Initial linux ppc backtrace implementation.

stepmania/autoconf/m4/backtrace.m4

@@ -56,6 +56,11 @@ AC_DEFUN([SM_CHECK_CRASH_HANDLER],
 	    AC_DEFINE([BACKTRACE_METHOD_TEXT],["x86 custom backtrace"],[Define backtrace type])
 	    have_backtrace=yes
 	    ;;
+	powerpc-*-linux* )
+	    AC_DEFINE([BACKTRACE_METHOD_PPC_LINUX],[1],[Define backtrace type])
+	    AC_DEFINE([BACKTRACE_METHOD_TEXT],["ppc custom backtrace"],[Define backtrace type])
+	    have_backtrace=yes
+	    ;;
     esac
 
     # Do we have a libdl with dladdr?

stepmania/src/archutils/Unix/Backtrace.cpp

@@ -466,6 +466,51 @@ void GetBacktrace( const void **buf, size_t size, const BacktraceContext *ctx )
 	buf[i] = NULL;
 }
 
+#elif defined(BACKTRACE_METHOD_PPC_LINUX)
+#include <asm/ptrace.h>
+
+struct Frame
+{
+	Frame *stackPointer;
+	void *linkReg;
+};
+
+void GetSignalBacktraceContext( BacktraceContext *ctx, const ucontext_t *uc )
+{
+	// Wow, this is an ugly structure...
+	ctx->PC = (void *)uc->uc_mcontext.uc_regs->gregs[PT_NIP];
+	ctx->FramePtr = (const Frame *)uc->uc_mcontext.uc_regs->gregs[PT_R1];
+}
+
+void InitializeBacktrace() { }
+
+void GetBacktrace( const void **buf, size_t size, const BacktraceContext *ctx )
+{
+	BacktraceContext CurrentCtx;
+
+	if( ctx == NULL )
+	{
+		ctx = &CurrentCtx;
+
+		register void *r1 __asm__("1");
+		CurrentCtx.FramePtr = (const Frame *)r1;
+		CurrentCtx.PC = NULL;
+	}
+
+	const Frame *frame = (const Frame *)ctx->FramePtr;
+	unsigned i = 0;
+
+	if( ctx->PC && i < size-1 )
+		buf[i++] = ctx->PC;
+
+	while( frame && i < size-1 )
+	{
+		if( frame->linkReg )
+			buf[i++] = frame->linkReg;
+	}
+	buf[i] = NULL;
+}
+
 #else
 
 #warning Undefined BACKTRACE_METHOD_*

stepmania/src/archutils/Unix/LinuxThreadHelpers.cpp

@@ -215,6 +215,7 @@ bool GetThreadBacktraceContext( uint64_t ThreadID, BacktraceContext *ctx )
 			return false;
 	}
 
+#if defined(CPU_X86_64) || defined(CPU_X86)
 	user_regs_struct regs;
 	if( ptrace( PTRACE_GETREGS, pid_t(ThreadID), NULL, &regs ) == -1 )
 		return false;
@@ -224,10 +225,19 @@ bool GetThreadBacktraceContext( uint64_t ThreadID, BacktraceContext *ctx )
 	ctx->ip = (void *) regs.rip;
 	ctx->bp = (void *) regs.rbp;
 	ctx->sp = (void *) regs.rsp;
-#elif defined(CPU_X86)
+#else
 	ctx->ip = (void *) regs.eip;
 	ctx->bp = (void *) regs.ebp;
 	ctx->sp = (void *) regs.esp;
+#endif
+#elif defined(CPU_PPC)
+	errno = 0;
+	ctx->FramePtr = (const Frame *)ptrace( PTRACE_PEEKUSER, pid_t(ThreadID), (void *)(PT_R1<<2), 0 );
+	if( errno )
+		return false;
+	ctx->PC = (void *)ptrace( PTRACE_PEEKUSER, pid_t(ThreadID), (void *)(PT_NIP<<2), 0 );
+	if( errno )
+		return false;
 #else
 #error GetThreadBacktraceContext: which arch?
 #endif