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Re: [PATCH] hurd: libgcc unwinding support over signal trampolines


From: Samuel Thibault
Subject: Re: [PATCH] hurd: libgcc unwinding support over signal trampolines
Date: Sat, 6 Jun 2020 23:42:20 +0200
User-agent: NeoMutt/20170609 (1.8.3)

Hello,

Any news on this?

Samuel

Samuel Thibault, le ven. 29 mai 2020 13:46:50 +0200, a ecrit:
> Hello,
> 
> libgcc is currently missing the support for unwinding over signal
> trampolines on GNU/Hurd. The attached patch implements it.
> 
> Samuel

> hurd: libgcc unwinding support over signal trampolines
> 
> * libgcc/config.host (md_unwind_header): Set to i386/gnu-unwind.h on
> i[34567]86-*-gnu*.
> * src/libgcc/config/i386/gnu-unwind.h: New file.
> 
> diff --git a/libgcc/config.host b/libgcc/config.host
> index 2cd42097167..044b34d53cc 100644
> --- a/libgcc/config.host
> +++ b/libgcc/config.host
> @@ -734,11 +734,17 @@ i[34567]86-*-linux*)
>       tm_file="${tm_file} i386/elf-lib.h"
>       md_unwind_header=i386/linux-unwind.h
>       ;;
> -i[34567]86-*-kfreebsd*-gnu | i[34567]86-*-gnu* | 
> i[34567]86-*-kopensolaris*-gnu)
> +i[34567]86-*-kfreebsd*-gnu | i[34567]86-*-kopensolaris*-gnu)
>       extra_parts="$extra_parts crtprec32.o crtprec64.o crtprec80.o 
> crtfastmath.o"
>       tmake_file="${tmake_file} i386/t-crtpc t-crtfm i386/t-crtstuff 
> t-dfprules"
>       tm_file="${tm_file} i386/elf-lib.h"
>       ;;
> +i[34567]86-*-gnu*)
> +     extra_parts="$extra_parts crtprec32.o crtprec64.o crtprec80.o 
> crtfastmath.o"
> +     tmake_file="${tmake_file} i386/t-crtpc t-crtfm i386/t-crtstuff 
> t-dfprules"
> +     tm_file="${tm_file} i386/elf-lib.h"
> +     md_unwind_header=i386/gnu-unwind.h
> +     ;;
>  x86_64-*-linux*)
>       extra_parts="$extra_parts crtprec32.o crtprec64.o crtprec80.o 
> crtfastmath.o"
>       tmake_file="${tmake_file} i386/t-crtpc t-crtfm i386/t-crtstuff 
> t-dfprules"
> diff --git a/src/libgcc/config/i386/gnu-unwind.h 
> b/src/libgcc/config/i386/gnu-unwind.h
> new file mode 100644
> index 00000000000..db47f0ac1d4
> --- /dev/null
> +++ b/src/libgcc/config/i386/gnu-unwind.h
> @@ -0,0 +1,107 @@
> +/* DWARF2 EH unwinding support for GNU Hurd: x86.
> +   Copyright (C) 2020 Free Software Foundation, Inc.
> +   Contributed by Samuel Thibault <samuel.thibault@gnu.org>
> +
> +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/>.  */
> +
> +/* Do code reading to identify a signal frame, and set the frame
> +   state data appropriately.  See unwind-dw2.c for the structs. */
> +
> +#ifndef inhibit_libc
> +
> +#include <signal.h>
> +
> +#define MD_FALLBACK_FRAME_STATE_FOR x86_gnu_fallback_frame_state
> +
> +static _Unwind_Reason_Code
> +x86_gnu_fallback_frame_state
> +(struct _Unwind_Context *context, _Unwind_FrameState *fs)
> +{
> +  struct handler_args {
> +    int signo;
> +    int sigcode;
> +    struct sigcontext *scp;
> +  } *handler_args;
> +  struct sigcontext *scp;
> +  unsigned long usp;
> +
> +/*
> + * i386 sigtramp frame we are looking for follows.
> + * (see glibc/sysdeps/mach/hurd/i386/trampoline.c assembly)
> + *
> + * rpc_wait_trampoline:
> + *   0:      b8 e7 ff ff ff          mov    $-25,%eax       mach_msg_trap
> + *   5:      9a 00 00 00 00 07 00    lcall  $7,$0
> + *  12:      89 01                   movl   %eax, (%ecx)
> + *  14:      89 dc                   movl   %ebx, %esp      switch to signal 
> stack
> + *
> + * trampoline:
> + *  16:      ff d2                   call   *%edx           call the handler 
> function
> + * RA HERE
> + *  18:      83 c4 0c                addl   $12, %esp       pop its args
> + *  21:      c3                      ret                    return to 
> sigreturn
> + *
> + * firewall:
> + *  22:      f4                      hlt
> + */
> +
> +  if (!(   *(unsigned int   *)(context->ra     ) == 0xc30cc483
> +        && *(unsigned char  *)(context->ra +  4) ==       0xf4
> +
> +        && *(unsigned int   *)(context->ra -  4) == 0xd2ffdc89
> +        && *(unsigned int   *)(context->ra -  8) == 0x01890007
> +        && *(unsigned int   *)(context->ra - 12) == 0x00000000
> +        && *(unsigned int   *)(context->ra - 16) == 0x9affffff
> +        && *(unsigned short *)(context->ra - 18) ==     0xe7b8))
> +    return _URC_END_OF_STACK;
> +
> +  handler_args = context->cfa;
> +  scp = handler_args->scp;
> +  usp = scp->sc_uesp;
> +
> +  fs->regs.cfa_how = CFA_REG_OFFSET;
> +  fs->regs.cfa_reg = 4;
> +  fs->regs.cfa_offset = usp - (unsigned long) context->cfa;
> +
> +  fs->regs.reg[0].how = REG_SAVED_OFFSET;
> +  fs->regs.reg[0].loc.offset = (unsigned long)&scp->sc_eax - usp;
> +  fs->regs.reg[1].how = REG_SAVED_OFFSET;
> +  fs->regs.reg[1].loc.offset = (unsigned long)&scp->sc_ecx - usp;
> +  fs->regs.reg[2].how = REG_SAVED_OFFSET;
> +  fs->regs.reg[2].loc.offset = (unsigned long)&scp->sc_edx - usp;
> +  fs->regs.reg[3].how = REG_SAVED_OFFSET;
> +  fs->regs.reg[3].loc.offset = (unsigned long)&scp->sc_ebx - usp;
> +  fs->regs.reg[5].how = REG_SAVED_OFFSET;
> +  fs->regs.reg[5].loc.offset = (unsigned long)&scp->sc_ebp - usp;
> +  fs->regs.reg[6].how = REG_SAVED_OFFSET;
> +  fs->regs.reg[6].loc.offset = (unsigned long)&scp->sc_esi - usp;
> +  fs->regs.reg[7].how = REG_SAVED_OFFSET;
> +  fs->regs.reg[7].loc.offset = (unsigned long)&scp->sc_edi - usp;
> +  fs->regs.reg[8].how = REG_SAVED_OFFSET;
> +  fs->regs.reg[8].loc.offset = (unsigned long)&scp->sc_eip - usp;
> +  fs->retaddr_column = 8;
> +  fs->signal_frame = 1;
> +
> +  return _URC_NO_REASON;
> +}
> +
> +#endif /* ifndef inhibit_libc */


-- 
Samuel
<c> xlnt comme sujet de stage je peux essayer de donner une description 
formelle de automake
 -+- #ens-mim -+-



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