[uml-devel] Patchset to implement PTRACE_SYSEMU_SINGLESTEP

[uml-devel] Patchset to implement PTRACE_SYSEMU_SINGLESTEP

[Bodo Stroesser]

[-- Attachment #1: Type: text/plain, Size: 1059 bytes --]

Attached are several patches. Four of them (patch-2.6.*-skas-v7-*) implement
PTRACE_SYSEMU_SINGLESTEP in the host. They are based on
linux-2.6.7-vanilla + host-skas3-2.6.7-v7.patch (resp. the 2.6.9 versions).
The "-reorganize" patches are a rework of the current patch without changing
the functionality. The "add-SYSEMU_SINGLESTEP" then implement the new features.
Please note: the differences between 2.6.7 and 2.6.9 are dependent on the
different handling of syscall singlestepping in the two versions.

To have UML using the new feature, there are two further patches named
patch-SYSEMU_SINGLESTEP-*. They are based on linux-2.6.9-vanilla +
all bb2-patches + patch-sysemu-tt + patch-fix-uml-hang-on-2.6.9-host.
To have all the patches complete, the latter two are attached also.

I tested on host 2.6.7 and host 2.6.9 with SKAS and TT mode. Currently I don't
know any problem with it.

Bodo

BTW: Today I tried the first time since weeks to do a reboot in SKAS. It simply
      exits UML, as it did weeks ago. Is there anybody involved with that problem?

[-- Attachment #2: patch-2.6.7-skas-v7-reorganize --]
[-- Type: text/plain, Size: 4253 bytes --]

From: Bodo Stroesser <bstroesser@fujitsu-siemens.com>

This patch is based on 2.6.7-vanilla + host-skas3-2.6.7-v7.patch
It reorganizes the code without changing the behavior of the
host kernel. This is done to free TIF_SYSCALL_EMU from double
use as a preparation for SYSEMU_SINGLESTEP extension.

Signed-off-by: Bodo Stroesser <bstroesser@fujitsu-siemens.com>
---

--- a/arch/i386/kernel/entry.S	2004-11-10 16:30:16.000000000 +0100
+++ b/arch/i386/kernel/entry.S	2004-11-10 16:44:03.000000000 +0100
@@ -341,12 +341,18 @@ syscall_trace_entry:
 	xorl %edx,%edx
 	call do_syscall_trace
 	cmpl $0, %eax
-	jne syscall_exit		# ret != 0 -> running under PTRACE_SYSEMU,
+	jne syscall_skip		# ret != 0 -> running under PTRACE_SYSEMU,
 					# so must skip actual syscall
 	movl ORIG_EAX(%esp), %eax
 	cmpl $(nr_syscalls), %eax
 	jnae syscall_call
 	jmp syscall_exit
+syscall_skip:
+	cli				# make sure we don't miss an interrupt
+					# setting need_resched or sigpending
+					# between sampling and the iret
+	movl TI_flags(%ebp), %ecx
+	jmp work_pending
 
 	# perform syscall exit tracing
 	ALIGN
--- a/arch/i386/kernel/ptrace.c	2004-11-10 16:29:56.000000000 +0100
+++ b/arch/i386/kernel/ptrace.c	2004-11-10 17:30:11.000000000 +0100
@@ -366,23 +366,19 @@ asmlinkage int sys_ptrace(long request, 
 		ret = -EIO;
 		if ((unsigned long) data > _NSIG)
 			break;
-		/* If we came here with PTRACE_SYSEMU and now continue with
-		 * PTRACE_SYSCALL, entry.S used to intercept the syscall return.
-		 * But it shouldn't!
-		 * So we don't clear TIF_SYSCALL_EMU, which is always unused in
-		 * this special case, to remember, we came from SYSEMU. That
-		 * flag will be cleared by do_syscall_trace().
-		 */
 		if (request == PTRACE_SYSEMU) {
 			set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
-		} else if (request == PTRACE_CONT) {
-			clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
+			clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 		}
-		if (request == PTRACE_SYSCALL) {
+		else if (request == PTRACE_SYSCALL) {
 			set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
-		} else {
+			clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
+		}
+		else {
+			clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
 			clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 		}
+		clear_tsk_thread_flag(child, TIF_SINGLESTEP);
 		child->exit_code = data;
 	/* make sure the single step bit is not set. */
 		tmp = get_stack_long(child, EFL_OFFSET) & ~TRAP_FLAG;
@@ -417,8 +413,7 @@ asmlinkage int sys_ptrace(long request, 
 		ret = -EIO;
 		if ((unsigned long) data > _NSIG)
 			break;
-		/* See do_syscall_trace to know why we don't clear
-		 * TIF_SYSCALL_EMU.*/
+		clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
 		clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 		if ((child->ptrace & PT_DTRACE) == 0) {
 			/* Spurious delayed TF traps may occur */
@@ -591,7 +586,7 @@ out:
 __attribute__((regparm(3)))
 int do_syscall_trace(struct pt_regs *regs, int entryexit)
 {
-	int is_sysemu, is_systrace, is_singlestep;
+	int is_sysemu;
 	if (unlikely(current->audit_context)) {
 		if (!entryexit)
 			audit_syscall_entry(current, regs->orig_eax,
@@ -601,20 +596,9 @@ int do_syscall_trace(struct pt_regs *reg
 			audit_syscall_exit(current, regs->eax);
 	}
 	is_sysemu = test_thread_flag(TIF_SYSCALL_EMU);
-	is_systrace = test_thread_flag(TIF_SYSCALL_TRACE);
-	is_singlestep = test_thread_flag(TIF_SINGLESTEP);
 
-	if (!is_systrace && !is_sysemu)
+	if (!test_thread_flag(TIF_SYSCALL_TRACE) && !is_sysemu)
 		return 0;
-	/* We can detect the case of coming from PTRACE_SYSEMU and now running
-	 * with PTRACE_SYSCALL or PTRACE_SINGLESTEP, by TIF_SYSCALL_EMU being
-	 * set additionally.
-	 * If so let's reset the flag and return without action.
-	 */
-	if (is_sysemu && (is_systrace || is_singlestep)) {
-		clear_thread_flag(TIF_SYSCALL_EMU);
-		return 0;
-	}
 	if (!(current->ptrace & PT_PTRACED))
 		return 0;
 	/* the 0x80 provides a way for the tracing parent to distinguish
@@ -632,5 +616,10 @@ int do_syscall_trace(struct pt_regs *reg
 		current->exit_code = 0;
 	}
 	/* != 0 if nullifying the syscall, 0 if running it normally */
-	return is_sysemu;
+	if ( !is_sysemu )
+		return 0;
+
+	if (unlikely(current->audit_context))
+		audit_syscall_exit(current, regs->eax);
+	return 1;
 }

[-- Attachment #3: patch-2.6.7-skas-v7-add-SYSEMU_SINGLESTEP --]
[-- Type: text/plain, Size: 3408 bytes --]

From: Bodo Stroesser <bstroesser@fujitsu-siemens.com>

This patch is based on
   2.6.7-vanilla +
   host-skas3-2.6.7-v7.patch +
   patch-2.6.7-skas-v7-reorganize
It implements the new ptrace option PTRACE_SYSEMU_SINGLESTEP
this new option can be used by UML to singlestep a process.
Then it will receive the common syscall interceptions plus
a singlestep trap for each non syscall instruction.

Signed-off-by: Bodo Stroesser <bstroesser@fujitsu-siemens.com>
---

--- a/include/linux/ptrace.h	2004-11-10 18:24:59.120850808 +0100
+++ b/include/linux/ptrace.h	2004-11-10 18:26:08.894243640 +0100
@@ -21,6 +21,7 @@
 
 #define PTRACE_SYSCALL		  24
 #define PTRACE_SYSEMU		  31
+#define PTRACE_SYSEMU_SINGLESTEP  32
 
 /* 0x4200-0x4300 are reserved for architecture-independent additions.  */
 #define PTRACE_SETOPTIONS	0x4200
--- a/arch/i386/kernel/ptrace.c	2004-11-10 18:20:02.047012896 +0100
+++ b/arch/i386/kernel/ptrace.c	2004-11-10 18:23:21.612674304 +0100
@@ -359,6 +359,7 @@ asmlinkage int sys_ptrace(long request, 
 		  break;
 
 	case PTRACE_SYSEMU: /* continue and stop at next syscall, which will not be executed */
+	case PTRACE_SYSEMU_SINGLESTEP: /* Same as SYSEMU, but singlestep if not syscall */
 	case PTRACE_SYSCALL: /* continue and stop at next (return from) syscall */
 	case PTRACE_CONT: { /* restart after signal. */
 		long tmp;
@@ -366,22 +367,31 @@ asmlinkage int sys_ptrace(long request, 
 		ret = -EIO;
 		if ((unsigned long) data > _NSIG)
 			break;
+		/* prepare to reset single step bit */
+		tmp = get_stack_long(child, EFL_OFFSET) & ~TRAP_FLAG;
 		if (request == PTRACE_SYSEMU) {
 			set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
 			clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
+			clear_tsk_thread_flag(child, TIF_SINGLESTEP);
+		}
+		else if (request == PTRACE_SYSEMU_SINGLESTEP) {
+			set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
+			set_tsk_thread_flag(child, TIF_SINGLESTEP);
+			clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
+			/* For SYSEMU_SINGLESTEP, set single step bit */
+			tmp |= TRAP_FLAG;
 		}
 		else if (request == PTRACE_SYSCALL) {
 			set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 			clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
+			clear_tsk_thread_flag(child, TIF_SINGLESTEP);
 		}
 		else {
 			clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
 			clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
+			clear_tsk_thread_flag(child, TIF_SINGLESTEP);
 		}
-		clear_tsk_thread_flag(child, TIF_SINGLESTEP);
 		child->exit_code = data;
-	/* make sure the single step bit is not set. */
-		tmp = get_stack_long(child, EFL_OFFSET) & ~TRAP_FLAG;
 		put_stack_long(child, EFL_OFFSET,tmp);
 		wake_up_process(child);
 		ret = 0;
@@ -596,6 +606,11 @@ int do_syscall_trace(struct pt_regs *reg
 			audit_syscall_exit(current, regs->eax);
 	}
 	is_sysemu = test_thread_flag(TIF_SYSCALL_EMU);
+	/* If a process stops on the 1st tracepoint with SYSCALL_TRACE
+         * and then is resumed with SYSCALL_EMU and TIF_SYSAUDIT is set,
+	 *  it will come in here. We have to check this and return */
+	if (is_sysemu && entryexit)
+		return 0;
 
 	if (!test_thread_flag(TIF_SYSCALL_TRACE) && !is_sysemu)
 		return 0;
@@ -619,6 +634,7 @@ int do_syscall_trace(struct pt_regs *reg
 	if ( !is_sysemu )
 		return 0;
 
+	regs->orig_eax = -1; /* force skip of syscall restarting */
 	if (unlikely(current->audit_context))
 		audit_syscall_exit(current, regs->eax);
 	return 1;

[-- Attachment #4: patch-2.6.9-skas-v7-reorganize --]
[-- Type: text/plain, Size: 4175 bytes --]

From: Bodo Stroesser <bstroesser@fujitsu-siemens.com>

This patch is based on 2.6.9-vanilla + host-skas3-2.6.9-v7.patch
It reorganizes the code without changing the behavior of the
host kernel. This is done to free TIF_SYSCALL_EMU from double
use as a preparation for SYSEMU_SINGLESTEP extension.

Signed-off-by: Bodo Stroesser <bstroesser@fujitsu-siemens.com>
---

--- a/arch/i386/kernel/entry.S	2004-11-10 16:30:16.000000000 +0100
+++ b/arch/i386/kernel/entry.S	2004-11-10 16:44:03.000000000 +0100
@@ -341,12 +341,18 @@ syscall_trace_entry:
 	xorl %edx,%edx
 	call do_syscall_trace
 	cmpl $0, %eax
-	jne syscall_exit		# ret != 0 -> running under PTRACE_SYSEMU,
+	jne syscall_skip		# ret != 0 -> running under PTRACE_SYSEMU,
 					# so must skip actual syscall
 	movl ORIG_EAX(%esp), %eax
 	cmpl $(nr_syscalls), %eax
 	jnae syscall_call
 	jmp syscall_exit
+syscall_skip:
+	cli				# make sure we don't miss an interrupt
+					# setting need_resched or sigpending
+					# between sampling and the iret
+	movl TI_flags(%ebp), %ecx
+	jmp work_pending
 
 	# perform syscall exit tracing
 	ALIGN
--- a/arch/i386/kernel/ptrace.c	2004-11-10 16:29:56.000000000 +0100
+++ b/arch/i386/kernel/ptrace.c	2004-11-10 17:30:11.000000000 +0100
@@ -367,21 +367,16 @@ asmlinkage int sys_ptrace(long request, 
 		ret = -EIO;
 		if ((unsigned long) data > _NSIG)
 			break;
-		/* If we came here with PTRACE_SYSEMU and now continue with
-		 * PTRACE_SYSCALL, entry.S used to intercept the syscall return.
-		 * But it shouldn't!
-		 * So we don't clear TIF_SYSCALL_EMU, which is always unused in
-		 * this special case, to remember, we came from SYSEMU. That
-		 * flag will be cleared by do_syscall_trace().
-		 */
 		if (request == PTRACE_SYSEMU) {
 			set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
-		} else if (request == PTRACE_CONT) {
-			clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
+			clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 		}
-		if (request == PTRACE_SYSCALL) {
+		else if (request == PTRACE_SYSCALL) {
 			set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
-		} else {
+			clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
+		}
+		else {
+			clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
 			clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 		}
 		clear_tsk_thread_flag(child, TIF_SINGLESTEP);
@@ -420,8 +415,7 @@ asmlinkage int sys_ptrace(long request, 
 		ret = -EIO;
 		if ((unsigned long) data > _NSIG)
 			break;
-		/*See do_syscall_trace to know why we don't clear
-		 * TIF_SYSCALL_EMU.*/
+		clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
 		clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 		if ((child->ptrace & PT_DTRACE) == 0) {
 			/* Spurious delayed TF traps may occur */
@@ -595,7 +589,7 @@ out:
 __attribute__((regparm(3)))
 int do_syscall_trace(struct pt_regs *regs, int entryexit)
 {
-	int is_sysemu, is_systrace, is_singlestep;
+	int is_sysemu, is_singlestep;
 	if (unlikely(current->audit_context)) {
 		if (!entryexit)
 			audit_syscall_entry(current, regs->orig_eax,
@@ -605,20 +599,11 @@ int do_syscall_trace(struct pt_regs *reg
 			audit_syscall_exit(current, regs->eax);
 	}
 	is_sysemu = test_thread_flag(TIF_SYSCALL_EMU);
-	is_systrace = test_thread_flag(TIF_SYSCALL_TRACE);
 	is_singlestep = test_thread_flag(TIF_SINGLESTEP);
 
-	if (!is_systrace && !is_singlestep && !is_sysemu)
+	if (!test_thread_flag(TIF_SYSCALL_TRACE) &&
+	    !is_singlestep && !is_sysemu)
 		return 0;
-	/* We can detect the case of coming from PTRACE_SYSEMU and now running
-	 * with PTRACE_SYSCALL or PTRACE_SINGLESTEP, by TIF_SYSCALL_EMU being
-	 * set additionally.
-	 * If so let's reset the flag and return without action.
-	 */
-	if (is_sysemu && (is_systrace || is_singlestep)) {
-		clear_thread_flag(TIF_SYSCALL_EMU);
-		return 0;
-	}
 	if (!(current->ptrace & PT_PTRACED))
 		return 0;
 	/* the 0x80 provides a way for the tracing parent to distinguish
@@ -636,5 +621,10 @@ int do_syscall_trace(struct pt_regs *reg
 		current->exit_code = 0;
 	}
 	/* != 0 if nullifying the syscall, 0 if running it normally */
-	return is_sysemu;
+	if ( !is_sysemu )
+		return 0;
+
+	if (unlikely(current->audit_context))
+		audit_syscall_exit(current, regs->eax);
+	return 1;
 }

[-- Attachment #5: patch-2.6.9-skas-v7-add-SYSEMU_SINGLESTEP --]
[-- Type: text/plain, Size: 3584 bytes --]

From: Bodo Stroesser <bstroesser@fujitsu-siemens.com>

This patch is based on
   2.6.9-vanilla +
   host-skas3-2.6.9-v7.patch +
   patch-2.6.9-skas-v7-reorganize
It implements the new ptrace option PTRACE_SYSEMU_SINGLESTEP
this new option can be used by UML to singlestep a process.
Then it will receive the common syscall interceptions plus
a singlestep trap for each non syscall instruction.

Signed-off-by: Bodo Stroesser <bstroesser@fujitsu-siemens.com>
---

--- a/include/linux/ptrace.h	2004-11-10 18:24:59.120850808 +0100
+++ b/include/linux/ptrace.h	2004-11-10 18:26:08.894243640 +0100
@@ -21,6 +21,7 @@
 
 #define PTRACE_SYSCALL		  24
 #define PTRACE_SYSEMU		  31
+#define PTRACE_SYSEMU_SINGLESTEP  32
 
 /* 0x4200-0x4300 are reserved for architecture-independent additions.  */
 #define PTRACE_SETOPTIONS	0x4200
--- a/arch/i386/kernel/ptrace.c	2004-11-10 18:20:02.047012896 +0100
+++ b/arch/i386/kernel/ptrace.c	2004-11-10 18:23:21.612674304 +0100
@@ -360,6 +360,7 @@ asmlinkage int sys_ptrace(long request, 
 		  break;
 
 	case PTRACE_SYSEMU: /* continue and stop at next syscall, which will not be executed */
+	case PTRACE_SYSEMU_SINGLESTEP: /* Same as SYSEMU, but singlestep if not syscall */
 	case PTRACE_SYSCALL: /* continue and stop at next (return from) syscall */
 	case PTRACE_CONT: { /* restart after signal. */
 		long tmp;
@@ -367,22 +368,31 @@ asmlinkage int sys_ptrace(long request, 
 		ret = -EIO;
 		if ((unsigned long) data > _NSIG)
 			break;
+		/* prepare to reset single step bit */
+		tmp = get_stack_long(child, EFL_OFFSET) & ~TRAP_FLAG;
 		if (request == PTRACE_SYSEMU) {
 			set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
 			clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
+			clear_tsk_thread_flag(child, TIF_SINGLESTEP);
+		}
+		else if (request == PTRACE_SYSEMU_SINGLESTEP) {
+			set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
+			set_tsk_thread_flag(child, TIF_SINGLESTEP);
+			clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
+			/* For SYSEMU_SINGLESTEP, set single step bit */
+			tmp |= TRAP_FLAG;
 		}
 		else if (request == PTRACE_SYSCALL) {
 			set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 			clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
+			clear_tsk_thread_flag(child, TIF_SINGLESTEP);
 		}
 		else {
 			clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
 			clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
+			clear_tsk_thread_flag(child, TIF_SINGLESTEP);
 		}
-		clear_tsk_thread_flag(child, TIF_SINGLESTEP);
 		child->exit_code = data;
-	/* make sure the single step bit is not set. */
-		tmp = get_stack_long(child, EFL_OFFSET) & ~TRAP_FLAG;
 		put_stack_long(child, EFL_OFFSET,tmp);
 		wake_up_process(child);
 		ret = 0;
@@ -599,7 +609,13 @@ int do_syscall_trace(struct pt_regs *reg
 			audit_syscall_exit(current, regs->eax);
 	}
 	is_sysemu = test_thread_flag(TIF_SYSCALL_EMU);
-	is_singlestep = test_thread_flag(TIF_SINGLESTEP);
+	/* If a process stops on the 1st tracepoint with SYSCALL_TRACE
+         * and then is resumed with SYSEMU_SINGLESTEP, it will come in
+	 * here. We have to check this and return */
+	if (is_sysemu && entryexit)
+		return 0;
+	/* With TIF_SYSCALL_EMU set we want to ignore TIF_SINGLESTEP */
+	is_singlestep = !is_sysemu && test_thread_flag(TIF_SINGLESTEP);
 
 	if (!test_thread_flag(TIF_SYSCALL_TRACE) &&
 	    !is_singlestep && !is_sysemu)
@@ -624,6 +640,7 @@ int do_syscall_trace(struct pt_regs *reg
 	if ( !is_sysemu )
 		return 0;
 
+	regs->orig_eax = -1; /* force skip of syscall restarting */
 	if (unlikely(current->audit_context))
 		audit_syscall_exit(current, regs->eax);
 	return 1;

[-- Attachment #6: patch-SYSEMU_SINGLESTEP-1 --]
[-- Type: text/plain, Size: 3774 bytes --]

From: Bodo Stroesser <bstroesser@fujitsu-siemens.com>

This patch is based on
   2.6.9-vanilla +
   all patches from uml-2.6.9-bb2-broken-out.tar.bz2 +
   patch-fix-sysemu-tt +
   patch-fix-uml-hang-on-2.6.9-host

It implements checking for the new ptrace option SYSEMU_SINGLESTEP
(advanced sysemu) and allows the values 0,1,2 for /proc/sysemu,
if advanced sysemu is available:
   0 = don't use sysemu
   1 = use sysemu, but don't use advanced sysemu
   2 = use sysemu and advanced sysemu

Signed-off-by: Bodo Stroesser <bstroesser@fujitsu-siemens.com>
---

--- a/include/linux/ptrace.h	2004-11-11 13:16:35.750434832 +0100
+++ b/include/linux/ptrace.h	2004-11-11 13:16:59.676797472 +0100
@@ -21,6 +21,7 @@
 
 #define PTRACE_SYSCALL		  24
 #define PTRACE_SYSEMU		  31
+#define PTRACE_SYSEMU_SINGLESTEP  32
 
 /* 0x4200-0x4300 are reserved for architecture-independent additions.  */
 #define PTRACE_SETOPTIONS	0x4200
--- a/arch/um/include/ptrace_user.h	2004-11-11 13:22:00.928000328 +0100
+++ b/arch/um/include/ptrace_user.h	2004-11-11 13:22:42.005755560 +0100
@@ -21,6 +21,9 @@ extern void ptrace_pokeuser(unsigned lon
 #ifndef PTRACE_SYSEMU
 #define PTRACE_SYSEMU 31
 #endif
+#ifndef PTRACE_SYSEMU_SINGLESTEP
+#define PTRACE_SYSEMU_SINGLESTEP 32
+#endif
 
 void set_using_sysemu(int value);
 int get_using_sysemu(void);
--- a/arch/um/kernel/process.c	2004-11-11 13:01:48.556308840 +0100
+++ b/arch/um/kernel/process.c	2004-11-11 13:33:34.089623744 +0100
@@ -241,7 +241,7 @@ __uml_setup("nosysemu", nosysemu_cmd_par
 static void __init check_sysemu(void)
 {
 	void *stack;
-	int pid, n, status;
+	int pid, syscall, n, status, count=0;
 
 	printk("Checking syscall emulation patch for ptrace...");
 	sysemu_supported = 0;
@@ -269,12 +269,46 @@ static void __init check_sysemu(void)
 	sysemu_supported = 1;
 	printk("OK\n");
 	set_using_sysemu(!force_sysemu_disabled);
+
+	printk("Checking advanced syscall emulation patch for ptrace...");
+	pid = start_ptraced_child(&stack);
+	while(1){
+		count++;
+		if(ptrace(PTRACE_SYSEMU_SINGLESTEP, pid, 0, 0) < 0)
+			goto fail;
+		CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
+		if(n < 0)
+			panic("check_ptrace : wait failed, errno = %d", errno);
+		if(!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGTRAP))
+			panic("check_ptrace : expected (SIGTRAP|SYSCALL_TRAP), "
+			      "got status = %d", status);
+		
+		syscall = ptrace(PTRACE_PEEKUSER, pid, PT_SYSCALL_NR_OFFSET,
+				 0);
+		if(syscall == __NR_getpid){
+			if (!count)
+				panic("check_ptrace : SYSEMU_SINGLESTEP doesn't singlestep");
+			n = ptrace(PTRACE_POKEUSER, pid, PT_SYSCALL_RET_OFFSET,
+				   os_getpid());
+			if(n < 0)
+				panic("check_sysemu : failed to modify system "
+				      "call return, errno = %d", errno);
+			break;
+		}
+	}
+	if (stop_ptraced_child(pid, stack, 0, 0) < 0)
+		goto fail_stopped;
+
+	sysemu_supported = 2;
+	printk("OK\n");
+
+	if ( !force_sysemu_disabled )
+		set_using_sysemu(sysemu_supported);
 	return;
 
 fail:
 	stop_ptraced_child(pid, stack, 1, 0);
 fail_stopped:
-	sysemu_supported = 0;
 	printk("missing\n");
 }
 
--- a/arch/um/kernel/process_kern.c	2004-11-11 12:41:33.029097064 +0100
+++ b/arch/um/kernel/process_kern.c	2004-11-11 12:44:56.451172208 +0100
@@ -405,7 +405,9 @@ int sysemu_supported;
 
 void set_using_sysemu(int value)
 {
-	atomic_set(&using_sysemu, sysemu_supported && value);
+	if (value > sysemu_supported)
+		return;
+	atomic_set(&using_sysemu, value);
 }
 
 int get_using_sysemu(void)
@@ -428,7 +430,7 @@ static int proc_write_sysemu(struct file
 	if (copy_from_user(tmp, buf, 1))
 		return -EFAULT;
 
-	if (tmp[0] == '0' || tmp[0] == '1')
+	if (tmp[0] >= '0' && tmp[0] <= '2')
 		set_using_sysemu(tmp[0] - '0');
 	return count; /*We use the first char, but pretend to write everything*/
 }

[-- Attachment #7: patch-SYSEMU_SINGLESTEP-2 --]
[-- Type: text/plain, Size: 4799 bytes --]

From: Bodo Stroesser <bstroesser@fujitsu-siemens.com>

This patch is based on
   2.6.9-vanilla +
   all patches from uml-2.6.9-bb2-broken-out.tar.bz2 +
   patch-fix-sysemu-tt +
   patch-fix-uml-hang-on-2.6.9-host
   patch-SYSEMU_SINGLESTEP-1

It implements using the new ptrace option SYSEMU_SINGLESTEP in UML
(advanced sysemu) in SKAS and TT modes.
To have a fast selection of the appropriate ptrace option to use next,
a 2 dimensional arry is used and singlestepping is modified to return
0,1 or 2:
    0 = don't do singlestepping
    1 = singlestep a syscall
    2 = singlestep a "non syscall" instruction

In do_syscall() writing of the syscall number is supressed, if the
advanced sysemu is in use (that does it itself).

Signed-off-by: Bodo Stroesser <bstroesser@fujitsu-siemens.com>
---

--- a/arch/um/include/ptrace_user.h	2004-11-11 14:00:58.000000000 +0100
+++ b/arch/um/include/ptrace_user.h	2004-11-11 14:24:24.000000000 +0100
@@ -29,4 +29,11 @@ void set_using_sysemu(int value);
 int get_using_sysemu(void);
 extern int sysemu_supported;
 
+#define SELECT_PTRACE_OPERATION(sysemu_mode, singlestep_mode) \
+	(((int[3][3] ) { \
+		{ PTRACE_SYSCALL, PTRACE_SYSCALL, PTRACE_SINGLESTEP }, \
+		{ PTRACE_SYSEMU, PTRACE_SYSEMU, PTRACE_SINGLESTEP }, \
+		{ PTRACE_SYSEMU, PTRACE_SYSEMU_SINGLESTEP, PTRACE_SYSEMU_SINGLESTEP }}) \
+		[sysemu_mode][singlestep_mode])
+
 #endif
--- a/arch/um/kernel/process_kern.c	2004-11-11 14:09:12.000000000 +0100
+++ b/arch/um/kernel/process_kern.c	2004-11-11 14:32:43.000000000 +0100
@@ -465,9 +465,9 @@ int singlestepping(void * t)
 		return(0);
 
 	if (task->thread.singlestep_syscall)
-		return(0);
+		return(1);
 
-	return 1;
+	return 2;
 }
 
 /*
--- a/arch/um/kernel/skas/process.c	2004-11-11 14:14:37.000000000 +0100
+++ b/arch/um/kernel/skas/process.c	2004-11-11 14:24:48.000000000 +0100
@@ -140,15 +140,15 @@ void start_userspace(int cpu)
 
 void userspace(union uml_pt_regs *regs)
 {
-	int err, status, op, pt_syscall_parm, pid = userspace_pid[0];
+	int err, status, op, pid = userspace_pid[0];
 	int local_using_sysemu; /*To prevent races if using_sysemu changes under us.*/
 
 	restore_registers(regs);
 		
 	local_using_sysemu = get_using_sysemu();
 
-	pt_syscall_parm = local_using_sysemu ? PTRACE_SYSEMU : PTRACE_SYSCALL;
-	err = ptrace(pt_syscall_parm, pid, 0, 0);
+	op = local_using_sysemu ? PTRACE_SYSEMU : PTRACE_SYSCALL;
+	err = ptrace(op, pid, 0, 0);
 
 	if(err)
 		panic("userspace - PTRACE_%s failed, errno = %d\n",
@@ -194,10 +194,8 @@ void userspace(union uml_pt_regs *regs)
 
 		/*Now we ended the syscall, so re-read local_using_sysemu.*/
 		local_using_sysemu = get_using_sysemu();
-		pt_syscall_parm = local_using_sysemu ? PTRACE_SYSEMU : PTRACE_SYSCALL;
 
-		op = singlestepping(NULL) ? PTRACE_SINGLESTEP :
-			pt_syscall_parm;
+		op = SELECT_PTRACE_OPERATION(local_using_sysemu, singlestepping(NULL));
 
 		err = ptrace(op, pid, 0, 0);
 		if(err)
--- a/arch/um/kernel/tt/tracer.c	2004-11-11 14:10:38.000000000 +0100
+++ b/arch/um/kernel/tt/tracer.c	2004-11-11 15:03:42.239460000 +0100
@@ -186,7 +186,7 @@ int tracer(int (*init_proc)(void *), voi
 	unsigned long eip = 0;
 	int status, pid = 0, sig = 0, cont_type, tracing = 0, op = 0;
 	int last_index, proc_id = 0, n, err, old_tracing = 0, strace = 0;
-	int pt_syscall_parm, local_using_sysemu = 0;
+	int local_using_sysemu = 0;
 
 	signal(SIGPIPE, SIG_IGN);
 	setup_tracer_winch();
@@ -383,18 +383,14 @@ int tracer(int (*init_proc)(void *), voi
 			}
 
 			local_using_sysemu = get_using_sysemu();
-			pt_syscall_parm = local_using_sysemu ? PTRACE_SYSEMU : PTRACE_SYSCALL;
 
-			if(tracing){
-				if(singlestepping(task))
-					cont_type = PTRACE_SINGLESTEP;
-				else cont_type = pt_syscall_parm;
-			}
-			else cont_type = PTRACE_CONT;
-
-			if((cont_type == PTRACE_CONT) && 
-			   (debugger_pid != -1) && strace)
+			if(tracing)
+				cont_type = SELECT_PTRACE_OPERATION(local_using_sysemu,
+				                                    singlestepping(task));
+			else if((debugger_pid != -1) && strace)
 				cont_type = PTRACE_SYSCALL;
+			else
+				cont_type = PTRACE_CONT;
 
 			if(ptrace(cont_type, pid, 0, sig) != 0){
 				tracer_panic("ptrace failed to continue "
--- a/arch/um/kernel/tt/syscall_user.c	2004-11-12 16:45:21.546136232 +0100
+++ b/arch/um/kernel/tt/syscall_user.c	2004-11-12 16:47:11.737384616 +0100
@@ -61,6 +61,10 @@ void do_syscall(void *task, int pid, int
 	   ((unsigned long *) PT_IP(proc_regs) <= &_etext))
 		tracer_panic("I'm tracing myself and I can't get out");
 
+	/* advanced sysemu mode set syscall number to -1 automatically */
+	if (local_using_sysemu==2)
+		return;
+
 	/* syscall number -1 in sysemu skips syscall restarting in host */
 	if(ptrace(PTRACE_POKEUSER, pid, PT_SYSCALL_NR_OFFSET, 
 		  local_using_sysemu ? -1 : __NR_getpid) < 0)

[-- Attachment #8: patch-fix-sysemu-tt --]
[-- Type: text/plain, Size: 3779 bytes --]

From: Bodo Stroesser <bstroesser@fujitsu-siemens.com>

The patch uml-use-sysemu-for-tt needs some small corrections:
1) local_using_sysemu must be sampled *before* the next
   ptrace(PTRACE_SYSEMU/SYSCALL) and must stay the same until do_syscall()
   has been done. Currently it is sampled before do_syscall() and is used
   after this for ptrace(PTRACE_SYSEMU/SYSCALL). Even if no problem is
   visible to the UML user, a single syscall could be executed on the host
   when switching on sysemu. The result of this then is overwritten by the
   syscall execution in UML.
   Since the first event the tracer has to handle is not a syscall, it's
   enough to initialize local_using_sysemu to 0;
2) Even if the host never *does* a syscall in SYSEMU, we have to write the
   syscall number with -1, to not have the host doing syscall restarting.
   This would happen only with an invalid syscall number equal to one of
   the -ERESTART values. But to be perfect ...
Additionally I changed do_syscall() to be void instead of int.

Signed-off-by: Bodo Stroesser <bstroesser@fujitsu-siemens.com>
---

--- a/arch/um/kernel/tt/include/tt.h	2004-11-11 21:27:08.405134680 +0100
+++ b/arch/um/kernel/tt/include/tt.h	2004-11-11 21:27:23.807793120 +0100
@@ -26,7 +26,7 @@ extern void set_tracing(void *t, int tra
 extern int is_tracing(void *task);
 extern void syscall_handler(int sig, union uml_pt_regs *regs);
 extern void exit_kernel(int pid, void *task);
-extern int do_syscall(void *task, int pid, int local_using_sysemu);
+extern void do_syscall(void *task, int pid, int local_using_sysemu);
 extern void do_sigtrap(void *task);
 extern int is_valid_pid(int pid);
 extern void remap_data(void *segment_start, void *segment_end, int w);
--- a/arch/um/kernel/tt/tracer.c	2004-11-12 10:28:46.776498528 +0100
+++ a/arch/um/kernel/tt/tracer.c	2004-11-12 10:34:41.381590360 +0100
@@ -186,7 +186,7 @@ int tracer(int (*init_proc)(void *), voi
 	unsigned long eip = 0;
 	int status, pid = 0, sig = 0, cont_type, tracing = 0, op = 0;
 	int last_index, proc_id = 0, n, err, old_tracing = 0, strace = 0;
-	int pt_syscall_parm, local_using_sysemu;
+	int pt_syscall_parm, local_using_sysemu = 0;
 
 	signal(SIGPIPE, SIG_IGN);
 	setup_tracer_winch();
@@ -305,9 +305,6 @@ int tracer(int (*init_proc)(void *), voi
 			if ( tracing ) /* Assume: no syscall, when coming from user */
 				do_sigtrap(task);
 
-			local_using_sysemu = get_using_sysemu();
-			pt_syscall_parm = local_using_sysemu ? PTRACE_SYSEMU : PTRACE_SYSCALL;
-
 			switch(sig){
 			case SIGUSR1:
 				sig = 0;
@@ -385,6 +382,9 @@ int tracer(int (*init_proc)(void *), voi
 				continue;
 			}
 
+			local_using_sysemu = get_using_sysemu();
+			pt_syscall_parm = local_using_sysemu ? PTRACE_SYSEMU : PTRACE_SYSCALL;
+
 			if(tracing){
 				if(singlestepping(task))
 					cont_type = PTRACE_SINGLESTEP;
--- a/arch/um/kernel/tt/syscall_user.c	2004-11-12 10:30:32.181474536 +0100
+++ b/arch/um/kernel/tt/syscall_user.c	2004-11-12 10:41:04.146401264 +0100
@@ -48,7 +48,7 @@ void do_sigtrap(void *task)
 	UPT_SYSCALL_NR(TASK_REGS(task)) = -1;
 }
 
-int do_syscall(void *task, int pid, int local_using_sysemu)
+void do_syscall(void *task, int pid, int local_using_sysemu)
 {
 	unsigned long proc_regs[FRAME_SIZE];
 
@@ -61,14 +61,11 @@ int do_syscall(void *task, int pid, int 
 	   ((unsigned long *) PT_IP(proc_regs) <= &_etext))
 		tracer_panic("I'm tracing myself and I can't get out");
 
-	if(local_using_sysemu)
-		return(1);
-
+	/* syscall number -1 in sysemu skips syscall restarting in host */
 	if(ptrace(PTRACE_POKEUSER, pid, PT_SYSCALL_NR_OFFSET, 
-		  __NR_getpid) < 0)
+		  local_using_sysemu ? -1 : __NR_getpid) < 0)
 		tracer_panic("do_syscall : Nullifying syscall failed, "
 			     "errno = %d", errno);
-	return(1);
 }
 
 /*

[-- Attachment #9: patch-fix-uml-hang-on-2.6.9-host --]
[-- Type: text/plain, Size: 6093 bytes --]

From: Bodo Stroesser <bstroesser@fujitsu-siemens.com>

The patch uml-hang-on-2.6.9-host needs to be corrected. The use
of os_kill_ptraced_process() is restricted to the tracer-thread!
No other process is allowed to do ptrace(PTRACE_KILL).
So I had "dead" processes hanging in my host system until UML
was shutdown. And I had panic()s, because processes were not
stopped.
Thus, I implemented request_kill_ptraced_process(), which lets
the tracer do the ptrace(PTRACE_KILL). Sorry, this method is
slow, but I didn't see an other solution.
Also, I modified some other places to use the new call instead
of os_kill_process(). But this didn't work on the first step.
kill_off_processes_tt() couldn't kill the remaining processes
on shutdown. This happens, because ptrace(PTRACE_KILL) doesn't
really send a SIGKILL to the process, but writes SIGKILL to the
exit_code. That does results in send_sig(SIGKILL) for processes
being stopped on a ptrace event only, but not even for all of
these events.
So I added an option to request_kill_ptraced_process() that
allows to force an additional os_kill_process() to be executed
before the os_kill_ptraced_process().
Summary: The behavior of 2.6.9 host is very uggly. You need to
do kill() and ptrace(PTRACE_KILL) to be shure, a process will
really exit. If the host is changed to be more consistent, we
should change all this again.

Signed-off-by: Bodo Stroesser <bstroesser@fujitsu-siemens.com>
---

--- a/include/asm-um/processor-generic.h	2004-11-11 20:08:28.382687160 +0100
+++ b/include/asm-um/processor-generic.h	2004-11-11 20:09:09.167486928 +0100
@@ -54,7 +54,8 @@ struct thread_struct {
 		union {
 			struct {
 				int pid;
-			} fork, exec;
+				int mode;
+			} fork, exec, kill;
 			struct {
 				int (*proc)(void *);
 				void *arg;
--- a/arch/um/kernel/tt/include/mode-tt.h	2004-11-11 20:05:55.383946504 +0100
+++ b/arch/um/kernel/tt/include/mode-tt.h	2004-11-11 20:06:44.263515680 +0100
@@ -8,7 +8,7 @@
 
 #include "sysdep/ptrace.h"
 
-enum { OP_NONE, OP_EXEC, OP_FORK, OP_TRACE_ON, OP_REBOOT, OP_HALT, OP_CB };
+enum { OP_NONE, OP_EXEC, OP_FORK, OP_KILL, OP_TRACE_ON, OP_REBOOT, OP_HALT, OP_CB };
 
 extern int tracing_pid;
 
--- a/arch/um/kernel/tt/exec_user.c	2004-11-11 19:43:38.511182056 +0100
+++ b/arch/um/kernel/tt/exec_user.c	2004-11-11 19:50:41.288910072 +0100
@@ -16,6 +16,7 @@
 #include "kern_util.h"
 #include "user.h"
 #include "ptrace_user.h"
+#include "os.h"
 
 void do_exec(int old_pid, int new_pid)
 {
@@ -36,7 +37,7 @@ void do_exec(int old_pid, int new_pid)
 		tracer_panic("do_exec failed to get registers - errno = %d",
 			     errno);
 
-	kill(old_pid, SIGKILL);
+	os_kill_ptraced_process(old_pid, 0);
 
 	if (ptrace(PTRACE_SETOPTIONS, new_pid, 0, (void *)PTRACE_O_TRACESYSGOOD) < 0)
 		tracer_panic("do_exec: PTRACE_SETOPTIONS failed, errno = %d", errno);
--- a/arch/um/kernel/tt/process_kern.c	2004-11-11 20:03:15.852199016 +0100
+++ b/arch/um/kernel/tt/process_kern.c	2004-11-11 21:03:59.624261464 +0100
@@ -82,7 +82,7 @@ void *switch_to_tt(void *prev, void *nex
 	prev_sched = current->thread.prev_sched;
 	if((prev_sched->state == TASK_ZOMBIE) ||
 	   (prev_sched->state == TASK_DEAD))
-		os_kill_ptraced_process(prev_sched->thread.mode.tt.extern_pid, 1);
+		request_kill_ptraced_process( prev_sched->thread.mode.tt.extern_pid, 1);
 
 	/* This works around a nasty race with 'jail'.  If we are switching
 	 * between two threads of a threaded app and the incoming process 
@@ -119,7 +119,7 @@ void release_thread_tt(struct task_struc
 	int pid = task->thread.mode.tt.extern_pid;
 
 	if(os_getpid() != pid)
-		os_kill_process(pid, 0);
+		request_kill_ptraced_process(pid, 0);
 }
 
 void exit_thread_tt(void)
@@ -330,10 +330,10 @@ void kill_off_processes_tt(void)
 	me = os_getpid();
         for_each_process(p){
 		if(p->thread.mode.tt.extern_pid != me) 
-			os_kill_process(p->thread.mode.tt.extern_pid, 0);
+			request_kill_ptraced_process(p->thread.mode.tt.extern_pid, 2);
 	}
 	if(init_task.thread.mode.tt.extern_pid != me) 
-		os_kill_process(init_task.thread.mode.tt.extern_pid, 0);
+		request_kill_ptraced_process(init_task.thread.mode.tt.extern_pid, 2);
 }
 
 void initial_thread_cb_tt(void (*proc)(void *), void *arg)
@@ -352,6 +352,20 @@ void initial_thread_cb_tt(void (*proc)(v
 	}
 }
 
+void request_kill_ptraced_process(int pid, int mode)
+{
+	/* The tracer has to do the kill, since killing must be
+	 * done with ptrace(PTRACE_KILL, pid), which is possible
+	 * from the father only! */
+	current->thread.request.op = OP_KILL;
+	current->thread.request.u.exec.pid = pid;
+	current->thread.request.u.exec.mode = mode;
+	os_usr1_process(os_getpid());
+	change_sig(SIGUSR1, 1);
+
+	change_sig(SIGUSR1, 0);
+}
+
 int do_proc_op(void *t, int proc_id)
 {
 	struct task_struct *task;
@@ -374,6 +388,12 @@ int do_proc_op(void *t, int proc_id)
 	case OP_FORK:
 		attach_process(thread->request.u.fork.pid);
 		break;
+	case OP_KILL:
+		if ( thread->request.u.kill.mode > 1 )
+			os_kill_process(thread->request.u.kill.pid, 0);
+		os_kill_ptraced_process(thread->request.u.kill.pid,
+		                        thread->request.u.kill.mode);
+		break;
 	case OP_CB:
 		(*thread->request.u.cb.proc)(thread->request.u.cb.arg);
 		break;
--- a/arch/um/kernel/tt/include/mode-tt.h	2004-11-12 12:14:24.239057776 +0100
+++ b/arch/um/kernel/tt/include/mode-tt.h	2004-11-12 12:15:17.496961344 +0100
@@ -20,6 +20,7 @@ extern void reboot_tt(void);
 extern void halt_tt(void);
 extern int is_tracer_winch(int pid, int fd, void *data);
 extern void kill_off_processes_tt(void);
+extern void request_kill_ptraced_process(int pid, int mode);
 
 #endif
 
--- a/arch/um/kernel/reboot.c	2004-11-12 12:18:29.356794216 +0100
+++ b/arch/um/kernel/reboot.c	2004-11-12 12:19:20.996943720 +0100
@@ -22,7 +22,7 @@ static void kill_idlers(int me)
 	for(i = 0; i < sizeof(idle_threads)/sizeof(idle_threads[0]); i++){
 		p = idle_threads[i];
 		if((p != NULL) && (p->thread.mode.tt.extern_pid != me))
-			os_kill_process(p->thread.mode.tt.extern_pid, 0);
+			request_kill_ptraced_process(p->thread.mode.tt.extern_pid, 2);
 	}
 #endif
 }

Re: [uml-devel] Patchset to implement PTRACE_SYSEMU_SINGLESTEP

[Blaisorblade]

On Friday 12 November 2004 21:05, Bodo Stroesser wrote:
> Attached are several patches. Four of them (patch-2.6.*-skas-v7-*)
> implement PTRACE_SYSEMU_SINGLESTEP in the host. They are based on
> linux-2.6.7-vanilla + host-skas3-2.6.7-v7.patch (resp. the 2.6.9 versions).
> The "-reorganize" patches are a rework of the current patch without
> changing the functionality. The "add-SYSEMU_SINGLESTEP" then implement the
> new features. Please note: the differences between 2.6.7 and 2.6.9 are
> dependent on the different handling of syscall singlestepping in the two
> versions.
>
> To have UML using the new feature, there are two further patches named
> patch-SYSEMU_SINGLESTEP-*. They are based on linux-2.6.9-vanilla +
> all bb2-patches + patch-sysemu-tt + patch-fix-uml-hang-on-2.6.9-host.
> To have all the patches complete, the latter two are attached also.
>
> I tested on host 2.6.7 and host 2.6.9 with SKAS and TT mode. Currently I
> don't know any problem with it.

> Bodo

> BTW: Today I tried the first time since weeks to do a reboot in SKAS. It
> simply exits UML, as it did weeks ago. Is there anybody involved with that
> problem?

It seems a bit randomical: on my system, it segfaults some times, after 
checking for /proc/mm and SKAS mode.

When applying my use-va_end patch, (it's also in Jeff incrementals), instead, 
it always gets this segfault.

If you look at the comment about exec(), it says that UML risks to get some 
signals after the exec(). It workarounds this for some signals, but this 
cannot be done anyway for SIGSEGV... actually SIGSEGV delivery happens to 
always be synchronous, since the process gets trapped before the signal is 
queued.

By comparison, all signals are normally asynchronous, i.e. they get queued and 
later delivered, so that deliverying a signal is slower than doing a context 
switch.

Quoting from signal(7) man page:

Multiple instances of real-time signals can be queued.  By contrast,  if  
multiple instances of  a standard  signal  are  delivered  while  that signal 
is currently blocked, then only one instance is queued.
-- 
Paolo Giarrusso, aka Blaisorblade
Linux registered user n. 292729



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Re: [uml-devel] Patchset to implement PTRACE_SYSEMU_SINGLESTEP

[Bodo Stroesser]

[-- Attachment #1: Type: text/plain, Size: 2696 bytes --]

Blaisorblade wrote:
> On Friday 12 November 2004 21:05, Bodo Stroesser wrote:
> 
>>Attached are several patches. Four of them (patch-2.6.*-skas-v7-*)
>>implement PTRACE_SYSEMU_SINGLESTEP in the host. They are based on
>>linux-2.6.7-vanilla + host-skas3-2.6.7-v7.patch (resp. the 2.6.9 versions).
>>The "-reorganize" patches are a rework of the current patch without
>>changing the functionality. The "add-SYSEMU_SINGLESTEP" then implement the
>>new features. Please note: the differences between 2.6.7 and 2.6.9 are
>>dependent on the different handling of syscall singlestepping in the two
>>versions.
>>
>>To have UML using the new feature, there are two further patches named
>>patch-SYSEMU_SINGLESTEP-*. They are based on linux-2.6.9-vanilla +
>>all bb2-patches + patch-sysemu-tt + patch-fix-uml-hang-on-2.6.9-host.
>>To have all the patches complete, the latter two are attached also.
>>
>>I tested on host 2.6.7 and host 2.6.9 with SKAS and TT mode. Currently I
>>don't know any problem with it.
> 
> 
>>Bodo
> 
> 
>>BTW: Today I tried the first time since weeks to do a reboot in SKAS. It
>>simply exits UML, as it did weeks ago. Is there anybody involved with that
>>problem?
> 
> 
> It seems a bit randomical: on my system, it segfaults some times, after 
> checking for /proc/mm and SKAS mode.
> 
> When applying my use-va_end patch, (it's also in Jeff incrementals), instead, 
> it always gets this segfault.
> 
> If you look at the comment about exec(), it says that UML risks to get some 
> signals after the exec(). It workarounds this for some signals, but this 
> cannot be done anyway for SIGSEGV... actually SIGSEGV delivery happens to 
> always be synchronous, since the process gets trapped before the signal is 
> queued.
> 
> By comparison, all signals are normally asynchronous, i.e. they get queued and 
> later delivered, so that deliverying a signal is slower than doing a context 
> switch.
> 
> Quoting from signal(7) man page:
> 
> Multiple instances of real-time signals can be queued.  By contrast,  if  
> multiple instances of  a standard  signal  are  delivered  while  that signal 
> is currently blocked, then only one instance is queued.

What happens on my system shows some other symptoms. After "Restarting system."
UML exits without further message. I could track this down to a SIGIO being
unblocked immediately before the execvp(). It is handled by sig_handler()
that calls sig_handler_common_skas(). Why this exits, I don't know.
Maybe, SKAS misses an reset of the handlers to empty handlers.
Since I didn't want to dig very deep here, I choosed a simple solution.
I attached the patch. For me it works fine.
Feel free to find a better solution!

Bodo

[-- Attachment #2: patch-fix-reboot-skas --]
[-- Type: text/plain, Size: 2466 bytes --]

From: Bodo Stroesser <bstroesser@fujitsu-siemens.com>

In most cases reboot failed on my system. After
"Restarting system.", UML exited without further messages.
I found an SIGIO being processed by sig_handler() resp.
sig_handler_common_skas(). Don't know, why this exits,
maybe the context is no longer valid at this time.
So, I changed the sequence in the reboot part of main()
to stop the timers and disable the fds before unblocking
the signals. Since this wasn't enough, I also added
set_handler(SIGXXX, SIG_IGN) calls to disable_timer() and
deactivate_all_fds().
Now reboot works fine in SKAS and it still works in TT.

Signed-off-by: Bodo Stroesser <bstroesser@fujitsu-siemens.com>
---

--- a/arch/um/kernel/main.c	2004-11-15 17:19:42.437975368 +0100
+++ b/arch/um/kernel/main.c	2004-11-15 17:35:34.901178952 +0100
@@ -157,18 +157,20 @@ int main(int argc, char **argv, char **e
 		int err;
 
 		printf("\n");
-
-		/* Let any pending signals fire, then disable them.  This
-		 * ensures that they won't be delivered after the exec, when
-		 * they are definitely not expected.
-		 */
-		unblock_signals();
+		/* stop timers and set SIG*ALRM to be ignored */
 		disable_timer();
+		/* disable SIGIO for the fds and set SIGIO to be ignored */
 		err = deactivate_all_fds();
 		if(err)
 			printf("deactivate_all_fds failed, errno = %d\n",
 			       -err);
 
+		/* Let any pending signals fire now.  This ensures
+		 * that they won't be delivered after the exec, when
+		 * they are definitely not expected.
+		 */
+		unblock_signals();
+
 		execvp(new_argv[0], new_argv);
 		perror("Failed to exec kernel");
 		ret = 1;
--- a/arch/um/kernel/time.c	2004-10-18 23:53:43.000000000 +0200
+++ b/arch/um/kernel/time.c	2004-11-15 17:32:41.057607192 +0100
@@ -60,6 +60,9 @@ void disable_timer(void)
 	   (setitimer(ITIMER_REAL, &disable, NULL) < 0))
 		printk("disnable_timer - setitimer failed, errno = %d\n",
 		       errno);
+	/* If there are signals already queued, after unblocking ignore them */
+	set_handler(SIGALRM, SIG_IGN, 0, -1);
+	set_handler(SIGVTALRM, SIG_IGN, 0, -1);
 }
 
 void switch_timers(int to_real)
--- a/arch/um/kernel/irq_user.c	2004-10-18 23:53:51.000000000 +0200
+++ b/arch/um/kernel/irq_user.c	2004-11-15 17:33:40.893510752 +0100
@@ -374,6 +374,8 @@ int deactivate_all_fds(void)
 		if(err)
 			return(err);
 	}
+	/* If there is a signal already queued, after unblocking ignore it */
+	set_handler(SIGIO, SIG_IGN, 0, -1);
 
 	return(0);
 }

Re: [uml-devel] Patchset to implement PTRACE_SYSEMU_SINGLESTEP

[Jeff Dike]

bstroesser@fujitsu-siemens.com said:
> What happens on my system shows some other symptoms. After "Restarting
> system." UML exits without further message. I could track this down to
> a SIGIO being unblocked immediately before the execvp(). It is handled
> by sig_handler() that calls sig_handler_common_skas(). Why this exits,
> I don't know. 

Try this patch.  It adds the missing closes that you found today, plus it
makes sure that netdevices get closed down correctly.

				Jeff

Index: 2.6.9/arch/um/drivers/net_kern.c
===================================================================
--- 2.6.9.orig/arch/um/drivers/net_kern.c	2004-11-17 22:25:19.000000000 -0500
+++ 2.6.9/arch/um/drivers/net_kern.c	2004-11-17 23:18:21.000000000 -0500
@@ -126,10 +126,6 @@
 	lp->tl.data = (unsigned long) &lp->user;
 	netif_start_queue(dev);
 
-	spin_lock(&opened_lock);
-	list_add(&lp->list, &opened);
-	spin_unlock(&opened_lock);
-
 	/* clear buffer - it can happen that the host side of the interface
 	 * is full when we get here.  In this case, new data is never queued,
 	 * SIGIOs never arrive, and the net never works.
@@ -150,11 +146,10 @@
 
 	free_irq_by_irq_and_dev(dev->irq, dev);
 	free_irq(dev->irq, dev);
-	if(lp->close != NULL) (*lp->close)(lp->fd, &lp->user);
-	lp->fd = -1;
-	spin_lock(&opened_lock);
-	list_del(&lp->list);
-	spin_unlock(&opened_lock);
+	if(lp->close != NULL){
+		(*lp->close)(lp->fd, &lp->user);
+		lp->fd = -1;
+	}
 
 	spin_unlock(&lp->lock);
 	return 0;
@@ -289,7 +284,7 @@
 static spinlock_t devices_lock = SPIN_LOCK_UNLOCKED;
 static struct list_head devices = LIST_HEAD_INIT(devices);
 
-static int eth_configure(int n, void *init, char *mac,
+static int eth_configure(int n, void *init, char *mac, 
 			 struct transport *transport)
 {
 	struct uml_net *device;
@@ -397,6 +392,11 @@
 
 	if (device->have_mac)
 		set_ether_mac(dev, device->mac);
+
+	spin_lock(&opened_lock);
+	list_add(&lp->list, &opened);
+	spin_unlock(&opened_lock);
+
 	return(0);
 }
 
@@ -705,7 +705,7 @@
 static void close_devices(void)
 {
 	struct list_head *ele;
-	struct uml_net_private *lp;	
+	struct uml_net_private *lp;
 
 	list_for_each(ele, &opened){
 		lp = list_entry(ele, struct uml_net_private, list);
Index: 2.6.9/arch/um/kernel/initrd_user.c
===================================================================
--- 2.6.9.orig/arch/um/kernel/initrd_user.c	2004-11-17 22:25:19.000000000 -0500
+++ 2.6.9/arch/um/kernel/initrd_user.c	2004-11-17 22:26:24.000000000 -0500
@@ -29,6 +29,8 @@
 		       filename, -n);
 		return(-1);
 	}
+
+	os_close_file(fd);
 	return(0);
 }
 
Index: 2.6.9/arch/um/kernel/mem_user.c
===================================================================
--- 2.6.9.orig/arch/um/kernel/mem_user.c	2004-11-17 22:25:19.000000000 -0500
+++ 2.6.9/arch/um/kernel/mem_user.c	2004-11-17 22:26:24.000000000 -0500
@@ -101,6 +101,8 @@
 	}
 	printf("OK\n");
 	munmap(addr, UM_KERN_PAGE_SIZE);
+
+	os_close_file(fd);
 }
 
 static int have_devanon = 0;



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Re: [uml-devel] Patchset to implement PTRACE_SYSEMU_SINGLESTEP

[Bodo Stroesser]

Jeff Dike wrote:
> bstroesser@fujitsu-siemens.com said:
> 
>>What happens on my system shows some other symptoms. After "Restarting
>>system." UML exits without further message. I could track this down to
>>a SIGIO being unblocked immediately before the execvp(). It is handled
>>by sig_handler() that calls sig_handler_common_skas(). Why this exits,
>>I don't know. 
> 
> 
> Try this patch.  It adds the missing closes that you found today, plus it
> makes sure that netdevices get closed down correctly.
> 
> 				Jeff

Yes. I've tested and mostly it works fine. Only one litte change is needed
to have the daemon-network working after "network stop" and "network start".
I commented it in the patch.

         Bodo

> 
> Index: 2.6.9/arch/um/drivers/net_kern.c
> ===================================================================
> --- 2.6.9.orig/arch/um/drivers/net_kern.c	2004-11-17 22:25:19.000000000 -0500
> +++ 2.6.9/arch/um/drivers/net_kern.c	2004-11-17 23:18:21.000000000 -0500
> @@ -126,10 +126,6 @@
>  	lp->tl.data = (unsigned long) &lp->user;
>  	netif_start_queue(dev);
>  
> -	spin_lock(&opened_lock);
> -	list_add(&lp->list, &opened);
> -	spin_unlock(&opened_lock);
> -
>  	/* clear buffer - it can happen that the host side of the interface
>  	 * is full when we get here.  In this case, new data is never queued,
>  	 * SIGIOs never arrive, and the net never works.
> @@ -150,11 +146,10 @@
>  
>  	free_irq_by_irq_and_dev(dev->irq, dev);
A little question: what about the "free_irq_by_irq_and_dev"? In my sources they
are missing, and I couldn't find a patch relating this. My daemon works without it.
>  	free_irq(dev->irq, dev);


> -	if(lp->close != NULL) (*lp->close)(lp->fd, &lp->user);
> -	lp->fd = -1;
These two lines should be unchanged. lp->fd must be set to -1, since net_kern
for all networks takes this as a "is-closed" flag and refuses to open,
if lp->fd != -1. Daemon stores its fds in a private struct and returns it in
case of an open(). Thus, lp->fd is set to daemon's fd on each open().


> -	spin_lock(&opened_lock);
> -	list_del(&lp->list);
> -	spin_unlock(&opened_lock);
Yes. This must be removed.


> +	if(lp->close != NULL){
> +		(*lp->close)(lp->fd, &lp->user);
> +		lp->fd = -1;
> +	}
No. This must not be inserted.


>  
>  	spin_unlock(&lp->lock);
>  	return 0;
> @@ -289,7 +284,7 @@
>  static spinlock_t devices_lock = SPIN_LOCK_UNLOCKED;
>  static struct list_head devices = LIST_HEAD_INIT(devices);
>  
> -static int eth_configure(int n, void *init, char *mac,
> +static int eth_configure(int n, void *init, char *mac, 
>  			 struct transport *transport)
>  {
>  	struct uml_net *device;
> @@ -397,6 +392,11 @@
>  
>  	if (device->have_mac)
>  		set_ether_mac(dev, device->mac);
> +
> +	spin_lock(&opened_lock);
> +	list_add(&lp->list, &opened);
> +	spin_unlock(&opened_lock);
> +
>  	return(0);
>  }
>  
> @@ -705,7 +705,7 @@
>  static void close_devices(void)
>  {
>  	struct list_head *ele;
> -	struct uml_net_private *lp;	
> +	struct uml_net_private *lp;
>  
>  	list_for_each(ele, &opened){
>  		lp = list_entry(ele, struct uml_net_private, list);
> Index: 2.6.9/arch/um/kernel/initrd_user.c
> ===================================================================
> --- 2.6.9.orig/arch/um/kernel/initrd_user.c	2004-11-17 22:25:19.000000000 -0500
> +++ 2.6.9/arch/um/kernel/initrd_user.c	2004-11-17 22:26:24.000000000 -0500
> @@ -29,6 +29,8 @@
>  		       filename, -n);
>  		return(-1);
>  	}
> +
> +	os_close_file(fd);
>  	return(0);
>  }
>  
> Index: 2.6.9/arch/um/kernel/mem_user.c
> ===================================================================
> --- 2.6.9.orig/arch/um/kernel/mem_user.c	2004-11-17 22:25:19.000000000 -0500
> +++ 2.6.9/arch/um/kernel/mem_user.c	2004-11-17 22:26:24.000000000 -0500
> @@ -101,6 +101,8 @@
>  	}
>  	printf("OK\n");
>  	munmap(addr, UM_KERN_PAGE_SIZE);
> +
> +	os_close_file(fd);
>  }
>  
>  static int have_devanon = 0;
> 



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Re: [uml-devel] Patchset to implement PTRACE_SYSEMU_SINGLESTEP

[Blaisorblade]

On Thursday 18 November 2004 15:19, Bodo Stroesser wrote:
> Jeff Dike wrote:
> > bstroesser@fujitsu-siemens.com said:
> >>What happens on my system shows some other symptoms. After "Restarting
> >>system." UML exits without further message. I could track this down to
> >>a SIGIO being unblocked immediately before the execvp(). It is handled
> >>by sig_handler() that calls sig_handler_common_skas(). Why this exits,
> >>I don't know.

> > Try this patch.  It adds the missing closes that you found today, plus it
> > makes sure that netdevices get closed down correctly.

> >     Jeff

> Yes. I've tested and mostly it works fine. Only one litte change is needed
> to have the daemon-network working after "network stop" and "network
> start". I commented it in the patch.
You mean restarting network support in the guest, right?

>          Bodo

> > Index: 2.6.9/arch/um/drivers/net_kern.c
> > ===================================================================
> > --- 2.6.9.orig/arch/um/drivers/net_kern.c 2004-11-17 22:25:19.000000000
> > -0500 +++ 2.6.9/arch/um/drivers/net_kern.c 2004-11-17 23:18:21.000000000
> > -0500 @@ -126,10 +126,6 @@
> >   lp->tl.data = (unsigned long) &lp->user;
> >   netif_start_queue(dev);
> >
> > - spin_lock(&opened_lock);
> > - list_add(&lp->list, &opened);
> > - spin_unlock(&opened_lock);
> > -
> >   /* clear buffer - it can happen that the host side of the interface
> >    * is full when we get here.  In this case, new data is never queued,
> >    * SIGIOs never arrive, and the net never works.
> > @@ -150,11 +146,10 @@
> >
> >   free_irq_by_irq_and_dev(dev->irq, dev);

> A little question: what about the "free_irq_by_irq_and_dev"? In my sources
> they are missing, and I couldn't find a patch relating this. My daemon
> works without it.

Use the 2.6.10-rc2 tree and you should find that - it's an update for IRQ 
handling changes in 2.6.10, i.e. the creation of generic IRQ support, in 
kernel/irq/*, merged by Ingo Molnar.

From arch/i386/kernel/irq.c:

/*
 * (mostly architecture independent, will move to kernel/irq.c in 2.5.)
 */
Well, Ingo Molnar did this. Other archs are not forced to upgrade to the new 
code, but UML was borrowing the i386 headers, which got converted, so we had 
no choice.
-- 
Paolo Giarrusso, aka Blaisorblade
Linux registered user n. 292729


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Re: [uml-devel] Patchset to implement PTRACE_SYSEMU_SINGLESTEP

[Bodo Stroesser]

Blaisorblade wrote:
> On Thursday 18 November 2004 15:19, Bodo Stroesser wrote:
> 
>>Jeff Dike wrote:
>>
>>>bstroesser@fujitsu-siemens.com said:
>>>
>>>>What happens on my system shows some other symptoms. After "Restarting
>>>>system." UML exits without further message. I could track this down to
>>>>a SIGIO being unblocked immediately before the execvp(). It is handled
>>>>by sig_handler() that calls sig_handler_common_skas(). Why this exits,
>>>>I don't know.
> 
> 
>>>Try this patch.  It adds the missing closes that you found today, plus it
>>>makes sure that netdevices get closed down correctly.
> 
> 
>>>    Jeff
> 
> 
>>Yes. I've tested and mostly it works fine. Only one litte change is needed
>>to have the daemon-network working after "network stop" and "network
>>start". I commented it in the patch.
> 
> You mean restarting network support in the guest, right?
Yes. There were some problems in reboot related to the way, daemon network
was closed on "network stop" while UML shutdown.
> 
> 
>>         Bodo
> 
> 
>>>Index: 2.6.9/arch/um/drivers/net_kern.c
>>>===================================================================
>>>--- 2.6.9.orig/arch/um/drivers/net_kern.c 2004-11-17 22:25:19.000000000
>>>-0500 +++ 2.6.9/arch/um/drivers/net_kern.c 2004-11-17 23:18:21.000000000
>>>-0500 @@ -126,10 +126,6 @@
>>>  lp->tl.data = (unsigned long) &lp->user;
>>>  netif_start_queue(dev);
>>>
>>>- spin_lock(&opened_lock);
>>>- list_add(&lp->list, &opened);
>>>- spin_unlock(&opened_lock);
>>>-
>>>  /* clear buffer - it can happen that the host side of the interface
>>>   * is full when we get here.  In this case, new data is never queued,
>>>   * SIGIOs never arrive, and the net never works.
>>>@@ -150,11 +146,10 @@
>>>
>>>  free_irq_by_irq_and_dev(dev->irq, dev);
> 
> 
>>A little question: what about the "free_irq_by_irq_and_dev"? In my sources
>>they are missing, and I couldn't find a patch relating this. My daemon
>>works without it.
> 
> 
> Use the 2.6.10-rc2 tree and you should find that - it's an update for IRQ 
> handling changes in 2.6.10, i.e. the creation of generic IRQ support, in 
> kernel/irq/*, merged by Ingo Molnar.
Aha! I'm still using 2.6.9-bb2 plus some of my patches.
> 
> From arch/i386/kernel/irq.c:
> 
> /*
>  * (mostly architecture independent, will move to kernel/irq.c in 2.5.)
>  */
> Well, Ingo Molnar did this. Other archs are not forced to upgrade to the new 
> code, but UML was borrowing the i386 headers, which got converted, so we had 
> no choice.



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Re: [uml-devel] Patchset to implement PTRACE_SYSEMU_SINGLESTEP

[Blaisorblade]

On Friday 12 November 2004 21:05, Bodo Stroesser wrote:
> Attached are several patches. Four of them (patch-2.6.*-skas-v7-*)
> implement PTRACE_SYSEMU_SINGLESTEP in the host. They are based on
> linux-2.6.7-vanilla + host-skas3-2.6.7-v7.patch (resp. the 2.6.9 versions).
> The "-reorganize" patches are a rework of the current patch without
> changing the functionality. The "add-SYSEMU_SINGLESTEP" then implement the
> new features. Please note: the differences between 2.6.7 and 2.6.9 are
> dependent on the different handling of syscall singlestepping in the two
> versions.

> To have UML using the new feature, there are two further patches named
> patch-SYSEMU_SINGLESTEP-*. They are based on linux-2.6.9-vanilla +
> all bb2-patches + patch-sysemu-tt + patch-fix-uml-hang-on-2.6.9-host.
> To have all the patches complete, the latter two are attached also.

> I tested on host 2.6.7 and host 2.6.9 with SKAS and TT mode. Currently I
> don't know any problem with it.
I have a problem... in recent host kernels, isn't SINGLESTEP also trapping for 
syscall instructions?

Also, you say that SINGLESTEP_SYSEMU does automatic syscall overwriting with 
-1 or emulates that - I suspect it being in the reorganize patches, but you 
don't mention it in the changelogs here, only about the UML patches.

So, I'd personally accept only the -reorganize ones and hold on the rest - 
which is probably achieved with mainline SINGLESTEP fixes in 2.6.9 (or which 
could be discussed).

Sorry for being so late (I'd say "Call me a lamer" :-) ) in discussing this, 
but I hadn't the time to study patches and realize this.
> Bodo

-- 
Paolo Giarrusso, aka Blaisorblade
Linux registered user n. 292729
http://www.user-mode-linux.org/~blaisorblade


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Re: [uml-devel] Patchset to implement PTRACE_SYSEMU_SINGLESTEP

[Bodo Stroesser]

Blaisorblade wrote:
> On Friday 12 November 2004 21:05, Bodo Stroesser wrote:
> 
>>Attached are several patches. Four of them (patch-2.6.*-skas-v7-*)
>>implement PTRACE_SYSEMU_SINGLESTEP in the host. They are based on
>>linux-2.6.7-vanilla + host-skas3-2.6.7-v7.patch (resp. the 2.6.9 versions).
>>The "-reorganize" patches are a rework of the current patch without
>>changing the functionality. The "add-SYSEMU_SINGLESTEP" then implement the
>>new features. Please note: the differences between 2.6.7 and 2.6.9 are
>>dependent on the different handling of syscall singlestepping in the two
>>versions.
> 
> 
>>To have UML using the new feature, there are two further patches named
>>patch-SYSEMU_SINGLESTEP-*. They are based on linux-2.6.9-vanilla +
>>all bb2-patches + patch-sysemu-tt + patch-fix-uml-hang-on-2.6.9-host.
>>To have all the patches complete, the latter two are attached also.
> 
> 
>>I tested on host 2.6.7 and host 2.6.9 with SKAS and TT mode. Currently I
>>don't know any problem with it.
> 
> I have a problem... in recent host kernels, isn't SINGLESTEP also trapping for 
> syscall instructions?
Yes. IIRC, this feature was included with i386 2.6.9. I'm sure 2.6.7 doesn't
have it, 2.6.9 has.
The difference between the host versions are the reason for the different
reorganize- and add- patches for 2.6.7 and 2.6.9.
But, please, tell me, what problem do you see? SYSEMU_SINGLESTEP is a new
function, that does SYSCALL_TRACE on syscalls and SINGLESTEP on all other
instructions. The function is added without changing the previous functions.
If available, the UML-kernel my use the new function, but users on UML
shouldn't see any changed behavior.
By the way: they also don't see the differences between host 2.6.7 and 2.6.9
regarding syscall-singlestepping.

> 
> Also, you say that SINGLESTEP_SYSEMU does automatic syscall overwriting with 
> -1 or emulates that - I suspect it being in the reorganize patches, but you 
> don't mention it in the changelogs here, only about the UML patches.
No. The overwrite is in the "add-" patches. The "reorganize-" patches are
intended to *only* reorganize SKAS3-V7 without changing any little bit of
its behavior. Everything else I would call an error.
But it would be easy to split the "add-" patches into an "overwrite-" and
an remaining "add-" patch.
I only wanted to make clear, that UML must not rely on overwriting done by
the host, unless it can detect the host to have a skas-sysemu-patch with
overwriting enabled. My idea was to take availability of SYSEMU_SINGLESTEP
as flag, that the host *will* do overwriting.

> 
> So, I'd personally accept only the -reorganize ones and hold on the rest - 
> which is probably achieved with mainline SINGLESTEP fixes in 2.6.9 (or which 
> could be discussed).
> 
> Sorry for being so late (I'd say "Call me a lamer" :-) ) in discussing this, 
> but I hadn't the time to study patches and realize this.
> 
>>Bodo
> 
> 


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