linux-kernel - [PATCH 4.9 41/42] objtool: Support GCC 9 cold subfunction naming scheme

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Message-Id: <20190805124929.851335655@linuxfoundation.org>
Date:   Mon,  5 Aug 2019 15:03:07 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH 4.9 41/42] objtool: Support GCC 9 cold subfunction naming scheme

From: Josh Poimboeuf <jpoimboe@...hat.com>

commit bcb6fb5da77c2a228adf07cc9cb1a0c2aa2001c6 upstream.

Starting with GCC 8, a lot of unlikely code was moved out of line to
"cold" subfunctions in .text.unlikely.

For example, the unlikely bits of:

  irq_do_set_affinity()

are moved out to the following subfunction:

  irq_do_set_affinity.cold.49()

Starting with GCC 9, the numbered suffix has been removed.  So in the
above example, the cold subfunction is instead:

  irq_do_set_affinity.cold()

Tweak the objtool subfunction detection logic so that it detects both
GCC 8 and GCC 9 naming schemes.

Reported-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Tested-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Link: https://lkml.kernel.org/r/015e9544b1f188d36a7f02fa31e9e95629aa5f50.1541040800.git.jpoimboe@redhat.com
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 tools/objtool/elf.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -305,7 +305,7 @@ static int read_symbols(struct elf *elf)
 			if (sym->type != STT_FUNC)
 				continue;
 			sym->pfunc = sym->cfunc = sym;
-			coldstr = strstr(sym->name, ".cold.");
+			coldstr = strstr(sym->name, ".cold");
 			if (!coldstr)
 				continue;