libunwind: Fix unw_step() for ARM EHABI.
This commit fixes the unw_step() for ARM EHABI. However, this commit
also changes the implementation details for ARM EHABI.
The first change is that the personality function should call
__gnu_unwind_frame() for default (or de facto) frame unwinding based on
the ARM-defined unwind opcode. The function __gnu_unwind_frame() will
in turn calls unw_step() which actually unwinds the frame.
The second change is that the implementation _Unwind_Backtrace() should
no longer calls unw_step() to unwind the frame; since according to ARM
EHABI, the personality function should unwind the frame for us.
Special thanks to Anton for helpful suggestion on the initial version of
this patch.
git-svn-id: https://llvm.org/svn/llvm-project/libunwind/trunk@238560 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/src/UnwindLevel1-gcc-ext.c b/src/UnwindLevel1-gcc-ext.c
index b1e3f77..2a8b24c 100644
--- a/src/UnwindLevel1-gcc-ext.c
+++ b/src/UnwindLevel1-gcc-ext.c
@@ -15,6 +15,7 @@
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
+#include <string.h>
#include "config.h"
#include "libunwind_ext.h"
@@ -110,10 +111,18 @@
_LIBUNWIND_TRACE_API("_Unwind_Backtrace(callback=%p)\n",
(void *)(uintptr_t)callback);
+#if LIBCXXABI_ARM_EHABI
+ // Create a mock exception object for force unwinding.
+ _Unwind_Exception ex;
+ memset(&ex, '\0', sizeof(ex));
+ ex.exception_class = 0x434C4E47554E5700; // CLNGUNW\0
+#endif
+
// walk each frame
while (true) {
_Unwind_Reason_Code result;
+#if !LIBCXXABI_ARM_EHABI
// ask libuwind to get next frame (skip over first frame which is
// _Unwind_Backtrace())
if (unw_step(&cursor) <= 0) {
@@ -122,48 +131,28 @@
_URC_END_OF_STACK);
return _URC_END_OF_STACK;
}
-
-#if LIBCXXABI_ARM_EHABI
+#else
// Get the information for this frame.
unw_proc_info_t frameInfo;
if (unw_get_proc_info(&cursor, &frameInfo) != UNW_ESUCCESS) {
return _URC_END_OF_STACK;
}
- struct _Unwind_Context *context = (struct _Unwind_Context *)&cursor;
+ // Update the pr_cache in the mock exception object.
const uint32_t* unwindInfo = (uint32_t *) frameInfo.unwind_info;
- if ((*unwindInfo & 0x80000000) == 0) {
- // 6.2: Generic Model
- // EHT entry is a prel31 pointing to the PR, followed by data understood
- // only by the personality routine. Since EHABI doesn't guarantee the
- // location or availability of the unwind opcodes in the generic model,
- // we have to call personality functions with (_US_VIRTUAL_UNWIND_FRAME |
- // _US_FORCE_UNWIND) state.
+ ex.pr_cache.fnstart = frameInfo.start_ip;
+ ex.pr_cache.ehtp = (_Unwind_EHT_Header *) unwindInfo;
+ ex.pr_cache.additional= frameInfo.flags;
- // Create a mock exception object for force unwinding.
- _Unwind_Exception ex;
- ex.exception_class = 0x434C4E47554E5700; // CLNGUNW\0
- ex.pr_cache.fnstart = frameInfo.start_ip;
- ex.pr_cache.ehtp = (_Unwind_EHT_Header *) unwindInfo;
- ex.pr_cache.additional= frameInfo.flags;
-
- // Get and call the personality function to unwind the frame.
- __personality_routine pr = (__personality_routine) readPrel31(unwindInfo);
- if (pr(_US_VIRTUAL_UNWIND_FRAME | _US_FORCE_UNWIND, &ex, context) !=
- _URC_CONTINUE_UNWIND) {
- return _URC_END_OF_STACK;
- }
- } else {
- size_t off, len;
- unwindInfo = decode_eht_entry(unwindInfo, &off, &len);
- if (unwindInfo == NULL) {
- return _URC_FAILURE;
- }
-
- result = _Unwind_VRS_Interpret(context, unwindInfo, off, len);
- if (result != _URC_CONTINUE_UNWIND) {
- return _URC_END_OF_STACK;
- }
+ struct _Unwind_Context *context = (struct _Unwind_Context *)&cursor;
+ // Get and call the personality function to unwind the frame.
+ __personality_routine handler = (__personality_routine) frameInfo.handler;
+ if (handler == NULL) {
+ return _URC_END_OF_STACK;
+ }
+ if (handler(_US_VIRTUAL_UNWIND_FRAME | _US_FORCE_UNWIND, &ex, context) !=
+ _URC_CONTINUE_UNWIND) {
+ return _URC_END_OF_STACK;
}
#endif // LIBCXXABI_ARM_EHABI