[PATCH 1/1] docs: makefile: move rustdoc check to the build wrapper

[PATCH 1/1] docs: makefile: move rustdoc check to the build wrapper

[Mauro Carvalho Chehab]

The makefile logic to detect if rust is enabled is not working
the way it was expected. Move it to be inside the wrapper
script.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
---
 Documentation/Makefile          |  6 -----
 tools/docs/sphinx-build-wrapper | 41 +++++++++++++++++++++++++--------
 2 files changed, 32 insertions(+), 15 deletions(-)

diff --git a/Documentation/Makefile b/Documentation/Makefile
index d514ab6761dc..d4c42aa89439 100644
--- a/Documentation/Makefile
+++ b/Documentation/Makefile
@@ -42,12 +42,6 @@ FONTS_CONF_DENY_VF ?= $(HOME)/deny-vf
 # User-friendly check for sphinx-build
 HAVE_SPHINX := $(shell if which $(SPHINXBUILD) >/dev/null 2>&1; then echo 1; else echo 0; fi)
 
-ifneq ($(wildcard $(srctree)/.config),)
-ifeq ($(CONFIG_RUST),y)
-	RUSTDOC=--rustdoc
-endif
-endif
-
 ifeq ($(HAVE_SPHINX),0)
 
 .DEFAULT:
diff --git a/tools/docs/sphinx-build-wrapper b/tools/docs/sphinx-build-wrapper
index 1efaca3d16aa..a554176b5a06 100755
--- a/tools/docs/sphinx-build-wrapper
+++ b/tools/docs/sphinx-build-wrapper
@@ -119,6 +119,29 @@ class SphinxBuilder:
 
         return path
 
+    def check_rust(self):
+        """
+        Checks if Rust is enabled
+        """
+        self.rustdoc = False
+
+        config = os.path.join(self.srctree, ".config")
+
+        if not os.path.isfile(config):
+            return
+
+        re_rust = re.compile(r"CONFIG_RUST=(m|y)")
+
+        try:
+            with open(config, "r", encoding="utf-8") as fp:
+                for line in fp:
+                    if re_rust.match(line):
+                        self.rustdoc = True
+                        return
+
+        except OSError as e:
+            print(f"Failed to open {config}", file=sys.stderr)
+
     def get_sphinx_extra_opts(self, n_jobs):
         """
         Get the number of jobs to be used for docs build passed via command
@@ -236,6 +259,8 @@ class SphinxBuilder:
 
         self.get_sphinx_extra_opts(n_jobs)
 
+        self.check_rust()
+
         #
         # If venv command line argument is specified, run Sphinx from venv
         #
@@ -306,7 +331,7 @@ class SphinxBuilder:
 
             return subprocess.call(cmd, *args, **pwargs)
 
-    def handle_html(self, css, output_dir, rustdoc):
+    def handle_html(self, css, output_dir):
         """
         Extra steps for HTML and epub output.
 
@@ -327,7 +352,8 @@ class SphinxBuilder:
             except (OSError, IOError) as e:
                 print(f"Warning: Failed to copy CSS: {e}", file=sys.stderr)
 
-        if rustdoc:
+        if self.rustdoc:
+            print("Building rust docs")
             if "MAKE" in self.env:
                 cmd = [self.env["MAKE"]]
             else:
@@ -622,7 +648,7 @@ class SphinxBuilder:
         shutil.rmtree(self.builddir, ignore_errors=True)
 
     def build(self, target, sphinxdirs=None,
-              theme=None, css=None, paper=None, deny_vf=None, rustdoc=False,
+              theme=None, css=None, paper=None, deny_vf=None,
               skip_sphinx=False):
         """
         Build documentation using Sphinx. This is the core function of this
@@ -671,7 +697,7 @@ class SphinxBuilder:
 
             args.extend(["-D", f"latex_elements.papersize={paper}paper"])
 
-        if rustdoc:
+        if self.rustdoc:
             args.extend(["-t", "rustdoc"])
 
         if not sphinxdirs:
@@ -749,7 +775,7 @@ class SphinxBuilder:
             # Ensure that each html/epub output will have needed static files
             #
             if target in ["htmldocs", "epubdocs"]:
-                self.handle_html(css, output_dir, rustdoc)
+                self.handle_html(css, output_dir)
 
         #
         # Step 2: Some targets (PDF and info) require an extra step once
@@ -804,9 +830,6 @@ def main():
     parser.add_argument('--deny-vf',
                         help="Configuration to deny variable fonts on pdf builds")
 
-    parser.add_argument('--rustdoc', action="store_true",
-                        help="Enable rustdoc build. Requires CONFIG_RUST")
-
     parser.add_argument("-v", "--verbose", action='store_true',
                         help="place build in verbose mode")
 
@@ -834,7 +857,7 @@ def main():
 
     builder.build(args.target, sphinxdirs=args.sphinxdirs,
                   theme=args.theme, css=args.css, paper=args.paper,
-                  rustdoc=args.rustdoc, deny_vf=args.deny_vf,
+                  deny_vf=args.deny_vf,
                   skip_sphinx=args.skip_sphinx_build)
 
 if __name__ == "__main__":
-- 
2.51.1

Re: [PATCH 1/1] docs: makefile: move rustdoc check to the build wrapper

[Miguel Ojeda]

On Mon, Nov 17, 2025 at 10:13 AM Mauro Carvalho Chehab
<mchehab+huawei@kernel.org> wrote:
>
> The makefile logic to detect if rust is enabled is not working
> the way it was expected. Move it to be inside the wrapper
> script.

Hmm... Could the commit explain a bit why this didn't work and why now it does?

Thanks!

Cheers,
Miguel

Re: [PATCH 1/1] docs: makefile: move rustdoc check to the build wrapper

[Mauro Carvalho Chehab]

On Mon, Nov 17, 2025 at 10:20:46AM +0100, Miguel Ojeda wrote:
> On Mon, Nov 17, 2025 at 10:13 AM Mauro Carvalho Chehab
> <mchehab+huawei@kernel.org> wrote:
> >
> > The makefile logic to detect if rust is enabled is not working
> > the way it was expected. Move it to be inside the wrapper
> > script.
> 
> Hmm... Could the commit explain a bit why this didn't work and why now it does?

I don't know exactly why this was not working.

I guess one of the issues is that the "rustdoc" target becomes
undefined if RUST is not enabled, e.g. rust/Makefile is lacking something
like:

    ifdef CONFIG_RUST
    ...
    else
    rustdoc rustdoc-core rustdoc-macros rustdoc-compiler_builtins:
            $(warning Rust is not enabled. Can't build $<)    
    endif

But this is not enough to explain the issues I'm getting.

Maybe the other issues are cache related.

In any case, here, with Fedora 43, on some cases, when I run:

    make htmldocs  # or make SPHINXDIRS=xxx htmldocs

it sometimes, after building the docs, it tries to run:

    make LLVM=1 rustdoc

as this is not a defined target when CONFIG_RUST is not
present, this causes it to build the entire code.

-- 
Thanks,
Mauro

Re: [PATCH 1/1] docs: makefile: move rustdoc check to the build wrapper

[Jonathan Corbet]

Mauro Carvalho Chehab <mchehab+huawei@kernel.org> writes:

> On Mon, Nov 17, 2025 at 10:20:46AM +0100, Miguel Ojeda wrote:
>> On Mon, Nov 17, 2025 at 10:13 AM Mauro Carvalho Chehab
>> <mchehab+huawei@kernel.org> wrote:
>> >
>> > The makefile logic to detect if rust is enabled is not working
>> > the way it was expected. Move it to be inside the wrapper
>> > script.
>> 
>> Hmm... Could the commit explain a bit why this didn't work and why now it does?
>
> I don't know exactly why this was not working.

I would feel a lot better if we knew what the real problem is before
applying fixes for it.  Otherwise something seems certain to come and
bite us at some point.

Thanks,

jon

Re: [PATCH 1/1] docs: makefile: move rustdoc check to the build wrapper

[Mauro Carvalho Chehab]

Em Tue, 18 Nov 2025 09:38:15 -0700
Jonathan Corbet <corbet@lwn.net> escreveu:

> Mauro Carvalho Chehab <mchehab+huawei@kernel.org> writes:
> 
> > On Mon, Nov 17, 2025 at 10:20:46AM +0100, Miguel Ojeda wrote:  
> >> On Mon, Nov 17, 2025 at 10:13 AM Mauro Carvalho Chehab
> >> <mchehab+huawei@kernel.org> wrote:  
> >> >
> >> > The makefile logic to detect if rust is enabled is not working
> >> > the way it was expected. Move it to be inside the wrapper
> >> > script.  
> >> 
> >> Hmm... Could the commit explain a bit why this didn't work and why now it does?  
> >
> > I don't know exactly why this was not working.  
> 
> I would feel a lot better if we knew what the real problem is before
> applying fixes for it.  Otherwise something seems certain to come and
> bite us at some point.

Me too, but the bug is very annoying ;-)

I'll try to seek for some time to better understand it, maybe
next week.

Thanks,
Mauro

Re: [PATCH 1/1] docs: makefile: move rustdoc check to the build wrapper

[Mauro Carvalho Chehab]

Em Tue, 18 Nov 2025 20:11:52 +0100
Mauro Carvalho Chehab <mchehab+huawei@kernel.org> escreveu:

> Em Tue, 18 Nov 2025 09:38:15 -0700
> Jonathan Corbet <corbet@lwn.net> escreveu:
> 
> > Mauro Carvalho Chehab <mchehab+huawei@kernel.org> writes:
> >   
> > > On Mon, Nov 17, 2025 at 10:20:46AM +0100, Miguel Ojeda wrote:    
> > >> On Mon, Nov 17, 2025 at 10:13 AM Mauro Carvalho Chehab
> > >> <mchehab+huawei@kernel.org> wrote:    
> > >> >
> > >> > The makefile logic to detect if rust is enabled is not working
> > >> > the way it was expected. Move it to be inside the wrapper
> > >> > script.    
> > >> 
> > >> Hmm... Could the commit explain a bit why this didn't work and why now it does?    
> > >
> > > I don't know exactly why this was not working.    
> > 
> > I would feel a lot better if we knew what the real problem is before
> > applying fixes for it.  Otherwise something seems certain to come and
> > bite us at some point.  
> 
> Me too, but the bug is very annoying ;-)
> 
> I'll try to seek for some time to better understand it, maybe
> next week.

Btw, at least here (Fedora 43, upgraded from 42), rustdoc doesn't build
for docs-next.

Perhaps the issue could be due to some weird things with Fedora 43.

That's what happens after sphinx-build-wrapper finishes handling
htmldocs (after this patch), when it runs "make LLVM=1 rustdoc":

Building rust docs
  DESCEND objtool
  INSTALL libsubcmd_headers
  CALL    scripts/checksyscalls.sh
  RUSTC L rust/bindings.o
  RUSTC L rust/build_error.o
  RUSTC L rust/uapi.o
error: mixing `-Zsanitizer` will cause an ABI mismatch in crate `build_error`
 --> rust/build_error.rs:3:1
  |
3 | //! Build-time error.
  | ^
  |
  = help: the `-Zsanitizer` flag modifies the ABI so Rust crates compiled with different values of this flag cannot be used together safely
  = note: unset `-Zsanitizer` in this crate is incompatible with `-Zsanitizer=kernel-address` in dependency `core`
  = help: set `-Zsanitizer=kernel-address` in this crate or unset `-Zsanitizer` in `core`
  = help: if you are sure this will not cause problems, you may use `-Cunsafe-allow-abi-mismatch=sanitizer` to silence this error

error: mixing `-Zsanitizer` will cause an ABI mismatch in crate `build_error`
 --> rust/build_error.rs:3:1
  |
3 | //! Build-time error.
  | ^
  |
  = help: the `-Zsanitizer` flag modifies the ABI so Rust crates compiled with different values of this flag cannot be used together safely
  = note: unset `-Zsanitizer` in this crate is incompatible with `-Zsanitizer=kernel-address` in dependency `compiler_builtins`
  = help: set `-Zsanitizer=kernel-address` in this crate or unset `-Zsanitizer` in `compiler_builtins`
  = help: if you are sure this will not cause problems, you may use `-Cunsafe-allow-abi-mismatch=sanitizer` to silence this error

error: aborting due to 2 previous errors

make[4]: *** [rust/Makefile:527: rust/build_error.o] Error 1
make[4]: ** Esperando que outros processos terminem.
make[3]: *** [Makefile:1286: prepare] Error 2
Ignored errors when building rustdoc: Command '['make', 'rustdoc']' returned non-zero exit status 2.. Is RUST enabled?

Relevant Rust configs:

$ grep RUST .config
CONFIG_RUSTC_VERSION=109100
CONFIG_RUST_IS_AVAILABLE=y
CONFIG_RUSTC_LLVM_VERSION=210103
CONFIG_RUSTC_HAS_COERCE_POINTEE=y
CONFIG_RUSTC_HAS_SPAN_FILE=y
CONFIG_RUSTC_HAS_UNNECESSARY_TRANSMUTES=y
CONFIG_RUSTC_HAS_FILE_WITH_NUL=y
CONFIG_RUSTC_HAS_FILE_AS_C_STR=y
CONFIG_RUST=y
CONFIG_RUSTC_VERSION_TEXT="rustc 1.91.0 (f8297e351 2025-10-28) (Fedora 1.91.0-1.fc43)"
# CONFIG_CPUFREQ_DT_RUST is not set
CONFIG_HAVE_RUST=y
# CONFIG_RUST_FW_LOADER_ABSTRACTIONS is not set
# CONFIG_BLK_DEV_RUST_NULL is not set
# CONFIG_RUST_PHYLIB_ABSTRACTIONS is not set
CONFIG_RADIO_TRUST=y
CONFIG_RADIO_TRUST_PORT=350
CONFIG_HID_THRUSTMASTER=y
CONFIG_THRUSTMASTER_FF=y
CONFIG_TRUSTED_KEYS=y
CONFIG_HAVE_TRUSTED_KEYS=y
CONFIG_TRUSTED_KEYS_TPM=y
CONFIG_TRUSTED_KEYS_TEE=y
CONFIG_TRUSTED_KEYS_CAAM=y
CONFIG_INTEGRITY_TRUSTED_KEYRING=y
CONFIG_IMA_SECURE_AND_OR_TRUSTED_BOOT=y
# CONFIG_RUST_BITMAP_HARDENED is not set
CONFIG_SYSTEM_TRUSTED_KEYRING=y
CONFIG_SYSTEM_TRUSTED_KEYS=""
CONFIG_SECONDARY_TRUSTED_KEYRING=y
CONFIG_SECONDARY_TRUSTED_KEYRING_SIGNED_BY_BUILTIN=y
# CONFIG_SAMPLES_RUST is not set
# CONFIG_FIND_BIT_BENCHMARK_RUST is not set
# CONFIG_RUST_DEBUG_ASSERTIONS is not set
CONFIG_RUST_OVERFLOW_CHECKS=y
# CONFIG_RUST_BUILD_ASSERT_ALLOW is not set
CONFIG_RUST_KERNEL_DOCTESTS=y



Thanks,
Mauro

Re: [PATCH 1/1] docs: makefile: move rustdoc check to the build wrapper

[Miguel Ojeda]

On Tue, Nov 18, 2025 at 9:32 PM Mauro Carvalho Chehab
<mchehab+huawei@kernel.org> wrote:
>
> Btw, at least here (Fedora 43, upgraded from 42), rustdoc doesn't build
> for docs-next.
>
> Perhaps the issue could be due to some weird things with Fedora 43.
>
> That's what happens after sphinx-build-wrapper finishes handling
> htmldocs (after this patch), when it runs "make LLVM=1 rustdoc":

That one is fixed with commit 16c43a56b79e ("rust: kbuild: treat
`build_error` and `rustdoc` as kernel objects") which is in -rc5.

Cheers,
Miguel

Re: [PATCH 1/1] docs: makefile: move rustdoc check to the build wrapper

[Miguel Ojeda]

On Tue, Nov 18, 2025 at 8:12 PM Mauro Carvalho Chehab
<mchehab+huawei@kernel.org> wrote:
>
> Me too, but the bug is very annoying ;-)
>
> I'll try to seek for some time to better understand it, maybe
> next week.

I will try to find a moment to take a look too... This happens with
only the new wrapper, right? Or is it something that happened even
before? If the latter, I remember testing the logic that Carlos added
a long time ago, but maybe something changed in the meantime.

Cheers,
Miguel

Re: [PATCH 1/1] docs: makefile: move rustdoc check to the build wrapper

[Mauro Carvalho Chehab]

Em Tue, 18 Nov 2025 22:40:09 +0100
Miguel Ojeda <miguel.ojeda.sandonis@gmail.com> escreveu:

> On Tue, Nov 18, 2025 at 8:12 PM Mauro Carvalho Chehab
> <mchehab+huawei@kernel.org> wrote:
> >
> > Me too, but the bug is very annoying ;-)
> >
> > I'll try to seek for some time to better understand it, maybe
> > next week.  
> 
> I will try to find a moment to take a look too... This happens with
> only the new wrapper, right? Or is it something that happened even
> before? If the latter, I remember testing the logic that Carlos added
> a long time ago, but maybe something changed in the meantime.

I'm testing here against docs/docs-next, so it is based on -rc1,
so, yeah this is after the cleanups. The problem could be introduced
by the Makefile cleanup, but I didn't find anything obvious
but I haven't time to revisit after sending the patch, as I got
sidetracked with unrelated issues (*).

I'll try testing it tomorrow against linux-next.

Thanks,
Mauro

---

(*) I was preparing a new rasdaemon release, which was launched
    today.