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) <[email protected]> --- 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
