Messages in this thread Patch in this message | | | From | Kees Cook <> | Subject | [PATCH 3/4] arch/arm: allow a scno of -1 to not cause a SIGILL | Date | Thu, 1 Nov 2012 17:14:59 -0700 |
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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> --- arch/arm/kernel/entry-common.S | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S index 8355d4b..0bef977 100644 --- a/arch/arm/kernel/entry-common.S +++ b/arch/arm/kernel/entry-common.S @@ -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 -- 1.7.9.5
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