linux-kernel - [PATCH] Makefile: use -gdwarf-{4|5} for assembler for DEBUG_INFO

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Message-ID: <20230315214059.395939-1-ndesaulniers@google.com>
Date:   Wed, 15 Mar 2023 14:40:59 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>, sashal@...nel.org,
        stable@...r.kernel.org
Cc:     Masahiro Yamada <masahiroy@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, Nick Desaulniers <ndesaulniers@...gle.com>,
        Lecopzer Chen <lecopzer.chen@...iatek.com>
Subject: [PATCH] Makefile: use -gdwarf-{4|5} for assembler for DEBUG_INFO_DWARF{4|5}

This is _not_ an upstream commit and just for 5.15.y only. It is based
on upstream
commit 32ef9e5054ec ("Makefile.debug: re-enable debug info for .S files").

When the user has chosen not to use their compiler's implicit default
DWARF version (which changes over time) via selecting
- CONFIG_DEBUG_INFO_DWARF4 or
- CONFIG_DEBUG_INFO_DWARF5
we need to tell the compiler this for Asm sources as well as C sources.
(We use the compiler to drive assembler jobs in kbuild, since most asm
needs to be preprocessed first).  Otherwise, we will get object files
built from Asm sources with the compiler's implicit default DWARF
version.

For example, selecting CONFIG_DEBUG_INFO_DWARF4 would produce a DWARFv5
vmlinux, since it was a mix of DWARFv4 object files from C sources and
DWARFv5 object files from Asm sources when using Clang as the assembler
(ex. `make LLVM=1`).

Fixes: 0ee2f0567a56 ("Makefile.debug: re-enable debug info for .S files")
Reported-by: Lecopzer Chen <lecopzer.chen@...iatek.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>
---
 Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Makefile b/Makefile
index a7b664680ea3..88b2b13bf35b 100644
--- a/Makefile
+++ b/Makefile
@@ -888,6 +888,7 @@ ifndef CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT
 dwarf-version-$(CONFIG_DEBUG_INFO_DWARF4) := 4
 dwarf-version-$(CONFIG_DEBUG_INFO_DWARF5) := 5
 DEBUG_CFLAGS	+= -gdwarf-$(dwarf-version-y)
+KBUILD_AFLAGS	+= -gdwarf-$(dwarf-version-y)
 endif
 
 ifdef CONFIG_DEBUG_INFO_REDUCED
-- 
2.40.0.rc1.284.g88254d51c5-goog