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Subject[patch 1/2] x86, ptrace: support for branch trace store(BTS)
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Changes to previous version(s):
- moved task arrives/departs notifications to __switch_to_xtra()
- added _TIF_BTS_TRACE and _TIF_BTS_TRACE_TS to _TIF_WORK_CTXSW_*
- split _TIF_WORK_CTXSW into ~_PREV and ~_NEXT for x86_64
- ptrace_bts_init_intel() function called from init_intel()
- removed PTRACE_BTS_INIT ptrace command
- cache DEBUGCTRL MSR
- replace struct declarations and operations struct with
configuration struct defining offset/size pairs and
generic operations
- added a patch for the ptrace.2 man page for discussing the API
in this forum


Signed-off-by: Markus Metzger <markus.t.metzger@intel.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
---
Index: linux-2.6/arch/x86/kernel/process_32.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/process_32.c 2007-11-22 11:03:44.%N +0100
+++ linux-2.6/arch/x86/kernel/process_32.c 2007-11-22 11:36:39.%N +0100
@@ -623,6 +623,19 @@
}
#endif

+ /*
+ * Last branch recording recofiguration of trace hardware and
+ * disentangling of trace data per task.
+ */
+ if (test_tsk_thread_flag(prev_p, TIF_BTS_TRACE) ||
+ test_tsk_thread_flag(prev_p, TIF_BTS_TRACE_TS))
+ ptrace_bts_task_departs(prev_p);
+
+ if (test_tsk_thread_flag(next_p, TIF_BTS_TRACE) ||
+ test_tsk_thread_flag(next_p, TIF_BTS_TRACE_TS))
+ ptrace_bts_task_arrives(next_p);
+
+
if (!test_tsk_thread_flag(next_p, TIF_IO_BITMAP)) {
/*
* Disable the bitmap via an invalid offset. We still cache
Index: linux-2.6/arch/x86/kernel/ptrace_32.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/ptrace_32.c 2007-11-22 11:03:44.%N +0100
+++ linux-2.6/arch/x86/kernel/ptrace_32.c 2007-11-22 11:36:39.%N +0100
@@ -24,6 +24,7 @@
#include <asm/debugreg.h>
#include <asm/ldt.h>
#include <asm/desc.h>
+#include <asm/ptrace_bts.h>

/*
* does not yet catch signals sent when the child dies.
@@ -274,6 +275,7 @@
{
clear_singlestep(child);
clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
+ ptrace_bts_task_detached(child);
}

/*
@@ -610,6 +612,32 @@
(struct user_desc __user *) data);
break;

+ case PTRACE_BTS_ALLOCATE_BUFFER:
+ ret = ptrace_bts_allocate_bts(child, data);
+ break;
+
+ case PTRACE_BTS_GET_BUFFER_SIZE:
+ ret = ptrace_bts_get_buffer_size(child);
+ break;
+
+ case PTRACE_BTS_GET_INDEX:
+ ret = ptrace_bts_get_index(child);
+ break;
+
+ case PTRACE_BTS_READ_RECORD:
+ ret = ptrace_bts_read_record
+ (child, data,
+ (struct ptrace_bts_record __user *) addr);
+ break;
+
+ case PTRACE_BTS_CONFIG:
+ ret = ptrace_bts_config(child, data);
+ break;
+
+ case PTRACE_BTS_STATUS:
+ ret = ptrace_bts_status(child);
+ break;
+
default:
ret = ptrace_request(child, request, addr, data);
break;
Index: linux-2.6/include/asm-x86/ptrace-abi.h
===================================================================
--- linux-2.6.orig/include/asm-x86/ptrace-abi.h 2007-11-22 11:03:45.%N +0100
+++ linux-2.6/include/asm-x86/ptrace-abi.h 2007-11-22 13:28:22.%N +0100
@@ -78,4 +78,49 @@
# define PTRACE_SYSEMU_SINGLESTEP 32
#endif

+/*
+ * Maximal BTS buffer size in number of records
+ * This is a macro, not a ptrace command.
+ */
+#define PTRACE_BTS_MAX_BTS_SIZE 4000
+
+
+/* Allocate new bts buffer (free old one, if exists) of size DATA bts records;
+ parameter ADDR is ignored.
+ Return 0, if successful; -1, otherwise.
+ ENXIO....ptrace bts not initialized
+ EINVAL...invalid size in records
+ ENOMEM...out of memory */
+#define PTRACE_BTS_ALLOCATE_BUFFER 41
+
+/* Return the size of the bts buffer in number of bts records,
+ if successful; -1, otherwise.
+ ENXIO....ptrace bts not initialized or no buffer allocated */
+#define PTRACE_BTS_GET_BUFFER_SIZE 42
+
+/* Return the index of the next bts record to be written,
+ if successful; -1, otherwise.
+ After the first warp-around, this is the start of the circular bts buffer.
+ ENXIO....ptrace bts not initialized or no buffer allocated */
+#define PTRACE_BTS_GET_INDEX 43
+
+/* Read the DATA'th bts record into a ptrace_bts_record buffer
provided in ADDR.
+ Return 0, if successful; -1, otherwise
+ ENXIO....ptrace bts not initialized or no buffer allocated
+ EINVAL...invalid index */
+#define PTRACE_BTS_READ_RECORD 44
+
+/* Configure last branch trace; the configuration is given as a bit-mask of
+ PTRACE_BTS_O_* options in DATA; parameter ADDR is ignored. */
+#define PTRACE_BTS_CONFIG 45
+
+/* Return the configuration as bit-mask of PTRACE_BTS_O_* options.*/
+#define PTRACE_BTS_STATUS 46
+
+/* Trace configuration options */
+/* Collect last branch trace */
+#define PTRACE_BTS_O_TRACE_TASK 0x1
+/* Take timestamps when the task arrives and departs */
+#define PTRACE_BTS_O_TIMESTAMPS 0x2
+
#endif
Index: linux-2.6/include/asm-x86/ptrace.h
===================================================================
--- linux-2.6.orig/include/asm-x86/ptrace.h 2007-11-22 11:03:45.%N +0100
+++ linux-2.6/include/asm-x86/ptrace.h 2007-11-22 11:36:39.%N +0100
@@ -4,8 +4,48 @@
#include <linux/compiler.h> /* For __user */
#include <asm/ptrace-abi.h>

+
#ifndef __ASSEMBLY__

+/* a branch trace record entry
+ *
+ * In order to unify the interface between various processor versions,
+ * we use the below data structure for all processors.
+ */
+enum ptrace_bts_qualifier {
+ PTRACE_BTS_INVALID = 0,
+ PTRACE_BTS_BRANCH,
+ PTRACE_BTS_TASK_ARRIVES,
+ PTRACE_BTS_TASK_DEPARTS
+};
+
+struct ptrace_bts_record {
+ enum ptrace_bts_qualifier qualifier;
+ union {
+ /* PTRACE_BTS_BRANCH */
+ struct {
+ void *from_ip;
+ void *to_ip;
+ } lbr;
+ /* PTRACE_BTS_TASK_ARRIVES or
+ PTRACE_BTS_TASK_DEPARTS */
+ unsigned long long timestamp;
+ } variant;
+};
+
+#ifdef __KERNEL__
+
+#include <linux/init.h>
+
+struct task_struct;
+struct cpuinfo_x86;
+
+extern __cpuinit void ptrace_bts_init_intel(struct cpuinfo_x86 *c);
+extern void ptrace_bts_task_arrives(struct task_struct *tsk);
+extern void ptrace_bts_task_departs(struct task_struct *tsk);
+
+#endif /* __KERNEL__ */
+
#ifdef __i386__
/* this struct defines the way the registers are stored on the
stack during a system call. */
@@ -64,6 +104,7 @@
#define regs_return_value(regs) ((regs)->eax)

extern unsigned long profile_pc(struct pt_regs *regs);
+
#endif /* __KERNEL__ */

#else /* __i386__ */
Index: linux-2.6/arch/x86/kernel/ptrace_bts.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6/arch/x86/kernel/ptrace_bts.c 2007-11-22 13:27:28.%N +0100
@@ -0,0 +1,453 @@
+/*
+ * Extend ptrace with execution trace support using the x86 last
+ * branch recording hardware feature.
+ *
+ * Copyright (C) 2007 Intel Corporation.
+ * Markus Metzger <markus.t.metzger@intel.com>, Oct 2007
+ */
+
+#include <asm/ptrace_bts.h>
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/ptrace.h>
+
+#include <asm/uaccess.h>
+
+
+struct ptrace_bts_configuration ptrace_bts_cfg;
+
+/*
+ * Allocate the DS configuration for the parameter task.
+ * Returns an error, if there was already a DS configuration allocated
+ * for the task.
+ * Returns 0, if successful; -Eerrno, otherwise.
+ */
+static int ptrace_bts_allocate_ds(struct task_struct *child)
+{
+ if (!ptrace_bts_cfg.sizeof_ds)
+ return -EOPNOTSUPP;
+
+ if (child->thread.ds_area)
+ return -EEXIST;
+
+ child->thread.ds_area =
+ (unsigned long)kzalloc(ptrace_bts_cfg.sizeof_ds, GFP_KERNEL);
+
+ if (!child->thread.ds_area)
+ return -ENOMEM;
+
+ return 0;
+}
+
+/*
+ * Allocate new BTS buffer for the parameter task.
+ * Allocate a new DS configuration, if needed.
+ * If there was an old buffer, that buffer is freed, provided the
+ * allocation of the new buffer succeeded.
+ * A size of zero deallocates the old buffer.
+ * The trace data is not copied to the new buffer.
+ * Returns 0, if successful; -Eerrno, otherwise.
+ */
+int ptrace_bts_allocate_bts(struct task_struct *child,
+ long size_in_records)
+{
+ void *ds = (void *)child->thread.ds_area;
+ size_t size_in_bytes =
+ size_in_records * ptrace_bts_cfg.sizeof_bts;
+ char *new_buffer = 0;
+
+ if (!ptrace_bts_cfg.sizeof_bts)
+ return -EOPNOTSUPP;
+
+ if (size_in_records < 0)
+ return -EINVAL;
+
+ if (size_in_records > PTRACE_BTS_MAX_BTS_SIZE)
+ return -EINVAL;
+
+ if (!ds) {
+ int err = ptrace_bts_allocate_ds(child);
+ if (err < 0)
+ return err;
+ ds = (void *)child->thread.ds_area;
+ }
+
+ if (size_in_bytes) {
+ new_buffer = kzalloc(size_in_bytes, GFP_KERNEL);
+
+ if (!new_buffer)
+ return -ENOMEM;
+ }
+
+ if (ds)
+ kfree(ptrace_bts_get_bts_buffer_base(ds));
+
+ ptrace_bts_set_bts_buffer_base(ds, new_buffer);
+ ptrace_bts_set_bts_index(ds, new_buffer);
+ ptrace_bts_set_bts_absolute_maximum(ds, new_buffer + size_in_bytes);
+ ptrace_bts_set_bts_interrupt_threshold(ds,
+ new_buffer + size_in_bytes + 1);
+
+ return 0;
+}
+
+/*
+ * Returns the size of the bts buffer in number of bts records
+ * Return -Eerrno, if an error occured
+ */
+int ptrace_bts_get_buffer_size(struct task_struct *child)
+{
+ void *ds = (void *)child->thread.ds_area;
+ size_t size_in_bytes;
+
+ if (!ptrace_bts_cfg.sizeof_bts)
+ return -EOPNOTSUPP;
+
+ if (!child->thread.ds_area)
+ return -ENXIO;
+
+ size_in_bytes =
+ ptrace_bts_get_bts_absolute_maximum(ds) -
+ ptrace_bts_get_bts_buffer_base(ds);
+ return size_in_bytes / ptrace_bts_cfg.sizeof_bts;
+}
+
+/*
+ * Returns the bts index of the next record to be written such that it
+ * could be used to access this record in a C array of records.
+ * Returns -Eerrno, if an error occured.
+ */
+int ptrace_bts_get_index(struct task_struct *child)
+{
+ void *ds = (void *)child->thread.ds_area;
+ size_t index_offset_in_bytes;
+
+ if (!ptrace_bts_cfg.sizeof_bts)
+ return -EOPNOTSUPP;
+
+ if (!child->thread.ds_area)
+ return -ENXIO;
+
+ index_offset_in_bytes =
+ ptrace_bts_get_bts_index(ds) -
+ ptrace_bts_get_bts_buffer_base(ds);
+ return index_offset_in_bytes / ptrace_bts_cfg.sizeof_bts;
+}
+
+/*
+ * Copies the index'th BTS record into out.
+ * Converts the internal BTS representation into the external one.
+ * Returns the number of bytes copied, if successful; -Eerrno, otherwise.
+ *
+ * pre: out points to a buffer big enough to hold one BTS record
+ */
+int ptrace_bts_read_record(struct task_struct *child,
+ long index,
+ struct ptrace_bts_record __user *out)
+{
+ void *ds = (void *)child->thread.ds_area;
+ struct ptrace_bts_record ret;
+ void *bts;
+
+ if (!ptrace_bts_cfg.sizeof_bts)
+ return -EOPNOTSUPP;
+
+ if (!child->thread.ds_area)
+ return -ENXIO;
+
+ if (index < 0)
+ return -EINVAL;
+
+ if (index >= ptrace_bts_get_buffer_size(child))
+ return -EINVAL;
+
+ bts = ptrace_bts_get_bts_buffer_base(ds);
+ bts = (char *)bts + (index * ptrace_bts_cfg.sizeof_bts);
+
+ memset(&ret, 0, sizeof(ret));
+ if (ptrace_bts_get_from_ip(bts) == PTRACE_BTS_ESCAPE_ADDRESS) {
+ ret.qualifier = ptrace_bts_get_info_type(bts);
+ ret.variant.timestamp = ptrace_bts_get_info_data(bts);
+ } else {
+ ret.qualifier = PTRACE_BTS_BRANCH;
+ ret.variant.lbr.from_ip = ptrace_bts_get_from_ip(bts);
+ ret.variant.lbr.to_ip = ptrace_bts_get_to_ip(bts);
+ }
+ if (copy_to_user(out, &ret, sizeof(ret)))
+ return -EFAULT;
+
+ return sizeof(ret);
+}
+
+/*
+ * Copies the parameter BTS record into the task's BTS buffer at
+ * ptrace_bts_get_index() and increments the index.
+ * Converts the external BTS info representation into the internal one.
+ * Returns the number of bytes copied, if successful; -Eerrno, otherwise.
+ *
+ * pre: child is not running
+ */
+static int ptrace_bts_write_record(struct task_struct *child,
+ const struct ptrace_bts_record *in)
+{
+ void *ds = (void *)child->thread.ds_area;
+ void *bts;
+
+ if (!ptrace_bts_cfg.sizeof_bts)
+ return -EOPNOTSUPP;
+
+ if (!child->thread.ds_area)
+ return -ENXIO;
+
+ if (ptrace_bts_get_buffer_size(child) <= 0)
+ return -ENXIO;
+
+ bts = ptrace_bts_get_bts_index(ds);
+
+ memset(bts, 0, ptrace_bts_cfg.sizeof_bts);
+ switch (in->qualifier) {
+ case PTRACE_BTS_INVALID:
+ break;
+
+ case PTRACE_BTS_BRANCH:
+ ptrace_bts_set_from_ip(bts, in->variant.lbr.from_ip);
+ ptrace_bts_set_to_ip(bts, in->variant.lbr.to_ip);
+ break;
+
+ case PTRACE_BTS_TASK_ARRIVES:
+ case PTRACE_BTS_TASK_DEPARTS:
+ ptrace_bts_set_from_ip(bts, PTRACE_BTS_ESCAPE_ADDRESS);
+ ptrace_bts_set_info_type(bts, in->qualifier);
+ ptrace_bts_set_info_data(bts, in->variant.timestamp);
+ break;
+
+ default:
+ return -EINVAL;
+ }
+ bts = (char *)bts + ptrace_bts_cfg.sizeof_bts;
+ if (bts >= ptrace_bts_get_bts_absolute_maximum(ds))
+ bts = ptrace_bts_get_bts_buffer_base(ds);
+ ptrace_bts_set_bts_index(ds, bts);
+
+ return ptrace_bts_cfg.sizeof_bts;
+}
+
+/*
+ * Configures ptrace_bts structure in traced task's task_struct.
+ */
+int ptrace_bts_config(struct task_struct *child,
+ unsigned long options)
+{
+ if (!ptrace_bts_cfg.sizeof_bts)
+ return -EOPNOTSUPP;
+
+ if (options & PTRACE_BTS_O_TRACE_TASK)
+ set_tsk_thread_flag(child, TIF_BTS_TRACE);
+ else
+ clear_tsk_thread_flag(child, TIF_BTS_TRACE);
+
+ if (options & PTRACE_BTS_O_TIMESTAMPS)
+ set_tsk_thread_flag(child, TIF_BTS_TRACE_TS);
+ else
+ clear_tsk_thread_flag(child, TIF_BTS_TRACE_TS);
+
+ return 0;
+}
+
+/*
+ * Returns the configuration in ptrace_bts structure in traced task's
+ * task_struct.
+ */
+int ptrace_bts_status(struct task_struct *child)
+{
+ int status = 0;
+
+ if (!ptrace_bts_cfg.sizeof_bts)
+ return -EOPNOTSUPP;
+
+ if (test_tsk_thread_flag(child, TIF_BTS_TRACE))
+ status |= PTRACE_BTS_O_TRACE_TASK;
+ if (test_tsk_thread_flag(child, TIF_BTS_TRACE_TS))
+ status |= PTRACE_BTS_O_TIMESTAMPS;
+
+ return status;
+}
+
+/*
+ * This function is called on a context switch for the arriving task
+ * It performs the following tasks:
+ * - enable tracing, if configured
+ * - take timestamp, if configured
+ * - reconfigure trace hardware to use task's DS area
+ *
+ * This function is called only for tasks that are being traced.
+ * Performance is down for those tasks, since tracing writes to memory
+ * on every branch. We need not be too concerned with performance.
+ */
+void ptrace_bts_task_arrives(struct task_struct *tsk)
+{
+ if (!ptrace_bts_cfg.sizeof_ds)
+ return;
+
+ if (test_tsk_thread_flag(tsk, TIF_BTS_TRACE_TS)) {
+ struct ptrace_bts_record rec = {
+ .qualifier = PTRACE_BTS_TASK_ARRIVES,
+ .variant.timestamp = sched_clock()
+ };
+
+ ptrace_bts_write_record(tsk, &rec);
+ }
+
+ if (test_tsk_thread_flag(tsk, TIF_BTS_TRACE)) {
+ wrmsrl(MSR_IA32_DS_AREA, tsk->thread.ds_area);
+ wrmsrl(MSR_IA32_DEBUGCTLMSR, ptrace_bts_cfg.debugctrl_enabled);
+ }
+}
+
+/*
+ * This function is called on a context switch for the departing task
+ * It performs the following tasks:
+ * - disable tracing, if configured
+ * - take timestamp, if configured
+ *
+ * This function is called only for tasks that are being traced.
+ * Performance is down for those tasks, since tracing writes to memory
+ * on every branch. We need not be too concerned with performance.
+ */
+void ptrace_bts_task_departs(struct task_struct *tsk)
+{
+ if (!ptrace_bts_cfg.sizeof_ds)
+ return;
+
+ if (test_tsk_thread_flag(tsk, TIF_BTS_TRACE))
+ wrmsrl(MSR_IA32_DEBUGCTLMSR, ptrace_bts_cfg.debugctrl_disabled);
+
+ if (test_tsk_thread_flag(tsk, TIF_BTS_TRACE_TS)) {
+ struct ptrace_bts_record rec = {
+ .qualifier = PTRACE_BTS_TASK_DEPARTS,
+ .variant.timestamp = sched_clock()
+ };
+
+ ptrace_bts_write_record(tsk, &rec);
+ }
+}
+
+/*
+ * Handle detaching from traced task
+ * - free bts buffer, if one was allocated
+ * - free ds configuration, if one was allocated
+ */
+void ptrace_bts_task_detached(struct task_struct *tsk)
+{
+ if (tsk->thread.ds_area) {
+ ptrace_bts_allocate_bts(tsk, /* size = */ 0);
+ kfree((void *)tsk->thread.ds_area);
+ }
+ ptrace_bts_config(tsk, /* options = */ 0);
+}
+
+/*
+ * Supported last branch trace operations configurations to be used as
+ * templates in ptrace_bts_init().
+ */
+#ifdef __i386__
+static const struct ptrace_bts_configuration ptrace_bts_cfg_netburst = {
+ .sizeof_ds = 9 * 4,
+ .bts_buffer_base = { 0, 4 },
+ .bts_index = { 4, 4 },
+ .bts_absolute_maximum = { 8, 4 },
+ .bts_interrupt_threshold = { 12, 4 },
+ .sizeof_bts = 3 * 4,
+ .from_ip = { 0, 4 },
+ .to_ip = { 4, 4 },
+ .info_type = { 4, 1 },
+ .info_data = { 5, 7 },
+ .debugctrl_mask = (1<<2)|(1<<3)
+};
+
+static const struct ptrace_bts_configuration ptrace_bts_cfg_pentium_m = {
+ .sizeof_ds = 9 * 4,
+ .bts_buffer_base = { 0, 4 },
+ .bts_index = { 4, 4 },
+ .bts_absolute_maximum = { 8, 4 },
+ .bts_interrupt_threshold = { 12, 4 },
+ .sizeof_bts = 3 * 4,
+ .from_ip = { 0, 4 },
+ .to_ip = { 4, 4 },
+ .info_type = { 4, 1 },
+ .info_data = { 5, 7 },
+ .debugctrl_mask = (1<<6)|(1<<7)
+};
+#endif /* _i386_ */
+
+static const struct ptrace_bts_configuration ptrace_bts_cfg_core2 = {
+ .sizeof_ds = 9 * 8,
+ .bts_buffer_base = { 0, 8 },
+ .bts_index = { 8, 8 },
+ .bts_absolute_maximum = { 16, 8 },
+ .bts_interrupt_threshold = { 24, 8 },
+ .sizeof_bts = 3 * 8,
+ .from_ip = { 0, 8 },
+ .to_ip = { 8, 8 },
+ .info_type = { 8, 1 },
+ .info_data = { 9, 7 },
+ .debugctrl_mask = (1<<6)|(1<<7)|(1<<9)
+};
+
+static inline void
+ptrace_bts_configure(const struct ptrace_bts_configuration *cfg)
+{
+ unsigned long long debugctl_msr = 0;
+
+ rdmsrl(MSR_IA32_DEBUGCTLMSR, debugctl_msr);
+
+ ptrace_bts_cfg = *cfg;
+ ptrace_bts_cfg.debugctrl_enabled =
+ debugctl_msr | ptrace_bts_cfg.debugctrl_mask;
+ ptrace_bts_cfg.debugctrl_disabled =
+ debugctl_msr & ~ptrace_bts_cfg.debugctrl_mask;
+}
+
+/*
+ * Initialize last branch tracing.
+ * Detect hardware and initialize the operations function table.
+ */
+__cpuinit void ptrace_bts_init_intel(struct cpuinfo_x86 *c)
+{
+ switch (c->x86) {
+ case 0x6:
+ switch (c->x86_model) {
+#ifdef __i386__
+ case 0xD:
+ case 0xE: /* Pentium M */
+ ptrace_bts_configure(&ptrace_bts_cfg_pentium_m);
+ break;
+#endif /* _i386_ */
+ case 0xF: /* Core2 */
+ ptrace_bts_configure(&ptrace_bts_cfg_core2);
+ break;
+ default:
+ /* sorry, don't know about them */
+ break;
+ }
+ break;
+ case 0xF:
+ switch (c->x86_model) {
+#ifdef __i386__
+ case 0x0:
+ case 0x1:
+ case 0x2: /* Netburst */
+ ptrace_bts_configure(&ptrace_bts_cfg_netburst);
+ break;
+#endif /* _i386_ */
+ default:
+ /* sorry, don't know about them */
+ break;
+ }
+ break;
+ default:
+ /* sorry, don't know about them */
+ break;
+ }
+}
Index: linux-2.6/include/asm-x86/ptrace_bts.h
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6/include/asm-x86/ptrace_bts.h 2007-11-22 11:36:39.%N +0100
@@ -0,0 +1,182 @@
+/*
+ * Extend ptrace with execution trace support using the x86 last
+ * branch recording hardware feature.
+ *
+ * Copyright (C) 2007 Intel Corporation.
+ * Markus Metzger <markus.t.metzger@intel.com>, Oct 2007
+ */
+
+#ifndef _ASM_X86_PTRACE_BTS_H
+#define _ASM_X86_PTRACE_BTS_H
+
+#include <asm/types.h>
+#include <linux/ptrace.h>
+
+
+/*
+ * Debug Store (DS) save area configurations for various processor
+ * variants.
+ * (see Intel64 and IA32 Architectures Software Developer's Manual,
+ * section 18.5)
+ *
+ * The DS configurations consist of the following fields; they vary in
+ * the size of those fields.
+ * - double-word aligned base linear address of the BTS buffer
+ * - write pointer into the BTS buffer
+ * - end linear address of the BTS buffer (one byte beyond the end of
+ * the buffer)
+ * - interrupt pointer into BTS buffer
+ * (interrupt occurs when write pointer passes interrupt pointer)
+ * - double-word aligned base linear address of the PEBS buffer
+ * - write pointer into the PEBS buffer
+ * - end linear address of the PEBS buffer (one byte beyond the end of
+ * the buffer)
+ * - interrupt pointer into PEBS buffer
+ * (interrupt occurs when write pointer passes interrupt pointer)
+ * - value to which counter is reset following counter overflow
+ *
+ * On later architectures, the last branch recording hardware uses
+ * 64bit pointers even in 32bit mode.
+ *
+ *
+ * Branch Trace Store (BTS) records store information about control
+ * flow changes. They at least provide the following information:
+ * - source linear address
+ * - destination linear address
+ *
+ *
+ * In order to abstract from the actual DS and BTS layout, we describe
+ * the access to the relevant fields.
+ * Thanks to Andi Kleen for proposing this design.
+ *
+ * The implementation, however, is not as general as it might seem. In
+ * order to stay somewhat simple and efficient, we assume an
+ * underlying unsigned type and we expect the field to be at least as
+ * big as that type.
+ */
+
+/*
+ * A field access descriptor
+ */
+struct ptrace_access_desc {
+ unsigned char offset;
+ unsigned char size;
+};
+
+/*
+ * The configuration for a particular DS/BTS hardware implementation.
+ */
+struct ptrace_bts_configuration {
+ /* the DS configuration */
+ unsigned char sizeof_ds;
+ struct ptrace_access_desc bts_buffer_base;
+ struct ptrace_access_desc bts_index;
+ struct ptrace_access_desc bts_absolute_maximum;
+ struct ptrace_access_desc bts_interrupt_threshold;
+ /* the BTS configuration */
+ unsigned char sizeof_bts;
+ struct ptrace_access_desc from_ip;
+ struct ptrace_access_desc to_ip;
+ /* BTS variants used to store additional information like
+ timestamps */
+ struct ptrace_access_desc info_type;
+ struct ptrace_access_desc info_data;
+ /* the cached DEBUGCTRL MSR */
+ unsigned long long debugctrl_mask;
+ unsigned long long debugctrl_enabled;
+ unsigned long long debugctrl_disabled;
+};
+
+extern struct ptrace_bts_configuration ptrace_bts_cfg;
+
+
+#define PTRACE_BTS_ESCAPE_ADDRESS ((void *)-1)
+
+static inline void *ptrace_bts_get_bts_buffer_base(char *base)
+{
+ return *(void **)(base + ptrace_bts_cfg.bts_buffer_base.offset);
+}
+static inline void ptrace_bts_set_bts_buffer_base(char *base, void *value)
+{
+ (*(void **)(base + ptrace_bts_cfg.bts_buffer_base.offset)) = value;
+}
+static inline void *ptrace_bts_get_bts_index(char *base)
+{
+ return *(void **)(base + ptrace_bts_cfg.bts_index.offset);
+}
+static inline void ptrace_bts_set_bts_index(char *base, void *value)
+{
+ (*(void **)(base + ptrace_bts_cfg.bts_index.offset)) = value;
+}
+static inline void *ptrace_bts_get_bts_absolute_maximum(char *base)
+{
+ return *(void **)(base + ptrace_bts_cfg.bts_absolute_maximum.offset);
+}
+static inline void ptrace_bts_set_bts_absolute_maximum(char *base, void *value)
+{
+ (*(void **)(base + ptrace_bts_cfg.bts_absolute_maximum.offset)) = value;
+}
+static inline void *ptrace_bts_get_bts_interrupt_threshold(char *base)
+{
+ return *(void **)(base + ptrace_bts_cfg.bts_interrupt_threshold.offset);
+}
+static inline void ptrace_bts_set_bts_interrupt_threshold(char *base,
void *value)
+{
+ (*(void **)(base + ptrace_bts_cfg.bts_interrupt_threshold.offset)) = value;
+}
+static inline void *ptrace_bts_get_from_ip(char *base)
+{
+ return *(void **)(base + ptrace_bts_cfg.from_ip.offset);
+}
+static inline void ptrace_bts_set_from_ip(char *base, void *value)
+{
+ (*(void **)(base + ptrace_bts_cfg.from_ip.offset)) = value;
+}
+static inline void *ptrace_bts_get_to_ip(char *base)
+{
+ return *(void **)(base + ptrace_bts_cfg.to_ip.offset);
+}
+static inline void ptrace_bts_set_to_ip(char *base, void *value)
+{
+ (*(void **)(base + ptrace_bts_cfg.to_ip.offset)) = value;
+}
+static inline unsigned char ptrace_bts_get_info_type(char *base)
+{
+ return *(unsigned char *)(base + ptrace_bts_cfg.info_type.offset);
+}
+static inline void ptrace_bts_set_info_type(char *base, unsigned char value)
+{
+ (*(unsigned char *)(base + ptrace_bts_cfg.info_type.offset)) = value;
+}
+/*
+ * The info data might overlap with the info type on some architectures.
+ * We therefore read and write the exact number of bytes.
+ */
+static inline unsigned long long ptrace_bts_get_info_data(char *base)
+{
+ unsigned long long value = 0;
+ memcpy(&value,
+ base + ptrace_bts_cfg.info_data.offset,
+ ptrace_bts_cfg.info_data.size);
+ return value;
+}
+static inline void ptrace_bts_set_info_data(char *base, unsigned long
long value)
+{
+ memcpy(base + ptrace_bts_cfg.info_data.offset,
+ &value,
+ ptrace_bts_cfg.info_data.size);
+}
+
+extern int ptrace_bts_allocate_bts(struct task_struct *child,
+ long size_in_records);
+extern int ptrace_bts_get_buffer_size(struct task_struct *child);
+extern int ptrace_bts_get_index(struct task_struct *child);
+extern int ptrace_bts_read_record(struct task_struct *child,
+ long index,
+ struct ptrace_bts_record __user *out);
+extern int ptrace_bts_config(struct task_struct *child,
+ unsigned long options);
+extern int ptrace_bts_status(struct task_struct *child);
+extern void ptrace_bts_task_detached(struct task_struct *tsk);
+
+#endif /* _ASM_X86_PTRACE_BTS_H */
Index: linux-2.6/arch/x86/kernel/Makefile_32
===================================================================
--- linux-2.6.orig/arch/x86/kernel/Makefile_32 2007-11-22 11:03:44.%N +0100
+++ linux-2.6/arch/x86/kernel/Makefile_32 2007-11-22 11:36:39.%N +0100
@@ -8,7 +8,8 @@
obj-y := process_32.o signal_32.o entry_32.o traps_32.o irq_32.o \
ptrace_32.o time_32.o ioport_32.o ldt_32.o setup_32.o i8259_32.o
sys_i386_32.o \
pci-dma_32.o i386_ksyms_32.o i387_32.o bootflag.o e820_32.o\
- quirks.o i8237.o topology.o alternative.o i8253.o tsc_32.o
+ quirks.o i8237.o topology.o alternative.o i8253.o tsc_32.o\
+ ptrace_bts.o

obj-$(CONFIG_STACKTRACE) += stacktrace.o
obj-y += cpu/
Index: linux-2.6/include/asm-x86/thread_info_32.h
===================================================================
--- linux-2.6.orig/include/asm-x86/thread_info_32.h 2007-11-22 11:03:45.%N +0100
+++ linux-2.6/include/asm-x86/thread_info_32.h 2007-11-22 11:36:39.%N +0100
@@ -137,6 +137,9 @@
#define TIF_IO_BITMAP 18 /* uses I/O bitmap */
#define TIF_FREEZE 19 /* is freezing for suspend */
#define TIF_NOTSC 20 /* TSC is not accessible in userland */
+/* gap to use same numbers for _32 and _64 variants */
+#define TIF_BTS_TRACE 24 /* record branches for this task */
+#define TIF_BTS_TRACE_TS 25 /* record scheduling event
timestamps */

#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
#define _TIF_SIGPENDING (1<<TIF_SIGPENDING)
@@ -151,6 +154,8 @@
#define _TIF_IO_BITMAP (1<<TIF_IO_BITMAP)
#define _TIF_FREEZE (1<<TIF_FREEZE)
#define _TIF_NOTSC (1<<TIF_NOTSC)
+#define _TIF_BTS_TRACE (1<<TIF_BTS_TRACE)
+#define _TIF_BTS_TRACE_TS (1<<TIF_BTS_TRACE_TS)

/* work to do on interrupt/exception return */
#define _TIF_WORK_MASK \
@@ -160,8 +165,11 @@
#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)
-#define _TIF_WORK_CTXSW_PREV (_TIF_IO_BITMAP | _TIF_NOTSC)
+#define _TIF_WORK_CTXSW_NEXT \
+ (_TIF_IO_BITMAP | _TIF_NOTSC | _TIF_DEBUG | \
+ _TIF_BTS_TRACE | _TIF_BTS_TRACE_TS)
+#define _TIF_WORK_CTXSW_PREV \
+ (_TIF_IO_BITMAP | _TIF_NOTSC | _TIF_BTS_TRACE | _TIF_BTS_TRACE_TS)

/*
* Thread-synchronous status.
Index: linux-2.6/include/asm-x86/processor_32.h
===================================================================
--- linux-2.6.orig/include/asm-x86/processor_32.h 2007-11-22 11:03:45.%N +0100
+++ linux-2.6/include/asm-x86/processor_32.h 2007-11-22 11:36:39.%N +0100
@@ -353,6 +353,9 @@
unsigned long esp;
unsigned long fs;
unsigned long gs;
+/* Debug Store - if not 0 points to a DS Save Area configuration;
+ * goes into MSR_IA32_DS_AREA */
+ unsigned long ds_area;
/* Hardware debugging registers */
unsigned long debugreg[8]; /* %%db0-7 debug registers */
/* fault info */
Index: linux-2.6/arch/x86/kernel/Makefile_64
===================================================================
--- linux-2.6.orig/arch/x86/kernel/Makefile_64 2007-11-22 11:03:44.%N +0100
+++ linux-2.6/arch/x86/kernel/Makefile_64 2007-11-22 11:36:39.%N +0100
@@ -11,7 +11,7 @@
x8664_ksyms_64.o i387_64.o syscall_64.o vsyscall_64.o \
setup64.o bootflag.o e820_64.o reboot_64.o quirks.o i8237.o \
pci-dma_64.o pci-nommu_64.o alternative.o hpet.o tsc_64.o bugs_64.o \
- i8253.o
+ i8253.o ptrace_bts.o

obj-$(CONFIG_STACKTRACE) += stacktrace.o
obj-y += cpu/
Index: linux-2.6/arch/x86/kernel/process_64.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/process_64.c 2007-11-22 11:03:44.%N +0100
+++ linux-2.6/arch/x86/kernel/process_64.c 2007-11-22 11:36:39.%N +0100
@@ -570,6 +570,18 @@
*/
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) ||
+ test_tsk_thread_flag(prev_p, TIF_BTS_TRACE_TS))
+ ptrace_bts_task_departs(prev_p);
+
+ if (test_tsk_thread_flag(next_p, TIF_BTS_TRACE) ||
+ test_tsk_thread_flag(next_p, TIF_BTS_TRACE_TS))
+ ptrace_bts_task_arrives(next_p);
}

/*
@@ -673,8 +685,8 @@
/*
* 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
Index: linux-2.6/arch/x86/kernel/ptrace_64.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/ptrace_64.c 2007-11-22 11:03:44.%N +0100
+++ linux-2.6/arch/x86/kernel/ptrace_64.c 2007-11-22 11:36:39.%N +0100
@@ -28,6 +28,7 @@
#include <asm/desc.h>
#include <asm/proto.h>
#include <asm/ia32.h>
+#include <asm/ptrace_bts.h>

/*
* does not yet catch signals sent when the child dies.
@@ -224,6 +225,7 @@
void ptrace_disable(struct task_struct *child)
{
clear_singlestep(child);
+ ptrace_bts_task_detached(child);
}

static int putreg(struct task_struct *child,
@@ -555,6 +557,32 @@
break;
}

+ case PTRACE_BTS_ALLOCATE_BUFFER:
+ ret = ptrace_bts_allocate_bts(child, data);
+ break;
+
+ case PTRACE_BTS_GET_BUFFER_SIZE:
+ ret = ptrace_bts_get_buffer_size(child);
+ break;
+
+ case PTRACE_BTS_GET_INDEX:
+ ret = ptrace_bts_get_index(child);
+ break;
+
+ case PTRACE_BTS_READ_RECORD:
+ ret = ptrace_bts_read_record
+ (child, data,
+ (struct ptrace_bts_record __user *) addr);
+ break;
+
+ case PTRACE_BTS_CONFIG:
+ ret = ptrace_bts_config(child, data);
+ break;
+
+ case PTRACE_BTS_STATUS:
+ ret = ptrace_bts_status(child);
+ break;
+
default:
ret = ptrace_request(child, request, addr, data);
break;
Index: linux-2.6/include/asm-x86/processor_64.h
===================================================================
--- linux-2.6.orig/include/asm-x86/processor_64.h 2007-11-22 11:03:45.%N +0100
+++ linux-2.6/include/asm-x86/processor_64.h 2007-11-22 11:36:39.%N +0100
@@ -223,6 +223,9 @@
unsigned long fs;
unsigned long gs;
unsigned short es, ds, fsindex, gsindex;
+/* Debug Store - if not 0 points to a DS Save Area configuration;
+ * goes into MSR_IA32_DS_AREA */
+ unsigned long ds_area;
/* Hardware debugging registers */
unsigned long debugreg0;
unsigned long debugreg1;
Index: linux-2.6/include/asm-x86/thread_info_64.h
===================================================================
--- linux-2.6.orig/include/asm-x86/thread_info_64.h 2007-11-22 11:03:45.%N +0100
+++ linux-2.6/include/asm-x86/thread_info_64.h 2007-11-22 11:36:39.%N +0100
@@ -123,6 +123,8 @@
#define TIF_DEBUG 21 /* uses debug registers */
#define TIF_IO_BITMAP 22 /* uses I/O bitmap */
#define TIF_FREEZE 23 /* is freezing for suspend */
+#define TIF_BTS_TRACE 24 /* record branches for this task */
+#define TIF_BTS_TRACE_TS 25 /* record scheduling event
timestamps */

#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
#define _TIF_SIGPENDING (1<<TIF_SIGPENDING)
@@ -139,6 +141,8 @@
#define _TIF_DEBUG (1<<TIF_DEBUG)
#define _TIF_IO_BITMAP (1<<TIF_IO_BITMAP)
#define _TIF_FREEZE (1<<TIF_FREEZE)
+#define _TIF_BTS_TRACE (1<<TIF_BTS_TRACE)
+#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)
+#define _TIF_WORK_CTXSW_NEXT \
+ (_TIF_DEBUG|_TIF_IO_BITMAP|_TIF_BTS_TRACE|_TIF_BTS_TRACE_TS)
+#define _TIF_WORK_CTXSW_PREV \
+ (_TIF_IO_BITMAP|_TIF_BTS_TRACE|_TIF_BTS_TRACE_TS)

#define PREEMPT_ACTIVE 0x10000000

Index: linux-2.6/arch/x86/kernel/cpu/intel.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/cpu/intel.c 2007-11-22 11:03:44.%N +0100
+++ linux-2.6/arch/x86/kernel/cpu/intel.c 2007-11-22 11:36:39.%N +0100
@@ -11,6 +11,7 @@
#include <asm/pgtable.h>
#include <asm/msr.h>
#include <asm/uaccess.h>
+#include <asm/ptrace.h>

#include "cpu.h"

@@ -219,6 +220,9 @@
if (!(l1 & (1<<12)))
set_bit(X86_FEATURE_PEBS, c->x86_capability);
}
+
+ if (cpu_has_bts)
+ ptrace_bts_init_intel(c);
}

static unsigned int __cpuinit intel_size_cache(struct cpuinfo_x86 *
c, unsigned int size)
Index: linux-2.6/arch/x86/kernel/setup_64.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/setup_64.c 2007-11-22 11:03:45.%N +0100
+++ linux-2.6/arch/x86/kernel/setup_64.c 2007-11-22 11:36:39.%N +0100
@@ -59,6 +59,7 @@
#include <asm/sections.h>
#include <asm/dmi.h>
#include <asm/cacheflush.h>
+#include <asm/ptrace_bts.h>

/*
* Machine setup..
@@ -795,6 +796,10 @@
set_bit(X86_FEATURE_PEBS, c->x86_capability);
}

+
+ if (cpu_has_bts)
+ ptrace_bts_init_intel(c);
+
n = c->extended_cpuid_level;
if (n >= 0x80000008) {
unsigned eax = cpuid_eax(0x80000008);
-
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