On 18/01/17 17:07, Jiong Wang wrote:
> On 12/01/17 18:10, Jiong Wang wrote:
>> On 06/01/17 11:47, Jiong Wang wrote:
>>> This is the update on libgcc unwinder support according to new DWARF
>>> proposal.
>>>
>>> As Joseph commented, duplication of unwind-dw2.c is not encouraged in
>>> libgcc,
>>> But from this patch, you can see there are a few places we need to
>>> modify for
>>> AArch64 in unwind-aarch64.c, so the file duplication approach is
>>> acceptable?
>>>
>>>
>>> libgcc/
>>>
>>> 2017-01-06 Jiong Wang <jiong.w...@arm.com>
>>>
>>> * config/aarch64/unwind-aarch64.c
>>> (DWARF_REGNUM_AARCH64_RA_STATE,
>>> RA_A_SIGNED_BIT): New macros.
>>> (execute_cfa_program): Multiplex DW_CFA_GNU_window_save on
>>> AArch64.
>>> (uw_frame_state_for): Clear bit[0] of
>>> DWARF_REGNUM_AARCH64_RA_STATE.
>>> (uw_update_context): Authenticate return address according to
>>> DWARF_REGNUM_AARCH64_RA_STATE.
>>> (uw_init_context_1): Strip signature of seed address.
>>> (uw_install_context): Re-authenticate EH handler's address.
>>>
>> Ping~
>>
>> For comparision, I have also attached the patch using the target macros.
>>
>> Four new target macros are introduced:
>>
>> MD_POST_EXTRACT_ROOT_ADDR
>> MD_POST_EXTRACT_FRAME_ADDR
>> MD_POST_FROB_EH_HANDLER_ADDR
>> MD_POST_INIT_CONTEXT
>>
>> MD_POST_EXTRACT_ROOT_ADDR is to do target private post processing on
>> the address
>> inside _Unwind* functions, they are serving as root address to start the
>> unwinding. MD_POST_EXTRACT_FRAME_ADDR is to do target private post
>> processing
>> on th address inside the real user program which throws the exceptions.
>>
>> MD_POST_FROB_EH_HANDLER_ADDR is to do target private frob on the EH
>> handler's
>> address before we install it into current context.
>>
>> MD_POST_INIT_CONTEXT it to do target private initialization on the
>> context
>> structure after common initialization.
>>
>> One "__aarch64__" macro check is needed to multiplex DW_CFA_window_save.
>
> Ping ~
>
> Could global reviewers or libgcc maintainers please give a review on the
> generic
> part change?
>
> One small change is I removed MD_POST_INIT_CONTEXT as I found there is
> MD_FROB_UPDATE_CONTEXT which serve the same purpose. I still need to
> define
>
> MD_POST_EXTRACT_ROOT_ADDR
> MD_POST_EXTRACT_FRAME_ADDR
> MD_POST_FROB_EH_HANDLER_ADDR
>
> And do one __aarch64__ check to multiplexing DW_CFA_GNU_window_save.
>
> Thanks.
>
> libgcc/ChangeLog:
>
> 2017-01-18 Jiong Wang <jiong.w...@arm.com>
>
> * config/aarch64/aarch64-unwind.h: New file.
> (DWARF_REGNUM_AARCH64_RA_STATE): Define.
> (MD_POST_EXTRACT_ROOT_ADDR): Define.
> (MD_POST_EXTRACT_FRAME_ADDR): Define.
> (MD_POST_FROB_EH_HANDLER_ADDR): Define.
> (MD_FROB_UPDATE_CONTEXT): Define.
> (aarch64_post_extract_frame_addr): New function.
> (aarch64_post_frob_eh_handler_addr): New function.
> (aarch64_frob_update_context): New function.
> * config/aarch64/linux-unwind.h: Include aarch64-unwind.h
> * config.host (aarch64*-*-elf, aarch64*-*-rtems*,
> aarch64*-*-freebsd*):
> Initialize md_unwind_header to include aarch64-unwind.h.
> * unwind-dw2.c (struct _Unwind_Context): Define "RA_A_SIGNED_BIT".
> (execute_cfa_program): Multiplex DW_CFA_GNU_window_save for
> __aarch64__.
> (uw_update_context): Honor MD_POST_EXTRACT_FRAME_ADDR.
> (uw_init_context_1): Honor MD_POST_EXTRACT_ROOT_ADDR.
> (uw_frob_return_addr): New function.
> (_Unwind_DebugHook): Use uw_frob_return_addr.
>
>
Comments inline.
> 1.patch
>
>
> diff --git a/libgcc/unwind-dw2.c b/libgcc/unwind-dw2.c
> index
> 8085a42ace15d53f4cb0c6681717012d906a6d47..cf640135275deb76b820f8209fa51eacfd64c4a2
> 100644
> --- a/libgcc/unwind-dw2.c
> +++ b/libgcc/unwind-dw2.c
> @@ -136,6 +136,8 @@ struct _Unwind_Context
> #define SIGNAL_FRAME_BIT ((~(_Unwind_Word) 0 >> 1) + 1)
> /* Context which has version/args_size/by_value fields. */
> #define EXTENDED_CONTEXT_BIT ((~(_Unwind_Word) 0 >> 2) + 1)
> + /* Bit reserved on AArch64, return address has been signed with A key. */
> +#define RA_A_SIGNED_BIT ((~(_Unwind_Word) 0 >> 3) + 1)
Why is this here? It appears to only be used within the
AArch64-specific header file.
> _Unwind_Word flags;
> /* 0 for now, can be increased when further fields are added to
> struct _Unwind_Context. */
> @@ -1185,6 +1187,11 @@ execute_cfa_program (const unsigned char *insn_ptr,
> break;
>
> case DW_CFA_GNU_window_save:
> +#ifdef __aarch64__
> + /* This CFA is multiplexed with Sparc. On AArch64 it's used to toggle
> + return address signing status. */
> + fs->regs.reg[DWARF_REGNUM_AARCH64_RA_STATE].loc.offset ^= 1;
> +#else
> /* ??? Hardcoded for SPARC register window configuration. */
> if (__LIBGCC_DWARF_FRAME_REGISTERS__ >= 32)
> for (reg = 16; reg < 32; ++reg)
> @@ -1192,6 +1199,7 @@ execute_cfa_program (const unsigned char *insn_ptr,
> fs->regs.reg[reg].how = REG_SAVED_OFFSET;
> fs->regs.reg[reg].loc.offset = (reg - 16) * sizeof (void *);
> }
> +#endif
> break;
>
> case DW_CFA_GNU_args_size:
> @@ -1513,10 +1521,15 @@ uw_update_context (struct _Unwind_Context *context,
> _Unwind_FrameState *fs)
> stack frame. */
> context->ra = 0;
> else
> - /* 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));
> + {
> + /* 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);
> +#endif
> + }
> }
>
> static void
> @@ -1550,6 +1563,9 @@ 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;
> @@ -1586,6 +1602,9 @@ 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 *)
> @@ -1608,6 +1627,20 @@ _Unwind_DebugHook (void *cfa __attribute__
> ((__unused__)),
> #endif
> }
>
> +/* Frob exception handler's address kept in TARGET before installing into
> + CURRENT context. */
> +
> +static void *
> +uw_frob_return_addr (struct _Unwind_Context *current,
> + 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;
> +}
> +
I think this function should be marked inline. The optimizers would
probably inline it anyway, but it seems wrong for us to rely on that.
> /* 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. */
> @@ -1616,7 +1649,7 @@ _Unwind_DebugHook (void *cfa __attribute__
> ((__unused__)),
> do \
> {
> \
> long offset = uw_install_context_1 ((CURRENT), (TARGET));
> \
> - void *handler = __builtin_frob_return_addr ((TARGET)->ra); \
> + void *handler = uw_frob_return_addr ((CURRENT), (TARGET)); \
> _Unwind_DebugHook ((TARGET)->cfa, handler); \
> __builtin_eh_return (offset, handler); \
> }
> \
> diff --git a/libgcc/config.host b/libgcc/config.host
> index
> 6f2e458e74e776a6b7a310919558bcca76389232..540bfa9635802adabb36a2d1b7cf3416462c59f3
> 100644
> --- a/libgcc/config.host
> +++ b/libgcc/config.host
> @@ -331,11 +331,13 @@ aarch64*-*-elf | aarch64*-*-rtems*)
> extra_parts="$extra_parts crtfastmath.o"
> tmake_file="${tmake_file} ${cpu_type}/t-aarch64"
> tmake_file="${tmake_file} ${cpu_type}/t-softfp t-softfp t-crtfm"
> + md_unwind_header=aarch64/aarch64-unwind.h
> ;;
> aarch64*-*-freebsd*)
> extra_parts="$extra_parts crtfastmath.o"
> tmake_file="${tmake_file} ${cpu_type}/t-aarch64"
> tmake_file="${tmake_file} ${cpu_type}/t-softfp t-softfp t-crtfm"
> + md_unwind_header=aarch64/aarch64-unwind.h
> ;;
> aarch64*-*-linux*)
> extra_parts="$extra_parts crtfastmath.o"
> diff --git a/libgcc/config/aarch64/aarch64-unwind.h
> b/libgcc/config/aarch64/aarch64-unwind.h
> new file mode 100644
> index
> 0000000000000000000000000000000000000000..a57cae0ff54ea7e11c32362677c0b51501a9f727
> --- /dev/null
> +++ b/libgcc/config/aarch64/aarch64-unwind.h
> @@ -0,0 +1,87 @@
> +/* Copyright (C) 2017 Free Software Foundation, Inc.
> + Contributed by ARM Ltd.
> +
> +This file is part of GCC.
> +
> +GCC is free software; you can redistribute it and/or modify it under
> +the terms of the GNU General Public License as published by the Free
> +Software Foundation; either version 3, or (at your option) any later
> +version.
> +
> +GCC is distributed in the hope that it will be useful, but WITHOUT ANY
> +WARRANTY; without even the implied warranty of MERCHANTABILITY or
> +FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
> +for more details.
> +
> +Under Section 7 of GPL version 3, you are granted additional
> +permissions described in the GCC Runtime Library Exception, version
> +3.1, as published by the Free Software Foundation.
> +
> +You should have received a copy of the GNU General Public License and
> +a copy of the GCC Runtime Library Exception along with this program;
> +see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
> +<http://www.gnu.org/licenses/>. */
> +
> +#ifndef AARCH64_UNWIND_H
> +#define AARCH64_UNWIND_H
> +
> +#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_FROB_UPDATE_CONTEXT(context, fs) \
> + aarch64_frob_update_context (context, fs)
> +
> +/* Do AArch64 private extraction on ADDR based on context info CONTEXT and
> + unwind frame info FS. If ADDR is signed, we do address authentication on
> it
> + using CFA of current frame. */
> +
All the functions in this HEADER file should be marked inline.
> +static void *
> +aarch64_post_extract_frame_addr (struct _Unwind_Context *context,
> + _Unwind_FrameState *fs, void *addr)
> +{
> + if (fs->regs.reg[DWARF_REGNUM_AARCH64_RA_STATE].loc.offset & 0x1)
> + {
> + _Unwind_Word salt = (_Unwind_Word) context->cfa;
> + return __builtin_aarch64_autia1716 (addr, salt);
> + }
> + else
> + 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 void *
> +aarch64_post_frob_eh_handler_addr (struct _Unwind_Context *current,
> + struct _Unwind_Context *target
> + ATTRIBUTE_UNUSED,
> + void *handler_addr)
> +{
> + if (current->flags & RA_A_SIGNED_BIT)
> + 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. */
> +
> +static void
> +aarch64_frob_update_context (struct _Unwind_Context *context,
> + _Unwind_FrameState *fs)
> +{
> + if (fs->regs.reg[DWARF_REGNUM_AARCH64_RA_STATE].loc.offset & 0x1)
> + /* The flag is used for re-authenticating EH handler's address. */
> + context->flags |= RA_A_SIGNED_BIT;
> +
> + return;
> +}
> +
> +#endif /* defined AARCH64_UNWIND_H */
> diff --git a/libgcc/config/aarch64/linux-unwind.h
> b/libgcc/config/aarch64/linux-unwind.h
> index
> 1256f010007ac964de8bb895379a7d893a446bd9..75774b30c080ad2361fb37c7208bcf3d3b57d77a
> 100644
> --- a/libgcc/config/aarch64/linux-unwind.h
> +++ b/libgcc/config/aarch64/linux-unwind.h
> @@ -24,6 +24,7 @@
>
> #include <signal.h>
> #include <sys/ucontext.h>
> +#include "aarch64-unwind.h"
>
>
> /* Since insns are always stored LE, on a BE system the opcodes will
>
R.
