Include <linux/vmalloc.h> explicitly on x86

[EricccTaiwan]

Newer kernel versions (>= 5.4) require explicitly including <linux/vmalloc.h> to use vmalloc() and vfree(). Older kernels might have included this implicitly through other headers, but this is no longer the case.

Without this include, builds will fail with implicit function declaration errors on recent kernels such as 6.11.

[jserv]

I would like to ask @rota1001 to review and check the connection with sysprog21/kxo#1

[EricccTaiwan]

I am using 6.11.0-21-generic,

$ uname -r
6.11.0-21-generic

Attempting to build without including <linux/vmalloc.h> results in the following errors:

/home/eric/linux2025/simrupt/simrupt.c: In function ‘simrupt_init’:
/home/eric/linux2025/simrupt/simrupt.c:359:20: error: implicit declaration of function ‘vmalloc’; did you mean ‘kmalloc’? [-Werror=implicit-function-declaration]
  359 |     fast_buf.buf = vmalloc(PAGE_SIZE);
      |                    ^~~~~~~
      |                    kmalloc
/home/eric/linux2025/simrupt/simrupt.c:359:18: warning: assignment to ‘char *’ from ‘int’ makes pointer from integer without a cast [-Wint-conversion]
  359 |     fast_buf.buf = vmalloc(PAGE_SIZE);
      |                  ^
/home/eric/linux2025/simrupt/simrupt.c:370:9: error: implicit declaration of function ‘vfree’; did you mean ‘kvfree’? [-Werror=implicit-function-declaration]
  370 |         vfree(fast_buf.buf);
      |         ^~~~~
      |         kvfree
cc1: some warnings being treated as errors
make[3]: *** [scripts/Makefile.build:244: /home/eric/linux2025/simrupt/simrupt.o] Error 1
make[2]: *** [/usr/src/linux-headers-6.11.0-21-generic/Makefile:1932: /home/eric/linux2025/simrupt] Error 2
make[1]: *** [Makefile:224: __sub-make] Error 2
make[1]: Leaving directory '/usr/src/linux-headers-6.11.0-21-generic'
make: *** [Makefile:9: all] Error 2

[EricccTaiwan]

The vmalloc() and vfree() functions are implemented in mm/vmalloc.c, while their interfaces are declared in include/linux/vmalloc.h.

The same issue regarding implicit declaration of vmalloc() can also be seen in this Stack Overflow discussion.

Therefore, I believe both simrupt and kxo should explicitly include <linux/vmalloc.h> to properly access these interfaces. Failing to include it will cause implicit declaration errors on newer kernels, such as 6.11.

[rota1001]

@jserv I've reviewed this change, and it looks like the same problem as what has been memtioned in sysprog21/kxo#1. Moreover, this change works for my environment (6.11.0-19-generic).

[jserv]

Append Tested-by: Chisheng Chen <johnny1001s000602@gmail.com> to acknowledge the review from @rota1001

See https://git-scm.com/docs/SubmittingPatches

[EricccTaiwan]

This patch also fixes sysprog21/kxo#1, which I have tested on my x86_64 system running kernel 6.11.0-21-generic.

Due to git commit message guidelines (72-character line limit), I've included the relevant kernel commit links here separately for reference:

• Full commit (all files):
  https://git.kernel.org/torvalds/c/1f059dfdf5d170dccbac92193be2fee3c1763384

• Limited commit (vmalloc.h only):
  https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/include/linux/vmalloc.h?id=1f059dfdf5d170dccbac92193be2fee3c1763384

[jserv]

See if the following statements were correct:

Commit 1f059dfdf5d1 ("mm/vmalloc: Add empty <asm/vmalloc.h> headers and use them from <linux/vmalloc.h>") restructured kernel header dependencies since kernel v6.14, necessitating explicit inclusion
of <linux/vmalloc.h> on x86 architectures.

This ensures compatibility across kernel versions and prevents build errors due to implicit declarations on recent kernels (>= 6.14).

Per @rota1001 reported, the affected kernel version is at least v6.11, and the above seems to be confusing. Clarify it.

[EricccTaiwan]

After re-checking, commit 1f059dfdf5d1 ("mm/vmalloc: Add empty <asm/vmalloc.h> headers and use them from <linux/vmalloc.h>") was first merged into kernel version v5.6-rc1. The original mention of >= 6.14 was incorrect and misleading. I've updated the commit message accordingly to clarify this.

[jserv]

The original mention of >= 6.14 was incorrect and misleading. I've updated the commit message accordingly to clarify this.

Clarify the following message:

Commit 1f059dfdf5d1 ("mm/vmalloc: Add empty <asm/vmalloc.h> headers
and use them from <linux/vmalloc.h>") restructured kernel header
dependencies since kernel v6.14, necessitating explicit inclusion
of <linux/vmalloc.h> on x86 architectures.

[jserv]

Thank @EricccTaiwan for contributing!