| Message ID | 1413189700-30322-1-git-send-email-anton@samba.org (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | bfe9a2cfe91a1c920f152ce5fd0a9ad74b3daf12 |
| Delegated to: | Michael Ellerman |
| Headers | show |
diff --git a/arch/powerpc/include/asm/perf_event.h b/arch/powerpc/include/asm/perf_event.h index 0bb2372..b058568 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] = *(unsigned long *)__get_SP(); \ + (regs)->gpr[1] = __get_SP(); \ 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 fe3f948..e539d7e 100644 --- a/arch/powerpc/include/asm/reg.h +++ b/arch/powerpc/include/asm/reg.h @@ -1265,8 +1265,7 @@ static inline unsigned long mfvtb (void) #define proc_trap() asm volatile("trap") -#define __get_SP() ({unsigned long sp; \ - asm volatile("mr %0,1": "=r" (sp)); sp;}) +extern unsigned long __get_SP(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/misc.S b/arch/powerpc/kernel/misc.S index 7ce26d4..120deb7 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 diff --git a/arch/powerpc/kernel/ppc_ksyms.c b/arch/powerpc/kernel/ppc_ksyms.c index c4dfff6..9d84efb 100644 --- a/arch/powerpc/kernel/ppc_ksyms.c +++ b/arch/powerpc/kernel/ppc_ksyms.c @@ -41,3 +41,5 @@ EXPORT_SYMBOL(giveup_spe); #ifdef CONFIG_EPAPR_PARAVIRT EXPORT_SYMBOL(epapr_hypercall_start); #endif + +EXPORT_SYMBOL(__get_SP); diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index aa1df89..3cc6439 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) - asm("mr %0,1" : "=r" (sp)); + sp = __get_SP(); else sp = tsk->thread.ksp; } diff --git a/arch/powerpc/kernel/stacktrace.c b/arch/powerpc/kernel/stacktrace.c index 3d30ef1..7f65bae 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; - asm("mr %0,1" : "=r" (sp)); + sp = __get_SP(); save_context_stack(trace, sp, current, 1); }
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 <zhong@linux.vnet.ibm.com> Signed-off-by: Anton Blanchard <anton@samba.org> --- arch/powerpc/include/asm/perf_event.h | 2 +- arch/powerpc/include/asm/reg.h | 3 +-- arch/powerpc/kernel/misc.S | 4 ++++ arch/powerpc/kernel/ppc_ksyms.c | 2 ++ arch/powerpc/kernel/process.c | 2 +- arch/powerpc/kernel/stacktrace.c | 2 +- 6 files changed, 10 insertions(+), 5 deletions(-)