vdso: Rename included Makefile

As the Makefile is included into other Makefiles it can not be used to
define objects to be built from the current source directory.
However the generic datastore will

vdso: Rename included Makefile

As the Makefile is included into other Makefiles it can not be used to
define objects to be built from the current source directory.
However the generic datastore will introduce such a local source file.
Rename the included Makefile so it is clear how it is to be used and to
make room for a regular Makefile in lib/vdso/.

Signed-off-by: Thomas Weißschuh <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Link: https://lore.kernel.org/all/[email protected]

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arm64/vdso: Remove --hash-style=sysv

glibc added support for .gnu.hash in 2006 and .hash has been obsoleted
for more than one decade in many Linux distributions. Using
--hash-style=sysv might imply

arm64/vdso: Remove --hash-style=sysv

glibc added support for .gnu.hash in 2006 and .hash has been obsoleted
for more than one decade in many Linux distributions. Using
--hash-style=sysv might imply unaddressed issues and confuse readers.

Just drop the option and rely on the linker default, which is likely
"both", or "gnu" when the distribution really wants to eliminate sysv
hash overhead.

Similar to commit 6b7e26547fad ("x86/vdso: Emit a GNU hash").

Signed-off-by: Fangrui Song <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Will Deacon <[email protected]>

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arch: use $(obj)/ instead of $(src)/ for preprocessed linker scripts

These are generated files. Prefix them with $(obj)/ instead of $(src)/.

Signed-off-by: Masahiro Yamada <[email protected]>
Ac

arch: use $(obj)/ instead of $(src)/ for preprocessed linker scripts

These are generated files. Prefix them with $(obj)/ instead of $(src)/.

Signed-off-by: Masahiro Yamada <[email protected]>
Acked-by: Helge Deller <[email protected]>
Reviewed-by: Nicolas Schier <[email protected]>

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arm64: vdso32: Remove unused vdso32-offsets.h

Commit 2d071968a405 ("arm64: compat: Remove 32-bit sigreturn code
from the vDSO") removed all VDSO_* symbols in the compat vDSO. As a
result, vdso32-off

arm64: vdso32: Remove unused vdso32-offsets.h

Commit 2d071968a405 ("arm64: compat: Remove 32-bit sigreturn code
from the vDSO") removed all VDSO_* symbols in the compat vDSO. As a
result, vdso32-offsets.h is now empty and therefore unused. Time to
remove it.

Signed-off-by: Kevin Brodsky <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Will Deacon <[email protected]>

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arm64: vdso32: rename 32-bit debug vdso to vdso32.so.dbg

'make vdso_install' renames arch/arm64/kernel/vdso32/vdso.so.dbg to
vdso32.so during installation, which allows 64-bit and 32-bit vdso
files

arm64: vdso32: rename 32-bit debug vdso to vdso32.so.dbg

'make vdso_install' renames arch/arm64/kernel/vdso32/vdso.so.dbg to
vdso32.so during installation, which allows 64-bit and 32-bit vdso
files to be installed in the same directory.

However, arm64 is the only architecture that requires this renaming.

To simplify the vdso_install logic, rename the in-tree vdso file so
its base name matches the installed file name.

Signed-off-by: Masahiro Yamada <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Will Deacon <[email protected]>

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kbuild: unify vdso_install rules

Currently, there is no standard implementation for vdso_install,
leading to various issues:

1. Code duplication

Many architectures duplicate similar code just

kbuild: unify vdso_install rules

Currently, there is no standard implementation for vdso_install,
leading to various issues:

1. Code duplication

Many architectures duplicate similar code just for copying files
to the install destination.

Some architectures (arm, sparc, x86) create build-id symlinks,
introducing more code duplication.

2. Unintended updates of in-tree build artifacts

The vdso_install rule depends on the vdso files to install.
It may update in-tree build artifacts. This can be problematic,
as explained in commit 19514fc665ff ("arm, kbuild: make
"make install" not depend on vmlinux").

3. Broken code in some architectures

Makefile code is often copied from one architecture to another
without proper adaptation.

'make vdso_install' for parisc does not work.

'make vdso_install' for s390 installs vdso64, but not vdso32.

To address these problems, this commit introduces a generic vdso_install
rule.

Architectures that support vdso_install need to define vdso-install-y
in arch/*/Makefile. vdso-install-y lists the files to install.

For example, arch/x86/Makefile looks like this:

vdso-install-$(CONFIG_X86_64) += arch/x86/entry/vdso/vdso64.so.dbg
vdso-install-$(CONFIG_X86_X32_ABI) += arch/x86/entry/vdso/vdsox32.so.dbg
vdso-install-$(CONFIG_X86_32) += arch/x86/entry/vdso/vdso32.so.dbg
vdso-install-$(CONFIG_IA32_EMULATION) += arch/x86/entry/vdso/vdso32.so.dbg

These files will be installed to $(MODLIB)/vdso/ with the .dbg suffix,
if exists, stripped away.

vdso-install-y can optionally take the second field after the colon
separator. This is needed because some architectures install a vdso
file as a different base name.

The following is a snippet from arch/arm64/Makefile.

vdso-install-$(CONFIG_COMPAT_VDSO) += arch/arm64/kernel/vdso32/vdso.so.dbg:vdso32.so

This will rename vdso.so.dbg to vdso32.so during installation. If such
architectures change their implementation so that the base names match,
this workaround will go away.

Signed-off-by: Masahiro Yamada <[email protected]>
Acked-by: Sven Schnelle <[email protected]> # s390
Reviewed-by: Nicolas Schier <[email protected]>
Reviewed-by: Guo Ren <[email protected]>
Acked-by: Helge Deller <[email protected]> # parisc
Acked-by: Catalin Marinas <[email protected]>
Acked-by: Russell King (Oracle) <[email protected]>

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kbuild: Drop -Wdeclaration-after-statement

With the advent on scope-based resource management it comes really
tedious to abide by the contraints of -Wdeclaration-after-statement.

It will still be r

kbuild: Drop -Wdeclaration-after-statement

With the advent on scope-based resource management it comes really
tedious to abide by the contraints of -Wdeclaration-after-statement.

It will still be recommeneded to place declarations at the start of a
scope where possible, but it will no longer be enforced.

Suggested-by: Linus Torvalds <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Link: https://lkml.kernel.org/r/CAHk-%3Dwi-RyoUhbChiVaJZoZXheAwnJ7OO%3DGxe85BkPAd93TwDA%40mail.gmail.com

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vdso: Improve cmd_vdso_check to check all dynamic relocations

The actual intention is that no dynamic relocation exists in the VDSO. For
this the VDSO build validates that the resulting .so file doe

vdso: Improve cmd_vdso_check to check all dynamic relocations

The actual intention is that no dynamic relocation exists in the VDSO. For
this the VDSO build validates that the resulting .so file does not have any
relocations which are specified via $(ARCH_REL_TYPE_ABS) per architecture,
which is fragile as e.g. ARM64 lacks an entry for R_AARCH64_RELATIVE. Aside
of that ARCH_REL_TYPE_ABS is a misnomer as it checks for relative
relocations too.

However, some GNU ld ports produce unneeded R_*_NONE relocation entries. If
a port fails to determine the exact .rel[a].dyn size, the trailing zeros
become R_*_NONE relocations. E.g. ld's powerpc port recently fixed
https://sourceware.org/bugzilla/show_bug.cgi?id=29540). R_*_NONE are
generally a no-op in the dynamic loaders. So just ignore them.

Remove the ARCH_REL_TYPE_ABS defines and just validate that the resulting
.so file does not contain any R_* relocation entries except R_*_NONE.

Signed-off-by: Fangrui Song <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Tested-by: Vincenzo Frascino <[email protected]> # for aarch64
Reviewed-by: Christophe Leroy <[email protected]>
Reviewed-by: Vincenzo Frascino <[email protected]> # for vDSO, aarch64
Acked-by: Michael Ellerman <[email protected]> (powerpc)
Link: https://lore.kernel.org/r/[email protected]

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kbuild: upgrade the orphan section warning to an error if CONFIG_WERROR is set

Andrew Cooper suggested upgrading the orphan section warning to a hard link
error. However Nathan Chancellor said outri

kbuild: upgrade the orphan section warning to an error if CONFIG_WERROR is set

Andrew Cooper suggested upgrading the orphan section warning to a hard link
error. However Nathan Chancellor said outright turning the warning into an
error with no escape hatch might be too aggressive, as we have had these
warnings triggered by new compiler generated sections, and suggested turning
orphan sections into an error only if CONFIG_WERROR is set. Kees Cook echoed
and emphasized that the mandate from Linus is that we should avoid breaking
builds. It wrecks bisection, it causes problems across compiler versions, etc.

Thus upgrade the orphan section warning to a hard link error only if
CONFIG_WERROR is set.

Suggested-by: Andrew Cooper <[email protected]>
Suggested-by: Nathan Chancellor <[email protected]>
Signed-off-by: Xin Li <[email protected]>
Reviewed-by: Nathan Chancellor <[email protected]>
Tested-by: Nathan Chancellor <[email protected]>
Signed-off-by: Kees Cook <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

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arm64: vdso32: enable orphan handling for VDSO

Like vmlinux, enable orphan-handling for the compat VDSO32. This can catch
subtle errors that might arise from unexpected sections being included.

Sig

arm64: vdso32: enable orphan handling for VDSO

Like vmlinux, enable orphan-handling for the compat VDSO32. This can catch
subtle errors that might arise from unexpected sections being included.

Signed-off-by: Joey Gouly <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Masahiro Yamada <[email protected]>
Cc: Vincenzo Frascino <[email protected]>
Cc: Kees Cook <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
Reviewed-by: Vincenzo Frascino <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Will Deacon <[email protected]>

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arm64: vdso: fix makefile dependency on vdso.so

There is currently no dependency for vdso*-wrap.S on vdso*.so, which means that
you can get a build that uses a stale vdso*-wrap.o.

In commit a5b8ca9

arm64: vdso: fix makefile dependency on vdso.so

There is currently no dependency for vdso*-wrap.S on vdso*.so, which means that
you can get a build that uses a stale vdso*-wrap.o.

In commit a5b8ca97fbf8, the file that includes the vdso.so was moved and renamed
from arch/arm64/kernel/vdso/vdso.S to arch/arm64/kernel/vdso-wrap.S, when this
happened the Makefile was not updated to force the dependcy on vdso.so.

Fixes: a5b8ca97fbf8 ("arm64: do not descend to vdso directories twice")
Signed-off-by: Joey Gouly <[email protected]>
Cc: Masahiro Yamada <[email protected]>
Cc: Vincenzo Frascino <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Will Deacon <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Will Deacon <[email protected]>

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Kbuild: move to -std=gnu11

During a patch discussion, Linus brought up the option of changing
the C standard version from gnu89 to gnu99, which allows using variable
declaration inside of a for() lo

Kbuild: move to -std=gnu11

During a patch discussion, Linus brought up the option of changing
the C standard version from gnu89 to gnu99, which allows using variable
declaration inside of a for() loop. While the C99, C11 and later standards
introduce many other features, most of these are already available in
gnu89 as GNU extensions as well.

An earlier attempt to do this when gcc-5 started defaulting to
-std=gnu11 failed because at the time that caused warnings about
designated initializers with older compilers. Now that gcc-5.1 is
the minimum compiler version used for building kernels, that is no
longer a concern. Similarly, the behavior of 'inline' functions changes
between gnu89 using gnu_inline behavior and gnu11 using standard c99+
behavior, but this was taken care of by defining 'inline' to include
__attribute__((gnu_inline)) in order to allow building with clang a
while ago.

Nathan Chancellor reported a new -Wdeclaration-after-statement
warning that appears in a system header on arm, this still needs a
workaround.

The differences between gnu99, gnu11, gnu1x and gnu17 are fairly
minimal and mainly impact warnings at the -Wpedantic level that the
kernel never enables. Between these, gnu11 is the newest version
that is supported by all supported compiler versions, though it is
only the default on gcc-5, while all other supported versions of
gcc or clang default to gnu1x/gnu17.

Link: https://lore.kernel.org/lkml/CAHk-=wiyCH7xeHcmiFJ-YgXUy2Jaj7pnkdKpcovt8fYbVFW3TA@mail.gmail.com/
Link: https://github.com/ClangBuiltLinux/linux/issues/1603
Suggested-by: Linus Torvalds <[email protected]>
Acked-by: Marco Elver <[email protected]>
Acked-by: Jani Nikula <[email protected]>
Acked-by: David Sterba <[email protected]>
Tested-by: Sedat Dilek <[email protected]>
Reviewed-by: Alex Shi <[email protected]>
Reviewed-by: Nick Desaulniers <[email protected]>
Reviewed-by: Miguel Ojeda <[email protected]>
Signed-off-by: Arnd Bergmann <[email protected]>
Reviewed-by: Nathan Chancellor <[email protected]>
Signed-off-by: Masahiro Yamada <[email protected]>

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Kbuild: use -Wdeclaration-after-statement

The kernel is moving from using `-std=gnu89` to `-std=gnu11`, permitting
the use of additional C11 features such as for-loop initial declarations.

One cont

Kbuild: use -Wdeclaration-after-statement

The kernel is moving from using `-std=gnu89` to `-std=gnu11`, permitting
the use of additional C11 features such as for-loop initial declarations.

One contentious aspect of C99 is that it permits mixed declarations and
code, and for now at least, it seems preferable to enforce that
declarations must come first.

These warnings were already enabled in the kernel itself, but not
for KBUILD_USERCFLAGS or the compat VDSO on arch/arm64, which uses
a separate set of CFLAGS.

This patch fixes an existing violation in modpost.c, which is not
reported because of the missing flag in KBUILD_USERCFLAGS:

| scripts/mod/modpost.c: In function ‘match’:
| scripts/mod/modpost.c:837:3: warning: ISO C90 forbids mixed declarations and code [-Wdeclaration-after-statement]
| 837 | const char *endp = p + strlen(p) - 1;
| | ^~~~~

Signed-off-by: Mark Rutland <[email protected]>
[arnd: don't add a duplicate flag to the default set, update changelog]
Signed-off-by: Arnd Bergmann <[email protected]>
Reviewed-by: Nathan Chancellor <[email protected]>
Reviewed-by: Nick Desaulniers <[email protected]>
Tested-by: Sedat Dilek <[email protected]> # LLVM/Clang v13.0.0 (x86-64)
Signed-off-by: Masahiro Yamada <[email protected]>

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arm64: vdso: remove -nostdlib compiler flag

The -nostdlib option requests the compiler to not use the standard
system startup files or libraries when linking. It is effective only
when $(CC) is used

arm64: vdso: remove -nostdlib compiler flag

The -nostdlib option requests the compiler to not use the standard
system startup files or libraries when linking. It is effective only
when $(CC) is used as a linker driver.

Since commit 691efbedc60d ("arm64: vdso: use $(LD) instead of $(CC)
to link VDSO"), $(LD) is directly used, hence -nostdlib is unneeded.

Signed-off-by: Masahiro Yamada <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Will Deacon <[email protected]>

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arm64: vdso32: require CROSS_COMPILE_COMPAT for gcc+bfd

Similar to
commit 231ad7f409f1 ("Makefile: infer --target from ARCH for CC=clang")
There really is no point in setting --target based on
$CROS

arm64: vdso32: require CROSS_COMPILE_COMPAT for gcc+bfd

Similar to
commit 231ad7f409f1 ("Makefile: infer --target from ARCH for CC=clang")
There really is no point in setting --target based on
$CROSS_COMPILE_COMPAT for clang when the integrated assembler is being
used, since
commit ef94340583ee ("arm64: vdso32: drop -no-integrated-as flag").

Allows COMPAT_VDSO to be selected without setting $CROSS_COMPILE_COMPAT
when using clang and lld together.

Before:
$ ARCH=arm64 CROSS_COMPILE_COMPAT=arm-linux-gnueabi- make -j72 LLVM=1 defconfig
$ grep CONFIG_COMPAT_VDSO .config
CONFIG_COMPAT_VDSO=y
$ ARCH=arm64 make -j72 LLVM=1 defconfig
$ grep CONFIG_COMPAT_VDSO .config
$

After:
$ ARCH=arm64 CROSS_COMPILE_COMPAT=arm-linux-gnueabi- make -j72 LLVM=1 defconfig
$ grep CONFIG_COMPAT_VDSO .config
CONFIG_COMPAT_VDSO=y
$ ARCH=arm64 make -j72 LLVM=1 defconfig
$ grep CONFIG_COMPAT_VDSO .config
CONFIG_COMPAT_VDSO=y

Reviewed-by: Nathan Chancellor <[email protected]>
Suggested-by: Nathan Chancellor <[email protected]>
Tested-by: Nathan Chancellor <[email protected]>
Signed-off-by: Nick Desaulniers <[email protected]>
Reviewed-by: Vincenzo Frascino <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Will Deacon <[email protected]>

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arm64: vdso32: suppress error message for 'make mrproper'

When running the following command without arm-linux-gnueabi-gcc in
one's $PATH, the following warning is observed:

$ ARCH=arm64 CROSS_COMP

arm64: vdso32: suppress error message for 'make mrproper'

When running the following command without arm-linux-gnueabi-gcc in
one's $PATH, the following warning is observed:

$ ARCH=arm64 CROSS_COMPILE_COMPAT=arm-linux-gnueabi- make -j72 LLVM=1 mrproper
make[1]: arm-linux-gnueabi-gcc: No such file or directory

This is because KCONFIG is not run for mrproper, so CONFIG_CC_IS_CLANG
is not set, and we end up eagerly evaluating various variables that try
to invoke CC_COMPAT.

This is a similar problem to what was observed in
commit dc960bfeedb0 ("h8300: suppress error messages for 'make clean'")

Reported-by: Lucas Henneman <[email protected]>
Suggested-by: Masahiro Yamada <[email protected]>
Signed-off-by: Nick Desaulniers <[email protected]>
Reviewed-by: Vincenzo Frascino <[email protected]>
Reviewed-by: Nathan Chancellor <[email protected]>
Tested-by: Nathan Chancellor <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Will Deacon <[email protected]>

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arm64: vdso32: drop test for -march=armv8-a

As Arnd points out:
gcc-4.8 already supported -march=armv8, and we require gcc-5.1 now, so
both this #if/#else construct and the corresponding
"cc32

arm64: vdso32: drop test for -march=armv8-a

As Arnd points out:
gcc-4.8 already supported -march=armv8, and we require gcc-5.1 now, so
both this #if/#else construct and the corresponding
"cc32-option,-march=armv8-a" check should be obsolete now.

Link: https://lore.kernel.org/lkml/CAK8P3a3UBEJ0Py2ycz=rHfgog8g3mCOeQOwO0Gmp-iz6Uxkapg@mail.gmail.com/
Suggested-by: Arnd Bergmann <[email protected]>
Signed-off-by: Nick Desaulniers <[email protected]>
Reviewed-by: Vincenzo Frascino <[email protected]>
Reviewed-by: Nathan Chancellor <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Will Deacon <[email protected]>

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arm64: vdso32: drop the test for dmb ishld

Binutils added support for this instruction in commit
e797f7e0b2bedc9328d4a9a0ebc63ca7a2dbbebc which shipped in 2.24 (just
missing the 2.23 release) but wa

arm64: vdso32: drop the test for dmb ishld

Binutils added support for this instruction in commit
e797f7e0b2bedc9328d4a9a0ebc63ca7a2dbbebc which shipped in 2.24 (just
missing the 2.23 release) but was cherry-picked into 2.23 in commit
27a50d6755bae906bc73b4ec1a8b448467f0bea1. Thanks to Christian and Simon
for helping me with the patch archaeology.

According to Documentation/process/changes.rst, the minimum supported
version of binutils is 2.23. Since all supported versions of GAS support
this instruction, drop the assembler invocation, preprocessor
flags/guards, and the cross assembler macro that's now unused.

This also avoids a recursive self reference in a follow up cleanup
patch.

Cc: Christian Biesinger <[email protected]>
Cc: Simon Marchi <[email protected]>
Signed-off-by: Nick Desaulniers <[email protected]>
Reviewed-by: Vincenzo Frascino <[email protected]>
Reviewed-by: Nathan Chancellor <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Will Deacon <[email protected]>

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arm64: vdso32: drop -no-integrated-as flag

Clang can assemble these files just fine; this is a relic from the top
level Makefile conditionally adding this. We no longer need --prefix,
--gcc-toolchai

arm64: vdso32: drop -no-integrated-as flag

Clang can assemble these files just fine; this is a relic from the top
level Makefile conditionally adding this. We no longer need --prefix,
--gcc-toolchain, or -Qunused-arguments flags either with this change, so
remove those too.

To test building:
$ ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- \
CROSS_COMPILE_COMPAT=arm-linux-gnueabi- make LLVM=1 LLVM_IAS=1 \
defconfig arch/arm64/kernel/vdso32/

Suggested-by: Nathan Chancellor <[email protected]>
Signed-off-by: Nick Desaulniers <[email protected]>
Reviewed-by: Nathan Chancellor <[email protected]>
Reviewed-by: Vincenzo Frascino <[email protected]>
Tested-by: Stephen Boyd <[email protected]>
Acked-by: Will Deacon <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Catalin Marinas <[email protected]>

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arm64: do not descend to vdso directories twice

arm64 descends into each vdso directory twice; first in vdso_prepare,
second during the ordinary build process.

PPC mimicked it and uncovered a probl

arm64: do not descend to vdso directories twice

arm64 descends into each vdso directory twice; first in vdso_prepare,
second during the ordinary build process.

PPC mimicked it and uncovered a problem [1]. In the first descend,
Kbuild directly visits the vdso directories, therefore it does not
inherit subdir-ccflags-y from upper directories.

This means the command line parameters may differ between the two.
If it happens, the offset values in the generated headers might be
different from real offsets of vdso.so in the kernel.

This potential danger should be avoided. The vdso directories are
built in the vdso_prepare stage, so the second descend is unneeded.

[1]: https://lore.kernel.org/linux-kbuild/CAK7LNARAkJ3_-4gX0VA2UkapbOftuzfSTVMBbgbw=HD8n7N+7w@mail.gmail.com/T/#ma10dcb961fda13f36d42d58fa6cb2da988b7e73a

Signed-off-by: Masahiro Yamada <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Will Deacon <[email protected]>

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arm64: lto: Strengthen READ_ONCE() to acquire when CONFIG_LTO=y

When building with LTO, there is an increased risk of the compiler
converting an address dependency headed by a READ_ONCE() invocation

arm64: lto: Strengthen READ_ONCE() to acquire when CONFIG_LTO=y

When building with LTO, there is an increased risk of the compiler
converting an address dependency headed by a READ_ONCE() invocation
into a control dependency and consequently allowing for harmful
reordering by the CPU.

Ensure that such transformations are harmless by overriding the generic
READ_ONCE() definition with one that provides acquire semantics when
building with LTO.

Acked-by: Peter Zijlstra (Intel) <[email protected]>
Acked-by: Mark Rutland <[email protected]>
Signed-off-by: Will Deacon <[email protected]>

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arm64: vdso32: Allow ld.lld to properly link the VDSO

As it stands now, the vdso32 Makefile hardcodes the linker to ld.bfd
using -fuse-ld=bfd with $(CC). This was taken from the arm vDSO
Makefile, a

arm64: vdso32: Allow ld.lld to properly link the VDSO

As it stands now, the vdso32 Makefile hardcodes the linker to ld.bfd
using -fuse-ld=bfd with $(CC). This was taken from the arm vDSO
Makefile, as the comment notes, done in commit d2b30cd4b722 ("ARM:
8384/1: VDSO: force use of BFD linker").

Commit fe00e50b2db8 ("ARM: 8858/1: vdso: use $(LD) instead of $(CC) to
link VDSO") changed that Makefile to use $(LD) directly instead of
through $(CC), which matches how the rest of the kernel operates. Since
then, LD=ld.lld means that the arm vDSO will be linked with ld.lld,
which has shown no problems so far.

Allow ld.lld to link this vDSO as we do the regular arm vDSO. To do
this, we need to do a few things:

* Add a LD_COMPAT variable, which defaults to $(CROSS_COMPILE_COMPAT)ld
with gcc and $(LD) if LLVM is 1, which will be ld.lld, or
$(CROSS_COMPILE_COMPAT)ld if not, which matches the logic of the main
Makefile. It is overrideable for further customization and avoiding
breakage.

* Eliminate cc32-ldoption, which matches commit 055efab3120b ("kbuild:
drop support for cc-ldoption").

With those, we can use $(LD_COMPAT) in cmd_ldvdso and change the flags
from compiler linker flags to linker flags directly. We eliminate
-mfloat-abi=soft because it is not handled by the linker.

Reported-by: Nick Desaulniers <[email protected]>
Signed-off-by: Nathan Chancellor <[email protected]>
Tested-by: Nick Desaulniers <[email protected]>
Reviewed-by: Nick Desaulniers <[email protected]>
Reviewed-by: Vincenzo Frascino <[email protected]>
Link: https://github.com/ClangBuiltLinux/linux/issues/1033
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Will Deacon <[email protected]>

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kbuild: explicitly specify the build id style

ld's --build-id defaults to "sha1" style, while lld defaults to "fast".
The build IDs are very different between the two, which may confuse
programs tha

kbuild: explicitly specify the build id style

ld's --build-id defaults to "sha1" style, while lld defaults to "fast".
The build IDs are very different between the two, which may confuse
programs that reference them.

Signed-off-by: Bill Wendling <[email protected]>
Acked-by: David S. Miller <[email protected]>
Signed-off-by: Masahiro Yamada <[email protected]>

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kbuild: remove cc-option test of -Werror=date-time

The minimal compiler versions, GCC 4.9 and Clang 10 support this flag.

Here is the godbolt:
https://godbolt.org/z/xvjcMa

Signed-off-by: Masahiro

kbuild: remove cc-option test of -Werror=date-time

The minimal compiler versions, GCC 4.9 and Clang 10 support this flag.

Here is the godbolt:
https://godbolt.org/z/xvjcMa

Signed-off-by: Masahiro Yamada <[email protected]>
Reviewed-by: Nathan Chancellor <[email protected]>
Acked-by: Will Deacon <[email protected]>

show more ...

kbuild: remove cc-option test of -fno-strict-overflow

The minimal compiler versions, GCC 4.9 and Clang 10 support this flag.

Here is the godbolt:
https://godbolt.org/z/odq8h9

Signed-off-by: Masahi

kbuild: remove cc-option test of -fno-strict-overflow

The minimal compiler versions, GCC 4.9 and Clang 10 support this flag.

Here is the godbolt:
https://godbolt.org/z/odq8h9

Signed-off-by: Masahiro Yamada <[email protected]>
Reviewed-by: Nathan Chancellor <[email protected]>
Acked-by: Will Deacon <[email protected]>

show more ...