On Tue, Nov 17, 2020 at 11:41:15AM -0800, Nick Desaulniers wrote:

On Fri, Nov 13, 2020 at 11:56 AM Nathan Chancellor
[off-list ref] wrote:

quoted

ld.lld 10.0.1 spews a bunch of various warnings about .rela sections,
along with a few others. Newer versions of ld.lld do not have these
warnings. As a result, do not add '--orphan-handling=warn' to
LDFLAGS_vmlinux if ld.lld's version is not new enough.

Reported-by: Arvind Sankar <redacted>
Reported-by: kernelci.org bot <redacted>
Reported-by: Mark Brown <broonie@kernel.org>
Link: https://github.com/ClangBuiltLinux/linux/issues/1187
Link: https://github.com/ClangBuiltLinux/linux/issues/1193
Signed-off-by: Nathan Chancellor <redacted>
---
 MAINTAINERS            |  1 +
 init/Kconfig           |  6 +++++-
 scripts/lld-version.sh | 20 ++++++++++++++++++++
 3 files changed, 26 insertions(+), 1 deletion(-)
 create mode 100755 scripts/lld-version.sh

diff --git a/MAINTAINERS b/MAINTAINERS
index 3da6d8c154e4..4b83d3591ec7 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS

@@ -4284,6 +4284,7 @@ B:        https://github.com/ClangBuiltLinux/linux/issues
 C:     irc://chat.freenode.net/clangbuiltlinux
 F:     Documentation/kbuild/llvm.rst
 F:     scripts/clang-tools/
+F:     scripts/lld-version.sh
 K:     \b(?i:clang|llvm)\b

 CLEANCACHE API

diff --git a/init/Kconfig b/init/Kconfig
index a270716562de..40c9ca60ac1d 100644
--- a/init/Kconfig
+++ b/init/Kconfig

@@ -47,6 +47,10 @@ config CLANG_VERSION
        int
        default $(shell,$(srctree)/scripts/clang-version.sh $(CC))

+config LLD_VERSION
+       int
+       default $(shell,$(srctree)/scripts/lld-version.sh $(LD))
+
 config CC_CAN_LINK
        bool
        default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m64-flag)) if 64BIT

@@ -1349,7 +1353,7 @@ config LD_DEAD_CODE_DATA_ELIMINATION
          own risk.

 config LD_ORPHAN_WARN
-       def_bool ARCH_WANT_LD_ORPHAN_WARN && $(ld-option,--orphan-handling=warn)
+       def_bool ARCH_WANT_LD_ORPHAN_WARN && $(ld-option,--orphan-handling=warn) && (!LD_IS_LLD || LLD_VERSION >= 110000)

 config SYSCTL
        bool

diff --git a/scripts/lld-version.sh b/scripts/lld-version.sh
new file mode 100755
index 000000000000..cc779f412e39
--- /dev/null
+++ b/scripts/lld-version.sh

@@ -0,0 +1,20 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+#
+# ld.lld-version ld.lld-command

^ it looks like this format was copied from scripts/gcc-version, but
it's kind of curious/cryptic to me for a comment about usage.  Is it
necessary?  A comment in the form:

# Usage: ./scripts/lld-version.sh ld.lld

Would be clearer to me.

quoted

+#
+# Print the linker version of `ld.lld-command' in a 5 or 6-digit form
+# such as `100001' for ld.lld 10.0.1 etc.
+
+linker="$*"
+
+if ! ( $linker --version | grep -q LLD ); then
+       echo 0
+       exit 1
+fi
+
+VERSION=$($linker --version | cut -d ' ' -f 2)

This is going to invoke the linker potentially twice if it's LLD.
Would it be nicer to capture the output of `$linker --version`, check
which linker it is, then slice that up via `cut` to get the version?

This version is fine to me, but if you're going to send a v2, that
might be a nice slight cleanup.  Otherwise,

Reviewed-by: Nick Desaulniers <redacted>
Tested-by: Nick Desaulniers <redacted>

(Please drop those tags if you modify this for v2 and I'll rereview/retest).

Below is the impending v2 if you wanted to give it an early test, I plan
to send it along formally Thursday morning with all of the addressed
feedback so far.

Cheers,
Nathan

======================================================================

From 1ef9b12daf2b19ed6687423483d5bb1f5cf82e13 Mon Sep 17 00:00:00 2001
From: Nathan Chancellor <redacted>
Date: Tue, 17 Nov 2020 20:11:26 -0700
Subject: [PATCH] kbuild: Disable CONFIG_LD_ORPHAN_WARN for ld.lld 10.0.1

ld.lld 10.0.1 spews a bunch of various warnings about .rela sections,
along with a few others. Newer versions of ld.lld do not have these
warnings. As a result, do not add '--orphan-handling=warn' to
LDFLAGS_vmlinux if ld.lld's version is not new enough.

Link: https://github.com/ClangBuiltLinux/linux/issues/1187
Link: https://github.com/ClangBuiltLinux/linux/issues/1193
Reported-by: Arvind Sankar <redacted>
Reported-by: kernelci.org bot <redacted>
Reported-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Kees Cook <redacted>
Signed-off-by: Nathan Chancellor <redacted>
---
 MAINTAINERS            |  1 +
 init/Kconfig           |  9 ++++++++-
 scripts/lld-version.sh | 20 ++++++++++++++++++++
 3 files changed, 29 insertions(+), 1 deletion(-)
 create mode 100755 scripts/lld-version.sh

diff --git a/MAINTAINERS b/MAINTAINERS
index e451dcce054f..e6f74f130ae1 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS

@@ -4284,6 +4284,7 @@ B:	https://github.com/ClangBuiltLinux/linux/issues
 C:	irc://chat.freenode.net/clangbuiltlinux
 F:	Documentation/kbuild/llvm.rst
 F:	scripts/clang-tools/
+F:	scripts/lld-version.sh
 K:	\b(?i:clang|llvm)\b
 
 CLEANCACHE API

diff --git a/init/Kconfig b/init/Kconfig
index a270716562de..b9037d6c5ab3 100644
--- a/init/Kconfig
+++ b/init/Kconfig

@@ -47,6 +47,10 @@ config CLANG_VERSION
 	int
 	default $(shell,$(srctree)/scripts/clang-version.sh $(CC))
 
+config LLD_VERSION
+	int
+	default $(shell,$(srctree)/scripts/lld-version.sh $(LD))
+
 config CC_CAN_LINK
 	bool
 	default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m64-flag)) if 64BIT

@@ -1349,7 +1353,10 @@ config LD_DEAD_CODE_DATA_ELIMINATION
 	  own risk.
 
 config LD_ORPHAN_WARN
-	def_bool ARCH_WANT_LD_ORPHAN_WARN && $(ld-option,--orphan-handling=warn)
+	def_bool y
+	depends on ARCH_WANT_LD_ORPHAN_WARN
+	depends on !LD_IS_LLD || LLD_VERSION >= 110000
+	depends on $(ld-option,--orphan-handling=warn)
 
 config SYSCTL
 	bool

diff --git a/scripts/lld-version.sh b/scripts/lld-version.sh
new file mode 100755
index 000000000000..d70edb4d8a4f
--- /dev/null
+++ b/scripts/lld-version.sh

@@ -0,0 +1,20 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+#
+# Usage: $ ./scripts/lld-version.sh ld.lld
+#
+# Print the linker version of `ld.lld' in a 5 or 6-digit form
+# such as `100001' for ld.lld 10.0.1 etc.
+
+linker_string="$($* --version)"
+
+if ! ( echo $linker_string | grep -q LLD ); then
+	echo 0
+	exit 1
+fi
+
+VERSION=$(echo $linker_string | cut -d ' ' -f 2)
+MAJOR=$(echo $VERSION | cut -d . -f 1)
+MINOR=$(echo $VERSION | cut -d . -f 2)
+PATCHLEVEL=$(echo $VERSION | cut -d . -f 3)
+printf "%d%02d%02d\\n" $MAJOR $MINOR $PATCHLEVEL

-- 
2.29.2


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