The 06/05/2020 17:51, Szabolcs Nagy wrote:
> 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.n...@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.
ping. (adding Ian on cc)
tested without regressions on aarch64 with pac-ret.
> ---
> 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
>
--
