linux-kernel - [FYI] objtool: .export_symbol…: data relocation to !ENDBR: stpcpy

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Message-ID: <20240801152836.xOJc9iaY@linutronix.de>
Date: Thu, 1 Aug 2024 17:28:36 +0200
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: x86@...nel.org, linux-kernel@...r.kernel.org
Cc: Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Ingo Molnar <mingo@...hat.com>,
	Josh Poimboeuf <jpoimboe@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [FYI] objtool: .export_symbol…:
 data relocation to !ENDBR: stpcpy

Hi,

defconfig on x86-64 with gcc-14 I get this:
| vmlinux.o: warning: objtool: .export_symbol+0x26980: data relocation to !ENDBR: stpcpy+0x0

objdump ->

| 0000000000000110 <stpcpy>:
|  110:   66 66 2e 0f 1f 84 00    data16 cs nopw 0x0(%rax,%rax,1)
|  117:   00 00 00 00 
|  11b:   0f 1f 44 00 00          nopl   0x0(%rax,%rax,1)
|  120:   f3 0f 1e fa             endbr64

okay, no endbr64 on entry label.

| $ make lib/string.s
->
|         .type   stpcpy, @function
| stpcpy:
|         .p2align 5
|         endbr64
| .L30:
| # lib/string.c:193:  while ((*dest++ = *src++) != '\0')
|         movzbl  (%rsi), %eax    # MEM[(const char *)src_8 + -1B], _1

an alignment request after the function label before endbr64 which gets
expanded into NOP_11+NOP_5.
I don't see this with gcc-13.
Reported as https://gcc.gnu.org/PR116174

Sebastian