Re: [PATCH v3 2/6] hurd: Implement longjmp for x86_64

[Samuel Thibault]

Applied, thanks!

Sergey Bugaev, le sam. 29 avril 2023 23:18:18 +0300, a ecrit:
> Checked on x86_64-gnu.
> 
> Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
> ---
> I have checked that setjmp/longjmp actually works sucessfully, with both
> __longjmp and ____longjmp_chk. I have not been able to check w/ sigaltstack
> because we don't yet have the proc server and signals.
> 
> Changes since v1:
> - drop the separate non-PIC version, we can always use %rip-relative access
>   on x86_64, and that's what the compiler generates anyway even with -fno-pic;
> - use "cmpb $0, __libc_tls_initialized(%rip)" over
>   "movb __libc_tls_initialized(%rip), %r10b; testb %r10b, %r10b" -- the former
>   is what the compiler generates, so better be consistent.
> 
>  sysdeps/mach/hurd/x86_64/____longjmp_chk.S | 118 +++++++++++++++++++++
>  sysdeps/mach/hurd/x86_64/__longjmp.S       |  96 +++++++++++++++++
>  2 files changed, 214 insertions(+)
>  create mode 100644 sysdeps/mach/hurd/x86_64/____longjmp_chk.S
>  create mode 100644 sysdeps/mach/hurd/x86_64/__longjmp.S
> 
> diff --git a/sysdeps/mach/hurd/x86_64/____longjmp_chk.S 
> b/sysdeps/mach/hurd/x86_64/____longjmp_chk.S
> new file mode 100644
> index 00000000..935b8575
> --- /dev/null
> +++ b/sysdeps/mach/hurd/x86_64/____longjmp_chk.S
> @@ -0,0 +1,118 @@
> +/* Checked longjmp support.  x86_64 Hurd version.
> +   Copyright (C) 2001-2023 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library 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
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#include <sysdep.h>
> +#include <pointer_guard.h>
> +#include <jmpbuf-offsets.h>
> +#include <asm-syntax.h>
> +#include <tcb-offsets.h>
> +#include <jmp_buf-ssp.h>
> +#include <signal-defines.h>
> +
> +#define SS_ONSTACK 1
> +
> +/* Don't restore shadow stack register if shadow stack isn't enabled.  */
> +#if !SHSTK_ENABLED
> +# undef SHADOW_STACK_POINTER_OFFSET
> +#endif
> +
> +     .section .rodata.str1.1,"aMS",@progbits,1
> +     .type   longjmp_msg,@object
> +longjmp_msg:
> +     .string "longjmp causes uninitialized stack frame"
> +     .size   longjmp_msg, .-longjmp_msg
> +
> +
> +# define CALL_FAIL   sub     $8, %RSP_LP;                                  \
> +                     cfi_remember_state;                                   \
> +                     cfi_def_cfa_offset(16);                               \
> +                     lea     longjmp_msg(%rip), %RDI_LP;                   \
> +                     call    HIDDEN_JUMPTARGET(__fortify_fail);            \
> +                     nop;                                                  \
> +                     cfi_restore_state
> +
> +/* Jump to the position specified by ENV, causing the
> +   setjmp call there to return VAL, or 1 if VAL is 0.
> +   void __longjmp (__jmp_buf env, int val).  */
> +     .text
> +ENTRY(____longjmp_chk)
> +     /* Restore registers.  */
> +     mov     (JB_RSP*8)(%rdi), %R8_LP
> +     mov     (JB_RBP*8)(%rdi),%R9_LP
> +     mov     (JB_PC*8)(%rdi), %RDX_LP
> +#ifdef PTR_DEMANGLE
> +     PTR_DEMANGLE (%R8_LP)
> +     PTR_DEMANGLE (%R9_LP)
> +     PTR_DEMANGLE (%RDX_LP)
> +#endif
> +
> +#if !defined (SHARED) || IS_IN (rtld)
> +     cmpb    $0, __libc_tls_initialized(%rip)
> +     jz      .Lok            /* TLS not initialized yet */
> +#endif
> +
> +     movq %fs:SIGSTATE_OFFSET, %R10_LP
> +     testq %R10_LP, %R10_LP
> +     jz      .Lok            /* sigstate not initialized yet */
> +
> +     testl   $SS_ONSTACK, (HURD_SIGSTATE__SIGALTSTACK__OFFSET + 
> SIGALTSTACK__SS_FLAGS__OFFSET)(%R10_LP)
> +     jnz     .Lonstack
> +
> +     /* We were on the main stack.  Jumping to a higher-address
> +           frame is always allowed, otherwise it's not allowed.  */
> +     cmp     %R8_LP, %RSP_LP
> +     jbe     .Lok
> +
> +.Lfail:      CALL_FAIL
> +
> +.Lonstack:
> +     cmpq    (HURD_SIGSTATE__SIGALTSTACK__OFFSET + 
> SIGALTSTACK__SS_SP__OFFSET)(%R10_LP), %R8_LP
> +     jb      .Loks           /* Jumping below the altstack, switch */
> +
> +     movq    (HURD_SIGSTATE__SIGALTSTACK__OFFSET + 
> SIGALTSTACK__SS_SP__OFFSET)(%R10_LP), %R11_LP
> +     addq    (HURD_SIGSTATE__SIGALTSTACK__OFFSET + 
> SIGALTSTACK__SS_SIZE__OFFSET)(%R10_LP), %R11_LP
> +     cmpq    %R11_LP, %R8_LP
> +     jb      .Lok            /* Jumping inside the altstack, do not switch */
> +
> +     /* Jumping above the altstack, switch */
> +
> +.Loks:
> +     andl    $~(SS_ONSTACK), (HURD_SIGSTATE__SIGALTSTACK__OFFSET + 
> SIGALTSTACK__SS_FLAGS__OFFSET)(%R10_LP)
> +
> +.Lok:
> +     /* We add unwind information for the target here.  */
> +     cfi_def_cfa(%rdi, 0)
> +     cfi_register(%rsp,%r8)
> +     cfi_register(%rbp,%r9)
> +     cfi_register(%rip,%rdx)
> +     cfi_offset(%rbx,JB_RBX*8)
> +     cfi_offset(%r12,JB_R12*8)
> +     cfi_offset(%r13,JB_R13*8)
> +     cfi_offset(%r14,JB_R14*8)
> +     cfi_offset(%r15,JB_R15*8)
> +     movq    (JB_RBX*8)(%rdi), %rbx
> +     movq    (JB_R12*8)(%rdi), %r12
> +     movq    (JB_R13*8)(%rdi), %r13
> +     movq    (JB_R14*8)(%rdi), %r14
> +     movq    (JB_R15*8)(%rdi), %r15
> +     /* Set return value for setjmp.  */
> +     movl    %esi, %eax
> +     mov     %R8_LP, %RSP_LP
> +     movq    %r9,%rbp
> +     jmpq    *%rdx
> +END (____longjmp_chk)
> diff --git a/sysdeps/mach/hurd/x86_64/__longjmp.S 
> b/sysdeps/mach/hurd/x86_64/__longjmp.S
> new file mode 100644
> index 00000000..389c1d16
> --- /dev/null
> +++ b/sysdeps/mach/hurd/x86_64/__longjmp.S
> @@ -0,0 +1,96 @@
> +/* longjmp support.  x86_64/Hurd version.
> +   Copyright (C) 2001-2023 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library 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
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#include <sysdep.h>
> +#include <pointer_guard.h>
> +#include <jmpbuf-offsets.h>
> +#include <asm-syntax.h>
> +#include <tcb-offsets.h>
> +#include <jmp_buf-ssp.h>
> +#include <signal-defines.h>
> +
> +#define SS_ONSTACK 1
> +
> +/* Don't restore shadow stack register if shadow stack isn't enabled.  */
> +#if !SHSTK_ENABLED
> +# undef SHADOW_STACK_POINTER_OFFSET
> +#endif
> +
> +/* Jump to the position specified by ENV, causing the
> +   setjmp call there to return VAL, or 1 if VAL is 0.
> +   void __longjmp (__jmp_buf env, int val).  */
> +     .text
> +ENTRY(__longjmp)
> +     /* Restore registers.  */
> +     mov     (JB_RSP*8)(%rdi), %R8_LP
> +     mov     (JB_RBP*8)(%rdi),%R9_LP
> +     mov     (JB_PC*8)(%rdi), %RDX_LP
> +#ifdef PTR_DEMANGLE
> +     PTR_DEMANGLE (%R8_LP)
> +     PTR_DEMANGLE (%R9_LP)
> +     PTR_DEMANGLE (%RDX_LP)
> +#endif
> +
> +#if !defined (SHARED) || IS_IN (rtld)
> +     cmpb    $0, __libc_tls_initialized(%rip)
> +     jz      .Lok            /* TLS not initialized yet */
> +#endif
> +
> +     movq %fs:SIGSTATE_OFFSET, %R10_LP
> +     testq %R10_LP, %R10_LP
> +     jz      .Lok            /* sigstate not initialized yet */
> +
> +     testl   $SS_ONSTACK, (HURD_SIGSTATE__SIGALTSTACK__OFFSET + 
> SIGALTSTACK__SS_FLAGS__OFFSET)(%R10_LP)
> +     jz      .Lok
> +
> +.Lonstack:
> +     cmpq    (HURD_SIGSTATE__SIGALTSTACK__OFFSET + 
> SIGALTSTACK__SS_SP__OFFSET)(%R10_LP), %R8_LP
> +     jb      .Loks           /* Jumping below the altstack, switch */
> +
> +     movq    (HURD_SIGSTATE__SIGALTSTACK__OFFSET + 
> SIGALTSTACK__SS_SP__OFFSET)(%R10_LP), %R11_LP
> +     addq    (HURD_SIGSTATE__SIGALTSTACK__OFFSET + 
> SIGALTSTACK__SS_SIZE__OFFSET)(%R10_LP), %R11_LP
> +     cmpq    %R11_LP, %R8_LP
> +     jb      .Lok            /* Jumping inside the altstack, do not switch */
> +
> +     /* Jumping above the altstack, switch */
> +
> +.Loks:
> +     andl    $~(SS_ONSTACK), (HURD_SIGSTATE__SIGALTSTACK__OFFSET + 
> SIGALTSTACK__SS_FLAGS__OFFSET)(%R10_LP)
> +
> +.Lok:
> +     /* We add unwind information for the target here.  */
> +     cfi_def_cfa(%rdi, 0)
> +     cfi_register(%rsp,%r8)
> +     cfi_register(%rbp,%r9)
> +     cfi_register(%rip,%rdx)
> +     cfi_offset(%rbx,JB_RBX*8)
> +     cfi_offset(%r12,JB_R12*8)
> +     cfi_offset(%r13,JB_R13*8)
> +     cfi_offset(%r14,JB_R14*8)
> +     cfi_offset(%r15,JB_R15*8)
> +     movq    (JB_RBX*8)(%rdi), %rbx
> +     movq    (JB_R12*8)(%rdi), %r12
> +     movq    (JB_R13*8)(%rdi), %r13
> +     movq    (JB_R14*8)(%rdi), %r14
> +     movq    (JB_R15*8)(%rdi), %r15
> +     /* Set return value for setjmp.  */
> +     movl    %esi, %eax
> +     mov     %R8_LP, %RSP_LP
> +     movq    %r9,%rbp
> +     jmpq    *%rdx
> +END (__longjmp)
> -- 
> 2.40.1
> 

-- 
Samuel
---
Pour une évaluation indépendante, transparente et rigoureuse !
Je soutiens la Commission d'Évaluation de l'Inria.