[POWERPC] irqtrace support for 64-bit powerpc

This adds the low level irq tracing hooks to the powerpc architecture
needed to enable full lockdep functionality.

This is partly based on Johannes Berg's initial version.  I removed
the asm trampoline that isn't needed (thus improving performance) and
modified all sorts of bits and pieces, reworking most of the assembly,
etc...

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/Kconfig

@@ -53,6 +53,15 @@ config STACKTRACE_SUPPORT
 	bool
 	default y
 
+config TRACE_IRQFLAGS_SUPPORT
+	bool
+	depends on PPC64
+	default y
+
+config LOCKDEP_SUPPORT
+	bool
+	default y
+
 config RWSEM_GENERIC_SPINLOCK
 	bool
 

arch/powerpc/kernel/entry_64.S

@@ -30,6 +30,7 @@
 #include <asm/firmware.h>
 #include <asm/bug.h>
 #include <asm/ptrace.h>
+#include <asm/irqflags.h>
 
 /*
  * System calls.
@@ -89,6 +90,14 @@ system_call_common:
 	addi	r9,r1,STACK_FRAME_OVERHEAD
 	ld	r11,exception_marker@toc(r2)
 	std	r11,-16(r9)		/* "regshere" marker */
+#ifdef CONFIG_TRACE_IRQFLAGS
+	bl	.trace_hardirqs_on
+	REST_GPR(0,r1)
+	REST_4GPRS(3,r1)
+	REST_2GPRS(7,r1)
+	addi	r9,r1,STACK_FRAME_OVERHEAD
+	ld	r12,_MSR(r1)
+#endif /* CONFIG_TRACE_IRQFLAGS */
 	li	r10,1
 	stb	r10,PACASOFTIRQEN(r13)
 	stb	r10,PACAHARDIRQEN(r13)
@@ -103,7 +112,7 @@ BEGIN_FW_FTR_SECTION
 	b	hardware_interrupt_entry
 2:
 END_FW_FTR_SECTION_IFSET(FW_FEATURE_ISERIES)
-#endif
+#endif /* CONFIG_PPC_ISERIES */
 	mfmsr	r11
 	ori	r11,r11,MSR_EE
 	mtmsrd	r11,1
@@ -505,6 +514,10 @@ BEGIN_FW_FTR_SECTION
 
 	li	r3,0
 	stb	r3,PACASOFTIRQEN(r13)	/* ensure we are soft-disabled */
+#ifdef CONFIG_TRACE_IRQFLAGS
+	bl	.trace_hardirqs_off
+	mfmsr	r10
+#endif
 	ori	r10,r10,MSR_EE
 	mtmsrd	r10			/* hard-enable again */
 	addi	r3,r1,STACK_FRAME_OVERHEAD
@@ -513,7 +526,7 @@ BEGIN_FW_FTR_SECTION
 4:
 END_FW_FTR_SECTION_IFSET(FW_FEATURE_ISERIES)
 #endif
-	stb	r5,PACASOFTIRQEN(r13)
+	TRACE_AND_RESTORE_IRQ(r5);
 
 	/* extract EE bit and use it to restore paca->hard_enabled */
 	ld	r3,_MSR(r1)
@@ -581,6 +594,16 @@ do_work:
 	bne	restore
 	/* here we are preempting the current task */
 1:
+#ifdef CONFIG_TRACE_IRQFLAGS
+	bl	.trace_hardirqs_on
+	/* Note: we just clobbered r10 which used to contain the previous
+	 * MSR before the hard-disabling done by the caller of do_work.
+	 * We don't have that value anymore, but it doesn't matter as
+	 * we will hard-enable unconditionally, we can just reload the
+	 * current MSR into r10
+	 */
+	mfmsr	r10
+#endif /* CONFIG_TRACE_IRQFLAGS */
 	li	r0,1
 	stb	r0,PACASOFTIRQEN(r13)
 	stb	r0,PACAHARDIRQEN(r13)

arch/powerpc/kernel/head_64.S

@@ -36,8 +36,7 @@
 #include <asm/firmware.h>
 #include <asm/page_64.h>
 #include <asm/exception.h>
-
-#define DO_SOFT_DISABLE
+#include <asm/irqflags.h>
 
 /*
  * We layout physical memory as follows:
@@ -450,8 +449,8 @@ bad_stack:
  */
 fast_exc_return_irq:			/* restores irq state too */
 	ld	r3,SOFTE(r1)
+	TRACE_AND_RESTORE_IRQ(r3);
 	ld	r12,_MSR(r1)
-	stb	r3,PACASOFTIRQEN(r13)	/* restore paca->soft_enabled */
 	rldicl	r4,r12,49,63		/* get MSR_EE to LSB */
 	stb	r4,PACAHARDIRQEN(r13)	/* restore paca->hard_enabled */
 	b	1f
@@ -824,7 +823,7 @@ _STATIC(load_up_altivec)
  * Hash table stuff
  */
 	.align	7
-_GLOBAL(do_hash_page)
+_STATIC(do_hash_page)
 	std	r3,_DAR(r1)
 	std	r4,_DSISR(r1)
 
@@ -835,6 +834,27 @@ BEGIN_FTR_SECTION
 	bne-	do_ste_alloc		/* If so handle it */
 END_FTR_SECTION_IFCLR(CPU_FTR_SLB)
 
+	/*
+	 * On iSeries, we soft-disable interrupts here, then
+	 * hard-enable interrupts so that the hash_page code can spin on
+	 * the hash_table_lock without problems on a shared processor.
+	 */
+	DISABLE_INTS
+
+	/*
+	 * Currently, trace_hardirqs_off() will be called by DISABLE_INTS
+	 * and will clobber volatile registers when irq tracing is enabled
+	 * so we need to reload them. It may be possible to be smarter here
+	 * and move the irq tracing elsewhere but let's keep it simple for
+	 * now
+	 */
+#ifdef CONFIG_TRACE_IRQFLAGS
+	ld	r3,_DAR(r1)
+	ld	r4,_DSISR(r1)
+	ld	r5,_TRAP(r1)
+	ld	r12,_MSR(r1)
+	clrrdi	r5,r5,4
+#endif /* CONFIG_TRACE_IRQFLAGS */
 	/*
 	 * We need to set the _PAGE_USER bit if MSR_PR is set or if we are
 	 * accessing a userspace segment (even from the kernel). We assume
@@ -847,13 +867,6 @@ END_FTR_SECTION_IFCLR(CPU_FTR_SLB)
 	ori	r4,r4,1			/* add _PAGE_PRESENT */
 	rlwimi	r4,r5,22+2,31-2,31-2	/* Set _PAGE_EXEC if trap is 0x400 */
 
-	/*
-	 * On iSeries, we soft-disable interrupts here, then
-	 * hard-enable interrupts so that the hash_page code can spin on
-	 * the hash_table_lock without problems on a shared processor.
-	 */
-	DISABLE_INTS
-
 	/*
 	 * r3 contains the faulting address
 	 * r4 contains the required access permissions
@@ -864,7 +877,6 @@ END_FTR_SECTION_IFCLR(CPU_FTR_SLB)
 	bl	.hash_page		/* build HPTE if possible */
 	cmpdi	r3,0			/* see if hash_page succeeded */
 
-#ifdef DO_SOFT_DISABLE
 BEGIN_FW_FTR_SECTION
 	/*
 	 * If we had interrupts soft-enabled at the point where the
@@ -876,7 +888,7 @@ BEGIN_FW_FTR_SECTION
 	 */
 	beq	13f
 END_FW_FTR_SECTION_IFSET(FW_FEATURE_ISERIES)
-#endif
+
 BEGIN_FW_FTR_SECTION
 	/*
 	 * Here we have interrupts hard-disabled, so it is sufficient
@@ -890,11 +902,12 @@ END_FW_FTR_SECTION_IFCLR(FW_FEATURE_ISERIES)
 
 	/*
 	 * hash_page couldn't handle it, set soft interrupt enable back
-	 * to what it was before the trap.  Note that .local_irq_restore
+	 * to what it was before the trap.  Note that .raw_local_irq_restore
 	 * handles any interrupts pending at this point.
 	 */
 	ld	r3,SOFTE(r1)
-	bl	.local_irq_restore
+	TRACE_AND_RESTORE_IRQ_PARTIAL(r3, 11f)
+	bl	.raw_local_irq_restore
 	b	11f
 
 /* Here we have a page fault that hash_page can't handle. */
@@ -1493,6 +1506,10 @@ _INIT_STATIC(start_here_multiplatform)
 	addi	r2,r2,0x4000
 	add	r2,r2,r26
 
+	/* Set initial ptr to current */
+	LOAD_REG_IMMEDIATE(r4, init_task)
+	std	r4,PACACURRENT(r13)
+
 	/* Do very early kernel initializations, including initial hash table,
 	 * stab and slb setup before we turn on relocation.	*/
 

arch/powerpc/kernel/irq.c

@@ -114,7 +114,7 @@ static inline void set_soft_enabled(unsigned long enable)
 	: : "r" (enable), "i" (offsetof(struct paca_struct, soft_enabled)));
 }
 
-void local_irq_restore(unsigned long en)
+void raw_local_irq_restore(unsigned long en)
 {
 	/*
 	 * get_paca()->soft_enabled = en;
@@ -174,6 +174,7 @@ void local_irq_restore(unsigned long en)
 
 	__hard_irq_enable();
 }
+EXPORT_SYMBOL(raw_local_irq_restore);
 #endif /* CONFIG_PPC64 */
 
 int show_interrupts(struct seq_file *p, void *v)

arch/powerpc/kernel/ppc_ksyms.c

@@ -45,10 +45,6 @@
 #include <asm/signal.h>
 #include <asm/dcr.h>
 
-#ifdef CONFIG_PPC64
-EXPORT_SYMBOL(local_irq_restore);
-#endif
-
 #ifdef CONFIG_PPC32
 extern void transfer_to_handler(void);
 extern void do_IRQ(struct pt_regs *regs);

arch/powerpc/kernel/setup_64.c

@@ -33,6 +33,7 @@
 #include <linux/serial_8250.h>
 #include <linux/bootmem.h>
 #include <linux/pci.h>
+#include <linux/lockdep.h>
 #include <linux/lmb.h>
 #include <asm/io.h>
 #include <asm/kdump.h>
@@ -178,6 +179,9 @@ void __init early_setup(unsigned long dt_ptr)
 	/* Enable early debugging if any specified (see udbg.h) */
 	udbg_early_init();
 
+	/* Initialize lockdep early or else spinlocks will blow */
+	lockdep_init();
+
  	DBG(" -> early_setup(), dt_ptr: 0x%lx\n", dt_ptr);
 
 	/*

include/asm-powerpc/exception.h

@@ -228,18 +228,18 @@ label##_pSeries:							\
 BEGIN_FW_FTR_SECTION;				\
 	stb	r11,PACAHARDIRQEN(r13);		\
 END_FW_FTR_SECTION_IFCLR(FW_FEATURE_ISERIES);	\
+	TRACE_DISABLE_INTS;			\
 BEGIN_FW_FTR_SECTION;				\
 	mfmsr	r10;				\
 	ori	r10,r10,MSR_EE;			\
 	mtmsrd	r10,1;				\
 END_FW_FTR_SECTION_IFSET(FW_FEATURE_ISERIES)
-
 #else
 #define DISABLE_INTS				\
 	li	r11,0;				\
 	stb	r11,PACASOFTIRQEN(r13);		\
-	stb	r11,PACAHARDIRQEN(r13)
-
+	stb	r11,PACAHARDIRQEN(r13);		\
+	TRACE_DISABLE_INTS
 #endif /* CONFIG_PPC_ISERIES */
 
 #define ENABLE_INTS				\

include/asm-powerpc/hw_irq.h

@@ -27,7 +27,7 @@ static inline unsigned long local_get_flags(void)
 	return flags;
 }
 
-static inline unsigned long local_irq_disable(void)
+static inline unsigned long raw_local_irq_disable(void)
 {
 	unsigned long flags, zero;
 
@@ -39,14 +39,15 @@ static inline unsigned long local_irq_disable(void)
 	return flags;
 }
 
-extern void local_irq_restore(unsigned long);
+extern void raw_local_irq_restore(unsigned long);
 extern void iseries_handle_interrupts(void);
 
-#define local_irq_enable()	local_irq_restore(1)
-#define local_save_flags(flags)	((flags) = local_get_flags())
-#define local_irq_save(flags)	((flags) = local_irq_disable())
+#define raw_local_irq_enable()		raw_local_irq_restore(1)
+#define raw_local_save_flags(flags)	((flags) = local_get_flags())
+#define raw_local_irq_save(flags)	((flags) = raw_local_irq_disable())
 
-#define irqs_disabled()		(local_get_flags() == 0)
+#define raw_irqs_disabled()		(local_get_flags() == 0)
+#define raw_irqs_disabled_flags(flags)	((flags) == 0)
 
 #define __hard_irq_enable()	__mtmsrd(mfmsr() | MSR_EE, 1)
 #define __hard_irq_disable()	__mtmsrd(mfmsr() & ~MSR_EE, 1)

include/asm-powerpc/irqflags.h

@@ -2,30 +2,43 @@
  * include/asm-powerpc/irqflags.h
  *
  * IRQ flags handling
- *
- * This file gets included from lowlevel asm headers too, to provide
- * wrapped versions of the local_irq_*() APIs, based on the
- * raw_local_irq_*() macros from the lowlevel headers.
  */
 #ifndef _ASM_IRQFLAGS_H
 #define _ASM_IRQFLAGS_H
 
+#ifndef __ASSEMBLY__
 /*
  * Get definitions for raw_local_save_flags(x), etc.
  */
 #include <asm-powerpc/hw_irq.h>
 
+#else
+#ifdef CONFIG_TRACE_IRQFLAGS
 /*
- * Do the CPU's IRQ-state tracing from assembly code. We call a
- * C function, so save all the C-clobbered registers:
+ * Most of the CPU's IRQ-state tracing is done from assembly code; we
+ * have to call a C function so call a wrapper that saves all the
+ * C-clobbered registers.
  */
-#ifdef CONFIG_TRACE_IRQFLAGS
-
-#error No support on PowerPC yet for CONFIG_TRACE_IRQFLAGS
-
+#define TRACE_ENABLE_INTS	bl .trace_hardirqs_on
+#define TRACE_DISABLE_INTS	bl .trace_hardirqs_off
+#define TRACE_AND_RESTORE_IRQ_PARTIAL(en,skip)	\
+	cmpdi	en, 0;				\
+	bne	95f;				\
+	stb	en,PACASOFTIRQEN(r13);		\
+	bl	.trace_hardirqs_off;		\
+	b	skip;				\
+95:	bl	.trace_hardirqs_on;		\
+	li	en,1;
+#define TRACE_AND_RESTORE_IRQ(en)		\
+	TRACE_AND_RESTORE_IRQ_PARTIAL(en,96f);	\
+96:	stb	en,PACASOFTIRQEN(r13)
 #else
-# define TRACE_IRQS_ON
-# define TRACE_IRQS_OFF
+#define TRACE_ENABLE_INTS
+#define TRACE_DISABLE_INTS
+#define TRACE_AND_RESTORE_IRQ_PARTIAL(en,skip)
+#define TRACE_AND_RESTORE_IRQ(en)		\
+	stb	en,PACASOFTIRQEN(r13)
+#endif
 #endif
 
 #endif