[PATCH 3/4] libgcc: fix the handling of return address mangling [PR94891]
Szabolcs Nagy
szabolcs.nagy@arm.com
Fri Jun 5 16:51:42 GMT 2020
Mangling, currently only used on AArch64 for return address signing,
is an internal representation that should not be exposed via
__builtin_return_address return value,
__builtin_eh_return handler argument,
_Unwind_DebugHook handler argument.
Note that a mangled address might not even fit into a void *, e.g.
with AArch64 ilp32 ABI the return address is stored as 64bit, so
the mangled return address cannot be accessed via _Unwind_GetPtr.
This patch changes the unwinder hooks as follows:
MD_POST_EXTRACT_ROOT_ADDR is removed: root address comes from
__builtin_return_address which is not mangled.
MD_POST_EXTRACT_FRAME_ADDR is renamed to MD_DEMANGLE_RETURN_ADDR,
it now operates on _Unwind_Word instead of void *, so the hook
should work when return address signing is enabled on AArch64 ilp32.
(But for that __builtin_aarch64_autia1716 should be fixed to operate
on 64bit input instead of a void *.)
MD_POST_FROB_EH_HANDLER_ADDR is removed: it is the responsibility of
__builtin_eh_return to do the mangling if necessary.
libgcc/ChangeLog:
2020-06-04 Szabolcs Nagy <szabolcs.nagy@arm.com>
* config/aarch64/aarch64-unwind.h (MD_POST_EXTRACT_ROOT_ADDR): Remove.
(MD_POST_FROB_EH_HANDLER_ADDR): Remove.
(MD_POST_EXTRACT_FRAME_ADDR): Rename to ...
(MD_DEMANGLE_RETURN_ADDR): This.
(aarch64_post_extract_frame_addr): Rename to ...
(aarch64_demangle_return_addr): This.
(aarch64_post_frob_eh_handler_addr): Remove.
* unwind-dw2.c (uw_update_context): Demangle return address.
(uw_frob_return_addr): Remove.
---
libgcc/config/aarch64/aarch64-unwind.h | 34 ++++----------------------
libgcc/unwind-dw2.c | 34 ++++++--------------------
2 files changed, 13 insertions(+), 55 deletions(-)
diff --git a/libgcc/config/aarch64/aarch64-unwind.h b/libgcc/config/aarch64/aarch64-unwind.h
index ed84a96db41..b1d732e0b2d 100644
--- a/libgcc/config/aarch64/aarch64-unwind.h
+++ b/libgcc/config/aarch64/aarch64-unwind.h
@@ -27,11 +27,8 @@ see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
#define DWARF_REGNUM_AARCH64_RA_STATE 34
-#define MD_POST_EXTRACT_ROOT_ADDR(addr) __builtin_aarch64_xpaclri (addr)
-#define MD_POST_EXTRACT_FRAME_ADDR(context, fs, addr) \
- aarch64_post_extract_frame_addr (context, fs, addr)
-#define MD_POST_FROB_EH_HANDLER_ADDR(current, target, addr) \
- aarch64_post_frob_eh_handler_addr (current, target, addr)
+#define MD_DEMANGLE_RETURN_ADDR(context, fs, addr) \
+ aarch64_demangle_return_addr (context, fs, addr)
#define MD_FROB_UPDATE_CONTEXT(context, fs) \
aarch64_frob_update_context (context, fs)
@@ -57,9 +54,10 @@ aarch64_cie_signed_with_b_key (struct _Unwind_Context *context)
using CFA of current frame. */
static inline void *
-aarch64_post_extract_frame_addr (struct _Unwind_Context *context,
- _Unwind_FrameState *fs, void *addr)
+aarch64_demangle_return_addr (struct _Unwind_Context *context,
+ _Unwind_FrameState *fs, _Unwind_Word addr_word)
{
+ void *addr = (void *)addr_word;
if (context->flags & RA_SIGNED_BIT)
{
_Unwind_Word salt = (_Unwind_Word) context->cfa;
@@ -71,28 +69,6 @@ aarch64_post_extract_frame_addr (struct _Unwind_Context *context,
return addr;
}
-/* Do AArch64 private frob on exception handler's address HANDLER_ADDR before
- installing it into current context CURRENT. TARGET is currently not used.
- We need to sign exception handler's address if CURRENT itself is signed. */
-
-static inline void *
-aarch64_post_frob_eh_handler_addr (struct _Unwind_Context *current,
- struct _Unwind_Context *target
- ATTRIBUTE_UNUSED,
- void *handler_addr)
-{
- if (current->flags & RA_SIGNED_BIT)
- {
- if (aarch64_cie_signed_with_b_key (current))
- return __builtin_aarch64_pacib1716 (handler_addr,
- (_Unwind_Word) current->cfa);
- return __builtin_aarch64_pacia1716 (handler_addr,
- (_Unwind_Word) current->cfa);
- }
- else
- return handler_addr;
-}
-
/* Do AArch64 private initialization on CONTEXT based on frame info FS. Mark
CONTEXT as return address signed if bit 0 of DWARF_REGNUM_AARCH64_RA_STATE is
set. */
diff --git a/libgcc/unwind-dw2.c b/libgcc/unwind-dw2.c
index 62d4a3d29a2..fe896565d2e 100644
--- a/libgcc/unwind-dw2.c
+++ b/libgcc/unwind-dw2.c
@@ -1538,11 +1538,14 @@ uw_update_context (struct _Unwind_Context *context, _Unwind_FrameState *fs)
{
/* Compute the return address now, since the return address column
can change from frame to frame. */
- context->ra = __builtin_extract_return_addr
- (_Unwind_GetPtr (context, fs->retaddr_column));
-#ifdef MD_POST_EXTRACT_FRAME_ADDR
- context->ra = MD_POST_EXTRACT_FRAME_ADDR (context, fs, context->ra);
+ void *ret_addr;
+#ifdef MD_DEMANGLE_RETURN_ADDR
+ _Unwind_Word ra = _Unwind_GetGR (context, fs->retaddr_column);
+ ret_addr = MD_DEMANGLE_RETURN_ADDR (context, fs, ra);
+#else
+ ret_addr = _Unwind_GetPtr (context, fs->retaddr_column);
#endif
+ context->ra = __builtin_extract_return_addr (ret_addr);
}
}
@@ -1577,9 +1580,6 @@ uw_init_context_1 (struct _Unwind_Context *context,
void *outer_cfa, void *outer_ra)
{
void *ra = __builtin_extract_return_addr (__builtin_return_address (0));
-#ifdef MD_POST_EXTRACT_ROOT_ADDR
- ra = MD_POST_EXTRACT_ROOT_ADDR (ra);
-#endif
_Unwind_FrameState fs;
_Unwind_SpTmp sp_slot;
_Unwind_Reason_Code code;
@@ -1616,9 +1616,6 @@ uw_init_context_1 (struct _Unwind_Context *context,
initialization context, then we can't see it in the given
call frame data. So have the initialization context tell us. */
context->ra = __builtin_extract_return_addr (outer_ra);
-#ifdef MD_POST_EXTRACT_ROOT_ADDR
- context->ra = MD_POST_EXTRACT_ROOT_ADDR (context->ra);
-#endif
}
static void _Unwind_DebugHook (void *, void *)
@@ -1641,21 +1638,6 @@ _Unwind_DebugHook (void *cfa __attribute__ ((__unused__)),
#endif
}
-/* Frob exception handler's address kept in TARGET before installing into
- CURRENT context. */
-
-static inline void *
-uw_frob_return_addr (struct _Unwind_Context *current
- __attribute__ ((__unused__)),
- struct _Unwind_Context *target)
-{
- void *ret_addr = __builtin_frob_return_addr (target->ra);
-#ifdef MD_POST_FROB_EH_HANDLER_ADDR
- ret_addr = MD_POST_FROB_EH_HANDLER_ADDR (current, target, ret_addr);
-#endif
- return ret_addr;
-}
-
/* Install TARGET into CURRENT so that we can return to it. This is a
macro because __builtin_eh_return must be invoked in the context of
our caller. FRAMES is a number of frames to be unwind.
@@ -1667,7 +1649,7 @@ uw_frob_return_addr (struct _Unwind_Context *current
do \
{ \
long offset = uw_install_context_1 ((CURRENT), (TARGET)); \
- void *handler = uw_frob_return_addr ((CURRENT), (TARGET)); \
+ void *handler = __builtin_frob_return_addr ((TARGET)->ra); \
_Unwind_DebugHook ((TARGET)->cfa, handler); \
_Unwind_Frames_Extra (FRAMES); \
__builtin_eh_return (offset, handler); \
--
2.17.1
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