On Wed, Mar 11, 2009 at 02:41:38PM +0100, Renzo Davoli wrote:
>> Please check Documentation/CodingStyle. Every second line above
>> violates it. scripts/checkpatch.pl can help out with the more
>> obvious ones.
>Ingo,
>
>Thank you for your comment.
>You are right, I beg your pardon.
>I have updated the patch, now it should be (more) consistent
>with the Coding Style specifications.
You can use scripts/checkpatch.pl to check it before sending.
>
>This patch adds the new PTRACE_VM_SKIPCALL and PTRACE_VM_SKIPEXIT
>tags for ptrace's addr parameter.
>In this way it is possible to (eventually) get rid of PTRACE_SYSEMU
>PTRACE_SYSEMU_SINGLESTEP, while providing not only the same features
>but a more general support for Virtual Machines.
>Part#2: user-mode Linux support.
>User-mode Linux by this patch uses PTRACE_VM of the hosting operating system
>and provides PTRACE_VM to its processes.
>UML tests at startup which features are provided and uses PTRACE_VM or
>PTRACE_SYSEMU (or nothing). PTRACE_VM and/or PTRACE_SYSEMU support can be
>disabled by command line flags.
>
So what? PTRACE_VM is only supported in UML with this patch,
UML still has to use PTRACE_SYSEMU on x86_32.
Am I missing something? :)
>
>Signed-off-by: Renzo Davoli <re...@cs.unibo.it>
Minor comments below.
>----
>diff -Naur linux-2.6.29-rc7-git4/arch/um/include/shared/kern_util.h
>linux-2.6.29-rc7-git4.vm2/arch/um/include/shared/kern_util.h
>--- linux-2.6.29-rc7-git4/arch/um/include/shared/kern_util.h 2009-03-11
>09:25:27.000000000 +0100
>+++ linux-2.6.29-rc7-git4.vm2/arch/um/include/shared/kern_util.h
>2009-03-11 09:35:23.000000000 +0100
>@@ -57,7 +57,7 @@
> extern unsigned long to_irq_stack(unsigned long *mask_out);
> extern unsigned long from_irq_stack(int nested);
>
>-extern void syscall_trace(struct uml_pt_regs *regs, int entryexit);
>+extern int syscall_trace(struct uml_pt_regs *regs, int entryexit);
> extern int singlestepping(void *t);
>
> extern void segv_handler(int sig, struct uml_pt_regs *regs);
>diff -Naur linux-2.6.29-rc7-git4/arch/um/include/shared/ptrace_user.h
>linux-2.6.29-rc7-git4.vm2/arch/um/include/shared/ptrace_user.h
>--- linux-2.6.29-rc7-git4/arch/um/include/shared/ptrace_user.h 2009-03-11
>09:25:27.000000000 +0100
>+++ linux-2.6.29-rc7-git4.vm2/arch/um/include/shared/ptrace_user.h
>2009-03-11 09:35:23.000000000 +0100
>@@ -40,9 +40,20 @@
> #define PTRACE_OLDSETOPTIONS PTRACE_SETOPTIONS
> #endif
>
>+/* these constant should eventually enter in sys/ptrace.h */
>+#ifndef PTRACE_SYSCALL_SKIPCALL
>+#define PTRACE_SYSCALL_SKIPCALL 0x6
>+#endif
>+#ifndef PTRACE_SYSCALL_SKIPEXIT
>+#define PTRACE_SYSCALL_SKIPEXIT 0x2
>+#endif
>+
> void set_using_sysemu(int value);
> int get_using_sysemu(void);
> extern int sysemu_supported;
>+void set_using_sysptvm(int value);
>+int get_using_sysptvm(void);
>+extern int sysptvm_supported;
>
> #define SELECT_PTRACE_OPERATION(sysemu_mode, singlestep_mode) \
> (((int[3][3] ) { \
>diff -Naur linux-2.6.29-rc7-git4/arch/um/kernel/process.c
>linux-2.6.29-rc7-git4.vm2/arch/um/kernel/process.c
>--- linux-2.6.29-rc7-git4/arch/um/kernel/process.c 2009-03-11
>09:25:27.000000000 +0100
>+++ linux-2.6.29-rc7-git4.vm2/arch/um/kernel/process.c 2009-03-11
>10:03:05.000000000 +0100
>@@ -322,7 +322,9 @@
> }
>
> static atomic_t using_sysemu = ATOMIC_INIT(0);
>+static atomic_t using_sysptvm = ATOMIC_INIT(0);
> int sysemu_supported;
>+int sysptvm_supported;
>
> void set_using_sysemu(int value)
> {
>@@ -336,7 +338,18 @@
> return atomic_read(&using_sysemu);
> }
>
>-static int proc_read_sysemu(char *buf, char **start, off_t offset, int
>size,int *eof, void *data)
>+void set_using_sysptvm(int value)
>+{
>+ atomic_set(&using_sysptvm, value);
>+}
>+
>+int get_using_sysptvm(void)
>+{
>+ return atomic_read(&using_sysptvm);
>+}
How about making it boolean? AFAIK, you use it as a boolean.
>+
>+static int proc_read_sysemu(char *buf, char **start, off_t offset,
>+ int size, int *eof, void *data)
> {
> if (snprintf(buf, size, "%d\n", get_using_sysemu()) < size)
> /* No overflow */
>@@ -345,7 +358,8 @@
> return strlen(buf);
> }
>
>-static int proc_write_sysemu(struct file *file,const char __user *buf,
>unsigned long count,void *data)
>+static int proc_write_sysemu(struct file *file, const char __user *buf,
>+ unsigned long count, void *data)
> {
> char tmp[2];
>
>@@ -358,27 +372,63 @@
> return count;
> }
>
>-int __init make_proc_sysemu(void)
>+
>+static int proc_read_sysptvm(char *buf, char **start, off_t offset,
>+ int size, int *eof, void *data)
> {
>- struct proc_dir_entry *ent;
>- if (!sysemu_supported)
>- return 0;
>+ int sysptvm = (get_using_sysptvm() != 0);
>+ if (snprintf(buf, size, "%d\n", sysptvm) < size)
>+ /* No overflow */
>+ *eof = 1;
>
>- ent = create_proc_entry("sysemu", 0600, NULL);
>+ return strlen(buf);
>+}
>
>- if (ent == NULL)
>- {
>- printk(KERN_WARNING "Failed to register /proc/sysemu\n");
>- return 0;
>- }
>+static int proc_write_sysptvm(struct file *file, const char __user *buf,
>+ unsigned long count, void *data)
>+{
>+ char tmp[2];
>+
>+ if (copy_from_user(tmp, buf, 1))
>+ return -EFAULT;
>+
>+ if (tmp[0] == '0')
>+ set_using_sysptvm(0);
>+ if (tmp[0] == '1')
>+ set_using_sysemu(/* XXX */ 6);
>+ /* We use the first char, but pretend to write everything */
>+ return count;
>+}
>
>- ent->read_proc = proc_read_sysemu;
>- ent->write_proc = proc_write_sysemu;
>+int __init make_proc_sysemu_or_sysptvm(void)
>+{
>+ struct proc_dir_entry *ent;
>
>+ if (sysptvm_supported) {
>+ ent = create_proc_entry("sysptvm", 0600, NULL);
>+
>+ if (ent == NULL) {
>+ printk(KERN_WARNING "Failed to register
>/proc/sysptvm\n");
>+ return 0;
>+ }
>+
>+ ent->read_proc = proc_read_sysptvm;
>+ ent->write_proc = proc_write_sysptvm;
>+ } else if (sysemu_supported) {
>+ ent = create_proc_entry("sysemu", 0600, NULL);
>+
>+ if (ent == NULL) {
>+ printk(KERN_WARNING "Failed to register
>/proc/sysemu\n");
>+ return 0;
>+ }
>+
>+ ent->read_proc = proc_read_sysemu;
>+ ent->write_proc = proc_write_sysemu;
>+ }
> return 0;
> }
>
>-late_initcall(make_proc_sysemu);
>+late_initcall(make_proc_sysemu_or_sysptvm);
>
> int singlestepping(void * t)
> {
>diff -Naur linux-2.6.29-rc7-git4/arch/um/kernel/ptrace.c
>linux-2.6.29-rc7-git4.vm2/arch/um/kernel/ptrace.c
>--- linux-2.6.29-rc7-git4/arch/um/kernel/ptrace.c 2009-03-11
>09:30:19.000000000 +0100
>+++ linux-2.6.29-rc7-git4.vm2/arch/um/kernel/ptrace.c 2009-03-11
>09:35:23.000000000 +0100
>@@ -81,6 +81,8 @@
> if (request == PTRACE_SYSCALL)
> set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
> else clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
>+ child->ptrace &= ~PT_SYSCALL_MASK;
>+ child->ptrace |= (addr & PTRACE_SYSCALL_MASK) << 28;
28, ditto.
> child->exit_code = data;
> wake_up_process(child);
> ret = 0;
>@@ -107,7 +109,9 @@
> ret = -EIO;
> if (!valid_signal(data))
> break;
>+ child->ptrace &= ~PT_SYSCALL_MASK;
> clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
>+ child->ptrace |= (addr & PTRACE_SYSCALL_MASK) << 28;
> set_singlestepping(child, 1);
> child->exit_code = data;
> /* give it a chance to run. */
>@@ -250,7 +254,7 @@
> * XXX Check PT_DTRACE vs TIF_SINGLESTEP for singlestepping check and
> * PT_PTRACED vs TIF_SYSCALL_TRACE for syscall tracing check
> */
>-void syscall_trace(struct uml_pt_regs *regs, int entryexit)
>+int syscall_trace(struct uml_pt_regs *regs, int entryexit)
> {
> int is_singlestep = (current->ptrace & PT_DTRACE) && entryexit;
> int tracesysgood;
>@@ -272,10 +276,13 @@
> send_sigtrap(current, regs, 0);
>
> if (!test_thread_flag(TIF_SYSCALL_TRACE))
>- return;
>+ return 0;
>
> if (!(current->ptrace & PT_PTRACED))
>- return;
>+ return 0;
>+
>+ if (entryexit && (current->ptrace & PT_SYSCALL_SKIPEXIT))
>+ return 0;
>
> /*
> * the 0x80 provides a way for the tracing parent to distinguish
>@@ -296,4 +303,8 @@
> send_sig(current->exit_code, current, 1);
> current->exit_code = 0;
> }
>+ if (!entryexit && (current->ptrace & PT_SYSCALL_SKIPCALL))
>+ return 1;
>+ else
>+ return 0;
> }
>diff -Naur linux-2.6.29-rc7-git4/arch/um/kernel/skas/syscall.c
>linux-2.6.29-rc7-git4.vm2/arch/um/kernel/skas/syscall.c
>--- linux-2.6.29-rc7-git4/arch/um/kernel/skas/syscall.c 2009-03-11
>09:25:27.000000000 +0100
>+++ linux-2.6.29-rc7-git4.vm2/arch/um/kernel/skas/syscall.c 2009-03-11
>09:41:29.000000000 +0100
>@@ -17,8 +17,9 @@
> struct pt_regs *regs = container_of(r, struct pt_regs, regs);
> long result;
> int syscall;
>+ int skip_call;
>
>- syscall_trace(r, 0);
>+ skip_call = syscall_trace(r, 0);
>
> /*
> * This should go in the declaration of syscall, but when I do that,
>@@ -29,12 +30,15 @@
> * gcc version 4.0.1 20050727 (Red Hat 4.0.1-5)
> * in case it's a compiler bug.
> */
>- syscall = UPT_SYSCALL_NR(r);
>- if ((syscall >= NR_syscalls) || (syscall < 0))
>- result = -ENOSYS;
>- else result = EXECUTE_SYSCALL(syscall, regs);
>+ if (skip_call == 0) {
>+ syscall = UPT_SYSCALL_NR(r);
>+ if ((syscall >= NR_syscalls) || (syscall < 0))
>+ result = -ENOSYS;
>+ else
>+ result = EXECUTE_SYSCALL(syscall, regs);
>
>- REGS_SET_SYSCALL_RETURN(r->gp, result);
>+ REGS_SET_SYSCALL_RETURN(r->gp, result);
>+ }
>
> syscall_trace(r, 1);
> }
>diff -Naur linux-2.6.29-rc7-git4/arch/um/os-Linux/skas/process.c
>linux-2.6.29-rc7-git4.vm2/arch/um/os-Linux/skas/process.c
>--- linux-2.6.29-rc7-git4/arch/um/os-Linux/skas/process.c 2009-03-11
>09:25:27.000000000 +0100
>+++ linux-2.6.29-rc7-git4.vm2/arch/um/os-Linux/skas/process.c 2009-03-11
>09:35:23.000000000 +0100
>@@ -157,7 +157,7 @@
> * (in local_using_sysemu
> */
> static void handle_trap(int pid, struct uml_pt_regs *regs,
>- int local_using_sysemu)
>+ int local_using_sysptvm_or_sysemu)
This argument name is too long. :)
> {
> int err, status;
>
>@@ -167,7 +167,7 @@
> /* Mark this as a syscall */
> UPT_SYSCALL_NR(regs) = PT_SYSCALL_NR(regs->gp);
>
>- if (!local_using_sysemu)
>+ if (!local_using_sysptvm_or_sysemu)
> {
> err = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_NR_OFFSET,
> __NR_getpid);
>@@ -354,6 +354,7 @@
> int err, status, op, pid = userspace_pid[0];
> /* To prevent races if using_sysemu changes under us.*/
> int local_using_sysemu;
>+ int local_using_sysptvm;
>
> if (getitimer(ITIMER_VIRTUAL, &timer))
> printk(UM_KERN_ERR "Failed to get itimer, errno = %d\n", errno);
>@@ -375,11 +376,12 @@
>
> /* Now we set local_using_sysemu to be used for one loop */
> local_using_sysemu = get_using_sysemu();
>+ local_using_sysptvm = get_using_sysptvm();
>
> op = SELECT_PTRACE_OPERATION(local_using_sysemu,
> singlestepping(NULL));
>
>- if (ptrace(op, pid, 0, 0)) {
>+ if (ptrace(op, pid, local_using_sysptvm, 0)) {
> printk(UM_KERN_ERR "userspace - ptrace continue "
> "failed, op = %d, errno = %d\n", op, errno);
> fatal_sigsegv();
>diff -Naur linux-2.6.29-rc7-git4/arch/um/os-Linux/start_up.c
>linux-2.6.29-rc7-git4.vm2/arch/um/os-Linux/start_up.c
>--- linux-2.6.29-rc7-git4/arch/um/os-Linux/start_up.c 2009-03-11
>09:25:27.000000000 +0100
>+++ linux-2.6.29-rc7-git4.vm2/arch/um/os-Linux/start_up.c 2009-03-11
>09:58:40.000000000 +0100
>@@ -198,6 +198,34 @@
> " See http://perso.wanadoo.fr/laurent.vivier/UML/ for further \n"
> " information.\n\n");
>
>+/* Changed only during early boot */
>+static int force_sysptvm_disabled;
>+
>+static int __init nosysptvm_cmd_param(char *str, int* add)
>+{
>+ force_sysptvm_disabled = 1;
>+ return 0;
>+}
>+
>+__uml_setup("nosysptvm", nosysptvm_cmd_param,
>+"nosysptvm\n"
>+" Turns off syscall emulation tags for ptrace (ptrace_vm) on.\n"
>+" Ptrace_vm is a feature introduced by Renzo Davoli. It changes\n"
>+" behaviour of ptrace() and helps reducing host context switch rate.\n\n");
>+
>+static int use_sysemu;
>+
>+static int __init usesysemu_cmd_param(char *str, int* add)
I don't like this function name either. :(
>+{
>+ use_sysemu = 1;
>+ return 0;
>+}
>+
>+__uml_setup("usesysemu", usesysemu_cmd_param,
>+"usesysemu\n"
>+" Use sysemu instead of sysptvm even when the kernel supports it.\n\n"
>+);
>+
> static void __init check_sysemu(void)
> {
> unsigned long regs[MAX_REG_NR];
>@@ -293,6 +321,114 @@
> non_fatal("missing\n");
> }
>
>+/*
>+ * test thread code. This thread is started only to test
>+ * which features are provided by the linux kernel
>+ */
>+static int sysptvm_child(void *arg)
>+{
>+ int *featurep = arg;
>+ int p[2] = {-1, -1};
>+ pid_t pid = os_getpid();
>+ if (ptrace(PTRACE_TRACEME, 0, 0, 0) < 0) {
>+ perror("ptrace test_ptracemulti");
>+ kill(pid, SIGKILL);
>+ }
>+ kill(pid, SIGSTOP);
>+ *featurep = 0;
>+ os_getpid();
>+ /*
>+ * if it reaches this point in 1 stop it means that
>+ * PTRACE_SYSCALL_SKIPEXIT works
>+ */
>+ *featurep = PTRACE_SYSCALL_SKIPEXIT;
>+ pipe(p);
>+ /*
>+ * if after a PTRACE_SYSCALL_SKIPCALL p[0] is already <0
>+ * pipe has been really skipped
>+ */
>+ if (p[0] < 0)
>+ *featurep = PTRACE_SYSCALL_SKIPCALL;
>+ else { /* clean up everything */
>+ close(p[0]);
>+ close(p[1]);
>+ }
>+ return 0;
>+}
>+
>+/*
>+ * kernel feature test:
>+ * it returns:
>+ * -1 error
>+ * 0 old PTRACE_SYSCALL (addr is ignored)
>+ * PTRACE_SYSCALL_SKIPEXIT: just skip_exit is provided
>+ * PTRACE_SYSCALL_SKIPCALL: the entire syntax is implemented
>+ * by the running kernel
>+ */
>+static int __init test_ptrace_sysptvm(void)
How about check_ptrace_sysptvm? Since it is consistent with
other check_XXX functions.
>+{
>+ int pid, status, rv, feature;
>+ static char stack[1024];
>+ feature = 0;
>+
>+ pid = clone(sysptvm_child, &stack[1020], SIGCHLD | CLONE_VM, &feature);
>+ if (pid < 0)
>+ return 0;
>+ if (waitpid(pid, &status, WUNTRACED) < 0) {
>+ kill(pid, SIGKILL);
>+ return 0;
>+ }
>+ /* restart and wait for the next syscall (getpid)*/
>+ rv = ptrace(PTRACE_SYSCALL, pid, 0, 0);
>+ if (waitpid(pid, &status, WUNTRACED) < 0)
>+ goto out;
>+ /* try to skip the exit call */
>+ rv = ptrace(PTRACE_SYSCALL, pid, PTRACE_SYSCALL_SKIPEXIT, 0);
>+ if (rv < 0)
>+ goto out;
>+ /* wait for the next stop */
>+ if (waitpid(pid, &status, WUNTRACED) < 0)
>+ goto out;
>+ /*
>+ * if feature is already 0 it means that this is the exit call,
>+ * and it has not been skipped, otherwise this is the
>+ * entry call for the system call "time"
>+ */
>+ if (feature < PTRACE_SYSCALL_SKIPEXIT)
>+ goto out;
>+ /* restart (time) and and try to skip the entire call */
>+ rv = ptrace(PTRACE_SYSCALL, pid, PTRACE_SYSCALL_SKIPCALL, 0);
>+ if (waitpid(pid, &status, WUNTRACED) < 0)
>+ return 0;
>+out:
>+ ptrace(PTRACE_KILL, pid, 0, 0);
>+ /* eliminate zombie */
>+ if (waitpid(pid, &status, WUNTRACED) < 0)
>+ return 0;
>+ return feature;
>+}
>+
>+static int __init check_sysptvm(void)
>+{
>+ int feature = test_ptrace_sysptvm();
>+
>+ non_fatal("Checking ptrace new tags for syscall emulation...");
>+ if (feature == PTRACE_SYSCALL_SKIPCALL) {
>+ sysptvm_supported = 1;
>+ non_fatal("OK");
>+ if (!force_sysptvm_disabled) {
>+ set_using_sysptvm(PTRACE_SYSCALL_SKIPCALL);
>+ non_fatal("\n");
>+ return 1;
>+ } else {
>+ non_fatal(" (disabled)\n");
>+ return 0;
>+ }
>+ } else
>+ non_fatal("unsupported\n");
>+ return 0;
>+}
>+
> static void __init check_ptrace(void)
> {
> int pid, syscall, n, status;
>@@ -330,7 +466,8 @@
> }
> stop_ptraced_child(pid, 0, 1);
> non_fatal("OK\n");
>- check_sysemu();
>+ if (use_sysemu || !check_sysptvm())
>+ check_sysemu();
> }
>
> extern void check_tmpexec(void);
--
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