x86: Implement prlimit proxy

RHEL6 is shipped with libc 2.12 where no prlimit
helper provided (which was pushed into libc itself
since 2.13). So we implement own proxy for convenience.

Note, if libc does support prlimit itself we simply
don't use any proxy and call it directly.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

arch/x86/Makefile

@@ -6,6 +6,7 @@ SYS-ASM		:= syscalls.S
 syscalls-asm-y	+= $(SYS-ASM:.S=).o
 crtools-obj-y	+= crtools.o
 crtools-obj-y	+= cpu.o
+crtools-obj-y	+= prlimit.o
 
 SYS-DEF		:= syscall-x86-64.def
 SYS-ASM-COMMON	:= syscall-common-x86-64.S

arch/x86/include/asm/prlimit.h

+#ifndef __CR_PRLIMIT_H__
+#define __CR_PRLIMIT_H__
+
+#include <sys/types.h>
+#include <sys/time.h>
+#include <sys/resource.h>
+
+#include "config.h"
+
+#ifndef CONFIG_HAS_PRLIMIT
+extern int prlimit(pid_t pid, int resource, const struct rlimit *new_rlimit, struct rlimit *old_rlimit);
+#endif
+
+#endif /* __CR_PRLIMIT_H__ */

arch/x86/include/asm/types.h

@@ -6,6 +6,7 @@
 
 #include "asm/bitops.h"
 #include "asm/int.h"
+#include "asm/prlimit.h"
 
 #include "protobuf/core.pb-c.h"
 

arch/x86/prlimit.c

+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+
+#include "asm/types.h"
+#include "asm/prlimit.h"
+
+#include "compiler.h"
+#include "syscall.h"
+#include "config.h"
+
+#ifndef CONFIG_HAS_PRLIMIT
+
+#ifndef RLIM64_INFINITY
+# define RLIM64_INFINITY	(~0ULL)
+#endif
+
+int prlimit(pid_t pid, int resource, const struct rlimit *new_rlimit, struct rlimit *old_rlimit)
+{
+	struct rlimit64 new_rlimit64_mem;
+	struct rlimit64 old_rlimit64_mem;
+	struct rlimit64 *new_rlimit64 = NULL;
+	struct rlimit64 *old_rlimit64 = NULL;
+	int ret;
+
+	if (old_rlimit)
+		old_rlimit64 = &old_rlimit64_mem;
+
+	if (new_rlimit) {
+		if (new_rlimit->rlim_cur == RLIM_INFINITY)
+			new_rlimit64_mem.rlim_cur = RLIM64_INFINITY;
+		else
+			new_rlimit64_mem.rlim_cur = new_rlimit->rlim_cur;
+		if (new_rlimit->rlim_max == RLIM_INFINITY)
+			new_rlimit64_mem.rlim_max = RLIM64_INFINITY;
+		else
+			new_rlimit64_mem.rlim_max = new_rlimit->rlim_max;
+		new_rlimit64 = &new_rlimit64_mem;
+	}
+
+	ret = sys_prlimit64(pid, resource, new_rlimit64, old_rlimit64);
+
+	if (ret == 0 && old_rlimit) {
+		old_rlimit->rlim_cur = old_rlimit64_mem.rlim_cur;
+		if (old_rlimit->rlim_cur != old_rlimit64_mem.rlim_cur) {
+			if (new_rlimit) {
+				errno = EOVERFLOW;
+				return -1;
+			}
+			old_rlimit->rlim_cur = RLIM_INFINITY;
+		}
+		old_rlimit->rlim_max = old_rlimit64_mem.rlim_max;
+		if (old_rlimit->rlim_max != old_rlimit64_mem.rlim_max) {
+			if (new_rlimit) {
+				errno = EOVERFLOW;
+				return -1;
+			}
+			old_rlimit->rlim_max = RLIM_INFINITY;
+		}
+	} else if (ret) {
+		errno = -ret;
+		ret = -1;
+	}
+
+	return ret;
+}
+
+#endif /* CONFIG_HAS_PRLIMIT */