[PATCH] powerpc: Add irqtrace support for 32-bit powerpc
Benjamin Herrenschmidt
benh at kernel.crashing.org
Wed Jun 17 19:01:53 EST 2009
Based on initial work from: Dale Farnsworth <dale at farnsworth.org>
Add the low level irq tracing hooks for 32-bit powerpc needed
to enable full lockdep functionality.
The approach taken to deal with the code in entry_32.S is that
we don't trace all the transitions of MSR:EE when we just turn
it off to peek at TI_FLAGS without races. Only when we are
calling into C code or returning from exceptions with a state
that have changed from what lockdep thinks.
There's a little bugger though: If we take an exception that
keeps interrupts enabled (such as an alignment exception) while
interrupts are enabled, we will call trace_hardirqs_on() on the
way back spurriously. Not a big deal, but to get rid of it would
require remembering in pt_regs that the exception was one of the
type that kept interrupts enabled which we don't know at this
stage. (Well, we could test all cases for regs->trap but that
sucks too much).
Signed-off-by: Benjamin Herrenschmidt <benh at kernel.crashing.org>
---
Not very well tested ... got issues with my u-boot on the 440
board and I didn't have much time to test elsewhere. FSL welcome
to test on funky configs. It's likely to still be subtely broken :-)
arch/powerpc/Kconfig | 1
arch/powerpc/include/asm/hw_irq.h | 20 +++---
arch/powerpc/kernel/entry_32.S | 126 ++++++++++++++++++++++++++++++++++++--
arch/powerpc/kernel/setup_32.c | 2
arch/powerpc/kernel/udbg.c | 1
5 files changed, 135 insertions(+), 15 deletions(-)
--- linux-work.orig/arch/powerpc/Kconfig 2009-06-17 16:45:15.000000000 +1000
+++ linux-work/arch/powerpc/Kconfig 2009-06-17 16:45:36.000000000 +1000
@@ -62,7 +62,6 @@ config HAVE_LATENCYTOP_SUPPORT
config TRACE_IRQFLAGS_SUPPORT
bool
- depends on PPC64
default y
config LOCKDEP_SUPPORT
Index: linux-work/arch/powerpc/kernel/entry_32.S
===================================================================
--- linux-work.orig/arch/powerpc/kernel/entry_32.S 2009-06-17 16:45:15.000000000 +1000
+++ linux-work/arch/powerpc/kernel/entry_32.S 2009-06-17 18:29:23.000000000 +1000
@@ -191,11 +191,49 @@ transfer_to_handler_cont:
mflr r9
lwz r11,0(r9) /* virtual address of handler */
lwz r9,4(r9) /* where to go when done */
+#ifdef CONFIG_TRACE_IRQFLAGS
+ lis r12,reenable_mmu at h
+ ori r12,r12,reenable_mmu at l
+ mtspr SPRN_SRR0,r12
+ mtspr SPRN_SRR1,r10
+ SYNC
+ RFI
+reenable_mmu: /* re-enable mmu so we can */
+ mfmsr r10
+ lwz r12,_MSR(r1)
+ xor r10,r10,r12
+ andi. r10,r10,MSR_EE /* Did EE change? */
+ beq 1f
+
+ /* Save handler and return address into the 2 unused words
+ * of the STACK_FRAME_OVERHEAD (sneak sneak sneak). Everything
+ * else can be recovered from the pt_regs except r3 which for
+ * normal interrupts has been set to pt_regs and for syscalls
+ * is an argument, so we temporarily use ORIG_GPR3 to save it
+ */
+ stw r9,8(r1)
+ stw r11,12(r1)
+ stw r3,ORIG_GPR3(r1)
+ bl trace_hardirqs_off
+ lwz r0,GPR0(r1)
+ lwz r3,ORIG_GPR3(r1)
+ lwz r4,GPR4(r1)
+ lwz r5,GPR5(r1)
+ lwz r6,GPR6(r1)
+ lwz r7,GPR7(r1)
+ lwz r8,GPR8(r1)
+ lwz r9,8(r1)
+ lwz r11,12(r1)
+1: mtctr r11
+ mtlr r9
+ bctr /* jump to handler */
+#else /* CONFIG_TRACE_IRQFLAGS */
mtspr SPRN_SRR0,r11
mtspr SPRN_SRR1,r10
mtlr r9
SYNC
RFI /* jump to handler, enable MMU */
+#endif /* CONFIG_TRACE_IRQFLAGS */
#if defined (CONFIG_6xx) || defined(CONFIG_E500)
4: rlwinm r12,r12,0,~_TLF_NAPPING
@@ -251,6 +289,31 @@ _GLOBAL(DoSyscall)
#ifdef SHOW_SYSCALLS
bl do_show_syscall
#endif /* SHOW_SYSCALLS */
+#ifdef CONFIG_TRACE_IRQFLAGS
+ /* Return from syscalls can (and generally will) hard enable
+ * interrupts. You aren't supposed to call a syscall with
+ * interrupts disabled in the first place. However, to ensure
+ * that we get it right vs. lockdep if it happens, we force
+ * that hard enable here with appropriate tracing if we see
+ * that we have been called with interrupts off
+ */
+ mfmsr r11
+ andi. r12,r11,MSR_EE
+ bne+ 1f
+ /* We came in with interrupts disabled, we enable them now */
+ bl trace_hardirqs_on
+ mfmsr r11
+ lwz r0,GPR0(r1)
+ lwz r3,GPR3(r1)
+ lwz r4,GPR4(r1)
+ ori r11,r11,MSR_EE
+ lwz r5,GPR5(r1)
+ lwz r6,GPR6(r1)
+ lwz r7,GPR7(r1)
+ lwz r8,GPR8(r1)
+ mtmsr r11
+1:
+#endif /* CONFIG_TRACE_IRQFLAGS */
rlwinm r10,r1,0,0,(31-THREAD_SHIFT) /* current_thread_info() */
lwz r11,TI_FLAGS(r10)
andi. r11,r11,_TIF_SYSCALL_T_OR_A
@@ -275,6 +338,7 @@ ret_from_syscall:
rlwinm r12,r1,0,0,(31-THREAD_SHIFT) /* current_thread_info() */
/* disable interrupts so current_thread_info()->flags can't change */
LOAD_MSR_KERNEL(r10,MSR_KERNEL) /* doesn't include MSR_EE */
+ /* Note: We don't bother telling lockdep about it */
SYNC
MTMSRD(r10)
lwz r9,TI_FLAGS(r12)
@@ -288,6 +352,19 @@ ret_from_syscall:
oris r11,r11,0x1000 /* Set SO bit in CR */
stw r11,_CCR(r1)
syscall_exit_cont:
+ lwz r8,_MSR(r1)
+#ifdef CONFIG_TRACE_IRQFLAGS
+ /* If we are going to return from the syscall with interrupts
+ * off, we trace that here. It shouldn't happen though but we
+ * want to catch the bugger if it does right ?
+ */
+ andi. r10,r8,MSR_EE
+ bne+ 1f
+ stw r3,GPR3(r1)
+ bl trace_hardirqs_off
+ lwz r3,GPR3(r1)
+1:
+#endif /* CONFIG_TRACE_IRQFLAGS */
#if defined(CONFIG_4xx) || defined(CONFIG_BOOKE)
/* If the process has its own DBCR0 value, load it up. The internal
debug mode bit tells us that dbcr0 should be loaded. */
@@ -311,7 +388,6 @@ END_FTR_SECTION_IFSET(CPU_FTR_NEED_PAIRE
mtlr r4
mtcr r5
lwz r7,_NIP(r1)
- lwz r8,_MSR(r1)
FIX_SRR1(r8, r0)
lwz r2,GPR2(r1)
lwz r1,GPR1(r1)
@@ -394,7 +470,9 @@ syscall_exit_work:
andi. r0,r9,(_TIF_SYSCALL_T_OR_A|_TIF_SINGLESTEP)
beq ret_from_except
- /* Re-enable interrupts */
+ /* Re-enable interrupts. There is no need to trace that with
+ * lockdep as we are supposed to have IRQs on at this point
+ */
ori r10,r10,MSR_EE
SYNC
MTMSRD(r10)
@@ -705,6 +783,7 @@ ret_from_except:
/* Hard-disable interrupts so that current_thread_info()->flags
* can't change between when we test it and when we return
* from the interrupt. */
+ /* Note: We don't bother telling lockdep about it */
LOAD_MSR_KERNEL(r10,MSR_KERNEL)
SYNC /* Some chip revs have problems here... */
MTMSRD(r10) /* disable interrupts */
@@ -744,11 +823,24 @@ resume_kernel:
beq+ restore
andi. r0,r3,MSR_EE /* interrupts off? */
beq restore /* don't schedule if so */
+#ifdef CONFIG_TRACE_IRQFLAGS
+ /* Lockdep thinks irqs are enabled, we need to call
+ * preempt_schedule_irq with IRQs off, so we inform lockdep
+ * now that we -did- turn them off already
+ */
+ bl trace_hardirqs_off
+#endif
1: bl preempt_schedule_irq
rlwinm r9,r1,0,0,(31-THREAD_SHIFT)
lwz r3,TI_FLAGS(r9)
andi. r0,r3,_TIF_NEED_RESCHED
bne- 1b
+#ifdef CONFIG_TRACE_IRQFLAGS
+ /* And now, to properly rebalance the above, we tell lockdep they
+ * are being turned back on, which will happen when we return
+ */
+ bl trace_hardirqs_on
+#endif
#else
resume_kernel:
#endif /* CONFIG_PREEMPT */
@@ -781,8 +873,28 @@ BEGIN_FTR_SECTION
END_FTR_SECTION_IFSET(CPU_FTR_NEED_PAIRED_STWCX)
stwcx. r0,0,r1 /* to clear the reservation */
-#if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
lwz r9,_MSR(r1)
+#ifdef CONFIG_TRACE_IRQFLAGS
+ /* Lockdep doesn't know about the fact that IRQs are temporarily turned
+ * off in this assembly code while peeking at TI_FLAGS() and such. However
+ * we need to inform it if the exception turned interrupts off, and we
+ * are about to trun them back on.
+ *
+ * The problem here sadly is that we don't know whether the exceptions was
+ * one that turned interrupts off or not. So we always tell lockdep about
+ * turning them on here when we go back to wherever we came from with EE
+ * on, even if that may meen some redudant calls being tracked. Maybe later
+ * we could encode what the exception did somewhere or test the exception
+ * type in the pt_regs but that sounds overkill
+ */
+ andi. r10,r9,MSR_EE
+ beq 1f
+ bl trace_hardirqs_on
+ lwz r9,_MSR(r1)
+1:
+#endif /* CONFIG_TRACE_IRQFLAGS */
+
+#if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
andi. r10,r9,MSR_RI /* check if this exception occurred */
beql nonrecoverable /* at a bad place (MSR:RI = 0) */
@@ -805,7 +917,6 @@ END_FTR_SECTION_IFSET(CPU_FTR_NEED_PAIRE
MTMSRD(r10) /* clear the RI bit */
.globl exc_exit_restart
exc_exit_restart:
- lwz r9,_MSR(r1)
lwz r12,_NIP(r1)
FIX_SRR1(r9,r10)
mtspr SPRN_SRR0,r12
@@ -1035,11 +1146,18 @@ do_work: /* r10 contains MSR_KERNEL he
beq do_user_signal
do_resched: /* r10 contains MSR_KERNEL here */
+ /* Note: We don't need to inform lockdep that we are enabling
+ * interrupts here. As far as it knows, they are already enabled
+ */
ori r10,r10,MSR_EE
SYNC
MTMSRD(r10) /* hard-enable interrupts */
bl schedule
recheck:
+ /* Note: And we don't tell it we are disabling them again
+ * neither. Those disable/enable cycles used to peek at
+ * TI_FLAGS aren't advertised.
+ */
LOAD_MSR_KERNEL(r10,MSR_KERNEL)
SYNC
MTMSRD(r10) /* disable interrupts */
Index: linux-work/arch/powerpc/kernel/setup_32.c
===================================================================
--- linux-work.orig/arch/powerpc/kernel/setup_32.c 2009-06-17 16:45:15.000000000 +1000
+++ linux-work/arch/powerpc/kernel/setup_32.c 2009-06-17 18:29:37.000000000 +1000
@@ -119,6 +119,8 @@ notrace unsigned long __init early_init(
*/
notrace void __init machine_init(unsigned long dt_ptr)
{
+ lockdep_init();
+
/* Enable early debugging if any specified (see udbg.h) */
udbg_early_init();
Index: linux-work/arch/powerpc/include/asm/hw_irq.h
===================================================================
--- linux-work.orig/arch/powerpc/include/asm/hw_irq.h 2009-06-17 16:45:15.000000000 +1000
+++ linux-work/arch/powerpc/include/asm/hw_irq.h 2009-06-17 16:45:36.000000000 +1000
@@ -68,13 +68,13 @@ static inline int irqs_disabled_flags(un
#if defined(CONFIG_BOOKE)
#define SET_MSR_EE(x) mtmsr(x)
-#define local_irq_restore(flags) __asm__ __volatile__("wrtee %0" : : "r" (flags) : "memory")
+#define raw_local_irq_restore(flags) __asm__ __volatile__("wrtee %0" : : "r" (flags) : "memory")
#else
#define SET_MSR_EE(x) mtmsr(x)
-#define local_irq_restore(flags) mtmsr(flags)
+#define raw_local_irq_restore(flags) mtmsr(flags)
#endif
-static inline void local_irq_disable(void)
+static inline void raw_local_irq_disable(void)
{
#ifdef CONFIG_BOOKE
__asm__ __volatile__("wrteei 0": : :"memory");
@@ -86,7 +86,7 @@ static inline void local_irq_disable(voi
#endif
}
-static inline void local_irq_enable(void)
+static inline void raw_local_irq_enable(void)
{
#ifdef CONFIG_BOOKE
__asm__ __volatile__("wrteei 1": : :"memory");
@@ -98,7 +98,7 @@ static inline void local_irq_enable(void
#endif
}
-static inline void local_irq_save_ptr(unsigned long *flags)
+static inline void raw_local_irq_save_ptr(unsigned long *flags)
{
unsigned long msr;
msr = mfmsr();
@@ -110,12 +110,12 @@ static inline void local_irq_save_ptr(un
#endif
}
-#define local_save_flags(flags) ((flags) = mfmsr())
-#define local_irq_save(flags) local_irq_save_ptr(&flags)
-#define irqs_disabled() ((mfmsr() & MSR_EE) == 0)
+#define raw_local_save_flags(flags) ((flags) = mfmsr())
+#define raw_local_irq_save(flags) raw_local_irq_save_ptr(&flags)
+#define raw_irqs_disabled() ((mfmsr() & MSR_EE) == 0)
+#define raw_irqs_disabled_flags(flags) (((flags) & MSR_EE) == 0)
-#define hard_irq_enable() local_irq_enable()
-#define hard_irq_disable() local_irq_disable()
+#define hard_irq_disable() raw_local_irq_disable()
static inline int irqs_disabled_flags(unsigned long flags)
{
Index: linux-work/arch/powerpc/kernel/udbg.c
===================================================================
--- linux-work.orig/arch/powerpc/kernel/udbg.c 2009-06-17 17:14:41.000000000 +1000
+++ linux-work/arch/powerpc/kernel/udbg.c 2009-06-17 17:14:43.000000000 +1000
@@ -65,6 +65,7 @@ void __init udbg_early_init(void)
#ifdef CONFIG_PPC_EARLY_DEBUG
console_loglevel = 10;
#endif
+ register_early_udbg_console();
}
/* udbg library, used by xmon et al */
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