powerpc: Fail build if using recordmcount with binutils v2.37

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@vger.kernel.org
Suggested-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Naveen N Rao <naveen@kernel.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230530061436.56925-1-naveen@kernel.org

diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
index 76fc7cc2678024308f579fe03b4b344c8c42fc41..449514ec1fdf3ad3d0e2a2465127bb498149b017 100644 (file)
--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile
@@ -409,3 +409,11 @@ 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