8242c6c84a
The goal is to integrate the SYSENTER and SYSCALL32 entry paths with the INT80 path. SYSENTER clobbers ESP and EIP. SYSCALL32 clobbers ECX (and, invisibly, R11). SYSRETL (long mode to compat mode) clobbers ECX and, invisibly, R11. SYSEXIT (which we only need for native 32-bit) clobbers ECX and EDX. This means that we'll need to provide ESP to the kernel in a register (I chose ECX, since it's only needed for SYSENTER) and we need to provide the args that normally live in ECX and EDX in memory. The epilogue needs to restore ECX and EDX, since user code relies on regs being preserved. We don't need to do anything special about EIP, since the kernel already knows where we are. The kernel will eventually need to know where int $0x80 lands, so add a vdso_image entry for it. The only user-visible effect of this code is that ptrace-induced changes to ECX and EDX during fast syscalls will be lost. This is already the case for the SYSENTER path. Signed-off-by: Andy Lutomirski <luto@kernel.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-kernel@vger.kernel.org Link: http://lkml.kernel.org/r/b860925adbee2d2627a0671fbfe23a7fd04127f8.1444091584.git.luto@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
48 lines
897 B
ArmAsm
48 lines
897 B
ArmAsm
/*
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* Code for the vDSO. This version uses the old int $0x80 method.
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*/
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#include <asm/dwarf2.h>
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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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#include "sigreturn.S"
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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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CFI_STARTPROC
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/*
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* Reshuffle regs so that all of any of the entry instructions
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* will preserve enough state.
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*/
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pushl %edx
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CFI_ADJUST_CFA_OFFSET 4
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CFI_REL_OFFSET edx, 0
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pushl %ecx
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CFI_ADJUST_CFA_OFFSET 4
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CFI_REL_OFFSET ecx, 0
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movl %esp, %ecx
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/* Enter using int $0x80 */
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movl (%esp), %ecx
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int $0x80
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GLOBAL(int80_landing_pad)
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/* Restore ECX and EDX in case they were clobbered. */
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popl %ecx
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CFI_RESTORE ecx
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CFI_ADJUST_CFA_OFFSET -4
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popl %edx
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CFI_RESTORE edx
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CFI_ADJUST_CFA_OFFSET -4
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ret
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CFI_ENDPROC
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.size __kernel_vsyscall,.-__kernel_vsyscall
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.previous
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