| // Copyright 2007 and onwards Google Inc. |
| // All rights reserved. |
| // |
| // Author: Craig Silverstein |
| // |
| // Produce stack trace. I'm guessing (hoping!) the code is much like |
| // for x86. For apple machines, at least, it seems to be; see |
| // http://developer.apple.com/documentation/mac/runtimehtml/RTArch-59.html |
| // http://www.linux-foundation.org/spec/ELF/ppc64/PPC-elf64abi-1.9.html#STACK |
| // Linux has similar code: http://patchwork.ozlabs.org/linuxppc/patch?id=8882 |
| |
| #include <stdio.h> |
| #include <stdint.h> // for uintptr_t |
| #include "stacktrace.h" |
| |
| _START_GOOGLE_NAMESPACE_ |
| |
| // Given a pointer to a stack frame, locate and return the calling |
| // stackframe, or return NULL if no stackframe can be found. Perform sanity |
| // checks (the strictness of which is controlled by the boolean parameter |
| // "STRICT_UNWINDING") to reduce the chance that a bad pointer is returned. |
| template<bool STRICT_UNWINDING> |
| static void **NextStackFrame(void **old_sp) { |
| void **new_sp = (void **) *old_sp; |
| |
| // Check that the transition from frame pointer old_sp to frame |
| // pointer new_sp isn't clearly bogus |
| if (STRICT_UNWINDING) { |
| // With the stack growing downwards, older stack frame must be |
| // at a greater address that the current one. |
| if (new_sp <= old_sp) return NULL; |
| // Assume stack frames larger than 100,000 bytes are bogus. |
| if ((uintptr_t)new_sp - (uintptr_t)old_sp > 100000) return NULL; |
| } else { |
| // In the non-strict mode, allow discontiguous stack frames. |
| // (alternate-signal-stacks for example). |
| if (new_sp == old_sp) return NULL; |
| // And allow frames upto about 1MB. |
| if ((new_sp > old_sp) |
| && ((uintptr_t)new_sp - (uintptr_t)old_sp > 1000000)) return NULL; |
| } |
| if ((uintptr_t)new_sp & (sizeof(void *) - 1)) return NULL; |
| return new_sp; |
| } |
| |
| // This ensures that GetStackTrace stes up the Link Register properly. |
| void StacktracePowerPCDummyFunction() __attribute__((noinline)); |
| void StacktracePowerPCDummyFunction() { __asm__ volatile(""); } |
| |
| // If you change this function, also change GetStackFrames below. |
| int GetStackTrace(void** result, int max_depth, int skip_count) { |
| void **sp; |
| // Apple OS X uses an old version of gnu as -- both Darwin 7.9.0 (Panther) |
| // and Darwin 8.8.1 (Tiger) use as 1.38. This means we have to use a |
| // different asm syntax. I don't know quite the best way to discriminate |
| // systems using the old as from the new one; I've gone with __APPLE__. |
| #ifdef __APPLE__ |
| __asm__ volatile ("mr %0,r1" : "=r" (sp)); |
| #else |
| __asm__ volatile ("mr %0,1" : "=r" (sp)); |
| #endif |
| |
| // On PowerPC, the "Link Register" or "Link Record" (LR), is a stack |
| // entry that holds the return address of the subroutine call (what |
| // instruction we run after our function finishes). This is the |
| // same as the stack-pointer of our parent routine, which is what we |
| // want here. While the compiler will always(?) set up LR for |
| // subroutine calls, it may not for leaf functions (such as this one). |
| // This routine forces the compiler (at least gcc) to push it anyway. |
| StacktracePowerPCDummyFunction(); |
| |
| // The LR save area is used by the callee, so the top entry is bogus. |
| skip_count++; |
| |
| int n = 0; |
| while (sp && n < max_depth) { |
| if (skip_count > 0) { |
| skip_count--; |
| } else { |
| // PowerPC has 3 main ABIs, which say where in the stack the |
| // Link Register is. For DARWIN and AIX (used by apple and |
| // linux ppc64), it's in sp[2]. For SYSV (used by linux ppc), |
| // it's in sp[1]. |
| #if defined(_CALL_AIX) || defined(_CALL_DARWIN) |
| result[n++] = *(sp+2); |
| #elif defined(_CALL_SYSV) |
| result[n++] = *(sp+1); |
| #elif defined(__APPLE__) || (defined(__linux) && defined(__PPC64__)) |
| // This check is in case the compiler doesn't define _CALL_AIX/etc. |
| result[n++] = *(sp+2); |
| #elif defined(__linux) |
| // This check is in case the compiler doesn't define _CALL_SYSV. |
| result[n++] = *(sp+1); |
| #else |
| #error Need to specify the PPC ABI for your archiecture. |
| #endif |
| } |
| // Use strict unwinding rules. |
| sp = NextStackFrame<true>(sp); |
| } |
| return n; |
| } |
| |
| // If you change this function, also change GetStackTrace above: |
| // |
| // This GetStackFrames routine shares a lot of code with GetStackTrace |
| // above. This code could have been refactored into a common routine, |
| // and then both GetStackTrace/GetStackFrames could call that routine. |
| // There are two problems with that: |
| // |
| // (1) The performance of the refactored-code suffers substantially - the |
| // refactored needs to be able to record the stack trace when called |
| // from GetStackTrace, and both the stack trace and stack frame sizes, |
| // when called from GetStackFrames - this introduces enough new |
| // conditionals that GetStackTrace performance can degrade by as much |
| // as 50%. |
| // |
| // (2) Whether the refactored routine gets inlined into GetStackTrace and |
| // GetStackFrames depends on the compiler, and we can't guarantee the |
| // behavior either-way, even with "__attribute__ ((always_inline))" |
| // or "__attribute__ ((noinline))". But we need this guarantee or the |
| // frame counts may be off by one. |
| // |
| // Both (1) and (2) can be addressed without this code duplication, by |
| // clever use of template functions, and by defining GetStackTrace and |
| // GetStackFrames as macros that expand to these template functions. |
| // However, this approach comes with its own set of problems - namely, |
| // macros and preprocessor trouble - for example, if GetStackTrace |
| // and/or GetStackFrames is ever defined as a member functions in some |
| // class, we are in trouble. |
| int GetStackFrames(void** pcs, int *sizes, int max_depth, int skip_count) { |
| void **sp; |
| #ifdef __APPLE__ |
| __asm__ volatile ("mr %0,r1" : "=r" (sp)); |
| #else |
| __asm__ volatile ("mr %0,1" : "=r" (sp)); |
| #endif |
| |
| StacktracePowerPCDummyFunction(); |
| // Note we do *not* increment skip_count here for the SYSV ABI. If |
| // we did, the list of stack frames wouldn't properly match up with |
| // the list of return addresses. Note this means the top pc entry |
| // is probably bogus for linux/ppc (and other SYSV-ABI systems). |
| |
| int n = 0; |
| while (sp && n < max_depth) { |
| // The GetStackFrames routine is called when we are in some |
| // informational context (the failure signal handler for example). |
| // Use the non-strict unwinding rules to produce a stack trace |
| // that is as complete as possible (even if it contains a few bogus |
| // entries in some rare cases). |
| void **next_sp = NextStackFrame<false>(sp); |
| if (skip_count > 0) { |
| skip_count--; |
| } else { |
| #if defined(_CALL_AIX) || defined(_CALL_DARWIN) |
| pcs[n++] = *(sp+2); |
| #elif defined(_CALL_SYSV) |
| pcs[n++] = *(sp+1); |
| #elif defined(__APPLE__) || (defined(__linux) && defined(__PPC64__)) |
| // This check is in case the compiler doesn't define _CALL_AIX/etc. |
| pcs[n++] = *(sp+2); |
| #elif defined(__linux) |
| // This check is in case the compiler doesn't define _CALL_SYSV. |
| pcs[n++] = *(sp+1); |
| #else |
| #error Need to specify the PPC ABI for your archiecture. |
| #endif |
| if (next_sp > sp) { |
| sizes[n] = (uintptr_t)next_sp - (uintptr_t)sp; |
| } else { |
| // A frame-size of 0 is used to indicate unknown frame size. |
| sizes[n] = 0; |
| } |
| n++; |
| } |
| sp = next_sp; |
| } |
| return n; |
| } |
| |
| _END_GOOGLE_NAMESPACE_ |