[RFC] PATCH 4/4 - Time virtualization : UML support

From: Jeff Dike
Date: Thu Apr 13 2006 - 14:20:42 EST

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Previous message: Jeff Dike: "[RFC] PATCH 3/4 - Time virtualization : PTRACE_SYSCALL_MASK"
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Add UML support for time namespaces. We call unshare(CLONE_TIME) to create
the new namespace, set gettimeofday to run untraced, and make settimeofday
call the host's settimeofday to update the namespace offset rather than
maintaining the offset locally.

Index: linux-2.6.17-mm-vtime/arch/um/os-Linux/skas/process.c
===================================================================
--- linux-2.6.17-mm-vtime.orig/arch/um/os-Linux/skas/process.c 2006-04-13 13:48:01.000000000 -0400
+++ linux-2.6.17-mm-vtime/arch/um/os-Linux/skas/process.c 2006-04-13 13:50:34.000000000 -0400
@@ -17,6 +17,7 @@
#include <sys/time.h>
#include <asm/unistd.h>
#include <asm/types.h>
+#include <asm/bitops.h>
#include "user.h"
#include "sysdep/ptrace.h"
#include "user_util.h"
@@ -209,11 +210,16 @@ static int userspace_tramp(void *stack)
#define NR_CPUS 1
int userspace_pid[NR_CPUS];

+#ifndef PTRACE_SYSCALL_MASK
+#define PTRACE_SYSCALL_MASK 27
+#endif
+
int start_userspace(unsigned long stub_stack)
{
void *stack;
unsigned long sp;
int pid, status, n, flags;
+ char mask[(KERNEL_NR_SYSCALLS + 7) / 8];

stack = mmap(NULL, PAGE_SIZE, PROT_READ | PROT_WRITE | PROT_EXEC,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
@@ -242,6 +248,12 @@ int start_userspace(unsigned long stub_s
panic("start_userspace : PTRACE_OLDSETOPTIONS failed, errno=%d\n",
errno);

+ memset(mask, 0xff, sizeof(mask));
+ clear_bit(__NR_gettimeofday, mask);
+ if(ptrace(PTRACE_SYSCALL_MASK, pid, mask, sizeof(mask)) < 0)
+ panic("start_userspace : PTRACE_SYSCALL_MASK failed, "
+ "errno = %d\n", errno);
+
if(munmap(stack, PAGE_SIZE) < 0)
panic("start_userspace : munmap failed, errno = %d\n", errno);

@@ -321,6 +333,7 @@ int copy_context_skas0(unsigned long new
struct stub_data *child_data = (struct stub_data *) new_stack;
__u64 new_offset;
int new_fd = phys_mapping(to_phys((void *)new_stack), &new_offset);
+ char mask[(KERNEL_NR_SYSCALLS + 7) / 8];

/* prepare offset and fd of child's stack as argument for parent's
* and child's mmap2 calls
@@ -377,6 +390,12 @@ int copy_context_skas0(unsigned long new
panic("copy_context_skas0 : PTRACE_OLDSETOPTIONS failed, "
"errno = %d\n", errno);

+ memset(mask, 0xff, sizeof(mask));
+ clear_bit(__NR_gettimeofday, mask);
+ if(ptrace(PTRACE_SYSCALL_MASK, pid, mask, sizeof(mask)) < 0)
+ panic("start_userspace : PTRACE_SYSCALL_MASK failed, "
+ "errno = %d\n", errno);
+
return pid;
}

@@ -492,11 +511,18 @@ static void (*cb_proc)(void *arg);
static void *cb_arg;
static sigjmp_buf *cb_back;

+#ifndef CLONE_TIME
+#define CLONE_TIME 0x04000000
+#endif
+
int start_idle_thread(void *stack, void *switch_buf_ptr, void **fork_buf_ptr)
{
sigjmp_buf **switch_buf = switch_buf_ptr;
- int n, enable;
+ int n, enable, err;

+ err = unshare(CLONE_TIME);
+ if(err)
+ panic("Couldn't create time namespace, err = %d", err);
set_handler(SIGWINCH, (__sighandler_t) sig_handler,
SA_ONSTACK | SA_RESTART, SIGUSR1, SIGIO, SIGALRM,
SIGVTALRM, -1);
Index: linux-2.6.17-mm-vtime/arch/um/include/sysdep-i386/kernel-offsets.h
===================================================================
--- linux-2.6.17-mm-vtime.orig/arch/um/include/sysdep-i386/kernel-offsets.h 2006-04-13 13:48:01.000000000 -0400
+++ linux-2.6.17-mm-vtime/arch/um/include/sysdep-i386/kernel-offsets.h 2006-04-13 13:50:34.000000000 -0400
@@ -1,6 +1,7 @@
#include <linux/stddef.h>
#include <linux/sched.h>
#include <linux/elf.h>
+#include <asm/unistd.h>

#define DEFINE(sym, val) \
asm volatile("\n->" #sym " %0 " #val : : "i" (val))
@@ -16,6 +17,7 @@
void foo(void)
{
OFFSET(HOST_TASK_DEBUGREGS, task_struct, thread.arch.debugregs);
+ DEFINE(KERNEL_NR_SYSCALLS, NR_syscalls);
#ifdef CONFIG_MODE_TT
OFFSET(HOST_TASK_EXTERN_PID, task_struct, thread.mode.tt.extern_pid);
#endif
Index: linux-2.6.17-mm-vtime/arch/um/include/os.h
===================================================================
--- linux-2.6.17-mm-vtime.orig/arch/um/include/os.h 2006-04-13 13:48:01.000000000 -0400
+++ linux-2.6.17-mm-vtime/arch/um/include/os.h 2006-04-13 13:50:34.000000000 -0400
@@ -281,6 +281,7 @@ extern void disable_timer(void);
extern void user_time_init(void);
extern void uml_idle_timer(void);
extern unsigned long long os_nsecs(void);
+extern int os_set_time(unsigned long long nsecs);

/* skas/mem.c */
extern long run_syscall_stub(struct mm_id * mm_idp,
Index: linux-2.6.17-mm-vtime/arch/um/kernel/time.c
===================================================================
--- linux-2.6.17-mm-vtime.orig/arch/um/kernel/time.c 2006-04-13 13:48:01.000000000 -0400
+++ linux-2.6.17-mm-vtime/arch/um/kernel/time.c 2006-04-13 13:50:50.000000000 -0400
@@ -129,7 +129,7 @@ void do_gettimeofday(struct timeval *tv)
clock_was_set();
}

-int do_settimeofday(struct timespec *tv)
+int do_settimeofday()
{
struct timeval now;
unsigned long flags;
@@ -138,15 +138,7 @@ int do_settimeofday(struct timespec *tv)
if ((unsigned long) tv->tv_nsec >= UM_NSEC_PER_SEC)
return -EINVAL;

- tv_in.tv_sec = tv->tv_sec;
- tv_in.tv_usec = tv->tv_nsec / 1000;
-
- flags = time_lock();
- gettimeofday(&now, NULL);
- timersub(&tv_in, &now, &local_offset);
- time_unlock(flags);
-
- return(0);
+ return os_set_time(tv);
}

void idle_sleep(int secs)
Index: linux-2.6.17-mm-vtime/arch/um/kernel/time_kern.c
===================================================================
--- linux-2.6.17-mm-vtime.orig/arch/um/kernel/time_kern.c 2006-04-13 13:48:01.000000000 -0400
+++ linux-2.6.17-mm-vtime/arch/um/kernel/time_kern.c 2006-04-13 13:50:34.000000000 -0400
@@ -151,19 +151,6 @@ void do_gettimeofday(struct timeval *tv)
tv->tv_usec = (unsigned long) nsecs / NSEC_PER_USEC;
}

-static inline void set_time(unsigned long long nsecs)
-{
- unsigned long long now;
- unsigned long flags;
-
- spin_lock_irqsave(&timer_spinlock, flags);
- now = os_nsecs();
- local_offset = nsecs - now;
- spin_unlock_irqrestore(&timer_spinlock, flags);
-
- clock_was_set();
-}
-
long um_stime(int __user *tptr)
{
int value;
@@ -171,16 +158,12 @@ long um_stime(int __user *tptr)
if (get_user(value, tptr))
return -EFAULT;

- set_time((unsigned long long) value * NSEC_PER_SEC);
-
- return 0;
+ return os_set_time((unsigned long long) value * NSEC_PER_SEC);
}

int do_settimeofday(struct timespec *tv)
{
- set_time((unsigned long long) tv->tv_sec * NSEC_PER_SEC + tv->tv_nsec);
-
- return 0;
+ return os_set_time((unsigned long long) tv->tv_sec * NSEC_PER_SEC + tv->tv_nsec);
}

void timer_handler(int sig, union uml_pt_regs *regs)
Index: linux-2.6.17-mm-vtime/arch/um/os-Linux/time.c
===================================================================
--- linux-2.6.17-mm-vtime.orig/arch/um/os-Linux/time.c 2006-04-13 13:48:01.000000000 -0400
+++ linux-2.6.17-mm-vtime/arch/um/os-Linux/time.c 2006-04-13 13:50:34.000000000 -0400
@@ -126,3 +126,21 @@ void user_time_init(void)
SIGVTALRM, SIGUSR2, -1);
set_interval(ITIMER_VIRTUAL);
}
+
+#define NSEC_PER_USEC 1000
+#define NSEC_PER_SEC (1000000 * NSEC_PER_USEC)
+
+int os_set_time(unsigned long long nsecs)
+{
+ struct timeval tv;
+ int err;
+
+ tv.tv_sec = nsecs / NSEC_PER_SEC;
+ nsecs -= tv.tv_sec * NSEC_PER_SEC;
+ tv.tv_usec = (unsigned long) nsecs / NSEC_PER_USEC;
+
+ err = settimeofday(&tv, NULL);
+ if(err)
+ return -errno;
+ return 0;
+}

-
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Next message: Jan Knutar: "Re: JVM performance on Linux (vs. Solaris/Windows)"
Previous message: Jeff Dike: "[RFC] PATCH 3/4 - Time virtualization : PTRACE_SYSCALL_MASK"
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