Commit Graph

21 Commits

Author SHA1 Message Date
Masahiro Yamada f65a486821 kbuild: change module.order to list *.o instead of *.ko
scripts/Makefile.build replaces the suffix .o with .ko, then
scripts/Makefile.modpost calls the sed command to change .ko back
to the original .o suffix.

Instead of converting the suffixes back-and-forth, store the .o paths
in modules.order, and replace it with .ko in 'make modules_install'.

This avoids the unneeded sed command.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
2022-12-14 15:42:40 +09:00
Masahiro Yamada 6768fa4bcb kbuild: add read-file macro
Since GNU Make 4.2, $(file ...) supports the read operater '<', which
is useful to read a file without forking a new process. No warning is
shown even if the input file is missing.

For older Make versions, it falls back to the cat command.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
Reviewed-by: Alexander Lobakin <alexandr.lobakin@intel.com>
Tested-by: Alexander Lobakin <alexandr.lobakin@intel.com>
2022-12-13 22:29:10 +09:00
Masahiro Yamada a5db80c65d kbuild: do not sort after reading modules.order
modules.order lists modules in the deterministic order (that is why
"modules order"), and there is no duplication in the list.

$(sort ) is pointless.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
2022-12-13 22:28:58 +09:00
Linus Torvalds 8afc66e8d4 Kbuild updates for v6.1
- Remove potentially incomplete targets when Kbuid is interrupted by
    SIGINT etc. in case GNU Make may miss to do that when stderr is piped
    to another program.
 
  - Rewrite the single target build so it works more correctly.
 
  - Fix rpm-pkg builds with V=1.
 
  - List top-level subdirectories in ./Kbuild.
 
  - Ignore auto-generated __kstrtab_* and __kstrtabns_* symbols in kallsyms.
 
  - Avoid two different modules in lib/zstd/ having shared code, which
    potentially causes building the common code as build-in and modular
    back-and-forth.
 
  - Unify two modpost invocations to optimize the build process.
 
  - Remove head-y syntax in favor of linker scripts for placing particular
    sections in the head of vmlinux.
 
  - Bump the minimal GNU Make version to 3.82.
 
  - Clean up misc Makefiles and scripts.
 -----BEGIN PGP SIGNATURE-----
 
 iQJJBAABCgAzFiEEbmPs18K1szRHjPqEPYsBB53g2wYFAmM+4vcVHG1hc2FoaXJv
 eUBrZXJuZWwub3JnAAoJED2LAQed4NsGY2IQAInr0JUNnkkxwUSXtOcQuA3IK8RJ
 FbU9HXJRoV9H+7+l3SMlN7mIbrs5eE5fTY3iwQ3CVe139d1+1q7nvTMRv8owywJx
 GBgzswncuu1lk7iQQ//CxiqMwSCG8GJdYn1uDVy4I5jg3o+DtFZJtyq2Wb7pqsMm
 ZhZ4PozRN+idYQJSF6Vx/zEVLHI7quMBwfe4CME8/0Kg2+hnYzbXV/aUf0ED2emq
 zdCMDQgIOK5AhY+8qgMXKYnBUJMTqBp6LoR4p3ApfUkwRFY0sGa0/LK3U/B22OE7
 uWyR4fCUExGyerlcHEVev+9eBfmsLLPyqlchNwpSDOPf5OSdnKmgqJEBR/Cvx0eh
 URerPk7EHxyH3G8yi+cU2GtofNTGc5RHPRgJE2ADsQEi5TAUKGmbXMlsFRL/51Vn
 lTANZObBNa1d4enljF6TfTL5nuccOa+DKvXnH9fQ49t0QdtSikv6J/lGwilwm1Sr
 BctmCsySPuURZfkpI9OQnLuouloMXl9f7Q/+S39haS/tSgvPpyITyO71nxDnXn/s
 BbFObZJUk9QkqOACjBP1hNErTLt83uBxQ9z+rDCw/SbLIe4nw0wyneuygfHI5rI8
 3RZB2DbGauuJHX2Zs6YGS14SLSY33IsLqKR1/Vy3LrPvOHuEvNiOR8LITq5E0YCK
 OffK2Y5cIlXR0QWf
 =DHiN
 -----END PGP SIGNATURE-----

Merge tag 'kbuild-v6.1' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull Kbuild updates from Masahiro Yamada:

 - Remove potentially incomplete targets when Kbuid is interrupted by
   SIGINT etc in case GNU Make may miss to do that when stderr is piped
   to another program.

 - Rewrite the single target build so it works more correctly.

 - Fix rpm-pkg builds with V=1.

 - List top-level subdirectories in ./Kbuild.

 - Ignore auto-generated __kstrtab_* and __kstrtabns_* symbols in
   kallsyms.

 - Avoid two different modules in lib/zstd/ having shared code, which
   potentially causes building the common code as build-in and modular
   back-and-forth.

 - Unify two modpost invocations to optimize the build process.

 - Remove head-y syntax in favor of linker scripts for placing
   particular sections in the head of vmlinux.

 - Bump the minimal GNU Make version to 3.82.

 - Clean up misc Makefiles and scripts.

* tag 'kbuild-v6.1' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (41 commits)
  docs: bump minimal GNU Make version to 3.82
  ia64: simplify esi object addition in Makefile
  Revert "kbuild: Check if linker supports the -X option"
  kbuild: rebuild .vmlinux.export.o when its prerequisite is updated
  kbuild: move modules.builtin(.modinfo) rules to Makefile.vmlinux_o
  zstd: Fixing mixed module-builtin objects
  kallsyms: ignore __kstrtab_* and __kstrtabns_* symbols
  kallsyms: take the input file instead of reading stdin
  kallsyms: drop duplicated ignore patterns from kallsyms.c
  kbuild: reuse mksysmap output for kallsyms
  mksysmap: update comment about __crc_*
  kbuild: remove head-y syntax
  kbuild: use obj-y instead extra-y for objects placed at the head
  kbuild: hide error checker logs for V=1 builds
  kbuild: re-run modpost when it is updated
  kbuild: unify two modpost invocations
  kbuild: move vmlinux.o rule to the top Makefile
  kbuild: move .vmlinux.objs rule to Makefile.modpost
  kbuild: list sub-directories in ./Kbuild
  Makefile.compiler: replace cc-ifversion with compiler-specific macros
  ...
2022-10-10 12:00:45 -07:00
Masahiro Yamada f73edc8951 kbuild: unify two modpost invocations
Currently, modpost is executed twice; first for vmlinux, second
for modules.

This commit merges them.

Current build flow
==================

  1) build obj-y and obj-m objects
    2) link vmlinux.o
      3) modpost for vmlinux
        4) link vmlinux
          5) modpost for modules
            6) link modules (*.ko)

The build steps 1) through 6) are serialized, that is, modules are
built after vmlinux. You do not get benefits of parallel builds when
scripts/link-vmlinux.sh is being run.

New build flow
==============

  1) build obj-y and obj-m objects
    2) link vmlinux.o
      3) modpost for vmlinux and modules
        4a) link vmlinux
        4b) link modules (*.ko)

In the new build flow, modpost is invoked just once.

vmlinux and modules are built in parallel. One exception is
CONFIG_DEBUG_INFO_BTF_MODULES=y, where modules depend on vmlinux.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
2022-09-29 06:07:58 +09:00
Miguel Ojeda 2f7ab1267d Kbuild: add Rust support
Having most of the new files in place, we now enable Rust support
in the build system, including `Kconfig` entries related to Rust,
the Rust configuration printer and a few other bits.

Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Co-developed-by: Alex Gaynor <alex.gaynor@gmail.com>
Signed-off-by: Alex Gaynor <alex.gaynor@gmail.com>
Co-developed-by: Finn Behrens <me@kloenk.de>
Signed-off-by: Finn Behrens <me@kloenk.de>
Co-developed-by: Adam Bratschi-Kaye <ark.email@gmail.com>
Signed-off-by: Adam Bratschi-Kaye <ark.email@gmail.com>
Co-developed-by: Wedson Almeida Filho <wedsonaf@google.com>
Signed-off-by: Wedson Almeida Filho <wedsonaf@google.com>
Co-developed-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Co-developed-by: Sven Van Asbroeck <thesven73@gmail.com>
Signed-off-by: Sven Van Asbroeck <thesven73@gmail.com>
Co-developed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Gary Guo <gary@garyguo.net>
Co-developed-by: Boris-Chengbiao Zhou <bobo1239@web.de>
Signed-off-by: Boris-Chengbiao Zhou <bobo1239@web.de>
Co-developed-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Co-developed-by: Douglas Su <d0u9.su@outlook.com>
Signed-off-by: Douglas Su <d0u9.su@outlook.com>
Co-developed-by: Dariusz Sosnowski <dsosnowski@dsosnowski.pl>
Signed-off-by: Dariusz Sosnowski <dsosnowski@dsosnowski.pl>
Co-developed-by: Antonio Terceiro <antonio.terceiro@linaro.org>
Signed-off-by: Antonio Terceiro <antonio.terceiro@linaro.org>
Co-developed-by: Daniel Xu <dxu@dxuuu.xyz>
Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
Co-developed-by: Björn Roy Baron <bjorn3_gh@protonmail.com>
Signed-off-by: Björn Roy Baron <bjorn3_gh@protonmail.com>
Co-developed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
Signed-off-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
2022-09-28 09:02:20 +02:00
Masahiro Yamada c25e1c5582 kbuild: do not create *.prelink.o for Clang LTO or IBT
When CONFIG_LTO_CLANG=y, additional intermediate *.prelink.o is created
for each module. Also, objtool is postponed until LLVM IR is converted
to ELF.

CONFIG_X86_KERNEL_IBT works in a similar way to postpone objtool until
objects are merged together.

This commit stops generating *.prelink.o, so the build flow will look
similar with/without LTO.

The following figures show how the LTO build currently works, and
how this commit is changing it.

Current build flow
==================

 [1] single-object module

                                      $(LD)
           $(CC)                     +objtool              $(LD)
    foo.c --------------------> foo.o -----> foo.prelink.o -----> foo.ko
                              (LLVM IR)          (ELF)       |    (ELF)
                                                             |
                                                 foo.mod.o --/
                                                 (LLVM IR)

 [2] multi-object module
                                      $(LD)
           $(CC)         $(AR)       +objtool               $(LD)
    foo1.c -----> foo1.o -----> foo.o -----> foo.prelink.o -----> foo.ko
                           |  (archive)          (ELF)       |    (ELF)
    foo2.c -----> foo2.o --/                                 |
                 (LLVM IR)                       foo.mod.o --/
                                                 (LLVM IR)

  One confusion is that foo.o in multi-object module is an archive
  despite of its suffix.

New build flow
==============

 [1] single-object module

  Since there is only one object, there is no need to keep the LLVM IR.
  Use $(CC)+$(LD) to generate an ELF object in one build rule. When LTO
  is disabled, $(LD) is unneeded because $(CC) produces an ELF object.

               $(CC)+$(LD)+objtool              $(LD)
    foo.c ----------------------------> foo.o ---------> foo.ko
                                        (ELF)     |      (ELF)
                                                  |
                                      foo.mod.o --/
                                      (LLVM IR)

 [2] multi-object module

  Previously, $(AR) was used to combine LLVM IR files into an archive,
  but there was no technical reason to do so. Use $(LD) to merge them
  into a single ELF object.

                               $(LD)
             $(CC)            +objtool          $(LD)
    foo1.c ---------> foo1.o ---------> foo.o ---------> foo.ko
                                 |      (ELF)     |      (ELF)
    foo2.c ---------> foo2.o ----/                |
                     (LLVM IR)        foo.mod.o --/
                                      (LLVM IR)

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM-14 (x86-64)
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
2022-05-29 18:39:35 +09:00
Jiri Olsa 9741e07ece kbuild: Unify options for BTF generation for vmlinux and modules
Using new PAHOLE_FLAGS variable to pass extra arguments to
pahole for both vmlinux and modules BTF data generation.

Adding new scripts/pahole-flags.sh script that detect and
prints pahole options.

[ fixed issues found by kernel test robot ]

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20211029125729.70002-1-jolsa@kernel.org
2021-11-01 18:09:58 -07:00
Kumar Kartikeya Dwivedi 0e32dfc80b bpf: Enable TCP congestion control kfunc from modules
This commit moves BTF ID lookup into the newly added registration
helper, in a way that the bbr, cubic, and dctcp implementation set up
their sets in the bpf_tcp_ca kfunc_btf_set list, while the ones not
dependent on modules are looked up from the wrapper function.

This lifts the restriction for them to be compiled as built in objects,
and can be loaded as modules if required. Also modify Makefile.modfinal
to call resolve_btfids for each module.

Note that since kernel kfunc_ids never overlap with module kfunc_ids, we
only match the owner for module btf id sets.

See following commits for background on use of:

 CONFIG_X86 ifdef:
 569c484f99 (bpf: Limit static tcp-cc functions in the .BTF_ids list to x86)

 CONFIG_DYNAMIC_FTRACE ifdef:
 7aae231ac9 (bpf: tcp: Limit calling some tcp cc functions to CONFIG_DYNAMIC_FTRACE)

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211002011757.311265-6-memxor@gmail.com
2021-10-05 17:07:41 -07:00
Sami Tolvanen 850ded46c6 kbuild: Fix TRIM_UNUSED_KSYMS with LTO_CLANG
With CONFIG_LTO_CLANG, we currently link modules into native
code just before modpost, which means with TRIM_UNUSED_KSYMS
enabled, we still look at the LLVM bitcode in the .o files when
generating the list of used symbols. As the bitcode doesn't
yet have calls to compiler intrinsics and llvm-nm doesn't see
function references that only exist in function-level inline
assembly, we currently need a whitelist for TRIM_UNUSED_KSYMS to
work with LTO.

This change moves module LTO linking to happen earlier, and
thus avoids the issue with LLVM bitcode and TRIM_UNUSED_KSYMS
entirely, allowing us to also drop the whitelist from
gen_autoksyms.sh.

Link: https://github.com/ClangBuiltLinux/linux/issues/1369
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Alexander Lobakin <alobakin@pm.me>
Tested-by: Alexander Lobakin <alobakin@pm.me>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2021-09-03 08:12:39 +09:00
Linus Torvalds 81361b837a Kbuild updates for v5.14
- Increase the -falign-functions alignment for the debug option.
 
  - Remove ugly libelf checks from the top Makefile.
 
  - Make the silent build (-s) more silent.
 
  - Re-compile the kernel if KBUILD_BUILD_TIMESTAMP is specified.
 
  - Various script cleanups
 -----BEGIN PGP SIGNATURE-----
 
 iQJJBAABCgAzFiEEbmPs18K1szRHjPqEPYsBB53g2wYFAmDon90VHG1hc2FoaXJv
 eUBrZXJuZWwub3JnAAoJED2LAQed4NsGWFUP/RGNwlGD/YV1xg0ZmM0/ynBzzOy2
 3dcr3etJZpipQDeqnHy3jt0esgMVlbkTdrHvP+2hpNaeXFwjF1fDHjhur9m8ZkVD
 efOA6nugOnNwhy2G3BvtCJv+Vhb+KZ0nNLB27z3Bl0LGP6LJdMRNAxFBJMv4k3aR
 F3sABugwCpnT2/YtuprxRl2/3/CyLur5NjY24FD+ugON3JIWfl6ETbHeFmxr1JE4
 mE+zaN5AwYuSuH9LpdRy85XVCcW/FFqP/DwOFllVvCCCNvvS0KWYSNHWfEsKdR75
 hmAAaS/rpi2eaL0vp88sNhAtYnhMSf+uFu0fyfYeWZuJqMt4Xz5xZKAzDsifCdif
 aQ6UEPDjiKABh9gpX26BMd2CXzkGR+L4qZ7iBPfO586Iy7opajrFX9kIj5U7ZtCl
 wsPat/9+18xpVJOTe0sss3idId7Ft4cRoW5FQMEAW2EWJ9fXAG1yDxEREj1V5gFx
 sMXtpmCoQag968qjfARvP08s3MB1P4Ij6tXcioGqHuEWeJLxOMK/KWyafQUg611d
 0kSWNO0OMo+odBj6j/vM+MIIaPhgwtZnPgw2q4uHGMcemzQxaEvGW+G/5a5qEpTv
 SKm8W24wXplNot4tuTGWq5/jANRJcMvVsyC48DYT81OZEOWrIc0kDV4v4qZToTxW
 97jn1NKa2H6L0J1V
 =Za8V
 -----END PGP SIGNATURE-----

Merge tag 'kbuild-v5.14' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull Kbuild updates from Masahiro Yamada:

 - Increase the -falign-functions alignment for the debug option.

 - Remove ugly libelf checks from the top Makefile.

 - Make the silent build (-s) more silent.

 - Re-compile the kernel if KBUILD_BUILD_TIMESTAMP is specified.

 - Various script cleanups

* tag 'kbuild-v5.14' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (27 commits)
  scripts: add generic syscallnr.sh
  scripts: check duplicated syscall number in syscall table
  sparc: syscalls: use pattern rules to generate syscall headers
  parisc: syscalls: use pattern rules to generate syscall headers
  nds32: add arch/nds32/boot/.gitignore
  kbuild: mkcompile_h: consider timestamp if KBUILD_BUILD_TIMESTAMP is set
  kbuild: modpost: Explicitly warn about unprototyped symbols
  kbuild: remove trailing slashes from $(KBUILD_EXTMOD)
  kconfig.h: explain IS_MODULE(), IS_ENABLED()
  kconfig: constify long_opts
  scripts/setlocalversion: simplify the short version part
  scripts/setlocalversion: factor out 12-chars hash construction
  scripts/setlocalversion: add more comments to -dirty flag detection
  scripts/setlocalversion: remove workaround for old make-kpkg
  scripts/setlocalversion: remove mercurial, svn and git-svn supports
  kbuild: clean up ${quiet} checks in shell scripts
  kbuild: sink stdout from cmd for silent build
  init: use $(call cmd,) for generating include/generated/compile.h
  kbuild: merge scripts/mkmakefile to top Makefile
  sh: move core-y in arch/sh/Makefile to arch/sh/Kbuild
  ...
2021-07-10 11:01:38 -07:00
Javier Martinez Canillas ff2e6efda0 kbuild: Quote OBJCOPY var to avoid a pahole call break the build
The ccache tool can be used to speed up cross-compilation, by calling the
compiler and binutils through ccache. For example, following should work:

    $ export ARCH=arm64 CROSS_COMPILE="ccache aarch64-linux-gnu-"

    $ make M=drivers/gpu/drm/rockchip/

but pahole fails to extract the BTF info from DWARF, breaking the build:

      CC [M]  drivers/gpu/drm/rockchip//rockchipdrm.mod.o
      LD [M]  drivers/gpu/drm/rockchip//rockchipdrm.ko
      BTF [M] drivers/gpu/drm/rockchip//rockchipdrm.ko
    aarch64-linux-gnu-objcopy: invalid option -- 'J'
    Usage: aarch64-linux-gnu-objcopy [option(s)] in-file [out-file]
     Copies a binary file, possibly transforming it in the process
    ...
    make[1]: *** [scripts/Makefile.modpost:156: __modpost] Error 2
    make: *** [Makefile:1866: modules] Error 2

this fails because OBJCOPY is set to "ccache aarch64-linux-gnu-copy" and
later pahole is executed with the following command line:

    LLVM_OBJCOPY=$(OBJCOPY) $(PAHOLE) -J --btf_base vmlinux $@

which gets expanded to:

    LLVM_OBJCOPY=ccache aarch64-linux-gnu-objcopy pahole -J ...

instead of:

    LLVM_OBJCOPY="ccache aarch64-linux-gnu-objcopy" pahole -J ...

Fixes: 5f9ae91f7c ("kbuild: Build kernel module BTFs if BTF is enabled and pahole supports it")
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Link: https://lore.kernel.org/bpf/20210526215228.3729875-1-javierm@redhat.com
2021-05-27 11:32:56 -07:00
Masahiro Yamada 0d989ac2c9 kbuild: remove libelf checks from top Makefile
I do not see a good reason why only the libelf development package must
be so carefully checked.

Kbuild generally does not check host tools or libraries.

For example, x86_64 defconfig fails to build with no libssl development
package installed.

scripts/extract-cert.c:21:10: fatal error: openssl/bio.h: No such file or directory
   21 | #include <openssl/bio.h>
      |          ^~~~~~~~~~~~~~~

To solve the build error, you need to install libssl-dev or openssl-devel
package, depending on your distribution.

'apt-file search', 'dnf provides', etc. is your frined to find a proper
package to install.

This commit removes all the libelf checks from the top Makefile.

If libelf is missing, objtool will fail to build in a similar pattern:

.../linux/tools/objtool/include/objtool/elf.h:10:10: fatal error: gelf.h: No such file or directory
   10 | #include <gelf.h>

You need to install libelf-dev, libelf-devel, or elfutils-libelf-devel
to proceed.

Another remarkable change is, CONFIG_STACK_VALIDATION (without
CONFIG_UNWINDER_ORC) previously continued to build with a warning,
but now it will treat missing libelf as an error.

This is just a one-time installation, so it should not hurt to break
a build and make a user install the package.

BTW, the traditional way to handle such checks is autotool, but according
to [1], I do not expect the kernel build would have similar scripting
like './configure' does.

[1]: https://lore.kernel.org/lkml/CA+55aFzr2HTZVOuzpHYDwmtRJLsVzE-yqg2DHpHi_9ePsYp5ug@mail.gmail.com/

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
2021-05-24 12:06:51 +09:00
Sami Tolvanen cf68fffb66 add support for Clang CFI
This change adds support for Clang’s forward-edge Control Flow
Integrity (CFI) checking. With CONFIG_CFI_CLANG, the compiler
injects a runtime check before each indirect function call to ensure
the target is a valid function with the correct static type. This
restricts possible call targets and makes it more difficult for
an attacker to exploit bugs that allow the modification of stored
function pointers. For more details, see:

  https://clang.llvm.org/docs/ControlFlowIntegrity.html

Clang requires CONFIG_LTO_CLANG to be enabled with CFI to gain
visibility to possible call targets. Kernel modules are supported
with Clang’s cross-DSO CFI mode, which allows checking between
independently compiled components.

With CFI enabled, the compiler injects a __cfi_check() function into
the kernel and each module for validating local call targets. For
cross-module calls that cannot be validated locally, the compiler
calls the global __cfi_slowpath_diag() function, which determines
the target module and calls the correct __cfi_check() function. This
patch includes a slowpath implementation that uses __module_address()
to resolve call targets, and with CONFIG_CFI_CLANG_SHADOW enabled, a
shadow map that speeds up module look-ups by ~3x.

Clang implements indirect call checking using jump tables and
offers two methods of generating them. With canonical jump tables,
the compiler renames each address-taken function to <function>.cfi
and points the original symbol to a jump table entry, which passes
__cfi_check() validation. This isn’t compatible with stand-alone
assembly code, which the compiler doesn’t instrument, and would
result in indirect calls to assembly code to fail. Therefore, we
default to using non-canonical jump tables instead, where the compiler
generates a local jump table entry <function>.cfi_jt for each
address-taken function, and replaces all references to the function
with the address of the jump table entry.

Note that because non-canonical jump table addresses are local
to each component, they break cross-module function address
equality. Specifically, the address of a global function will be
different in each module, as it's replaced with the address of a local
jump table entry. If this address is passed to a different module,
it won’t match the address of the same function taken there. This
may break code that relies on comparing addresses passed from other
components.

CFI checking can be disabled in a function with the __nocfi attribute.
Additionally, CFI can be disabled for an entire compilation unit by
filtering out CC_FLAGS_CFI.

By default, CFI failures result in a kernel panic to stop a potential
exploit. CONFIG_CFI_PERMISSIVE enables a permissive mode, where the
kernel prints out a rate-limited warning instead, and allows execution
to continue. This option is helpful for locating type mismatches, but
should only be enabled during development.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210408182843.1754385-2-samitolvanen@google.com
2021-04-08 16:04:20 -07:00
Sami Tolvanen b1a1a1a09b kbuild: lto: postpone objtool
With LTO, LLVM bitcode won't be compiled into native code until
modpost_link, or modfinal for modules. This change postpones calls
to objtool until after these steps, and moves objtool_args to
Makefile.lib, so the arguments can be reused in Makefile.modfinal.

As we didn't have objects to process earlier, we use --duplicate
when processing vmlinux.o. This change also disables unreachable
instruction warnings with LTO to avoid warnings about the int3
padding between functions.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
2021-02-23 12:46:57 -08:00
Sami Tolvanen dc5723b02e kbuild: add support for Clang LTO
This change adds build system support for Clang's Link Time
Optimization (LTO). With -flto, instead of ELF object files, Clang
produces LLVM bitcode, which is compiled into native code at link
time, allowing the final binary to be optimized globally. For more
details, see:

  https://llvm.org/docs/LinkTimeOptimization.html

The Kconfig option CONFIG_LTO_CLANG is implemented as a choice,
which defaults to LTO being disabled. To use LTO, the architecture
must select ARCH_SUPPORTS_LTO_CLANG and support:

  - compiling with Clang,
  - compiling all assembly code with Clang's integrated assembler,
  - and linking with LLD.

While using CONFIG_LTO_CLANG_FULL results in the best runtime
performance, the compilation is not scalable in time or
memory. CONFIG_LTO_CLANG_THIN enables ThinLTO, which allows
parallel optimization and faster incremental builds. ThinLTO is
used by default if the architecture also selects
ARCH_SUPPORTS_LTO_CLANG_THIN:

  https://clang.llvm.org/docs/ThinLTO.html

To enable LTO, LLVM tools must be used to handle bitcode files, by
passing LLVM=1 and LLVM_IAS=1 options to make:

  $ make LLVM=1 LLVM_IAS=1 defconfig
  $ scripts/config -e LTO_CLANG_THIN
  $ make LLVM=1 LLVM_IAS=1

To prepare for LTO support with other compilers, common parts are
gated behind the CONFIG_LTO option, and LTO can be disabled for
specific files by filtering out CC_FLAGS_LTO.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20201211184633.3213045-3-samitolvanen@google.com
2021-01-14 08:21:08 -08:00
Andrii Nakryiko e732b538f4 kbuild: Skip module BTF generation for out-of-tree external modules
In some modes of operation, Kbuild allows to build modules without having
vmlinux image around. In such case, generation of module BTF is impossible.
This patch changes the behavior to emit a warning about impossibility of
generating kernel module BTF, instead of breaking the build. This is especially
important for out-of-tree external module builds.

In vmlinux-less mode:

$ make clean
$ make modules_prepare
$ touch drivers/acpi/button.c
$ make M=drivers/acpi
...
  CC [M]  drivers/acpi/button.o
  MODPOST drivers/acpi/Module.symvers
  LD [M]  drivers/acpi/button.ko
  BTF [M] drivers/acpi/button.ko
Skipping BTF generation for drivers/acpi/button.ko due to unavailability of vmlinux
...
$ readelf -S ~/linux-build/default/drivers/acpi/button.ko | grep BTF -A1
... empty ...

Now with normal build:

$ make all
...
LD [M]  drivers/acpi/button.ko
BTF [M] drivers/acpi/button.ko
...
$ readelf -S ~/linux-build/default/drivers/acpi/button.ko | grep BTF -A1
  [60] .BTF              PROGBITS         0000000000000000  00029310
       000000000000ab3f  0000000000000000           0     0     1

Fixes: 5f9ae91f7c ("kbuild: Build kernel module BTFs if BTF is enabled and pahole supports it")
Reported-by: Bruce Allan <bruce.w.allan@intel.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Jessica Yu <jeyu@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Link: https://lore.kernel.org/bpf/20201121070829.2612884-1-andrii@kernel.org
2020-11-25 00:05:01 +01:00
Andrii Nakryiko 5f9ae91f7c kbuild: Build kernel module BTFs if BTF is enabled and pahole supports it
Detect if pahole supports split BTF generation, and generate BTF for each
selected kernel module, if it does. This is exposed to Makefiles and C code as
CONFIG_DEBUG_INFO_BTF_MODULES flag.

Kernel module BTF has to be re-generated if either vmlinux's BTF changes or
module's .ko changes. To achieve that, I needed a helper similar to
if_changed, but that would allow to filter out vmlinux from the list of
updated dependencies for .ko building. I've put it next to the only place that
uses and needs it, but it might be a better idea to just add it along the
other if_changed variants into scripts/Kbuild.include.

Each kernel module's BTF deduplication is pretty fast, as it does only
incremental BTF deduplication on top of already deduplicated vmlinux BTF. To
show the added build time, I've first ran make only just built kernel (to
establish the baseline) and then forced only BTF re-generation, without
regenerating .ko files. The build was performed with -j60 parallelization on
56-core machine. The final time also includes bzImage building, so it's not
a pure BTF overhead.

$ time make -j60
...
make -j60  27.65s user 10.96s system 782% cpu 4.933 total
$ touch ~/linux-build/default/vmlinux && time make -j60
...
make -j60  123.69s user 27.85s system 1566% cpu 9.675 total

So 4.6 seconds real time, with noticeable part spent in compressed vmlinux and
bzImage building.

To show size savings, I've built my kernel configuration with about 700 kernel
modules with full BTF per each kernel module (without deduplicating against
vmlinux) and with split BTF against deduplicated vmlinux (approach in this
patch). Below are top 10 modules with biggest BTF sizes. And total size of BTF
data across all kernel modules.

It shows that split BTF "compresses" 115MB down to 5MB total. And the biggest
kernel modules get a downsize from 500-570KB down to 200-300KB.

FULL BTF
========

$ for f in $(find . -name '*.ko'); do size -A -d $f | grep BTF | awk '{print $2}'; done | awk '{ s += $1 } END { print s }'
115710691

$ for f in $(find . -name '*.ko'); do printf "%s %d\n" $f $(size -A -d $f | grep BTF | awk '{print $2}'); done | sort -nr -k2 | head -n10
./drivers/gpu/drm/i915/i915.ko 570570
./drivers/net/ethernet/mellanox/mlx5/core/mlx5_core.ko 520240
./drivers/gpu/drm/radeon/radeon.ko 503849
./drivers/infiniband/hw/mlx5/mlx5_ib.ko 491777
./fs/xfs/xfs.ko 411544
./drivers/net/ethernet/intel/i40e/i40e.ko 403904
./drivers/net/ethernet/broadcom/bnx2x/bnx2x.ko 398754
./drivers/infiniband/core/ib_core.ko 397224
./fs/cifs/cifs.ko 386249
./fs/nfsd/nfsd.ko 379738

SPLIT BTF
=========

$ for f in $(find . -name '*.ko'); do size -A -d $f | grep BTF | awk '{print $2}'; done | awk '{ s += $1 } END { print s }'
5194047

$ for f in $(find . -name '*.ko'); do printf "%s %d\n" $f $(size -A -d $f | grep BTF | awk '{print $2}'); done | sort -nr -k2 | head -n10
./drivers/gpu/drm/i915/i915.ko 293206
./drivers/gpu/drm/radeon/radeon.ko 282103
./fs/xfs/xfs.ko 222150
./drivers/net/ethernet/mellanox/mlx5/core/mlx5_core.ko 198503
./drivers/infiniband/hw/mlx5/mlx5_ib.ko 198356
./drivers/net/ethernet/broadcom/bnx2x/bnx2x.ko 113444
./fs/cifs/cifs.ko 109379
./arch/x86/kvm/kvm.ko 100225
./drivers/gpu/drm/drm.ko 94827
./drivers/infiniband/core/ib_core.ko 91188

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20201110011932.3201430-4-andrii@kernel.org
2020-11-10 15:25:53 -08:00
Masahiro Yamada 596b0474d3 kbuild: preprocess module linker script
There was a request to preprocess the module linker script like we
do for the vmlinux one. (https://lkml.org/lkml/2020/8/21/512)

The difference between vmlinux.lds and module.lds is that the latter
is needed for external module builds, thus must be cleaned up by
'make mrproper' instead of 'make clean'. Also, it must be created
by 'make modules_prepare'.

You cannot put it in arch/$(SRCARCH)/kernel/, which is cleaned up by
'make clean'. I moved arch/$(SRCARCH)/kernel/module.lds to
arch/$(SRCARCH)/include/asm/module.lds.h, which is included from
scripts/module.lds.S.

scripts/module.lds is fine because 'make clean' keeps all the
build artifacts under scripts/.

You can add arch-specific sections in <asm/module.lds.h>.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Tested-by: Jessica Yu <jeyu@kernel.org>
Acked-by: Will Deacon <will@kernel.org>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Palmer Dabbelt <palmerdabbelt@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Jessica Yu <jeyu@kernel.org>
2020-09-25 00:36:41 +09:00
Masahiro Yamada eb27ea5ce7 kbuild: move modkern_{c,a}flags to Makefile.lib from Makefile.build
Makefile.lib is included by Makefile.modfinal as well as Makefile.build.

Move modkern_cflags to Makefile.lib in order to simplify cmd_cc_o_c
in Makefile.modfinal. Move modkern_cflags as well for consistency.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2019-08-22 01:14:11 +09:00
Masahiro Yamada 9b9a3f20cb kbuild: split final module linking out into Makefile.modfinal
I think splitting the modpost and linking modules into separate
Makefiles will be useful especially when more complex build steps
come in. The main motivation of this commit is to integrate the
proposed klp-convert feature cleanly.

I moved the logging 'Building modules, stage 2.' to Makefile.modpost
to avoid the code duplication although I do not know whether or not
this message is needed in the first place.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2019-08-22 01:08:15 +09:00