[Suggestion] Latest Linux failed to compile under musl due to swab.h `missing __always_inline`

[owl4ce]

Hi I'm using the latest kernel (5.12.10) but I compile it doesn't work at all, after I looked around I found it had to be patched for musl libc because the linux/swab.h API Header was broken. Apply this patch on Linux API Headers installation.

include-uapi-linux-swab-Fix-potentially-missing-__always_inline.patch

From: Matt Redfearn <matt.redfearn@mips.com>
Subject: [PATCH] include/uapi/linux/swab: Fix potentially missing __always_inline
Date: Wed, 3 Jan 2018 09:57:30 +0000
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Commit bc27fb68aaad ("include/uapi/linux/byteorder, swab: force inlining
of some byteswap operations") added __always_inline to swab functions
and commit 283d75737837 ("uapi/linux/stddef.h: Provide __always_inline to
userspace headers") added a definition of __always_inline for use in
exported headers when the kernel's compiler.h is not available.

However, since swab.h does not include stddef.h, if the header soup does
not indirectly include it, the definition of __always_inline is missing,
resulting in a compilation failure, which was observed compiling the
perf tool using exported headers containing this commit:

In file included from /usr/include/linux/byteorder/little_endian.h:12:0,
                 from /usr/include/asm/byteorder.h:14,
                 from tools/include/uapi/linux/perf_event.h:20,
                 from perf.h:8,
                 from builtin-bench.c:18:
/usr/include/linux/swab.h:160:8: error: unknown type name ‘__always_inline’
 static __always_inline __u16 __swab16p(const __u16 *p)

Fix this by replacing the inclusion of linux/compiler.h with
linux/stddef.h to ensure that we pick up that definition if required,
without relying on it's indirect inclusion. compiler.h is then included
indirectly, via stddef.h.

Fixes: 283d75737837 ("uapi/linux/stddef.h: Provide __always_inline to userspace headers")
Signed-off-by: Matt Redfearn <matt.redfearn@mips.com>

---

 include/uapi/linux/swab.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/uapi/linux/swab.h b/include/uapi/linux/swab.h
index 23cd84868cc3..f6a8cf737abf 100644
--- a/include/uapi/linux/swab.h
+++ b/include/uapi/linux/swab.h
@@ -3,7 +3,7 @@
 #define _UAPI_LINUX_SWAB_H

 #include <linux/types.h>
-#include <linux/compiler.h>
+#include <linux/stddef.h>
 #include <asm/bitsperlong.h>
 #include <asm/swab.h>

 /*
-- 
2.7.4

I added a little above, on #include <asm/bitsperlong.h>

Related Issues @ Alpine Linux Related Issues @ LKML Merge Request @ Alpine Linux

[dslm4515]

Awesome! I did run into this issue and used kernel 5.10.16 in the mean time

[dslm4515]

wow. Strange. I did see that posted fix, but it didnt work for me. I unpacked the source again and now issue is gone. Will add a patch,

[dslm4515]

Master and branch v9.0.0 has this fixed.