Merge tag 'for_linus-3.4-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/jwessel/kgdb

Pull KGDB/KDB regression fixes from Jason Wessel:
 - Fix a Smatch warning that appeared in the 3.4 merge window
 - Fix kgdb test suite with SMP for all archs without HW single stepping
 - Fix kgdb sw breakpoints with CONFIG_DEBUG_RODATA=y limitations on x86
 - Fix oops on kgdb test suite with CONFIG_DEBUG_RODATA
 - Fix kgdb test suite with SMP for all archs with HW single stepping

* tag 'for_linus-3.4-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/jwessel/kgdb:
  x86,kgdb: Fix DEBUG_RODATA limitation using text_poke()
  kgdb,debug_core: pass the breakpoint struct instead of address and memory
  kgdbts: (2 of 2) fix single step awareness to work correctly with SMP
  kgdbts: (1 of 2) fix single step awareness to work correctly with SMP
  kgdbts: Fix kernel oops with CONFIG_DEBUG_RODATA
  kdb: Fix smatch warning on dbg_io_ops->is_console

arch/x86/kernel/kgdb.c

@@ -43,6 +43,8 @@
 #include <linux/smp.h>
 #include <linux/nmi.h>
 #include <linux/hw_breakpoint.h>
+#include <linux/uaccess.h>
+#include <linux/memory.h>
 
 #include <asm/debugreg.h>
 #include <asm/apicdef.h>
@@ -741,6 +743,64 @@ void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long ip)
 	regs->ip = ip;
 }
 
+int kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
+{
+	int err;
+	char opc[BREAK_INSTR_SIZE];
+
+	bpt->type = BP_BREAKPOINT;
+	err = probe_kernel_read(bpt->saved_instr, (char *)bpt->bpt_addr,
+				BREAK_INSTR_SIZE);
+	if (err)
+		return err;
+	err = probe_kernel_write((char *)bpt->bpt_addr,
+				 arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE);
+#ifdef CONFIG_DEBUG_RODATA
+	if (!err)
+		return err;
+	/*
+	 * It is safe to call text_poke() because normal kernel execution
+	 * is stopped on all cores, so long as the text_mutex is not locked.
+	 */
+	if (mutex_is_locked(&text_mutex))
+		return -EBUSY;
+	text_poke((void *)bpt->bpt_addr, arch_kgdb_ops.gdb_bpt_instr,
+		  BREAK_INSTR_SIZE);
+	err = probe_kernel_read(opc, (char *)bpt->bpt_addr, BREAK_INSTR_SIZE);
+	if (err)
+		return err;
+	if (memcmp(opc, arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE))
+		return -EINVAL;
+	bpt->type = BP_POKE_BREAKPOINT;
+#endif /* CONFIG_DEBUG_RODATA */
+	return err;
+}
+
+int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
+{
+#ifdef CONFIG_DEBUG_RODATA
+	int err;
+	char opc[BREAK_INSTR_SIZE];
+
+	if (bpt->type != BP_POKE_BREAKPOINT)
+		goto knl_write;
+	/*
+	 * It is safe to call text_poke() because normal kernel execution
+	 * is stopped on all cores, so long as the text_mutex is not locked.
+	 */
+	if (mutex_is_locked(&text_mutex))
+		goto knl_write;
+	text_poke((void *)bpt->bpt_addr, bpt->saved_instr, BREAK_INSTR_SIZE);
+	err = probe_kernel_read(opc, (char *)bpt->bpt_addr, BREAK_INSTR_SIZE);
+	if (err || memcmp(opc, bpt->saved_instr, BREAK_INSTR_SIZE))
+		goto knl_write;
+	return err;
+knl_write:
+#endif /* CONFIG_DEBUG_RODATA */
+	return probe_kernel_write((char *)bpt->bpt_addr,
+				  (char *)bpt->saved_instr, BREAK_INSTR_SIZE);
+}
+
 struct kgdb_arch arch_kgdb_ops = {
 	/* Breakpoint instruction: */
 	.gdb_bpt_instr		= { 0xcc },

include/linux/kgdb.h

@@ -63,7 +63,8 @@ enum kgdb_bptype {
 	BP_HARDWARE_BREAKPOINT,
 	BP_WRITE_WATCHPOINT,
 	BP_READ_WATCHPOINT,
-	BP_ACCESS_WATCHPOINT
+	BP_ACCESS_WATCHPOINT,
+	BP_POKE_BREAKPOINT,
 };
 
 enum kgdb_bpstate {
@@ -207,8 +208,8 @@ extern void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long pc);
 
 /* Optional functions. */
 extern int kgdb_validate_break_address(unsigned long addr);
-extern int kgdb_arch_set_breakpoint(unsigned long addr, char *saved_instr);
-extern int kgdb_arch_remove_breakpoint(unsigned long addr, char *bundle);
+extern int kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt);
+extern int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt);
 
 /**
  *	kgdb_arch_late - Perform any architecture specific initalization.

kernel/debug/debug_core.c

@@ -160,37 +160,39 @@ early_param("nokgdbroundup", opt_nokgdbroundup);
  * Weak aliases for breakpoint management,
  * can be overriden by architectures when needed:
  */
-int __weak kgdb_arch_set_breakpoint(unsigned long addr, char *saved_instr)
+int __weak kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
 {
 	int err;
 
-	err = probe_kernel_read(saved_instr, (char *)addr, BREAK_INSTR_SIZE);
+	err = probe_kernel_read(bpt->saved_instr, (char *)bpt->bpt_addr,
+				BREAK_INSTR_SIZE);
 	if (err)
 		return err;
-
-	return probe_kernel_write((char *)addr, arch_kgdb_ops.gdb_bpt_instr,
-				  BREAK_INSTR_SIZE);
+	err = probe_kernel_write((char *)bpt->bpt_addr,
+				 arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE);
+	return err;
 }
 
-int __weak kgdb_arch_remove_breakpoint(unsigned long addr, char *bundle)
+int __weak kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
 {
-	return probe_kernel_write((char *)addr,
-				  (char *)bundle, BREAK_INSTR_SIZE);
+	return probe_kernel_write((char *)bpt->bpt_addr,
+				  (char *)bpt->saved_instr, BREAK_INSTR_SIZE);
 }
 
 int __weak kgdb_validate_break_address(unsigned long addr)
 {
-	char tmp_variable[BREAK_INSTR_SIZE];
+	struct kgdb_bkpt tmp;
 	int err;
-	/* Validate setting the breakpoint and then removing it.  In the
+	/* Validate setting the breakpoint and then removing it.  If the
 	 * remove fails, the kernel needs to emit a bad message because we
 	 * are deep trouble not being able to put things back the way we
 	 * found them.
 	 */
-	err = kgdb_arch_set_breakpoint(addr, tmp_variable);
+	tmp.bpt_addr = addr;
+	err = kgdb_arch_set_breakpoint(&tmp);
 	if (err)
 		return err;
-	err = kgdb_arch_remove_breakpoint(addr, tmp_variable);
+	err = kgdb_arch_remove_breakpoint(&tmp);
 	if (err)
 		printk(KERN_ERR "KGDB: Critical breakpoint error, kernel "
 		   "memory destroyed at: %lx", addr);
@@ -234,7 +236,6 @@ static void kgdb_flush_swbreak_addr(unsigned long addr)
  */
 int dbg_activate_sw_breakpoints(void)
 {
-	unsigned long addr;
 	int error;
 	int ret = 0;
 	int i;
@@ -243,16 +244,15 @@ int dbg_activate_sw_breakpoints(void)
 		if (kgdb_break[i].state != BP_SET)
 			continue;
 
-		addr = kgdb_break[i].bpt_addr;
-		error = kgdb_arch_set_breakpoint(addr,
-				kgdb_break[i].saved_instr);
+		error = kgdb_arch_set_breakpoint(&kgdb_break[i]);
 		if (error) {
 			ret = error;
-			printk(KERN_INFO "KGDB: BP install failed: %lx", addr);
+			printk(KERN_INFO "KGDB: BP install failed: %lx",
+			       kgdb_break[i].bpt_addr);
 			continue;
 		}
 
-		kgdb_flush_swbreak_addr(addr);
+		kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr);
 		kgdb_break[i].state = BP_ACTIVE;
 	}
 	return ret;
@@ -301,7 +301,6 @@ int dbg_set_sw_break(unsigned long addr)
 
 int dbg_deactivate_sw_breakpoints(void)
 {
-	unsigned long addr;
 	int error;
 	int ret = 0;
 	int i;
@@ -309,15 +308,14 @@ int dbg_deactivate_sw_breakpoints(void)
 	for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 		if (kgdb_break[i].state != BP_ACTIVE)
 			continue;
-		addr = kgdb_break[i].bpt_addr;
-		error = kgdb_arch_remove_breakpoint(addr,
-					kgdb_break[i].saved_instr);
+		error = kgdb_arch_remove_breakpoint(&kgdb_break[i]);
 		if (error) {
-			printk(KERN_INFO "KGDB: BP remove failed: %lx\n", addr);
+			printk(KERN_INFO "KGDB: BP remove failed: %lx\n",
+			       kgdb_break[i].bpt_addr);
 			ret = error;
 		}
 
-		kgdb_flush_swbreak_addr(addr);
+		kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr);
 		kgdb_break[i].state = BP_SET;
 	}
 	return ret;
@@ -351,7 +349,6 @@ int kgdb_isremovedbreak(unsigned long addr)
 
 int dbg_remove_all_break(void)
 {
-	unsigned long addr;
 	int error;
 	int i;
 
@@ -359,12 +356,10 @@ int dbg_remove_all_break(void)
 	for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 		if (kgdb_break[i].state != BP_ACTIVE)
 			goto setundefined;
-		addr = kgdb_break[i].bpt_addr;
-		error = kgdb_arch_remove_breakpoint(addr,
-				kgdb_break[i].saved_instr);
+		error = kgdb_arch_remove_breakpoint(&kgdb_break[i]);
 		if (error)
 			printk(KERN_ERR "KGDB: breakpoint remove failed: %lx\n",
-			   addr);
+			       kgdb_break[i].bpt_addr);
 setundefined:
 		kgdb_break[i].state = BP_UNDEFINED;
 	}

kernel/debug/kdb/kdb_io.c

@@ -743,7 +743,7 @@ int vkdb_printf(const char *fmt, va_list ap)
 		kdb_input_flush();
 		c = console_drivers;
 
-		if (!dbg_io_ops->is_console) {
+		if (dbg_io_ops && !dbg_io_ops->is_console) {
 			len = strlen(moreprompt);
 			cp = moreprompt;
 			while (len--) {