e7d6eefaaa
This vDSO code only gets used by 64-bit kernels, not 32-bit ones. On 64-bit kernels, the data segment is the same for 32-bit and 64-bit userspace, and the SYSRET instruction loads %ss with its selector. So there's no need to repeat it by hand. Segment loads are somewhat expensive: tens of cycles. Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com> [ Removed unnecessary comment. ] Signed-off-by: Andy Lutomirski <luto@kernel.org> Cc: Alexei Starovoitov <ast@plumgrid.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Kees Cook <keescook@chromium.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Will Drewry <wad@chromium.org> Link: http://lkml.kernel.org/r/63da6d778f69fd0f1345d9287f6764d58be519fa.1427482099.git.luto@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
76 lines
2 KiB
ArmAsm
76 lines
2 KiB
ArmAsm
/*
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* Code for the vDSO. This version uses the syscall instruction.
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*
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* First get the common code for the sigreturn entry points.
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* This must come first.
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*/
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#define SYSCALL_ENTER_KERNEL syscall
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#include "sigreturn.S"
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#include <asm/segment.h>
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.text
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.globl __kernel_vsyscall
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.type __kernel_vsyscall,@function
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ALIGN
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__kernel_vsyscall:
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.LSTART_vsyscall:
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push %ebp
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.Lpush_ebp:
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movl %ecx, %ebp
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syscall
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movl %ebp, %ecx
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popl %ebp
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.Lpop_ebp:
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ret
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.LEND_vsyscall:
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.size __kernel_vsyscall,.-.LSTART_vsyscall
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.section .eh_frame,"a",@progbits
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.LSTARTFRAME:
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.long .LENDCIE-.LSTARTCIE
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.LSTARTCIE:
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.long 0 /* CIE ID */
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.byte 1 /* Version number */
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.string "zR" /* NUL-terminated augmentation string */
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.uleb128 1 /* Code alignment factor */
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.sleb128 -4 /* Data alignment factor */
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.byte 8 /* Return address register column */
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.uleb128 1 /* Augmentation value length */
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.byte 0x1b /* DW_EH_PE_pcrel|DW_EH_PE_sdata4. */
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.byte 0x0c /* DW_CFA_def_cfa */
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.uleb128 4
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.uleb128 4
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.byte 0x88 /* DW_CFA_offset, column 0x8 */
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.uleb128 1
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.align 4
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.LENDCIE:
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.long .LENDFDE1-.LSTARTFDE1 /* Length FDE */
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.LSTARTFDE1:
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.long .LSTARTFDE1-.LSTARTFRAME /* CIE pointer */
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.long .LSTART_vsyscall-. /* PC-relative start address */
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.long .LEND_vsyscall-.LSTART_vsyscall
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.uleb128 0 /* Augmentation length */
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/* What follows are the instructions for the table generation.
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We have to record all changes of the stack pointer. */
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.byte 0x40 + .Lpush_ebp-.LSTART_vsyscall /* DW_CFA_advance_loc */
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.byte 0x0e /* DW_CFA_def_cfa_offset */
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.uleb128 8
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.byte 0x85, 0x02 /* DW_CFA_offset %ebp -8 */
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.byte 0x40 + .Lpop_ebp-.Lpush_ebp /* DW_CFA_advance_loc */
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.byte 0xc5 /* DW_CFA_restore %ebp */
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.byte 0x0e /* DW_CFA_def_cfa_offset */
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.uleb128 4
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.align 4
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.LENDFDE1:
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.previous
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/*
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* Pad out the segment to match the size of the sysenter.S version.
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*/
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VDSO32_vsyscall_eh_frame_size = 0x40
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.section .data,"aw",@progbits
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.space VDSO32_vsyscall_eh_frame_size-(.LENDFDE1-.LSTARTFRAME), 0
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.previous
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