From: Vineet Gupta Date: Tue, 7 Oct 2014 08:42:13 +0000 (+0530) Subject: ARCv2: STAR 9000808988: signals involving Delay Slot X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=0d7b8855a05c099a5c65a8d49a1e604198021f56;p=openwrt%2Fstaging%2Fblogic.git ARCv2: STAR 9000808988: signals involving Delay Slot Reported by Anton as LTP:munmap01 failing with Illegal Instruction Exception. --------------------->8-------------------------------------- mmap2(NULL, 24576, PROT_READ|PROT_WRITE, MAP_SHARED, 3, 0) = 0x200d2000 munmap(0x200d2000, 24576) = 0 --- SIGSEGV {si_signo=SIGSEGV, si_code=SEGV_MAPERR, si_addr=0x200d2000} --- potentially unexpected fatal signal 4. Path: /munmap01 CPU: 0 PID: 61 Comm: munmap01 Not tainted 3.13.0-g5d5c46d9a556 #8 task: 9f1a8000 ti: 9f154000 task.ti: 9f154000 [ECR ]: 0x00020100 => Illegal Insn [EFA ]: 0x0001354c [BLINK ]: 0x200515d4 [ERET ]: 0x1354c @off 0x1354c in [/munmap01] VMA: 0x00010000 to 0x00018000 [STAT32]: 0x800802c0 ... --------------------->8-------------------------------------- The issue was 1. munmap01 accessed unmapped memory (on purpose) with signal handler installed for SIGSEGV 2. The faulting instruction happened to be in Delay Slot 00011864
: 11908: bl.d 13284 1190c: stb r16,[r2] 3. kernel sets up the reg file for signal handler and correctly clears the DE bit in pt_regs->status32 placeholder 4. However RESTORE_CALLEE_SAVED_USER macro is not adjusted for ARCv2, and it over-writes the above with orig/stale value of status32 5. After RTIE, userspace signal handler executes a non branch instruction with DE bit set, triggering Illegal Instruction Exception. Reported-by: Anton Kolesov Signed-off-by: Vineet Gupta --- diff --git a/arch/arc/include/asm/entry.h b/arch/arc/include/asm/entry.h index 29d0ab6e10f5..ad7860c5ce15 100644 --- a/arch/arc/include/asm/entry.h +++ b/arch/arc/include/asm/entry.h @@ -125,8 +125,6 @@ POP r13 .endm -#define OFF_USER_R25_FROM_R24 (SZ_CALLEE_REGS + SZ_PT_REGS - 8)/4 - /*-------------------------------------------------------------- * Collect User Mode callee regs as struct callee_regs - needed by * fork/do_signal/unaligned-access-emulation. @@ -139,12 +137,13 @@ *-------------------------------------------------------------*/ .macro SAVE_CALLEE_SAVED_USER + mov r12, sp ; save SP as ref to pt_regs SAVE_R13_TO_R24 #ifdef CONFIG_ARC_CURR_IN_REG - ; Retrieve orig r25 and save it on stack - ld.as r12, [sp, OFF_USER_R25_FROM_R24] - st.a r12, [sp, -4] + ; Retrieve orig r25 and save it with rest of callee_regs + ld.as r12, [r12, PT_user_r25] + PUSH r12 #else PUSH r25 #endif @@ -191,12 +190,16 @@ .macro RESTORE_CALLEE_SAVED_USER #ifdef CONFIG_ARC_CURR_IN_REG - ld.ab r12, [sp, 4] - st.as r12, [sp, OFF_USER_R25_FROM_R24] + POP r12 #else POP r25 #endif RESTORE_R24_TO_R13 + + ; SP is back to start of pt_regs +#ifdef CONFIG_ARC_CURR_IN_REG + st.as r12, [sp, PT_user_r25] +#endif .endm /*-------------------------------------------------------------- diff --git a/arch/arc/kernel/asm-offsets.c b/arch/arc/kernel/asm-offsets.c index b9cf23313273..605281f5b301 100644 --- a/arch/arc/kernel/asm-offsets.c +++ b/arch/arc/kernel/asm-offsets.c @@ -60,5 +60,7 @@ int main(void) DEFINE(SZ_CALLEE_REGS, sizeof(struct callee_regs)); DEFINE(SZ_PT_REGS, sizeof(struct pt_regs)); + DEFINE(PT_user_r25, offsetof(struct pt_regs, user_r25)); + return 0; }