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Simplify recvmmsg code.

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Now we can assume a kernel with recvmmsg support, this patch
simplifies the implementation to be similar to that for accept4:
either using socketcall or the syscall according to whether the
syscall is known to be available, without further fallback
implementations.

(In fact further simplification is possible, getting rid of the
__ASSUME_*_SYSCALL_WITH_SOCKETCALL macros now that the minimum kernel
is guaranteed support for all of accept4, recvmmsg, sendmmsg, whether
through syscalls or through socketcall.  I intend to do that for all
of accept4 / recvmmsg / sendmmsg together - so making their
implementations just like those for older socket functions - once the
basic cleanup for 3.2 minimum kernel is done for sendmmsg as well as
recvmmsg.)

Tested for x86_64 and x86.

	* sysdeps/unix/sysv/linux/kernel-features.h
	(__ASSUME_RECVMMSG_SYSCALL): Define unconditionally.
	(__ASSUME_RECVMMSG_SOCKETCALL): Remove macro.
	(__ASSUME_RECVMMSG): Likewise.
	* sysdeps/unix/sysv/linux/recvmmsg.c (recvmmsg): Define using
	recvmmsg syscall if it can be assumed to be present, socketcall
	otherwise, with no fallback for runtime failure.
This commit is contained in:
Joseph Myers
2017-05-09 20:01:01 +00:00
parent 4fc12f0eda
commit 9a45f54310
3 changed files with 21 additions and 69 deletions
Download Patch File Download Diff File Expand all files Collapse all files

72
sysdeps/unix/sysv/linux/recvmmsg.c
View File

@ -21,73 +21,21 @@
#include <sysdep-cancel.h>
#include <sys/syscall.h>
#include <socketcall.h>
#include <kernel-features.h>
/* Do not use the recvmmsg syscall on socketcall architectures unless
it was added at the same time as the socketcall support or can be
assumed to be present. */
int
recvmmsg (int fd, struct mmsghdr *vmessages, unsigned int vlen, int flags,
struct timespec *tmo)
{
/* Do not use the recvmmsg syscall on socketcall architectures unless
it was added at the same time as the socketcall support or can be
assumed to be present. */
#if defined __ASSUME_SOCKETCALL \
&& !defined __ASSUME_RECVMMSG_SYSCALL_WITH_SOCKETCALL \
&& !defined __ASSUME_RECVMMSG_SYSCALL
# undef __NR_recvmmsg
#endif
#ifdef __NR_recvmmsg
int
recvmmsg (int fd, struct mmsghdr *vmessages, unsigned int vlen, int flags,
struct timespec *tmo)
{
return SYSCALL_CANCEL (recvmmsg, fd, vmessages, vlen, flags, tmo);
}
#elif defined __NR_socketcall
# include <socketcall.h>
# ifdef __ASSUME_RECVMMSG_SOCKETCALL
int
recvmmsg (int fd, struct mmsghdr *vmessages, unsigned int vlen, int flags,
struct timespec *tmo)
{
return SOCKETCALL_CANCEL (recvmmsg, fd, vmessages, vlen, flags, tmo);
}
# else
static int have_recvmmsg;
int
recvmmsg (int fd, struct mmsghdr *vmessages, unsigned int vlen, int flags,
struct timespec *tmo)
{
if (__glibc_likely (have_recvmmsg >= 0))
{
int ret = SOCKETCALL_CANCEL (recvmmsg, fd, vmessages, vlen, flags,
tmo);
/* The kernel returns -EINVAL for unknown socket operations.
We need to convert that error to an ENOSYS error. */
if (__builtin_expect (ret < 0, 0)
&& have_recvmmsg == 0
&& errno == EINVAL)
{
/* Try another call, this time with an invalid file
descriptor and all other parameters cleared. This call
will not cause any harm and it will return
immediately. */
ret = SOCKETCALL_CANCEL (invalid, -1);
if (errno == EINVAL)
{
have_recvmmsg = -1;
__set_errno (ENOSYS);
}
else
{
have_recvmmsg = 1;
__set_errno (EINVAL);
}
return -1;
}
return ret;
}
__set_errno (ENOSYS);
return -1;
}
# endif /* __ASSUME_RECVMMSG_SOCKETCALL */
#else
# include <socket/recvmmsg.c>
return SYSCALL_CANCEL (recvmmsg, fd, vmessages, vlen, flags, tmo);
#endif
}