Without dwarf2 unwind tables available _Unwind_Backtrace() is not
able to return the full backtrace.
This patch adds a fallback function on powerpc to get the backtrace
by doing a backchain, this code was originally at glibc.
libgcc/ChangeLog:
* config/rs6000/linux-unwind.h (struct rt_sigframe): Move it to
outside of get_regs() in order to use it in another function, this
is done twice: for __powerpc64__ and for !__powerpc64__.
(struct trace_arg): New struct.
(struct layout): New struct.
(ppc_backchain_fallback): New function.
* unwind.inc (_Unwind_Backtrace): Look for _URC_NORMAL_STOP code
state and call MD_BACKCHAIN_FALLBACK.
gcc/testsuite/ChangeLog:
* gcc.target/powerpc/unwind-backchain.c: New test.
---
.../gcc.target/powerpc/unwind-backchain.c | 24 +
libgcc/config/rs6000/linux-unwind.h | 102 +++---
libgcc/unwind.inc | 14 ++-
3 files changed, 124 insertions(+), 16 deletions(-)
create mode 100644 gcc/testsuite/gcc.target/powerpc/unwind-backchain.c
diff --git a/gcc/testsuite/gcc.target/powerpc/unwind-backchain.c
b/gcc/testsuite/gcc.target/powerpc/unwind-backchain.c
new file mode 100644
index 000..affa9b2efec
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/unwind-backchain.c
@@ -0,0 +1,24 @@
+/* -linux* targets have a fallback for the absence of unwind tables, thus are
+ the only ones we can guarantee backtrace returns all addresses. */
+/* { dg-do run { target { *-*-linux* } } } */
+/* { dg-options "-fno-asynchronous-unwind-tables" } */
+
+#include
+
+void
+test_backtrace()
+{
+ int addresses;
+ void *buffer[10];
+
+ addresses = backtrace(buffer, 10);
+ if(addresses != 4)
+__builtin_abort();
+}
+
+int
+main()
+{
+ test_backtrace();
+ return 0;
+}
diff --git a/libgcc/config/rs6000/linux-unwind.h
b/libgcc/config/rs6000/linux-unwind.h
index acdc948f85d..8deccc1d650 100644
--- a/libgcc/config/rs6000/linux-unwind.h
+++ b/libgcc/config/rs6000/linux-unwind.h
@@ -94,6 +94,15 @@ struct gcc_ucontext
enum { SIGNAL_FRAMESIZE = 128 };
+struct rt_sigframe {
+ char gap[SIGNAL_FRAMESIZE];
+ struct gcc_ucontext uc;
+ unsigned long pad[2];
+ int tramp[6];
+ void *pinfo;
+ struct gcc_ucontext *puc;
+};
+
/* If PC is at a sigreturn trampoline, return a pointer to the
regs. Otherwise return NULL. */
@@ -136,14 +145,7 @@ get_regs (struct _Unwind_Context *context)
#endif
{
/* This works for 2.4.21 and later kernels. */
- struct rt_sigframe {
- char gap[SIGNAL_FRAMESIZE];
- struct gcc_ucontext uc;
- unsigned long pad[2];
- int tramp[6];
- void *pinfo;
- struct gcc_ucontext *puc;
- } *frame = (struct rt_sigframe *) context->cfa;
+ struct rt_sigframe *frame = (struct rt_sigframe *) context->cfa;
return frame->uc.regs;
}
}
@@ -154,6 +156,12 @@ get_regs (struct _Unwind_Context *context)
enum { SIGNAL_FRAMESIZE = 64 };
+struct rt_sigframe {
+ char gap[SIGNAL_FRAMESIZE + 16];
+ char siginfo[128];
+ struct gcc_ucontext uc;
+};
+
static struct gcc_regs *
get_regs (struct _Unwind_Context *context)
{
@@ -176,11 +184,7 @@ get_regs (struct _Unwind_Context *context)
}
else if (pc[0] == 0x3800 || pc[0] == 0x38AC)
{
- struct rt_sigframe {
- char gap[SIGNAL_FRAMESIZE + 16];
- char siginfo[128];
- struct gcc_ucontext uc;
- } *frame = (struct rt_sigframe *) context->cfa;
+ struct rt_sigframe *frame = (struct rt_sigframe *) context->cfa;
return frame->uc.regs;
}
return NULL;
@@ -203,7 +207,7 @@ ppc_fallback_frame_state (struct _Unwind_Context *context,
int i;
if (regs == NULL)
-return _URC_END_OF_STACK;
+return _URC_NORMAL_STOP;
new_cfa = regs->gpr[__LIBGCC_STACK_POINTER_REGNUM__];
fs->regs.cfa_how = CFA_REG_OFFSET;
@@ -352,3 +356,73 @@ frob_update_context (struct _Unwind_Context *context,
_Unwind_FrameState *fs ATT
}
#endif
}
+
+#define MD_BACKCHAIN_FALLBACK ppc_backchain_fallback
+
+struct trace_arg
+{
+ /* Stores the list of addresses. */
+ void **array;
+ struct unwind_link *unwind_link;
+ _Unwind_Word cfa;
+ /* Number of addresses currently stored. */
+ int count;
+ /* Maximum number of addresses. */
+ int size;
+};
+
+/* This is the stack layout we see with every stack frame.
+ Note that every routine is required by the ABI to lay out the stack
+ like this.
+
+ +++-+
+%r1 -> | previous frame> | previous frame--->... --> NULL
+ ||| |
+ | cr save|| cr save |
+ ||| |
+ | (unused) || lr save |
+ +++-+
+
+ The CR save is only present
