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    Subject[tip:x86/pti] x86/retpoline/ftrace: Convert ftrace assembler indirect jumps
    Commit-ID:  42f7c812022441ffba2d5ccca3acf6380201f19e
    Gitweb: https://git.kernel.org/tip/42f7c812022441ffba2d5ccca3acf6380201f19e
    Author: David Woodhouse <dwmw@amazon.co.uk>
    AuthorDate: Tue, 9 Jan 2018 14:43:12 +0000
    Committer: Thomas Gleixner <tglx@linutronix.de>
    CommitDate: Wed, 10 Jan 2018 19:36:24 +0100

    x86/retpoline/ftrace: Convert ftrace assembler indirect jumps

    Convert all indirect jumps in ftrace assembler code to use non-speculative
    sequences when CONFIG_RETPOLINE is enabled.

    Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Acked-by: Arjan van de Ven <arjan@linux.intel.com>
    Acked-by: Ingo Molnar <mingo@kernel.org>
    Cc: gnomes@lxorguk.ukuu.org.uk
    Cc: Rik van Riel <riel@redhat.com>
    Cc: Andi Kleen <ak@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: Kees Cook <keescook@google.com>
    Cc: Tim Chen <tim.c.chen@linux.intel.com>
    Cc: Greg Kroah-Hartman <gregkh@linux-foundation.org>
    Cc: Paul Turner <pjt@google.com>
    Link: https://lkml.kernel.org/r/1515508997-6154-7-git-send-email-dwmw@amazon.co.uk


    ---
    arch/x86/kernel/ftrace_32.S | 6 ++++--
    arch/x86/kernel/ftrace_64.S | 8 ++++----
    2 files changed, 8 insertions(+), 6 deletions(-)

    diff --git a/arch/x86/kernel/ftrace_32.S b/arch/x86/kernel/ftrace_32.S
    index b6c6468..4c8440d 100644
    --- a/arch/x86/kernel/ftrace_32.S
    +++ b/arch/x86/kernel/ftrace_32.S
    @@ -8,6 +8,7 @@
    #include <asm/segment.h>
    #include <asm/export.h>
    #include <asm/ftrace.h>
    +#include <asm/nospec-branch.h>

    #ifdef CC_USING_FENTRY
    # define function_hook __fentry__
    @@ -197,7 +198,8 @@ ftrace_stub:
    movl 0x4(%ebp), %edx
    subl $MCOUNT_INSN_SIZE, %eax

    - call *ftrace_trace_function
    + movl ftrace_trace_function, %ecx
    + CALL_NOSPEC %ecx

    popl %edx
    popl %ecx
    @@ -241,5 +243,5 @@ return_to_handler:
    movl %eax, %ecx
    popl %edx
    popl %eax
    - jmp *%ecx
    + JMP_NOSPEC %ecx
    #endif
    diff --git a/arch/x86/kernel/ftrace_64.S b/arch/x86/kernel/ftrace_64.S
    index c832291..7cb8ba0 100644
    --- a/arch/x86/kernel/ftrace_64.S
    +++ b/arch/x86/kernel/ftrace_64.S
    @@ -7,7 +7,7 @@
    #include <asm/ptrace.h>
    #include <asm/ftrace.h>
    #include <asm/export.h>
    -
    +#include <asm/nospec-branch.h>

    .code64
    .section .entry.text, "ax"
    @@ -286,8 +286,8 @@ trace:
    * ip and parent ip are used and the list function is called when
    * function tracing is enabled.
    */
    - call *ftrace_trace_function
    -
    + movq ftrace_trace_function, %r8
    + CALL_NOSPEC %r8
    restore_mcount_regs

    jmp fgraph_trace
    @@ -329,5 +329,5 @@ GLOBAL(return_to_handler)
    movq 8(%rsp), %rdx
    movq (%rsp), %rax
    addq $24, %rsp
    - jmp *%rdi
    + JMP_NOSPEC %rdi
    #endif
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