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ARM: 7579/1: arch/allow a scno of -1 to not cause a SIGILL

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On tracehook-friendly platforms, a system call number of -1 falls
through without running much code or taking much action.

ARM is different. This adds a short-circuit check in the trace path to
avoid any additional work, as suggested by Russell King, to make sure
that ARM behaves the same way as other platforms.

Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Will Drewry <wad@chromium.org>
Reviewed-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Kees Cook 2012-11-15 22:12:17 +01:00 committed by Russell King
parent 9b790d71d5
commit ad75b51459
1 changed files with 4 additions and 1 deletions
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5
arch/arm/kernel/entry-common.S
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@ -448,7 +448,10 @@ __sys_trace:
ldmccia r1, {r0 - r6} @ have to reload r0 - r6
stmccia sp, {r4, r5} @ and update the stack args
ldrcc pc, [tbl, scno, lsl #2] @ call sys_* routine
b 2b
cmp scno, #-1 @ skip the syscall?
bne 2b
add sp, sp, #S_OFF @ restore stack
b ret_slow_syscall
__sys_trace_return:
str r0, [sp, #S_R0 + S_OFF]! @ save returned r0