Commit Graph

6 Commits

Author SHA1 Message Date
Nick Desaulniers
3519c4d6e0 Documentation: add minimum clang/llvm version
Based on a vote at the LLVM BoF at Plumbers 2020, we decided to start
small, supporting just one formal upstream release of LLVM for now.

We can probably widen the support window of supported versions over
time.  Also, note that LLVM's release process is different than GCC's.
GCC tends to have 1 major release per year while releasing minor updates
to the past 3 major versions.  LLVM tends to support one major release
and one minor release every six months.

Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20200826191555.3350406-1-ndesaulniers@google.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2020-08-31 16:30:20 -06:00
Alexander A. Klimov
16a122c743 kbuild: Replace HTTP links with HTTPS ones
Rationale:
Reduces attack surface on kernel devs opening the links for MITM
as HTTPS traffic is much harder to manipulate.

Deterministic algorithm:
For each file:
  If not .svg:
    For each line:
      If doesn't contain `\bxmlns\b`:
        For each link, `\bhttp://[^# \t\r\n]*(?:\w|/)`:
	  If neither `\bgnu\.org/license`, nor `\bmozilla\.org/MPL\b`:
            If both the HTTP and HTTPS versions
            return 200 OK and serve the same content:
              Replace HTTP with HTTPS.

Signed-off-by: Alexander A. Klimov <grandmaster@al2klimov.de>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2020-08-10 01:32:59 +09:00
Masahiro Yamada
a0d1c951ef kbuild: support LLVM=1 to switch the default tools to Clang/LLVM
As Documentation/kbuild/llvm.rst implies, building the kernel with a
full set of LLVM tools gets very verbose and unwieldy.

Provide a single switch LLVM=1 to use Clang and LLVM tools instead
of GCC and Binutils. You can pass it from the command line or as an
environment variable.

Please note LLVM=1 does not turn on the integrated assembler. You need
to pass LLVM_IAS=1 to use it. When the upstream kernel is ready for the
integrated assembler, I think we can make it default.

We discussed what we need, and we agreed to go with a simple boolean
flag that switches both target and host tools:

  https://lkml.org/lkml/2020/3/28/494
  https://lkml.org/lkml/2020/4/3/43

Some items discussed, but not adopted:

- LLVM_DIR

  When multiple versions of LLVM are installed, I just thought supporting
  LLVM_DIR=/path/to/my/llvm/bin/ might be useful.

  CC      = $(LLVM_DIR)clang
  LD      = $(LLVM_DIR)ld.lld
    ...

  However, we can handle this by modifying PATH. So, we decided to not do
  this.

- LLVM_SUFFIX

  Some distributions (e.g. Debian) package specific versions of LLVM with
  naming conventions that use the version as a suffix.

  CC      = clang$(LLVM_SUFFIX)
  LD      = ld.lld(LLVM_SUFFIX)
    ...

  will allow a user to pass LLVM_SUFFIX=-11 to use clang-11 etc.,
  but the suffixed versions in /usr/bin/ are symlinks to binaries in
  /usr/lib/llvm-#/bin/, so this can also be handled by PATH.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Tested-by: Nathan Chancellor <natechancellor@gmail.com> # build
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
2020-04-09 03:18:21 +09:00
Masahiro Yamada
7e20e47c70 kbuild: replace AS=clang with LLVM_IAS=1
The 'AS' variable is unused for building the kernel. Only the remaining
usage is to turn on the integrated assembler. A boolean flag is a better
fit for this purpose.

AS=clang was added for experts. So, I replaced it with LLVM_IAS=1,
breaking the backward compatibility.

Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
2020-04-09 03:18:09 +09:00
Fangrui Song
0f44fbc162 Documentation/llvm: fix the name of llvm-size
The tool is called llvm-size, not llvm-objsize.

Fixes: fcf1b6a35c ("Documentation/llvm: add documentation on building w/ Clang/LLVM")
Signed-off-by: Fangrui Song <maskray@google.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2020-04-09 00:13:45 +09:00
Nick Desaulniers
fcf1b6a35c Documentation/llvm: add documentation on building w/ Clang/LLVM
Added to kbuild documentation. Provides more official info on building
kernels with Clang and LLVM than our wiki.

Suggested-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2020-03-03 20:49:21 +09:00