From mboxrd@z Thu Jan 1 00:00:00 1970 From: keescook@chromium.org (Kees Cook) Date: Sat, 10 Nov 2012 14:44:44 -0800 Subject: [PATCH 3/4] arch/arm: allow a scno of -1 to not cause a SIGILL In-Reply-To: <1352587485-18348-1-git-send-email-keescook@chromium.org> References: <1352587485-18348-1-git-send-email-keescook@chromium.org> Message-ID: <1352587485-18348-4-git-send-email-keescook@chromium.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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 --- 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