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    Subject[tip:x86/pti] x86/entry/64: Use PUSH_AND_CLEAN_REGS in more cases
    Commit-ID:  0e61b0142a4bdbe855c1d80342d2ca00241488b6
    Gitweb: https://git.kernel.org/tip/0e61b0142a4bdbe855c1d80342d2ca00241488b6
    Author: Dominik Brodowski <linux@dominikbrodowski.net>
    AuthorDate: Sun, 11 Feb 2018 11:49:46 +0100
    Committer: Ingo Molnar <mingo@kernel.org>
    CommitDate: Mon, 12 Feb 2018 08:06:36 +0100

    x86/entry/64: Use PUSH_AND_CLEAN_REGS in more cases

    entry_SYSCALL_64_after_hwframe() and nmi() can be converted to use
    PUSH_AND_CLEAN_REGS instead of opencoded variants thereof. Due to
    the interleaving, the additional XOR-based clearing of R8 and R9
    in entry_SYSCALL_64_after_hwframe() should not have any noticeable
    negative implications.

    Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
    Cc: Andy Lutomirski <luto@kernel.org>
    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: Josh Poimboeuf <jpoimboe@redhat.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: dan.j.williams@intel.com
    Link: http://lkml.kernel.org/r/20180211104949.12992-6-linux@dominikbrodowski.net
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    ---
    arch/x86/entry/calling.h | 6 ++---
    arch/x86/entry/entry_64.S | 65 +++--------------------------------------------
    2 files changed, 6 insertions(+), 65 deletions(-)

    diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h
    index 57b1b87..d6a97e2 100644
    --- a/arch/x86/entry/calling.h
    +++ b/arch/x86/entry/calling.h
    @@ -137,7 +137,7 @@ For 32-bit we have the following conventions - kernel is built with
    UNWIND_HINT_REGS offset=\offset
    .endm

    - .macro PUSH_AND_CLEAR_REGS
    + .macro PUSH_AND_CLEAR_REGS rdx=%rdx rax=%rax
    /*
    * Push registers and sanitize registers of values that a
    * speculation attack might otherwise want to exploit. The
    @@ -147,9 +147,9 @@ For 32-bit we have the following conventions - kernel is built with
    */
    pushq %rdi /* pt_regs->di */
    pushq %rsi /* pt_regs->si */
    - pushq %rdx /* pt_regs->dx */
    + pushq \rdx /* pt_regs->dx */
    pushq %rcx /* pt_regs->cx */
    - pushq %rax /* pt_regs->ax */
    + pushq \rax /* pt_regs->ax */
    pushq %r8 /* pt_regs->r8 */
    xorq %r8, %r8 /* nospec r8 */
    pushq %r9 /* pt_regs->r9 */
    diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
    index cf4a9ae..b06a4b5 100644
    --- a/arch/x86/entry/entry_64.S
    +++ b/arch/x86/entry/entry_64.S
    @@ -227,35 +227,8 @@ ENTRY(entry_SYSCALL_64)
    pushq %rcx /* pt_regs->ip */
    GLOBAL(entry_SYSCALL_64_after_hwframe)
    pushq %rax /* pt_regs->orig_ax */
    - pushq %rdi /* pt_regs->di */
    - pushq %rsi /* pt_regs->si */
    - pushq %rdx /* pt_regs->dx */
    - pushq %rcx /* pt_regs->cx */
    - pushq $-ENOSYS /* pt_regs->ax */
    - pushq %r8 /* pt_regs->r8 */
    - pushq %r9 /* pt_regs->r9 */
    - pushq %r10 /* pt_regs->r10 */
    - /*
    - * Clear extra registers that a speculation attack might
    - * otherwise want to exploit. Interleave XOR with PUSH
    - * for better uop scheduling:
    - */
    - xorq %r10, %r10 /* nospec r10 */
    - pushq %r11 /* pt_regs->r11 */
    - xorq %r11, %r11 /* nospec r11 */
    - pushq %rbx /* pt_regs->rbx */
    - xorl %ebx, %ebx /* nospec rbx */
    - pushq %rbp /* pt_regs->rbp */
    - xorl %ebp, %ebp /* nospec rbp */
    - pushq %r12 /* pt_regs->r12 */
    - xorq %r12, %r12 /* nospec r12 */
    - pushq %r13 /* pt_regs->r13 */
    - xorq %r13, %r13 /* nospec r13 */
    - pushq %r14 /* pt_regs->r14 */
    - xorq %r14, %r14 /* nospec r14 */
    - pushq %r15 /* pt_regs->r15 */
    - xorq %r15, %r15 /* nospec r15 */
    - UNWIND_HINT_REGS
    +
    + PUSH_AND_CLEAR_REGS rax=$-ENOSYS

    TRACE_IRQS_OFF

    @@ -1388,39 +1361,7 @@ ENTRY(nmi)
    pushq 1*8(%rdx) /* pt_regs->rip */
    UNWIND_HINT_IRET_REGS
    pushq $-1 /* pt_regs->orig_ax */
    - pushq %rdi /* pt_regs->di */
    - pushq %rsi /* pt_regs->si */
    - pushq (%rdx) /* pt_regs->dx */
    - pushq %rcx /* pt_regs->cx */
    - pushq %rax /* pt_regs->ax */
    - /*
    - * Sanitize registers of values that a speculation attack
    - * might otherwise want to exploit. The lower registers are
    - * likely clobbered well before they could be put to use in
    - * a speculative execution gadget. Interleave XOR with PUSH
    - * for better uop scheduling:
    - */
    - pushq %r8 /* pt_regs->r8 */
    - xorq %r8, %r8 /* nospec r8 */
    - pushq %r9 /* pt_regs->r9 */
    - xorq %r9, %r9 /* nospec r9 */
    - pushq %r10 /* pt_regs->r10 */
    - xorq %r10, %r10 /* nospec r10 */
    - pushq %r11 /* pt_regs->r11 */
    - xorq %r11, %r11 /* nospec r11*/
    - pushq %rbx /* pt_regs->rbx */
    - xorl %ebx, %ebx /* nospec rbx*/
    - pushq %rbp /* pt_regs->rbp */
    - xorl %ebp, %ebp /* nospec rbp*/
    - pushq %r12 /* pt_regs->r12 */
    - xorq %r12, %r12 /* nospec r12*/
    - pushq %r13 /* pt_regs->r13 */
    - xorq %r13, %r13 /* nospec r13*/
    - pushq %r14 /* pt_regs->r14 */
    - xorq %r14, %r14 /* nospec r14*/
    - pushq %r15 /* pt_regs->r15 */
    - xorq %r15, %r15 /* nospec r15*/
    - UNWIND_HINT_REGS
    + PUSH_AND_CLEAR_REGS rdx=(%rdx)
    ENCODE_FRAME_POINTER

    /*
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