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From: Nathan Chancellor <nathan@kernel.org>
To: paul.walmsley@sifive.com, palmer@dabbelt.com,
	aou@eecs.berkeley.edu,  conor@kernel.org
Cc: maskray@google.com, ndesaulniers@google.com,
	 linux-riscv@lists.infradead.org, llvm@lists.linux.dev,
	 patches@lists.linux.dev, Nathan Chancellor <nathan@kernel.org>
Subject: [PATCH v2 3/3] lib/Kconfig.debug: Update AS_HAS_NON_CONST_LEB128 comment and name
Date: Tue, 05 Dec 2023 16:53:52 -0700	[thread overview]
Message-ID: <20231205-riscv-restrict-dwarf5-llvm-v2-3-aedf00a382ac@kernel.org> (raw)
In-Reply-To: <20231205-riscv-restrict-dwarf5-llvm-v2-0-aedf00a382ac@kernel.org>

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: Fangrui Song <maskray@google.com>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---
 lib/Kconfig.debug | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index a0ebce05a368..76c2cc697573 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -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

-- 
2.43.0


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  parent reply	other threads:[~2023-12-05 23:54 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-12-05 23:53 [PATCH v2 0/3] RISC-V: Disable DWARF5 with known broken LLVM versions Nathan Chancellor
2023-12-05 23:53 ` [PATCH v2 1/3] riscv: Hoist linker relaxation disabling logic into Kconfig Nathan Chancellor
2023-12-05 23:53 ` [PATCH v2 2/3] riscv: Restrict DWARF5 when building with LLVM to known working versions Nathan Chancellor
2023-12-06  2:11   ` Fangrui Song
2023-12-05 23:53 ` Nathan Chancellor [this message]
2023-12-14  0:12   ` [PATCH v2 3/3] lib/Kconfig.debug: Update AS_HAS_NON_CONST_LEB128 comment and name Charlie Jenkins
2024-01-18  2:11 ` [PATCH v2 0/3] RISC-V: Disable DWARF5 with known broken LLVM versions Palmer Dabbelt
2024-01-20 21:09 ` patchwork-bot+linux-riscv

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