[Xenomai-core] [PATCH] kgdb/x86 over I-pipe

[Philippe Gerum <rpm@xenomai.org>]

[-- Attachment #1: Type: text/plain, Size: 1866 bytes --]


Hi Jan,

Based on your previous work, here is a set of patches coupling KGDB and 
the I-pipe. Basically, I've attempted to shrink the extra patches needed 
against the original KGDB + I-pipe ones to the bare minimum. This has 
been obtained by having the I-pipe provide ipipe_current_safe(), and 
drastically reduce the amount of fiddling with smp_processor_id().

The key difference with the former implementation is that a domain (e.g. 
Xenomai) is now expected to tell the I-pipe when it's switching to a 
non-Linux stack, and the I-pipe makes good use of this information to 
return the proper "current" value when asked to through 
ipipe_safe_current() from the KGDB code. The issue of swapping 
smp_processor_id() with ipipe_processor_id() has been addressed the hard 
way: smp_processor_id() is simply defined as ipipe_processor_id() when 
CONFIG_IPIPE and CONFIG_KGDB are both enabled in include/linux/smp.h. 
This approach was actually used during the old Adeos times when pipeline 
domain had their own separate stack. I take for granted that the CPU 
penalty taken in doing this is perfectly acceptable, since well, we are 
debugging after all.

Aside of the small patches attached, you will need the latest I-pipe 
1.3-05 patch for x86, adding the foreign stack notifier and the 
ipipe_safe_current() support:
http://download.gna.org/adeos/patches/v2.6/i386/adeos-ipipe-2.6.16-i386-1.3-05.patch

Patches should be applied in this order on a vanilla 2.6.16 kernel:

- KGDB 2.4 patch series over 2.6.16 (quilt)
- pre-kgdb-ipipe-i386.patch
- adeos-ipipe-2.6.16-i386-1.3-05.patch
- kgdb-ipipe.patch
- post-kgdb-ipipe-i386.patch

Xenomai's trunk/ should be used. Older code won't work and likely crash 
since the I-pipe would not be notified about foreign stack switches.

Now the surprise: I did not test this stuff, I mean, at all. Eh. :o)

-- 

Philippe.

[-- Attachment #2: kgdb-ipipe.patch --]
[-- Type: text/x-patch, Size: 5760 bytes --]

--- 2.6.16-base/kernel/kgdb.c	2006-06-07 16:40:21.000000000 +0200
+++ 2.6.16-kgdb/kernel/kgdb.c	2006-06-07 16:43:36.000000000 +0200
@@ -740,10 +740,10 @@
 	unsigned long flags;
 	int processor;
 
-	local_irq_save(flags);
+	local_irq_save_hw(flags);
 	processor = smp_processor_id();
 	kgdb_info[processor].debuggerinfo = regs;
-	kgdb_info[processor].task = current;
+	kgdb_info[processor].task = ipipe_safe_current();
 	atomic_set(&procindebug[processor], 1);
 
 	/* Wait till master processor goes completely into the debugger.
@@ -769,7 +769,7 @@
 	/* Signal the master processor that we are done */
 	atomic_set(&procindebug[processor], 0);
 	spin_unlock(&slavecpulocks[processor]);
-	local_irq_restore(flags);
+	local_irq_restore_hw(flags);
 }
 #endif
 
@@ -883,8 +883,8 @@
 					kgdb_break[i].saved_instr)))
 			return error;
 
-		if (CACHE_FLUSH_IS_SAFE && current->mm &&
-				addr < TASK_SIZE)
+		if (CACHE_FLUSH_IS_SAFE && ipipe_safe_current() == current &&
+				current->mm && addr < TASK_SIZE)
 			flush_cache_range(current->mm->mmap_cache,
 					addr, addr + BREAK_INSTR_SIZE);
 		else if (CACHE_FLUSH_IS_SAFE)
@@ -1032,7 +1032,7 @@
 	 * Interrupts will be restored by the 'trap return' code, except when
 	 * single stepping.
 	 */
-	local_irq_save(flags);
+	local_irq_save_hw(flags);
 
 	/* Hold debugger_active */
 	procid = smp_processor_id();
@@ -1055,7 +1055,7 @@
 	if (atomic_read(&cpu_doing_single_step) != -1 &&
 	    atomic_read(&cpu_doing_single_step) != procid) {
 		atomic_set(&debugger_active, 0);
-		local_irq_restore(flags);
+		local_irq_restore_hw(flags);
 		goto acquirelock;
 	}
 
@@ -1068,7 +1068,7 @@
 		goto kgdb_restore;
 
 	kgdb_info[processor].debuggerinfo = linux_regs;
-	kgdb_info[processor].task = current;
+	kgdb_info[processor].task = ipipe_safe_current();
 
 	kgdb_disable_hw_debug(linux_regs);
 
@@ -1120,7 +1120,8 @@
 		*ptr++ = hexchars[(signo >> 4) % 16];
 		*ptr++ = hexchars[signo % 16];
 		ptr += strlen(strcpy(ptr, "thread:"));
-		int_to_threadref(&thref, shadow_pid(current->pid));
+		int_to_threadref(&thref,
+		                 shadow_pid(ipipe_safe_current()->pid));
 		ptr = pack_threadid(ptr, &thref);
 		*ptr++ = ';';
 
@@ -1212,7 +1213,8 @@
 			kgdb_hex2mem(&remcom_in_buffer[1], (char *)gdb_regs,
 				     NUMREGBYTES);
 
-			if (kgdb_usethread && kgdb_usethread != current)
+			if (kgdb_usethread &&
+			    kgdb_usethread != ipipe_safe_current())
 				error_packet(remcom_out_buffer, -EINVAL);
 			else {
 				gdb_regs_to_regs(gdb_regs, linux_regs);
@@ -1333,7 +1335,8 @@
 				/* Current thread id */
 				strcpy(remcom_out_buffer, "QC");
 
-				threadid = shadow_pid(current->pid);
+				threadid =
+					shadow_pid(ipipe_safe_current()->pid);
 
 				int_to_threadref(&thref, threadid);
 				pack_threadid(remcom_out_buffer + 2, &thref);
@@ -1487,7 +1490,8 @@
 			break;
 		case 'c':
 		case 's':
-			if (kgdb_contthread && kgdb_contthread != current) {
+			if (kgdb_contthread &&
+			    kgdb_contthread != ipipe_safe_current()) {
 				/* Can't switch threads in kgdb */
 				error_packet(remcom_out_buffer, -EINVAL);
 				break;
@@ -1555,7 +1559,7 @@
 kgdb_restore:
 	/* Free debugger_active */
 	atomic_set(&debugger_active, 0);
-	local_irq_restore(flags);
+	local_irq_restore_hw(flags);
 
 	return error;
 }
@@ -1924,9 +1928,9 @@
 	if (!kgdb_connected || atomic_read(&debugger_active) != 0)
 		return 0;
 	if ((code == SYS_RESTART) || (code == SYS_HALT) || (code == SYS_POWER_OFF)){
-		local_irq_save(flags);
+		local_irq_save_hw(flags);
 		put_packet("X00");
-		local_irq_restore(flags);
+		local_irq_restore_hw(flags);
 	}
 	return NOTIFY_DONE;
 }		
@@ -1941,10 +1945,10 @@
 	if (!kgdb_connected || atomic_read(&debugger_active) != 0)
 		return;
 
-	local_irq_save(flags);
+	local_irq_save_hw(flags);
 	kgdb_msg_write(s, count);
-	local_irq_restore(flags);
+	local_irq_restore_hw(flags);
 }
 
 static struct console kgdbcons = {
--- 2.6.16-base/lib/Kconfig.debug	2006-06-07 16:40:21.000000000 +0200
+++ 2.6.16-kgdb/lib/Kconfig.debug	2006-06-06 16:01:26.000000000 +0200
@@ -250,7 +250,7 @@
 
 config KGDB_ONLY_MODULES
 	bool "KGDB: Use only kernel modules for I/O"
-	depends on MODULES
+	depends on MODULES && !IPIPE
 	help
 	  Use only kernel modules to configure KGDB I/O after the
 	  kernel is booted.
@@ -295,8 +295,8 @@
 endchoice
 
 config KGDBOE
-	tristate "KGDB: On ethernet" if !KGDBOE_NOMODULE
+	tristate "KGDB: On ethernet" if !KGDBOE_NOMODULE && !IPIPE
 	depends on m && KGDB
 	select NETPOLL
 	select NETPOLL_TRAP
--- 2.6.16-base/drivers/serial/8250_kgdb.c	2006-06-07 16:40:20.000000000 +0200
+++ 2.6.16-kgdb/drivers/serial/8250_kgdb.c	2006-06-06 16:01:26.000000000 +0200
@@ -301,6 +301,10 @@
 			"GDB-stub", current_port) < 0)
 		printk(KERN_ERR "KGDB failed to request the serial IRQ (%d)\n",
 		       current_port->irq);
+#ifdef CONFIG_IPIPE
+	ipipe_control_irq(current_port->irq, 0,
+			IPIPE_HANDLE_MASK|IPIPE_STICKY_MASK|IPIPE_SYSTEM_MASK);
+#endif /* CONFIG_IPIPE */
 }
 
 static __init int kgdb_init_io(void)
--- 2.6.16/include/linux/smp.h	2006-03-20 06:53:29.000000000 +0100
+++ 2.6.16-kgdb/include/linux/smp.h	2006-06-07 17:59:13.000000000 +0200
@@ -116,12 +116,16 @@
  * which use for some reason is legal). Don't use this to hack around
  * the warning message, as your code might not work under PREEMPT.
  */
+#if defined(CONFIG_KGDB) && defined(CONFIG_IPIPE)
+#define smp_processor_id() ipipe_processor_id()
+#else /* CONFIG_KGDB && CONFIG_IPIPE */
 #ifdef CONFIG_DEBUG_PREEMPT
   extern unsigned int debug_smp_processor_id(void);
 # define smp_processor_id() debug_smp_processor_id()
 #else
 # define smp_processor_id() raw_smp_processor_id()
 #endif
+#endif
 
 #define get_cpu()		({ preempt_disable(); smp_processor_id(); })
 #define put_cpu()		preempt_enable()

[-- Attachment #3: post-kgdb-ipipe-i386.patch --]
[-- Type: text/x-patch, Size: 834 bytes --]

Index: linux-2.6.16.16/arch/i386/kernel/entry.S
===================================================================
--- linux-2.6.16.16.orig/arch/i386/kernel/entry.S
+++ linux-2.6.16.16/arch/i386/kernel/entry.S
@@ -194,7 +194,7 @@ VM_MASK		= 0x00020000
 .previous
 
 
-ENTRY(ret_from_fork)
+KPROBE_ENTRY(ret_from_fork)
 	STI_COND_HW
 	pushl %eax
 	call schedule_tail
@@ -584,7 +584,7 @@ ENTRY(simd_coprocessor_error)
 	PUSH_XCODE(do_simd_coprocessor_error)
 	jmp error_code
 
-ENTRY(device_not_available)
+KPROBE_ENTRY(device_not_available)
 	pushl $-1			# mark this as an int
 	SAVE_ALL
 	DIVERT_EXCEPTION(device_not_available)
@@ -769,7 +769,7 @@ ENTRY(machine_check)
 	jmp error_code
 #endif
 
-ENTRY(spurious_interrupt_bug)
+KPROBE_ENTRY(spurious_interrupt_bug)
 	pushl $0
 	PUSH_XCODE(do_spurious_interrupt_bug)
 	jmp error_code

[-- Attachment #4: pre-kgdb-ipipe-i386.patch --]
[-- Type: text/x-patch, Size: 811 bytes --]

Index: linux-2.6.16.16/arch/i386/kernel/entry.S
===================================================================
--- linux-2.6.16.16.orig/arch/i386/kernel/entry.S
+++ linux-2.6.16.16/arch/i386/kernel/entry.S
@@ -123,7 +123,7 @@ VM_MASK		= 0x00020000
 .previous
 
 
-KPROBE_ENTRY(ret_from_fork)
+ENTRY(ret_from_fork)
 	pushl %eax
 	call schedule_tail
 	GET_THREAD_INFO(%ebp)
@@ -472,7 +472,7 @@ ENTRY(simd_coprocessor_error)
 	pushl $do_simd_coprocessor_error
 	jmp error_code
 
-KPROBE_ENTRY(device_not_available)
+ENTRY(device_not_available)
 	pushl $-1			# mark this as an int
 	SAVE_ALL
 	movl %cr0, %eax
@@ -654,7 +654,7 @@ ENTRY(machine_check)
 	jmp error_code
 #endif
 
-KPROBE_ENTRY(spurious_interrupt_bug)
+ENTRY(spurious_interrupt_bug)
 	pushl $0
 	pushl $do_spurious_interrupt_bug
 	jmp error_code