Unverified Commit ae84ff9a authored by Nathan Chancellor's avatar Nathan Chancellor Committed by Palmer Dabbelt
Browse files

riscv: Restrict DWARF5 when building with LLVM to known working versions 

LLVM prior to 18.0.0 would generate incorrect debug info for DWARF5 due
to linker relaxation, which was worked around in clang by defaulting
RISC-V to DWARF4 [1]. Unfortunately, this workaround does not work for
the kernel because the DWARF version can be independently changed from
the default in Kconfig.

Do not allow DWARF5 to be selected for RISC-V when using linker
relaxation (ld.lld >= 15.0.0) and a version of LLVM that does not have
the fixes (the integrated assembler [2] and ld.lld [3] < 18.0.0)
necessary to generate the correct debug info.

Link: https://github.com/llvm/llvm-project/commit/bbc0f99f3bc96f1db16f649fc21dd18e5b0918f6 [1]
Link: https://github.com/llvm/llvm-project/commit/1df5ea29b43690b6622db2cad7b745607ca4de6a [2]
Link: https://github.com/llvm/llvm-project/commit/7ffabb61a5569444b5ac9322e22e5471cc5e4a77

 [3]
Signed-off-by: default avatarNathan Chancellor <nathan@kernel.org>
Reviewed-by: default avatarFangrui Song <maskray@google.com>
Link: https://lore.kernel.org/r/20231205-riscv-restrict-dwarf5-llvm-v2-2-aedf00a382ac@kernel.org


Signed-off-by: default avatarPalmer Dabbelt <palmer@rivosinc.com>
parent 55b71d2c

arch/riscv/Kconfig

+9 −0
Original line number Diff line number Diff line
@@ -186,6 +186,15 @@ config RISCV_USE_LINKER_RELAXATION 
	# https://github.com/llvm/llvm-project/commit/6611d58f5bbcbec77262d392e2923e1d680f6985

	depends on !LD_IS_LLD || LLD_VERSION >= 150000



# https://github.com/llvm/llvm-project/commit/bbc0f99f3bc96f1db16f649fc21dd18e5b0918f6

config ARCH_HAS_BROKEN_DWARF5

	def_bool y

	depends on RISCV_USE_LINKER_RELAXATION

	# https://github.com/llvm/llvm-project/commit/1df5ea29b43690b6622db2cad7b745607ca4de6a

	depends on AS_IS_LLVM && AS_VERSION < 180000

	# https://github.com/llvm/llvm-project/commit/7ffabb61a5569444b5ac9322e22e5471cc5e4a77

	depends on LD_IS_LLD && LLD_VERSION < 180000



config ARCH_MMAP_RND_BITS_MIN

	default 18 if 64BIT

	default 8

lib/Kconfig.debug

+1 −0
Original line number Diff line number Diff line
@@ -282,6 +282,7 @@ config DEBUG_INFO_DWARF4 
config DEBUG_INFO_DWARF5

	bool "Generate DWARF Version 5 debuginfo"

	select DEBUG_INFO

	depends on !ARCH_HAS_BROKEN_DWARF5

	depends on !CC_IS_CLANG || AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502 && AS_HAS_NON_CONST_LEB128)

	help

	  Generate DWARF v5 debug info. Requires binutils 2.35.2, gcc 5.0+ (gcc