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    Subject[PATCH 4.4 165/193] x86/retpoline: Remove the esp/rsp thunk
    Date
    4.4-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Waiman Long <longman@redhat.com>

    commit 1df37383a8aeabb9b418698f0bcdffea01f4b1b2 upstream.

    It doesn't make sense to have an indirect call thunk with esp/rsp as
    retpoline code won't work correctly with the stack pointer register.
    Removing it will help compiler writers to catch error in case such
    a thunk call is emitted incorrectly.

    Fixes: 76b043848fd2 ("x86/retpoline: Add initial retpoline support")
    Suggested-by: Jeff Law <law@redhat.com>
    Signed-off-by: Waiman Long <longman@redhat.com>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Acked-by: David Woodhouse <dwmw@amazon.co.uk>
    Cc: Tom Lendacky <thomas.lendacky@amd.com>
    Cc: Kees Cook <keescook@google.com>
    Cc: Andi Kleen <ak@linux.intel.com>
    Cc: Tim Chen <tim.c.chen@linux.intel.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Jiri Kosina <jikos@kernel.org>
    Cc: Andy Lutomirski <luto@amacapital.net>
    Cc: Dave Hansen <dave.hansen@intel.com>
    Cc: Josh Poimboeuf <jpoimboe@redhat.com>
    Cc: Arjan van de Ven <arjan@linux.intel.com>
    Cc: Greg Kroah-Hartman <gregkh@linux-foundation.org>
    Cc: Paul Turner <pjt@google.com>
    Link: https://lkml.kernel.org/r/1516658974-27852-1-git-send-email-longman@redhat.com
    Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
    [jwang: cherry pick to 4.4]
    Signed-off-by: Jack Wang <jinpu.wang@profitbricks.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    arch/x86/include/asm/asm-prototypes.h | 1 -
    arch/x86/lib/retpoline.S | 1 -
    2 files changed, 2 deletions(-)

    --- a/arch/x86/include/asm/asm-prototypes.h
    +++ b/arch/x86/include/asm/asm-prototypes.h
    @@ -37,5 +37,4 @@ INDIRECT_THUNK(dx)
    INDIRECT_THUNK(si)
    INDIRECT_THUNK(di)
    INDIRECT_THUNK(bp)
    -INDIRECT_THUNK(sp)
    #endif /* CONFIG_RETPOLINE */
    --- a/arch/x86/lib/retpoline.S
    +++ b/arch/x86/lib/retpoline.S
    @@ -36,7 +36,6 @@ GENERATE_THUNK(_ASM_DX)
    GENERATE_THUNK(_ASM_SI)
    GENERATE_THUNK(_ASM_DI)
    GENERATE_THUNK(_ASM_BP)
    -GENERATE_THUNK(_ASM_SP)
    #ifdef CONFIG_64BIT
    GENERATE_THUNK(r8)
    GENERATE_THUNK(r9)

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