add posix_madvise.c

Signed-off-by: Peter S. Mazinger <ps.m@gmx.net>
Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>

libc/sysdeps/linux/common/Makefile.in

@@ -81,7 +81,7 @@ CSRC-$(UCLIBC_HAS_REALTIME) += clock_getres.c clock_gettime.c clock_settime.c \
 	sched_get_priority_max.c sched_get_priority_min.c sched_getscheduler.c \
 	sched_rr_get_interval.c sched_setparam.c sched_setscheduler.c sigqueue.c
 # clock_getcpuclockid|clock_nanosleep|mq_timedreceive|mq_timedsend|posix_fadvise|posix_fallocate|posix_madvise|posix_memalign|posix_mem_offset|posix_spawnattr_destroy|posix_spawnattr_init|posix_spawnattr_getflags|posix_spawnattr_setflags|posix_spawnattr_getpgroup|posix_spawnattr_setpgroup|posix_spawnattr_getschedparam|posix_spawnattr_setschedparam|posix_spawnattr_getschedpolicy|posix_spawnattr_setschedpolicy|posix_spawnattr_getsigdefault|posix_spawnattr_setsigdefault|posix_spawnattr_getsigmask|posix_spawnattr_setsigmask|posix_spawnattr_init|posix_spawnattr_setflags|posix_spawnattr_setpgroup|posix_spawnattr_setschedparam|posix_spawnattr_setschedpolicy|posix_spawnattr_setsigdefault|posix_spawnattr_setsigmask|posix_spawn_file_actions_addclose|posix_spawn_file_actions_addopen|posix_spawn_file_actions_adddup2|posix_spawn_file_actions_addopen|posix_spawn_file_actions_destroy|posix_spawn_file_actions_init|posix_spawn_file_actions_init|posix_spawn|posix_spawnp|posix_spawnp|posix_typed_mem_get_info|pthread_mutex_timedlock|sem_timedwait
-CSRC-$(UCLIBC_HAS_ADVANCED_REALTIME) += posix_fadvise64.c posix_fadvise.c
+CSRC-$(UCLIBC_HAS_ADVANCED_REALTIME) += posix_fadvise64.c posix_fadvise.c posix_madvise.c
 CSRC-$(UCLIBC_SUSV4_LEGACY) += utime.c
 CSRC-$(UCLIBC_HAS_EPOLL) += epoll.c
 CSRC-$(UCLIBC_HAS_XATTR) += xattr.c

libc/sysdeps/linux/common/posix_madvise.c

@@ -0,0 +1,25 @@
+/* vi: set sw=4 ts=4: */
+/* Licensed under the LGPL v2.1, see the file LICENSE in this tarball. */
+
+#include <sys/mman.h>
+#include <sys/syscall.h>
+
+#if defined __NR_madvise && defined __USE_XOPEN2K && defined __UCLIBC_HAS_ADVANCED_REALTIME__
+int posix_madvise(void *addr, size_t len, int advice)
+{
+	int result;
+	/* We have one problem: the kernel's MADV_DONTNEED does not
+	 * correspond to POSIX's POSIX_MADV_DONTNEED.  The former simply
+	 * discards changes made to the memory without writing it back to
+	 * disk, if this would be necessary.  The POSIX behaviour does not
+	 * allow this.  There is no functionality mapping for the POSIX
+	 * behaviour so far so we ignore that advice for now. */
+	if (advice == POSIX_MADV_DONTNEED)
+		return 0;
+
+	/* this part might use madvise function */
+	INTERNAL_SYSCALL_DECL (err);
+	result = INTERNAL_SYSCALL (madvise, err, 3, addr, len, advice);
+	return INTERNAL_SYSCALL_ERRNO (result, err);
+}
+#endif