libgcc: fix the handling of return address mangling [PR94891]
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. 2020-07-13 Szabolcs Nagy <szabolcs.nagy@arm.com> libgcc/ChangeLog: PR target/94891 * 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.
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Szabolcs Nagy
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2bc95be3bb
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b097c7a27f
@ -27,11 +27,8 @@ see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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#define DWARF_REGNUM_AARCH64_RA_STATE 34
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#define MD_POST_EXTRACT_ROOT_ADDR(addr) __builtin_aarch64_xpaclri (addr)
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#define MD_POST_EXTRACT_FRAME_ADDR(context, fs, addr) \
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aarch64_post_extract_frame_addr (context, fs, addr)
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#define MD_POST_FROB_EH_HANDLER_ADDR(current, target, addr) \
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aarch64_post_frob_eh_handler_addr (current, target, addr)
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#define MD_DEMANGLE_RETURN_ADDR(context, fs, addr) \
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aarch64_demangle_return_addr (context, fs, addr)
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#define MD_FROB_UPDATE_CONTEXT(context, fs) \
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aarch64_frob_update_context (context, fs)
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@ -52,14 +49,15 @@ aarch64_cie_signed_with_b_key (struct _Unwind_Context *context)
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return 0;
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}
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/* Do AArch64 private extraction on ADDR based on context info CONTEXT and
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unwind frame info FS. If ADDR is signed, we do address authentication on it
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using CFA of current frame. */
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/* Do AArch64 private extraction on ADDR_WORD based on context info CONTEXT and
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unwind frame info FS. If ADDR_WORD is signed, we do address authentication
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on it using CFA of current frame. */
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static inline void *
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aarch64_post_extract_frame_addr (struct _Unwind_Context *context,
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_Unwind_FrameState *fs, void *addr)
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aarch64_demangle_return_addr (struct _Unwind_Context *context,
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_Unwind_FrameState *fs, _Unwind_Word addr_word)
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{
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void *addr = (void *)addr_word;
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if (context->flags & RA_SIGNED_BIT)
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{
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_Unwind_Word salt = (_Unwind_Word) context->cfa;
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@ -71,28 +69,6 @@ aarch64_post_extract_frame_addr (struct _Unwind_Context *context,
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return addr;
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}
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/* Do AArch64 private frob on exception handler's address HANDLER_ADDR before
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installing it into current context CURRENT. TARGET is currently not used.
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We need to sign exception handler's address if CURRENT itself is signed. */
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static inline void *
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aarch64_post_frob_eh_handler_addr (struct _Unwind_Context *current,
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struct _Unwind_Context *target
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ATTRIBUTE_UNUSED,
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void *handler_addr)
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{
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if (current->flags & RA_SIGNED_BIT)
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{
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if (aarch64_cie_signed_with_b_key (current))
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return __builtin_aarch64_pacib1716 (handler_addr,
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(_Unwind_Word) current->cfa);
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return __builtin_aarch64_pacia1716 (handler_addr,
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(_Unwind_Word) current->cfa);
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}
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else
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return handler_addr;
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}
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/* Do AArch64 private initialization on CONTEXT based on frame info FS. Mark
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CONTEXT as return address signed if bit 0 of DWARF_REGNUM_AARCH64_RA_STATE is
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set. */
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@ -1538,11 +1538,14 @@ uw_update_context (struct _Unwind_Context *context, _Unwind_FrameState *fs)
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{
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/* Compute the return address now, since the return address column
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can change from frame to frame. */
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context->ra = __builtin_extract_return_addr
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(_Unwind_GetPtr (context, fs->retaddr_column));
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#ifdef MD_POST_EXTRACT_FRAME_ADDR
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context->ra = MD_POST_EXTRACT_FRAME_ADDR (context, fs, context->ra);
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void *ret_addr;
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#ifdef MD_DEMANGLE_RETURN_ADDR
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_Unwind_Word ra = _Unwind_GetGR (context, fs->retaddr_column);
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ret_addr = MD_DEMANGLE_RETURN_ADDR (context, fs, ra);
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#else
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ret_addr = _Unwind_GetPtr (context, fs->retaddr_column);
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#endif
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context->ra = __builtin_extract_return_addr (ret_addr);
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}
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}
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@ -1577,9 +1580,6 @@ uw_init_context_1 (struct _Unwind_Context *context,
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void *outer_cfa, void *outer_ra)
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{
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void *ra = __builtin_extract_return_addr (__builtin_return_address (0));
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#ifdef MD_POST_EXTRACT_ROOT_ADDR
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ra = MD_POST_EXTRACT_ROOT_ADDR (ra);
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#endif
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_Unwind_FrameState fs;
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_Unwind_SpTmp sp_slot;
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_Unwind_Reason_Code code;
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@ -1616,9 +1616,6 @@ uw_init_context_1 (struct _Unwind_Context *context,
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initialization context, then we can't see it in the given
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call frame data. So have the initialization context tell us. */
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context->ra = __builtin_extract_return_addr (outer_ra);
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#ifdef MD_POST_EXTRACT_ROOT_ADDR
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context->ra = MD_POST_EXTRACT_ROOT_ADDR (context->ra);
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#endif
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}
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static void _Unwind_DebugHook (void *, void *)
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@ -1641,21 +1638,6 @@ _Unwind_DebugHook (void *cfa __attribute__ ((__unused__)),
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#endif
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}
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/* Frob exception handler's address kept in TARGET before installing into
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CURRENT context. */
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static inline void *
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uw_frob_return_addr (struct _Unwind_Context *current
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__attribute__ ((__unused__)),
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struct _Unwind_Context *target)
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{
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void *ret_addr = __builtin_frob_return_addr (target->ra);
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#ifdef MD_POST_FROB_EH_HANDLER_ADDR
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ret_addr = MD_POST_FROB_EH_HANDLER_ADDR (current, target, ret_addr);
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#endif
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return ret_addr;
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}
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/* Install TARGET into CURRENT so that we can return to it. This is a
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macro because __builtin_eh_return must be invoked in the context of
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our caller. FRAMES is a number of frames to be unwind.
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@ -1667,7 +1649,7 @@ uw_frob_return_addr (struct _Unwind_Context *current
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do \
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{ \
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long offset = uw_install_context_1 ((CURRENT), (TARGET)); \
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void *handler = uw_frob_return_addr ((CURRENT), (TARGET)); \
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void *handler = __builtin_frob_return_addr ((TARGET)->ra); \
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_Unwind_DebugHook ((TARGET)->cfa, handler); \
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_Unwind_Frames_Extra (FRAMES); \
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__builtin_eh_return (offset, handler); \
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