6)
#define CALL_CLOBBER_5 "0", "1", "14", "cc", "memory"
#define CALL_CLOBBER_4 CALL_CLOBBER_5
@ -117,7 +121,7 @@ struct stack_frame {
" brasl 14,%[_fn]\n" \
" la 15,0(%[_prev])\n" \
: [_prev] "=&a" (prev), CALL_FMT_##nr \
[_stack] "R" (stack), \
: [_stack] "R" (stack), \
[_bc] "i" (offsetof(struct stack_frame, back_chain)), \
[_frame] "d" (frame), \
[_fn] "X" (fn) : CALL_CLOBBER_##nr); \