[PATCH] lib/Kconfig.debug: Restrict DEBUG_INFO_SPLIT for RISC-V

[Nathan Chancellor]

When building for ARCH=riscv using LLVM < 14, there is an error with
CONFIG_DEBUG_INFO_SPLIT=y:

  error: A dwo section may not contain relocations

This was worked around in LLVM 15 by disallowing '-gsplit-dwarf' with
'-mrelax' (the default), so CONFIG_DEBUG_INFO_SPLIT is not selectable
with newer versions of LLVM:

  $ clang --target=riscv64-linux-gnu -gsplit-dwarf -c -o /dev/null -x c /dev/null
  clang: error: -gsplit-dwarf is unsupported with RISC-V linker relaxation (-mrelax)

GCC silently had a similar issue that was resolved with GCC 12.x.
Restrict CONFIG_DEBUG_INFO_SPLIT for RISC-V when using LLVM or GCC <
12.x to avoid these known issues.

Link: https://github.com/ClangBuiltLinux/linux/issues/1914
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99090
Reported-by: kernel test robot <lkp at intel.com>
Closes: https://lore.kernel.org/all/202308090204.9yZffBWo-lkp@intel.com/
Signed-off-by: Nathan Chancellor <nathan at kernel.org>
---
Since this only impacts RISC-V, it seems reasonable that this would go
in via their tree but I have added Andrew in case he wants to take it.
---
 lib/Kconfig.debug | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index d6798513a8c2..bd51274f4771 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -355,6 +355,11 @@ endchoice # "Compressed Debug information"
 config DEBUG_INFO_SPLIT
 	bool "Produce split debuginfo in .dwo files"
 	depends on $(cc-option,-gsplit-dwarf)
+	# RISC-V linker relaxation + -gsplit-dwarf has issues with LLVM and GCC
+	# prior to 12.x:
+	# https://github.com/llvm/llvm-project/issues/56642
+	# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99090
+	depends on !RISCV || GCC_VERSION >= 120000
 	help
 	  Generate debug info into separate .dwo files. This significantly
 	  reduces the build directory size for builds with DEBUG_INFO,

---
base-commit: 2ccdd1b13c591d306f0401d98dedc4bdcd02b421
change-id: 20230816-riscv-debug_info_split-0713571a1ac2

Best regards,
-- 
Nathan Chancellor <nathan at kernel.org>