Re: [PATCH 11/11] UAPI: Check headers build for C++ [ver #2]

Arnd Bergmann
2018-09-14T09:10:54Z

On Thu, Sep 6, 2018 at 11:21 AM David Howells <dhowells@redhat.com> wrote:

> +
> +typedef __s8 int8_t;
> +typedef __s16 int16_t;
> +typedef __s32 int32_t;
> +typedef __s64 int64_t;
> +typedef __u8 uint8_t;
> +typedef __u16 uint16_t;
> +typedef __u32 uint32_t;
> +typedef __u64 uint64_t;
> +typedef long int intptr_t;
> +typedef unsigned long int uintptr_t;
> +typedef unsigned short u_short;
> +typedef unsigned int u_int;
> +typedef unsigned long u_long;
> +typedef char *caddr_t;
> +
> +typedef __kernel_clockid_t clockid_t;
> +typedef __kernel_ino_t ino_t;
> +typedef __kernel_pid_t pid_t;
> +typedef __kernel_sa_family_t sa_family_t;
> +typedef __kernel_size_t size_t;
> +typedef __kernel_uid_t uid_t;
> +
> +typedef unsigned long elf_greg_t;
> +typedef elf_greg_t elf_gregset_t[1];
> +typedef unsigned long long elf_fpregset_t[1];
> +typedef unsigned long long elf_fpxregset_t[1];
> +
> +#define INT_MIN ((int)0x80000000)
> +#define INT_MAX ((int)0x7fffffff)
> +
> +extern size_t strlen(const char *);
> +extern void *memset(void *, int, size_t);
> +extern void *memcpy(void *, const void *, size_t);
> +extern __u16 ntohs(__u16);
> +extern __u16 htons(__u16);
> +extern __u32 ntohl(__u32);
> +extern __u32 htonl(__u32);
> +
> +typedef uint32_t grant_ref_t;
> +typedef uint16_t domid_t;
> +typedef unsigned long xen_pfn_t;
> +
> +#define MSG_FIN 0x200
> +
> +typedef int SVGA3dMSPattern;
> +typedef int SVGA3dMSQualityLevel;
> +
> +struct sockaddr
> +{
> + sa_family_t sa_family;
> + char sa_data[14];
> +};
> +#define sockaddr_storage __kernel_sockaddr_storage

I think we need to reduce that list as much as we can. In
https://patchwork.ozlabs.org/patch/968814/, Joseph Myers pointed
out header file (linux/elfcore.h) that simply cannot be included from
user space at all, because its dependencies cannot be met without
running into conflicting type definitions, and he would like to include
that file in order to automatically check that it's compatible with
the glibc version (I pointed out a couple of architectures on which
it is in fact incompatible right now).

In the list above, I see multiple classes of bugs that could be
addressed:

- references to identifiers that are only present in kernel internal
headers: SVGA3dMSPattern, MSG_FIN, xen_pfn_t, ...
I think these are all simple bugs, and we should either remove
the references, or make sure the respective dependencies are
included in the uapi headers as well, possibly renamed with
a __kernel_ prefix to avoid clashing with user space headers.

- references to user space types that should use the uapi
internal types: sockaddr_storage, clockid_t, uid_t, ...
I think these just need to get the __kernel_prefix
consistently as we did a few years ago. Note that using
the headers otherwise is broken anyway when the types
in libc are different from the ones in the kernel.

- standard types (uint32_t): either include the correct user
space headers ifndef __KERNEL__ or use the kernel types

- standard functions (memcpy(), ntohs(), ...): These should
already be handled in the headers by including the user space.
If we missed any, we should probably do the same thing
there.

Arnd