Unverified Commit a4426641 authored by Nathan Chancellor's avatar Nathan Chancellor Committed by Palmer Dabbelt
Browse files

lib/Kconfig.debug: Update AS_HAS_NON_CONST_LEB128 comment and name 



Fangrui noted that the comment around CONFIG_AS_HAS_NON_CONST_LEB128
could be made more accurate because explicit .sleb128 directives are not
emitted, only .uleb128 directives are. Rename the symbol to
CONFIG_AS_HAS_NON_CONST_ULEB128 as a result.

Further clarifications include replacing "symbol deltas" with the more
accurate "label differences", noting that this issue has been resolved
in newer binutils (2.41+), and it only occurs when a port uses RISC-V
style linker relaxation.

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


Signed-off-by: default avatarPalmer Dabbelt <palmer@rivosinc.com>
parent ae84ff9a

lib/Kconfig.debug

+6 −5
Original line number Diff line number Diff line
@@ -231,9 +231,10 @@ config DEBUG_INFO 
	  in the "Debug information" choice below, indicating that debug

	  information will be generated for build targets.



# Clang is known to generate .{s,u}leb128 with symbol deltas with DWARF5, which

# some targets may not support: https://sourceware.org/bugzilla/show_bug.cgi?id=27215

config AS_HAS_NON_CONST_LEB128

# Clang generates .uleb128 with label differences for DWARF v5, a feature that

# older binutils ports do not support when utilizing RISC-V style linker

# relaxation: https://sourceware.org/bugzilla/show_bug.cgi?id=27215

config AS_HAS_NON_CONST_ULEB128

	def_bool $(as-instr,.uleb128 .Lexpr_end4 - .Lexpr_start3\n.Lexpr_start3:\n.Lexpr_end4:)



choice
@@ -258,7 +259,7 @@ config DEBUG_INFO_NONE 
config DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT

	bool "Rely on the toolchain's implicit default DWARF version"

	select DEBUG_INFO

	depends on !CC_IS_CLANG || AS_IS_LLVM || CLANG_VERSION < 140000 || (AS_IS_GNU && AS_VERSION >= 23502 && AS_HAS_NON_CONST_LEB128)

	depends on !CC_IS_CLANG || AS_IS_LLVM || CLANG_VERSION < 140000 || (AS_IS_GNU && AS_VERSION >= 23502 && AS_HAS_NON_CONST_ULEB128)

	help

	  The implicit default version of DWARF debug info produced by a

	  toolchain changes over time.
@@ -283,7 +284,7 @@ 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)

	depends on !CC_IS_CLANG || AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502 && AS_HAS_NON_CONST_ULEB128)

	help

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

	  5.0+ accepts the -gdwarf-5 flag but only had partial support for some