From bfe9a2cfe91a1c920f152ce5fd0a9ad74b3daf12 Mon Sep 17 00:00:00 2001 From: Anton Blanchard Date: Mon, 13 Oct 2014 19:41:38 +1100 Subject: powerpc: Reimplement __get_SP() as a function not a define Li Zhong points out an issue with our current __get_SP() implementation. If ftrace function tracing is enabled (ie -pg profiling using _mcount) we spill a stack frame on 64bit all the time. If a function calls __get_SP() and later calls a function that is tail call optimised, we will pop the stack frame and the value returned by __get_SP() is no longer valid. An example from Li can be found in save_stack_trace -> save_context_stack: c0000000000432c0 <.save_stack_trace>: c0000000000432c0: mflr r0 c0000000000432c4: std r0,16(r1) c0000000000432c8: stdu r1,-128(r1) <-- stack frame for _mcount c0000000000432cc: std r3,112(r1) c0000000000432d0: bl <._mcount> c0000000000432d4: nop c0000000000432d8: mr r4,r1 <-- __get_SP() c0000000000432dc: ld r5,632(r13) c0000000000432e0: ld r3,112(r1) c0000000000432e4: li r6,1 c0000000000432e8: addi r1,r1,128 <-- pop stack frame c0000000000432ec: ld r0,16(r1) c0000000000432f0: mtlr r0 c0000000000432f4: b <.save_context_stack> <-- tail call optimized save_context_stack ends up with a stack pointer below the current one, and it is likely to be scribbled over. Fix this by making __get_SP() a function which returns the callers stack frame. Also replace inline assembly which grabs the stack pointer in save_stack_trace and show_stack with __get_SP(). This also fixes an issue with perf_arch_fetch_caller_regs(). It currently unwinds the stack once, which will skip a valid stack frame on a leaf function. With the __get_SP() fixes in this patch, we never need to unwind the stack frame to get to the first interesting frame. We have to export __get_SP() because perf_arch_fetch_caller_regs() (which is used in modules) calls it from a header file. Reported-by: Li Zhong Signed-off-by: Anton Blanchard Signed-off-by: Michael Ellerman --- arch/powerpc/kernel/misc.S | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'arch/powerpc/kernel/misc.S') diff --git a/arch/powerpc/kernel/misc.S b/arch/powerpc/kernel/misc.S index 7ce26d45777e..120deb713bc8 100644 --- a/arch/powerpc/kernel/misc.S +++ b/arch/powerpc/kernel/misc.S @@ -114,3 +114,7 @@ _GLOBAL(longjmp) mtlr r0 mr r3,r4 blr + +_GLOBAL(__get_SP) + PPC_LL r3,0(r1) + blr -- cgit v1.2.3 From acf620ecf56cfc4edaffaf158250e128539cdd26 Mon Sep 17 00:00:00 2001 From: Anton Blanchard Date: Mon, 13 Oct 2014 19:41:39 +1100 Subject: powerpc: Rename __get_SP() to current_stack_pointer() Michael points out that __get_SP() is a pretty horrible function name. Let's give it a better name. Signed-off-by: Anton Blanchard Signed-off-by: Michael Ellerman --- arch/powerpc/include/asm/perf_event.h | 2 +- arch/powerpc/include/asm/reg.h | 2 +- arch/powerpc/kernel/irq.c | 2 +- arch/powerpc/kernel/misc.S | 2 +- arch/powerpc/kernel/ppc_ksyms.c | 2 +- arch/powerpc/kernel/process.c | 2 +- arch/powerpc/kernel/stacktrace.c | 2 +- 7 files changed, 7 insertions(+), 7 deletions(-) (limited to 'arch/powerpc/kernel/misc.S') diff --git a/arch/powerpc/include/asm/perf_event.h b/arch/powerpc/include/asm/perf_event.h index b058568a850d..8bf1b6351716 100644 --- a/arch/powerpc/include/asm/perf_event.h +++ b/arch/powerpc/include/asm/perf_event.h @@ -34,7 +34,7 @@ do { \ (regs)->result = 0; \ (regs)->nip = __ip; \ - (regs)->gpr[1] = __get_SP(); \ + (regs)->gpr[1] = current_stack_pointer(); \ asm volatile("mfmsr %0" : "=r" ((regs)->msr)); \ } while (0) #endif diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h index e539d7e71451..c998279bd85b 100644 --- a/arch/powerpc/include/asm/reg.h +++ b/arch/powerpc/include/asm/reg.h @@ -1265,7 +1265,7 @@ static inline unsigned long mfvtb (void) #define proc_trap() asm volatile("trap") -extern unsigned long __get_SP(void); +extern unsigned long current_stack_pointer(void); extern unsigned long scom970_read(unsigned int address); extern void scom970_write(unsigned int address, unsigned long value); diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c index 8eb857f216c1..c14383575fe8 100644 --- a/arch/powerpc/kernel/irq.c +++ b/arch/powerpc/kernel/irq.c @@ -466,7 +466,7 @@ static inline void check_stack_overflow(void) #ifdef CONFIG_DEBUG_STACKOVERFLOW long sp; - sp = __get_SP() & (THREAD_SIZE-1); + sp = current_stack_pointer() & (THREAD_SIZE-1); /* check for stack overflow: is there less than 2KB free? */ if (unlikely(sp < (sizeof(struct thread_info) + 2048))) { diff --git a/arch/powerpc/kernel/misc.S b/arch/powerpc/kernel/misc.S index 120deb713bc8..0d432194c018 100644 --- a/arch/powerpc/kernel/misc.S +++ b/arch/powerpc/kernel/misc.S @@ -115,6 +115,6 @@ _GLOBAL(longjmp) mr r3,r4 blr -_GLOBAL(__get_SP) +_GLOBAL(current_stack_pointer) PPC_LL r3,0(r1) blr diff --git a/arch/powerpc/kernel/ppc_ksyms.c b/arch/powerpc/kernel/ppc_ksyms.c index 9d84efbd7b7a..202963ee013a 100644 --- a/arch/powerpc/kernel/ppc_ksyms.c +++ b/arch/powerpc/kernel/ppc_ksyms.c @@ -42,4 +42,4 @@ EXPORT_SYMBOL(giveup_spe); EXPORT_SYMBOL(epapr_hypercall_start); #endif -EXPORT_SYMBOL(__get_SP); +EXPORT_SYMBOL(current_stack_pointer); diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index 3cc643988101..923cd2daba89 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -1545,7 +1545,7 @@ void show_stack(struct task_struct *tsk, unsigned long *stack) tsk = current; if (sp == 0) { if (tsk == current) - sp = __get_SP(); + sp = current_stack_pointer(); else sp = tsk->thread.ksp; } diff --git a/arch/powerpc/kernel/stacktrace.c b/arch/powerpc/kernel/stacktrace.c index 7f65baec29f6..ea43a347a104 100644 --- a/arch/powerpc/kernel/stacktrace.c +++ b/arch/powerpc/kernel/stacktrace.c @@ -50,7 +50,7 @@ void save_stack_trace(struct stack_trace *trace) { unsigned long sp; - sp = __get_SP(); + sp = current_stack_pointer(); save_context_stack(trace, sp, current, 1); } -- cgit v1.2.3