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    SubjectRe: linux-next: build warnings after merge of the tip tree
    On Mon, Mar 21, 2022 at 02:04:05PM +0100, Peter Zijlstra wrote:
    > On Mon, Mar 21, 2022 at 01:55:49PM +0100, Peter Zijlstra wrote:
    > > On Mon, Mar 21, 2022 at 02:03:27PM +1100, Stephen Rothwell wrote:
    > > > Hi all,
    > > >
    > > > After merging the tip tree, today's linux-next build (x864 allmodconfig)
    > > > produced these new warnings:
    > > >
    > > > vmlinux.o: warning: objtool: arch_rethook_prepare()+0x55: relocation to !ENDBR: arch_rethook_trampoline+0x0
    > > > vmlinux.o: warning: objtool: arch_rethook_trampoline_callback()+0x3e: relocation to !ENDBR: arch_rethook_trampoline+0x0
    > > > vmlinux.o: warning: objtool: unwind_next_frame()+0x93e: relocation to !ENDBR: arch_rethook_trampoline+0x0
    > > > vmlinux.o: warning: objtool: unwind_next_frame()+0x5f2: relocation to !ENDBR: arch_rethook_trampoline+0x0
    > > > vmlinux.o: warning: objtool: unwind_next_frame()+0x4a7: relocation to !ENDBR: arch_rethook_trampoline+0x0
    > > > vmlinux.o: warning: objtool: __rethook_find_ret_addr()+0x81: relocation to !ENDBR: arch_rethook_trampoline+0x0
    > > > vmlinux.o: warning: objtool: __rethook_find_ret_addr()+0x90: relocation to !ENDBR: arch_rethook_trampoline+0x0
    > > > vmlinux.o: warning: objtool: rethook_trampoline_handler()+0x8c: relocation to !ENDBR: arch_rethook_trampoline+0x0
    > > > vmlinux.o: warning: objtool: rethook_trampoline_handler()+0x9b: relocation to !ENDBR: arch_rethook_trampoline+0x0
    > >
    > > Hurmph, lemme go figure out where that code comes from, I've not seen
    > > those.
    >
    > Ahh, something tracing. I'll go do some patches on top of it.

    The below gets rid of the objtool warnings.

    But I still think it's fairly terrible to get a (flawed) carbon copy of
    the kretprobe code. Also, I think both should fix regs->ss.

    ---
    diff --git a/arch/x86/kernel/rethook.c b/arch/x86/kernel/rethook.c
    index f0f2f0608282..227a1890a984 100644
    --- a/arch/x86/kernel/rethook.c
    +++ b/arch/x86/kernel/rethook.c
    @@ -20,6 +20,7 @@ asm(
    ".type arch_rethook_trampoline, @function\n"
    "arch_rethook_trampoline:\n"
    #ifdef CONFIG_X86_64
    + ANNOTATE_NOENDBR
    /* Push a fake return address to tell the unwinder it's a kretprobe. */
    " pushq $arch_rethook_trampoline\n"
    UNWIND_HINT_FUNC
    @@ -48,7 +49,7 @@ asm(
    " addl $4, %esp\n"
    " popfl\n"
    #endif
    - " ret\n"
    + ASM_RET
    ".size arch_rethook_trampoline, .-arch_rethook_trampoline\n"
    );
    NOKPROBE_SYMBOL(arch_rethook_trampoline);
    \
     
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