| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <20251026221208.1938173-6-hpa@zytor.com>
Date: Sun, 26 Oct 2025 15:12:05 -0700
From: "H. Peter Anvin" <hpa@...or.com>
To: "H. Peter Anvin" <hpa@...or.com>, "Jason A. Donenfeld" <Jason@...c4.com>,
"Peter Zijlstra (Intel)" <peterz@...radead.org>,
"Theodore Ts'o" <tytso@....edu>,
Thomas Weißschuh <thomas.weissschuh@...utronix.de>,
Xin Li <xin@...or.com>, Andrew Cooper <andrew.cooper3@...rix.com>,
Andy Lutomirski <luto@...nel.org>, Ard Biesheuvel <ardb@...nel.org>,
Borislav Petkov <bp@...en8.de>, Brian Gerst <brgerst@...il.com>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Ingo Molnar <mingo@...hat.com>, James Morse <james.morse@....com>,
Jarkko Sakkinen <jarkko@...nel.org>,
Josh Poimboeuf <jpoimboe@...nel.org>, Kees Cook <kees@...nel.org>,
Nam Cao <namcao@...utronix.de>, Oleg Nesterov <oleg@...hat.com>,
Perry Yuan <perry.yuan@....com>, Thomas Gleixner <tglx@...utronix.de>,
Thomas Huth <thuth@...hat.com>, Uros Bizjak <ubizjak@...il.com>,
linux-kernel@...r.kernel.org, linux-mm@...ck.org,
linux-sgx@...r.kernel.org, x86@...nel.org
Subject: [PATCH 5/6] x86/entry/vdso32: remove open-coded DWARF in sigreturn.S
The vdso32 sigreturn.S contains open-coded DWARF bytecode, which
includes a hack for gdb to not try to step back to a previous call
instruction when backtracing from a signal handler.
Neither of those are necessary anymore: the backtracing issue is
handled by ".cfi_entry simple" and ".cfi_signal_frame", both of which
have been supported for a very long time now, which allows the
remaining frame to be built using regular .cfi annotations.
Add a few more register offsets to the signal frame just for good
measure.
Replace the nop on fallthrough of the system call (which should never,
ever happen) with a ud2a trap.
Signed-off-by: H. Peter Anvin (Intel) <hpa@...or.com>
---
arch/x86/entry/vdso/vdso32/sigreturn.S | 146 ++++++-------------------
arch/x86/include/asm/dwarf2.h | 1 +
arch/x86/kernel/asm-offsets.c | 6 +
3 files changed, 39 insertions(+), 114 deletions(-)
diff --git a/arch/x86/entry/vdso/vdso32/sigreturn.S b/arch/x86/entry/vdso/vdso32/sigreturn.S
index 965900c6763b..25b0ac4b4bfe 100644
--- a/arch/x86/entry/vdso/vdso32/sigreturn.S
+++ b/arch/x86/entry/vdso/vdso32/sigreturn.S
@@ -1,136 +1,54 @@
/* SPDX-License-Identifier: GPL-2.0 */
#include <linux/linkage.h>
#include <asm/unistd_32.h>
+#include <asm/dwarf2.h>
#include <asm/asm-offsets.h>
+.macro STARTPROC_SIGNAL_FRAME sc
+ CFI_STARTPROC simple
+ CFI_SIGNAL_FRAME
+ /* -4 as pretcode has already been popped */
+ CFI_DEF_CFA esp, \sc - 4
+ CFI_OFFSET eip, IA32_SIGCONTEXT_ip
+ CFI_OFFSET eax, IA32_SIGCONTEXT_ax
+ CFI_OFFSET ebx, IA32_SIGCONTEXT_bx
+ CFI_OFFSET ecx, IA32_SIGCONTEXT_cx
+ CFI_OFFSET edx, IA32_SIGCONTEXT_dx
+ CFI_OFFSET esp, IA32_SIGCONTEXT_sp
+ CFI_OFFSET ebp, IA32_SIGCONTEXT_bp
+ CFI_OFFSET esi, IA32_SIGCONTEXT_si
+ CFI_OFFSET edi, IA32_SIGCONTEXT_di
+ CFI_OFFSET es, IA32_SIGCONTEXT_es
+ CFI_OFFSET cs, IA32_SIGCONTEXT_cs
+ CFI_OFFSET ss, IA32_SIGCONTEXT_ss
+ CFI_OFFSET ds, IA32_SIGCONTEXT_ds
+ CFI_OFFSET eflags, IA32_SIGCONTEXT_flags
+.endm
+
.text
.globl __kernel_sigreturn
.type __kernel_sigreturn,@function
- nop /* this guy is needed for .LSTARTFDEDLSI1 below (watch for HACK) */
ALIGN
__kernel_sigreturn:
-.LSTART_sigreturn:
- popl %eax /* XXX does this mean it needs unwind info? */
+ STARTPROC_SIGNAL_FRAME IA32_SIGFRAME_sigcontext
+ popl %eax
+ CFI_ADJUST_CFA_OFFSET -4
movl $__NR_sigreturn, %eax
int $0x80
-.LEND_sigreturn:
SYM_INNER_LABEL(vdso32_sigreturn_landing_pad, SYM_L_GLOBAL)
- nop
- .size __kernel_sigreturn,.-.LSTART_sigreturn
+ ud2a
+ CFI_ENDPROC
+ .size __kernel_sigreturn,.-__kernel_sigreturn
.globl __kernel_rt_sigreturn
.type __kernel_rt_sigreturn,@function
ALIGN
__kernel_rt_sigreturn:
-.LSTART_rt_sigreturn:
+ STARTPROC_SIGNAL_FRAME IA32_RT_SIGFRAME_sigcontext
movl $__NR_rt_sigreturn, %eax
int $0x80
-.LEND_rt_sigreturn:
SYM_INNER_LABEL(vdso32_rt_sigreturn_landing_pad, SYM_L_GLOBAL)
- nop
- .size __kernel_rt_sigreturn,.-.LSTART_rt_sigreturn
- .previous
-
- .section .eh_frame,"a",@progbits
-.LSTARTFRAMEDLSI1:
- .long .LENDCIEDLSI1-.LSTARTCIEDLSI1
-.LSTARTCIEDLSI1:
- .long 0 /* CIE ID */
- .byte 1 /* Version number */
- .string "zRS" /* NUL-terminated augmentation string */
- .uleb128 1 /* Code alignment factor */
- .sleb128 -4 /* Data alignment factor */
- .byte 8 /* Return address register column */
- .uleb128 1 /* Augmentation value length */
- .byte 0x1b /* DW_EH_PE_pcrel|DW_EH_PE_sdata4. */
- .byte 0 /* DW_CFA_nop */
- .align 4
-.LENDCIEDLSI1:
- .long .LENDFDEDLSI1-.LSTARTFDEDLSI1 /* Length FDE */
-.LSTARTFDEDLSI1:
- .long .LSTARTFDEDLSI1-.LSTARTFRAMEDLSI1 /* CIE pointer */
- /* HACK: The dwarf2 unwind routines will subtract 1 from the
- return address to get an address in the middle of the
- presumed call instruction. Since we didn't get here via
- a call, we need to include the nop before the real start
- to make up for it. */
- .long .LSTART_sigreturn-1-. /* PC-relative start address */
- .long .LEND_sigreturn-.LSTART_sigreturn+1
- .uleb128 0 /* Augmentation */
- /* What follows are the instructions for the table generation.
- We record the locations of each register saved. This is
- complicated by the fact that the "CFA" is always assumed to
- be the value of the stack pointer in the caller. This means
- that we must define the CFA of this body of code to be the
- saved value of the stack pointer in the sigcontext. Which
- also means that there is no fixed relation to the other
- saved registers, which means that we must use DW_CFA_expression
- to compute their addresses. It also means that when we
- adjust the stack with the popl, we have to do it all over again. */
-
-#define do_cfa_expr(offset) \
- .byte 0x0f; /* DW_CFA_def_cfa_expression */ \
- .uleb128 1f-0f; /* length */ \
-0: .byte 0x74; /* DW_OP_breg4 */ \
- .sleb128 offset; /* offset */ \
- .byte 0x06; /* DW_OP_deref */ \
-1:
-
-#define do_expr(regno, offset) \
- .byte 0x10; /* DW_CFA_expression */ \
- .uleb128 regno; /* regno */ \
- .uleb128 1f-0f; /* length */ \
-0: .byte 0x74; /* DW_OP_breg4 */ \
- .sleb128 offset; /* offset */ \
-1:
-
- do_cfa_expr(IA32_SIGCONTEXT_sp+4)
- do_expr(0, IA32_SIGCONTEXT_ax+4)
- do_expr(1, IA32_SIGCONTEXT_cx+4)
- do_expr(2, IA32_SIGCONTEXT_dx+4)
- do_expr(3, IA32_SIGCONTEXT_bx+4)
- do_expr(5, IA32_SIGCONTEXT_bp+4)
- do_expr(6, IA32_SIGCONTEXT_si+4)
- do_expr(7, IA32_SIGCONTEXT_di+4)
- do_expr(8, IA32_SIGCONTEXT_ip+4)
-
- .byte 0x42 /* DW_CFA_advance_loc 2 -- nop; popl eax. */
-
- do_cfa_expr(IA32_SIGCONTEXT_sp)
- do_expr(0, IA32_SIGCONTEXT_ax)
- do_expr(1, IA32_SIGCONTEXT_cx)
- do_expr(2, IA32_SIGCONTEXT_dx)
- do_expr(3, IA32_SIGCONTEXT_bx)
- do_expr(5, IA32_SIGCONTEXT_bp)
- do_expr(6, IA32_SIGCONTEXT_si)
- do_expr(7, IA32_SIGCONTEXT_di)
- do_expr(8, IA32_SIGCONTEXT_ip)
-
- .align 4
-.LENDFDEDLSI1:
-
- .long .LENDFDEDLSI2-.LSTARTFDEDLSI2 /* Length FDE */
-.LSTARTFDEDLSI2:
- .long .LSTARTFDEDLSI2-.LSTARTFRAMEDLSI1 /* CIE pointer */
- /* HACK: See above wrt unwind library assumptions. */
- .long .LSTART_rt_sigreturn-1-. /* PC-relative start address */
- .long .LEND_rt_sigreturn-.LSTART_rt_sigreturn+1
- .uleb128 0 /* Augmentation */
- /* What follows are the instructions for the table generation.
- We record the locations of each register saved. This is
- slightly less complicated than the above, since we don't
- modify the stack pointer in the process. */
-
- do_cfa_expr(IA32_RT_SIGFRAME_sigcontext-4 + IA32_SIGCONTEXT_sp)
- do_expr(0, IA32_RT_SIGFRAME_sigcontext-4 + IA32_SIGCONTEXT_ax)
- do_expr(1, IA32_RT_SIGFRAME_sigcontext-4 + IA32_SIGCONTEXT_cx)
- do_expr(2, IA32_RT_SIGFRAME_sigcontext-4 + IA32_SIGCONTEXT_dx)
- do_expr(3, IA32_RT_SIGFRAME_sigcontext-4 + IA32_SIGCONTEXT_bx)
- do_expr(5, IA32_RT_SIGFRAME_sigcontext-4 + IA32_SIGCONTEXT_bp)
- do_expr(6, IA32_RT_SIGFRAME_sigcontext-4 + IA32_SIGCONTEXT_si)
- do_expr(7, IA32_RT_SIGFRAME_sigcontext-4 + IA32_SIGCONTEXT_di)
- do_expr(8, IA32_RT_SIGFRAME_sigcontext-4 + IA32_SIGCONTEXT_ip)
-
- .align 4
-.LENDFDEDLSI2:
+ ud2a
+ CFI_ENDPROC
+ .size __kernel_rt_sigreturn,.-__kernel_rt_sigreturn
.previous
diff --git a/arch/x86/include/asm/dwarf2.h b/arch/x86/include/asm/dwarf2.h
index 302e11b15da8..09c9684d3ad6 100644
--- a/arch/x86/include/asm/dwarf2.h
+++ b/arch/x86/include/asm/dwarf2.h
@@ -20,6 +20,7 @@
#define CFI_RESTORE_STATE .cfi_restore_state
#define CFI_UNDEFINED .cfi_undefined
#define CFI_ESCAPE .cfi_escape
+#define CFI_SIGNAL_FRAME .cfi_signal_frame
#ifndef BUILD_VDSO
/*
diff --git a/arch/x86/kernel/asm-offsets.c b/arch/x86/kernel/asm-offsets.c
index 32ba599a51f8..a7e7df837405 100644
--- a/arch/x86/kernel/asm-offsets.c
+++ b/arch/x86/kernel/asm-offsets.c
@@ -63,8 +63,14 @@ static void __used common(void)
OFFSET(IA32_SIGCONTEXT_bp, sigcontext_32, bp);
OFFSET(IA32_SIGCONTEXT_sp, sigcontext_32, sp);
OFFSET(IA32_SIGCONTEXT_ip, sigcontext_32, ip);
+ OFFSET(IA32_SIGCONTEXT_es, sigcontext_32, es);
+ OFFSET(IA32_SIGCONTEXT_cs, sigcontext_32, cs);
+ OFFSET(IA32_SIGCONTEXT_ss, sigcontext_32, ss);
+ OFFSET(IA32_SIGCONTEXT_ds, sigcontext_32, ds);
+ OFFSET(IA32_SIGCONTEXT_flags, sigcontext_32, flags);
BLANK();
+ OFFSET(IA32_SIGFRAME_sigcontext, sigframe_ia32, sc);
OFFSET(IA32_RT_SIGFRAME_sigcontext, rt_sigframe_ia32, uc.uc_mcontext);
#endif
--
2.51.1
Powered by blists - more mailing lists