On 2020-11-04, Nathan Chancellor wrote:
On Tue, Nov 03, 2020 at 04:53:41PM -0800, Nick Desaulniers wrote:
Clang's integrated assembler produces the warning for assembly files:
warning: DWARF2 only supports one section per compilation unit
If -Wa,-gdwarf-* is unspecified, then debug info is not emitted. This
Is this something that should be called out somewhere? If I understand
this correctly, LLVM_IAS=1 + CONFIG_DEBUG_INFO=y won't work? Maybe this
should be handled in Kconfig?
will be re-enabled for new DWARF versions in a follow up patch.
Enables defconfig+CONFIG_DEBUG_INFO to build cleanly with
LLVM=1 LLVM_IAS=1 for x86_64 and arm64.
Cc: <stable@xxxxxxxxxxxxxxx>
Link: https://github.com/ClangBuiltLinux/linux/issues/716
Reported-by: Nathan Chancellor <natechancellor@xxxxxxxxx>
Suggested-by: Dmitry Golovin <dima@xxxxxxxxxx>
If you happen to respin, Dmitry deserves a Reported-by tag too :)
Suggested-by: Sedat Dilek <sedat.dilek@xxxxxxxxx>
Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Regardless of the other two comments, this is fine as is as a fix for
stable to unblock Android + CrOS since we have been running something
similar to it in CI:
Reviewed-by: Nathan Chancellor <natechancellor@xxxxxxxxx>
---
Makefile | 2 ++
1 file changed, 2 insertions(+)
diff --git a/Makefile b/Makefile
index f353886dbf44..75b1a3dcbf30 100644
--- a/Makefile
+++ b/Makefile
@@ -826,7 +826,9 @@ else
DEBUG_CFLAGS += -g
endif
+ifndef LLVM_IAS
Nit: this should probably match the existing LLVM_IAS check
ifneq ($(LLVM_IAS),1)
KBUILD_AFLAGS += -Wa,-gdwarf-2
+endif
ifdef CONFIG_DEBUG_INFO_DWARF4
DEBUG_CFLAGS += -gdwarf-4
--
2.29.1.341.ge80a0c044ae-goog
The root cause is that DWARF v2 has no DW_AT_ranges, so it cannot
represent non-contiguous address ranges. It seems that GNU as -gdwarf-3
emits DW_AT_ranges as well and emits an entry for a non-executable section.
In any case, the option is of very low value, at least for LLVM.
Reviewed-by: Fangrui Song <maskray@xxxxxxxxxx>
