x86, ptrace: support for branch trace store(BTS)

PATCH In review Markus Metzger 2 participants 2 messages Dec 5, 2007

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x86 ptrace support

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Markus Metzger

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2007-12-05 19:00 UTC #0 lore raw

PATCH 1/2 x86, ptrace: support for branch trace store(BTS)

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Changes to the last version:
- split implementation into two layers: ds/bts and ptrace
- renamed TIF's
- save/restore ds save area msr in __switch_to_xtra()
- make block-stepping only look at BTF bit

Signed-off-by Markus Metzger <[email protected]>

Signed-off-by Suresh Siddha <[email protected]>

---

arch/x86/kernel/process_32.c +18 -1

Index: linux-2.6-x86/arch/x86/kernel/process_32.c
===================================================================
@@ -594,11 +594,21 @@
 		 struct tss_struct *tss)
 {
 	struct thread_struct *prev, *next;
+	unsigned long debugctl;
 
 	prev = &prev_p->thread;
 	next = &next_p->thread;
 
-	if (next->debugctlmsr != prev->debugctlmsr)
+	debugctl = prev->debugctlmsr;
+	if (next->ds_area_msr != prev->ds_area_msr) {
+		/* we clear debugctl to make sure DS
+		 * is not in use when we change it */
+		debugctl = 0;
+		wrmsrl(MSR_IA32_DEBUGCTLMSR, 0);
+		wrmsr(MSR_IA32_DS_AREA, next->ds_area_msr, 0);
+	}
+
+	if (next->debugctlmsr != debugctl)
 		wrmsr(MSR_IA32_DEBUGCTLMSR, next->debugctlmsr, 0);
 
 	if (test_tsk_thread_flag(next_p, TIF_DEBUG)) {

@@ -622,6 +632,13 @@
 	}
 #endif
 
+	if (test_tsk_thread_flag(prev_p, TIF_BTS_TRACE_TS))
+		ptrace_bts_take_timestamp(prev_p, BTS_TASK_DEPARTS);
+
+	if (test_tsk_thread_flag(next_p, TIF_BTS_TRACE_TS))
+		ptrace_bts_take_timestamp(next_p, BTS_TASK_ARRIVES);
+
+
 	if (!test_tsk_thread_flag(next_p, TIF_IO_BITMAP)) {
 		/*
 		 * Disable the bitmap via an invalid offset. We still cache

include/asm-x86/ptrace-abi.h +52 -0

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include/asm-x86/ptrace.h +11 -0

Index: linux-2.6-x86/include/asm-x86/ptrace.h
===================================================================
@@ -4,8 +4,19 @@
 #include <linux/compiler.h>	/* For __user */
 #include <asm/ptrace-abi.h>
 
+
 #ifndef __ASSEMBLY__
 
+#ifdef __KERNEL__
+
+#include <asm/ds.h>
+
+struct task_struct;
+extern void ptrace_bts_take_timestamp(struct task_struct *, enum bts_qualifier);
+
+#endif /* __KERNEL__ */
+
+
 #ifdef __i386__
 /* this struct defines the way the registers are stored on the
    stack during a system call. */

arch/x86/kernel/Makefile_32 +1 -0

Index: linux-2.6-x86/arch/x86/kernel/Makefile_32
===================================================================
@@ -11,6 +11,7 @@
 		quirks.o i8237.o topology.o alternative.o i8253.o tsc_32.o rtc.o
 
 obj-y				+= ptrace.o
+obj-y				+= ds.o
 obj-y				+= tls.o
 obj-y				+= step.o
 obj-$(CONFIG_STACKTRACE)	+= stacktrace.o

include/asm-x86/thread_info_32.h +10 -2

Index: linux-2.6-x86/include/asm-x86/thread_info_32.h
===================================================================
@@ -139,6 +139,8 @@
 #define TIF_NOTSC		20	/* TSC is not accessible in userland */
 #define TIF_FORCED_TF		21	/* true if TF in eflags artificially */
 #define TIF_DEBUGCTLMSR		22	/* uses thread_struct.debugctlmsr */
+#define TIF_DS_AREA_MSR 	23      /* uses thread_struct.ds_area_msr */
+#define TIF_BTS_TRACE_TS        24      /* record scheduling event timestamps */
 
 #define _TIF_SYSCALL_TRACE	(1<<TIF_SYSCALL_TRACE)
 #define _TIF_SIGPENDING		(1<<TIF_SIGPENDING)

@@ -155,6 +157,8 @@
 #define _TIF_NOTSC		(1<<TIF_NOTSC)
 #define _TIF_FORCED_TF		(1<<TIF_FORCED_TF)
 #define _TIF_DEBUGCTLMSR	(1<<TIF_DEBUGCTLMSR)
+#define _TIF_DS_AREA_MSR	(1<<TIF_DS_AREA_MSR)
+#define _TIF_BTS_TRACE_TS	(1<<TIF_BTS_TRACE_TS)
 
 /* work to do on interrupt/exception return */
 #define _TIF_WORK_MASK \

@@ -164,8 +168,12 @@
 #define _TIF_ALLWORK_MASK	(0x0000FFFF & ~_TIF_SECCOMP)
 
 /* flags to check in __switch_to() */
-#define _TIF_WORK_CTXSW_NEXT (_TIF_IO_BITMAP | _TIF_NOTSC | _TIF_DEBUG | _TIF_DEBUGCTLMSR)
-#define _TIF_WORK_CTXSW_PREV (_TIF_IO_BITMAP | _TIF_NOTSC | _TIF_DEBUGCTLMSR)
+#define _TIF_WORK_CTXSW \
+    (_TIF_IO_BITMAP | _TIF_NOTSC | _TIF_DEBUGCTLMSR | \
+     _TIF_DS_AREA_MSR | _TIF_BTS_TRACE_TS)
+#define _TIF_WORK_CTXSW_PREV _TIF_WORK_CTXSW
+#define _TIF_WORK_CTXSW_NEXT (_TIF_WORK_CTXSW | _TIF_DEBUG)
+
 
 /*
  * Thread-synchronous status.

include/asm-x86/processor_32.h +3 -0

Index: linux-2.6-x86/include/asm-x86/processor_32.h
===================================================================
@@ -360,6 +360,9 @@
 	unsigned long	io_bitmap_max;
 /* MSR_IA32_DEBUGCTLMSR value to switch in if TIF_DEBUGCTLMSR is set.  */
 	unsigned long	debugctlmsr;
+/* Debug Store - if not 0 points to a DS Save Area configuration;
+ *               goes into MSR_IA32_DS_AREA */
+	unsigned long	ds_area_msr;
 };
 
 #define INIT_THREAD  {							\

arch/x86/kernel/process_64.c +23 -3

Index: linux-2.6-x86/arch/x86/kernel/process_64.c
===================================================================
@@ -550,11 +550,21 @@
 				    struct tss_struct *tss)
 {
 	struct thread_struct *prev, *next;
+	unsigned long debugctl;
 
 	prev = &prev_p->thread,
 	next = &next_p->thread;
 
-	if (next->debugctlmsr != prev->debugctlmsr)
+	debugctl = prev->debugctlmsr;
+	if (next->ds_area_msr != prev->ds_area_msr) {
+		/* we clear debugctl to make sure DS
+		 * is not in use when we change it */
+		debugctl = 0;
+		wrmsrl(MSR_IA32_DEBUGCTLMSR, 0);
+		wrmsrl(MSR_IA32_DS_AREA, next->ds_area_msr);
+	}
+
+	if (next->debugctlmsr != debugctl)
 		wrmsrl(MSR_IA32_DEBUGCTLMSR, next->debugctlmsr);
 
 	if (test_tsk_thread_flag(next_p, TIF_DEBUG)) {

@@ -580,6 +590,16 @@
 		 */
 		memset(tss->io_bitmap, 0xff, prev->io_bitmap_max);
 	}
+
+	/*
+	 * Last branch recording recofiguration of trace hardware and
+	 * disentangling of trace data per task.
+	 */
+	if (test_tsk_thread_flag(prev_p, TIF_BTS_TRACE_TS))
+		ptrace_bts_take_timestamp(prev_p, BTS_TASK_DEPARTS);
+
+	if (test_tsk_thread_flag(next_p, TIF_BTS_TRACE_TS))
+		ptrace_bts_take_timestamp(next_p, BTS_TASK_ARRIVES);
 }
 
 /*

@@ -683,8 +703,8 @@
 	/*
 	 * Now maybe reload the debug registers and handle I/O bitmaps
 	 */
-	if (unlikely((task_thread_info(next_p)->flags & _TIF_WORK_CTXSW))
-	    || test_tsk_thread_flag(prev_p, TIF_IO_BITMAP))
+	if (unlikely(task_thread_info(next_p)->flags & _TIF_WORK_CTXSW_NEXT ||
+		     task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV))
 		__switch_to_xtra(prev_p, next_p, tss);
 
 	/* If the task has used fpu the last 5 timeslices, just do a full

include/asm-x86/processor_64.h +3 -0

Index: linux-2.6-x86/include/asm-x86/processor_64.h
===================================================================
@@ -240,6 +240,9 @@
 	unsigned io_bitmap_max;
 /* MSR_IA32_DEBUGCTLMSR value to switch in if TIF_DEBUGCTLMSR is set.  */
 	unsigned long	debugctlmsr;
+/* Debug Store - if not 0 points to a DS Save Area configuration;
+ *               goes into MSR_IA32_DS_AREA */
+	unsigned long	ds_area_msr;
 /* cached TLS descriptors. */
 	u64 tls_array[GDT_ENTRY_TLS_ENTRIES];
 } __attribute__((aligned(16)));

include/asm-x86/thread_info_64.h +8 -1

Index: linux-2.6-x86/include/asm-x86/thread_info_64.h
===================================================================
@@ -121,6 +121,8 @@
 #define TIF_IO_BITMAP		22	/* uses I/O bitmap */
 #define TIF_FREEZE		23	/* is freezing for suspend */
 #define TIF_DEBUGCTLMSR		24	/* uses thread_struct.debugctlmsr */
+#define TIF_DS_AREA_MSR 	25      /* uses thread_struct.ds_area_msr */
+#define TIF_BTS_TRACE_TS	26      /* record scheduling event timestamps */
 
 #define _TIF_SYSCALL_TRACE	(1<<TIF_SYSCALL_TRACE)
 #define _TIF_SIGPENDING		(1<<TIF_SIGPENDING)

@@ -139,6 +141,8 @@
 #define _TIF_IO_BITMAP		(1<<TIF_IO_BITMAP)
 #define _TIF_FREEZE		(1<<TIF_FREEZE)
 #define _TIF_DEBUGCTLMSR	(1<<TIF_DEBUGCTLMSR)
+#define _TIF_DS_AREA_MSR	(1<<TIF_DS_AREA_MSR)
+#define _TIF_BTS_TRACE_TS	(1<<TIF_BTS_TRACE_TS)
 
 /* work to do on interrupt/exception return */
 #define _TIF_WORK_MASK \

@@ -147,7 +151,10 @@
 #define _TIF_ALLWORK_MASK (0x0000FFFF & ~_TIF_SECCOMP)
 
 /* flags to check in __switch_to() */
-#define _TIF_WORK_CTXSW (_TIF_DEBUG|_TIF_IO_BITMAP|_TIF_DEBUGCTLMSR)
+#define _TIF_WORK_CTXSW \
+    (_TIF_IO_BITMAP|_TIF_DEBUGCTLMSR|_TIF_DS_AREA_MSR|_TIF_BTS_TRACE_TS)
+#define _TIF_WORK_CTXSW_PREV _TIF_WORK_CTXSW
+#define _TIF_WORK_CTXSW_NEXT (_TIF_WORK_CTXSW|_TIF_DEBUG)
 
 #define PREEMPT_ACTIVE     0x10000000

arch/x86/kernel/cpu/intel.c +5 -0

Index: linux-2.6-x86/arch/x86/kernel/cpu/intel.c
===================================================================
@@ -11,6 +11,8 @@
 #include <asm/pgtable.h>
 #include <asm/msr.h>
 #include <asm/uaccess.h>
+#include <asm/ptrace.h>
+#include <asm/ds.h>
 
 #include "cpu.h"

@@ -219,6 +221,9 @@
 		if (!(l1 & (1<<12)))
 			set_bit(X86_FEATURE_PEBS, c->x86_capability);
 	}
+
+	if (cpu_has_bts)
+		ds_init_intel(c);
 }
 
 static unsigned int __cpuinit intel_size_cache(struct cpuinfo_x86 * c, unsigned int size)

arch/x86/kernel/setup_64.c +5 -0

Index: linux-2.6-x86/arch/x86/kernel/setup_64.c
===================================================================
@@ -60,6 +60,7 @@
 #include <asm/dmi.h>
 #include <asm/cacheflush.h>
 #include <asm/mce.h>
+#include <asm/ds.h>
 
 /*
  * Machine setup..

@@ -850,6 +851,10 @@
 			set_cpu_cap(c, X86_FEATURE_PEBS);
 	}
 
+
+	if (cpu_has_bts)
+		ds_init_intel(c);
+
 	n = c->extended_cpuid_level;
 	if (n >= 0x80000008) {
 		unsigned eax = cpuid_eax(0x80000008);

arch/x86/kernel/ptrace.c +212 -0

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arch/x86/kernel/Makefile_64 +1 -0

Index: linux-2.6-x86/arch/x86/kernel/Makefile_64
===================================================================
@@ -13,6 +13,7 @@
 		i8253.o rtc.o
 
 obj-y				+= ptrace.o
+obj-y				+= ds.o
 obj-y				+= step.o
 
 obj-$(CONFIG_IA32_EMULATION)	+= tls.o

arch/x86/kernel/step.c +13 -5

Index: linux-2.6-x86/arch/x86/kernel/step.c
===================================================================
@@ -169,9 +169,14 @@
 	 */
 	if (enable_single_step(child) && block) {
 		set_tsk_thread_flag(child, TIF_DEBUGCTLMSR);
-		write_debugctlmsr(child, DEBUGCTLMSR_BTF);
-	} else if (test_and_clear_tsk_thread_flag(child, TIF_DEBUGCTLMSR)) {
-		write_debugctlmsr(child, 0);
+		write_debugctlmsr(child,
+				  child->thread.debugctlmsr | DEBUGCTLMSR_BTF);
+	} else {
+	    write_debugctlmsr(child,
+			      child->thread.debugctlmsr & ~TIF_DEBUGCTLMSR);
+
+	    if (!child->thread.debugctlmsr)
+		    clear_tsk_thread_flag(child, TIF_DEBUGCTLMSR);
 	}
 }

@@ -190,8 +195,11 @@
 	/*
 	 * Make sure block stepping (BTF) is disabled.
 	 */
-	if (test_and_clear_tsk_thread_flag(child, TIF_DEBUGCTLMSR))
-		write_debugctlmsr(child, 0);
+	write_debugctlmsr(child,
+			  child->thread.debugctlmsr & ~TIF_DEBUGCTLMSR);
+
+	if (!child->thread.debugctlmsr)
+		clear_tsk_thread_flag(child, TIF_DEBUGCTLMSR);
 
 	/* Always clear TIF_SINGLESTEP... */
 	clear_tsk_thread_flag(child, TIF_SINGLESTEP);

arch/x86/kernel/ds.c new file +429 -0

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include/asm-x86/ds.h new file +65 -0

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Ingo Molnar

2007-12-05 20:27 UTC #1 lore raw

Quoted 1 line · Markus Metzger

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thanks, this one applied fine to x86.git.

Ingo