linux-kernel - [PATCH] objtool: Support GCC 9 cold subfunction naming scheme

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Message-Id: <015e9544b1f188d36a7f02fa31e9e95629aa5f50.1541040800.git.jpoimboe@redhat.com>
Date:   Wed, 31 Oct 2018 21:57:30 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     x86@...nel.org
Cc:     linux-kernel@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>
Subject: [PATCH] objtool: Support GCC 9 cold subfunction naming scheme

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-and-tested-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
---
 tools/objtool/elf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index f7082de1ee82..6dbb9fae0f9d 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -301,7 +301,7 @@ 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;
 
-- 
2.17.2