[PATCH 4.19 095/129] powerpc: Fail build if using recordmcount with binutils v2.37

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4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Naveen N Rao <naveen@xxxxxxxxxx>

[ Upstream commit 25ea739ea1d4d3de41acc4f4eb2d1a97eee0eb75 ]

binutils v2.37 drops unused section symbols, which prevents recordmcount
from capturing mcount locations in sections that have no non-weak
symbols. This results in a build failure with a message such as:
	Cannot find symbol for section 12: .text.perf_callchain_kernel.
	kernel/events/callchain.o: failed

The change to binutils was reverted for v2.38, so this behavior is
specific to binutils v2.37:
https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=c09c8b42021180eee9495bd50d8b35e683d3901b

Objtool is able to cope with such sections, so this issue is specific to
recordmcount.

Fail the build and print a warning if binutils v2.37 is detected and if
we are using recordmcount.

Cc: stable@xxxxxxxxxxxxxxx
Suggested-by: Joel Stanley <joel@xxxxxxxxx>
Signed-off-by: Naveen N Rao <naveen@xxxxxxxxxx>
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Link: https://msgid.link/20230530061436.56925-1-naveen@xxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 arch/powerpc/Makefile | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
index 2fad158173485..daddada1a3902 100644
--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile
@@ -439,3 +439,11 @@ checkbin:
 		echo -n '*** Please use a different binutils version.' ; \
 		false ; \
 	fi
+	@if test "x${CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT}" = "xy" -a \
+		"x${CONFIG_LD_IS_BFD}" = "xy" -a \
+		"${CONFIG_LD_VERSION}" = "23700" ; then \
+		echo -n '*** binutils 2.37 drops unused section symbols, which recordmcount ' ; \
+		echo 'is unable to handle.' ; \
+		echo '*** Please use a different binutils version.' ; \
+		false ; \
+	fi
-- 
2.40.1






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