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    Subject[PATCH v2 21/39] x86/ibt: Annotate text references
    Annotate away some of the generic code references. This is things
    where we take the address of a symbol for exception handling or return
    addresses (eg. context switch).

    Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    ---
    arch/x86/entry/entry_64.S | 9 +++++++++
    arch/x86/entry/entry_64_compat.S | 1 +
    arch/x86/kernel/alternative.c | 4 +++-
    arch/x86/kernel/head_64.S | 4 ++++
    arch/x86/kernel/kprobes/core.c | 1 +
    arch/x86/kernel/relocate_kernel_64.S | 2 ++
    arch/x86/lib/error-inject.c | 2 ++
    arch/x86/lib/retpoline.S | 2 ++
    8 files changed, 24 insertions(+), 1 deletion(-)

    --- a/arch/x86/entry/entry_64.S
    +++ b/arch/x86/entry/entry_64.S
    @@ -277,6 +277,7 @@ SYM_FUNC_END(__switch_to_asm)
    .pushsection .text, "ax"
    SYM_CODE_START(ret_from_fork)
    UNWIND_HINT_EMPTY
    + ANNOTATE_NOENDBR // copy_thread
    movq %rax, %rdi
    call schedule_tail /* rdi: 'prev' task parameter */

    @@ -563,12 +564,14 @@ SYM_CODE_END(\asmsym)
    .align 16
    .globl __irqentry_text_start
    __irqentry_text_start:
    + ANNOTATE_NOENDBR // unwinders

    #include <asm/idtentry.h>

    .align 16
    .globl __irqentry_text_end
    __irqentry_text_end:
    + ANNOTATE_NOENDBR

    SYM_CODE_START_LOCAL(common_interrupt_return)
    SYM_INNER_LABEL(swapgs_restore_regs_and_return_to_usermode, SYM_L_GLOBAL)
    @@ -646,6 +651,7 @@ SYM_INNER_LABEL_ALIGN(native_iret, SYM_L
    #endif

    SYM_INNER_LABEL(native_irq_return_iret, SYM_L_GLOBAL)
    + ANNOTATE_NOENDBR // exc_double_fault
    /*
    * This may fault. Non-paranoid faults on return to userspace are
    * handled by fixup_bad_iret. These include #SS, #GP, and #NP.
    @@ -740,6 +746,7 @@ SYM_FUNC_START(asm_load_gs_index)
    FRAME_BEGIN
    swapgs
    .Lgs_change:
    + ANNOTATE_NOENDBR // error_entry
    movl %edi, %gs
    2: ALTERNATIVE "", "mfence", X86_BUG_SWAPGS_FENCE
    swapgs
    @@ -1317,6 +1324,7 @@ SYM_CODE_START(asm_exc_nmi)
    #endif

    repeat_nmi:
    + ANNOTATE_NOENDBR // this code
    /*
    * If there was a nested NMI, the first NMI's iret will return
    * here. But NMIs are still enabled and we can take another
    @@ -1345,6 +1353,7 @@ SYM_CODE_START(asm_exc_nmi)
    .endr
    subq $(5*8), %rsp
    end_repeat_nmi:
    + ANNOTATE_NOENDBR // this code

    /*
    * Everything below this point can be preempted by a nested NMI.
    --- a/arch/x86/entry/entry_64_compat.S
    +++ b/arch/x86/entry/entry_64_compat.S
    @@ -148,6 +148,7 @@ SYM_INNER_LABEL(entry_SYSENTER_compat_af
    popfq
    jmp .Lsysenter_flags_fixed
    SYM_INNER_LABEL(__end_entry_SYSENTER_compat, SYM_L_GLOBAL)
    + ANNOTATE_NOENDBR // is_sysenter_singlestep
    SYM_CODE_END(entry_SYSENTER_compat)

    /*
    --- a/arch/x86/kernel/alternative.c
    +++ b/arch/x86/kernel/alternative.c
    @@ -713,6 +713,7 @@ asm (
    " .pushsection .init.text, \"ax\", @progbits\n"
    " .type int3_magic, @function\n"
    "int3_magic:\n"
    + ANNOTATE_NOENDBR
    " movl $1, (%" _ASM_ARG1 ")\n"
    ASM_RET
    " .size int3_magic, .-int3_magic\n"
    @@ -757,7 +758,8 @@ static void __init int3_selftest(void)
    * then trigger the INT3, padded with NOPs to match a CALL instruction
    * length.
    */
    - asm volatile ("1: int3; nop; nop; nop; nop\n\t"
    + asm volatile (ANNOTATE_NOENDBR
    + "1: int3; nop; nop; nop; nop\n\t"
    ".pushsection .init.data,\"aw\"\n\t"
    ".align " __ASM_SEL(4, 8) "\n\t"
    ".type int3_selftest_ip, @object\n\t"
    --- a/arch/x86/kernel/head_64.S
    +++ b/arch/x86/kernel/head_64.S
    @@ -99,6 +99,7 @@ SYM_CODE_END(startup_64)

    SYM_CODE_START(secondary_startup_64)
    UNWIND_HINT_EMPTY
    + ANNOTATE_NOENDBR
    /*
    * At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 0,
    * and someone has loaded a mapped page table.
    @@ -127,6 +128,7 @@ SYM_CODE_START(secondary_startup_64)
    */
    SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL)
    UNWIND_HINT_EMPTY
    + ANNOTATE_NOENDBR

    /*
    * Retrieve the modifier (SME encryption mask if SME is active) to be
    @@ -192,6 +194,7 @@ SYM_INNER_LABEL(secondary_startup_64_no_
    jmp *%rax
    1:
    UNWIND_HINT_EMPTY
    + ANNOTATE_NOENDBR // above

    /*
    * We must switch to a new descriptor in kernel space for the GDT
    @@ -299,6 +302,7 @@ SYM_INNER_LABEL(secondary_startup_64_no_
    pushq %rax # target address in negative space
    lretq
    .Lafter_lret:
    + ANNOTATE_NOENDBR
    SYM_CODE_END(secondary_startup_64)

    #include "verify_cpu.S"
    --- a/arch/x86/kernel/kprobes/core.c
    +++ b/arch/x86/kernel/kprobes/core.c
    @@ -1023,6 +1023,7 @@ asm(
    ".type __kretprobe_trampoline, @function\n"
    "__kretprobe_trampoline:\n"
    #ifdef CONFIG_X86_64
    + ANNOTATE_NOENDBR
    /* Push a fake return address to tell the unwinder it's a kretprobe. */
    " pushq $__kretprobe_trampoline\n"
    UNWIND_HINT_FUNC
    --- a/arch/x86/kernel/relocate_kernel_64.S
    +++ b/arch/x86/kernel/relocate_kernel_64.S
    @@ -42,6 +42,7 @@
    .code64
    SYM_CODE_START_NOALIGN(relocate_kernel)
    UNWIND_HINT_EMPTY
    + ANNOTATE_NOENDBR
    /*
    * %rdi indirection_page
    * %rsi page_list
    @@ -215,6 +216,7 @@ SYM_CODE_END(identity_mapped)

    SYM_CODE_START_LOCAL_NOALIGN(virtual_mapped)
    UNWIND_HINT_EMPTY
    + ANNOTATE_NOENDBR // RET target, above
    movq RSP(%r8), %rsp
    movq CR4(%r8), %rax
    movq %rax, %cr4
    --- a/arch/x86/lib/error-inject.c
    +++ b/arch/x86/lib/error-inject.c
    @@ -3,6 +3,7 @@
    #include <linux/linkage.h>
    #include <linux/error-injection.h>
    #include <linux/kprobes.h>
    +#include <linux/objtool.h>

    asmlinkage void just_return_func(void);

    @@ -11,6 +12,7 @@ asm(
    ".type just_return_func, @function\n"
    ".globl just_return_func\n"
    "just_return_func:\n"
    + ANNOTATE_NOENDBR
    ASM_RET
    ".size just_return_func, .-just_return_func\n"
    );
    --- a/arch/x86/lib/retpoline.S
    +++ b/arch/x86/lib/retpoline.S
    @@ -12,6 +12,8 @@

    .section .text.__x86.indirect_thunk

    + ANNOTATE_NOENDBR // apply_retpolines
    +
    .macro RETPOLINE reg
    ANNOTATE_INTRA_FUNCTION_CALL
    call .Ldo_rop_\@

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