x86, ptrace: new ptrace BTS API
Here's the new ptrace BTS API that supports two different overflow handling mechanisms (wrap-around and buffer-full-signal) to support two different use cases (debugging and profiling).
It further combines buffer allocation and configuration.
Opens:
- memory rlimit
- overflow signal
What would be the right signal to use?
Signed-off-by: Markus Metzger <markus.t.metzger@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/arch/x86/kernel/ds.c b/arch/x86/kernel/ds.c
index e7855de..6eb5d49 100644
--- a/arch/x86/kernel/ds.c
+++ b/arch/x86/kernel/ds.c
@@ -177,18 +177,20 @@
}
-int ds_allocate(void **dsp, size_t bts_size_in_records)
+int ds_allocate(void **dsp, size_t bts_size_in_bytes)
{
- size_t bts_size_in_bytes = 0;
- void *bts = 0;
- void *ds = 0;
+ size_t bts_size_in_records;
+ void *bts;
+ void *ds;
if (!ds_cfg.sizeof_ds || !ds_cfg.sizeof_bts)
return -EOPNOTSUPP;
- if (bts_size_in_records < 0)
+ if (bts_size_in_bytes < 0)
return -EINVAL;
+ bts_size_in_records =
+ bts_size_in_bytes / ds_cfg.sizeof_bts;
bts_size_in_bytes =
bts_size_in_records * ds_cfg.sizeof_bts;
@@ -233,9 +235,21 @@
if (!ds_cfg.sizeof_ds || !ds_cfg.sizeof_bts)
return -EOPNOTSUPP;
+ if (!ds)
+ return 0;
+
size_in_bytes =
get_bts_absolute_maximum(ds) -
get_bts_buffer_base(ds);
+ return size_in_bytes;
+}
+
+int ds_get_bts_end(void *ds)
+{
+ size_t size_in_bytes = ds_get_bts_size(ds);
+
+ if (size_in_bytes <= 0)
+ return size_in_bytes;
return size_in_bytes / ds_cfg.sizeof_bts;
}
@@ -254,6 +268,38 @@
return index_offset_in_bytes / ds_cfg.sizeof_bts;
}
+int ds_set_overflow(void *ds, int method)
+{
+ switch (method) {
+ case DS_O_SIGNAL:
+ return -EOPNOTSUPP;
+ case DS_O_WRAP:
+ return 0;
+ default:
+ return -EINVAL;
+ }
+}
+
+int ds_get_overflow(void *ds)
+{
+ return DS_O_WRAP;
+}
+
+int ds_clear(void *ds)
+{
+ int bts_size = ds_get_bts_size(ds);
+ void *bts_base;
+
+ if (bts_size <= 0)
+ return bts_size;
+
+ bts_base = get_bts_buffer_base(ds);
+ memset(bts_base, 0, bts_size);
+
+ set_bts_index(ds, bts_base);
+ return 0;
+}
+
int ds_read_bts(void *ds, size_t index, struct bts_struct *out)
{
void *bts;
diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index 3e78c12..18972a3 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -33,12 +33,6 @@
/*
- * The maximal size of a BTS buffer per traced task in number of BTS
- * records.
- */
-#define PTRACE_BTS_BUFFER_MAX 4000
-
-/*
* does not yet catch signals sent when the child dies.
* in exit.c or in signal.c.
*/
@@ -466,17 +460,12 @@
return 0;
}
-static int ptrace_bts_max_buffer_size(void)
-{
- return PTRACE_BTS_BUFFER_MAX;
-}
-
-static int ptrace_bts_get_buffer_size(struct task_struct *child)
+static int ptrace_bts_get_size(struct task_struct *child)
{
if (!child->thread.ds_area_msr)
return -ENXIO;
- return ds_get_bts_size((void *)child->thread.ds_area_msr);
+ return ds_get_bts_index((void *)child->thread.ds_area_msr);
}
static int ptrace_bts_read_record(struct task_struct *child,
@@ -485,7 +474,7 @@
{
struct bts_struct ret;
int retval;
- int bts_size;
+ int bts_end;
int bts_index;
if (!child->thread.ds_area_msr)
@@ -494,15 +483,15 @@
if (index < 0)
return -EINVAL;
- bts_size = ds_get_bts_size((void *)child->thread.ds_area_msr);
- if (bts_size <= index)
+ bts_end = ds_get_bts_end((void *)child->thread.ds_area_msr);
+ if (bts_end <= index)
return -EINVAL;
/* translate the ptrace bts index into the ds bts index */
bts_index = ds_get_bts_index((void *)child->thread.ds_area_msr);
bts_index -= (index + 1);
if (bts_index < 0)
- bts_index += bts_size;
+ bts_index += bts_end;
retval = ds_read_bts((void *)child->thread.ds_area_msr,
bts_index, &ret);
@@ -530,19 +519,97 @@
return sizeof(*in);
}
-static int ptrace_bts_config(struct task_struct *child,
- unsigned long options)
+static int ptrace_bts_clear(struct task_struct *child)
{
- unsigned long debugctl_mask = ds_debugctl_mask();
- int retval;
-
- retval = ptrace_bts_get_buffer_size(child);
- if (retval < 0)
- return retval;
- if (retval == 0)
+ if (!child->thread.ds_area_msr)
return -ENXIO;
- if (options & PTRACE_BTS_O_TRACE_TASK) {
+ return ds_clear((void *)child->thread.ds_area_msr);
+}
+
+static int ptrace_bts_drain(struct task_struct *child,
+ struct bts_struct __user *out)
+{
+ int end, i;
+ void *ds = (void *)child->thread.ds_area_msr;
+
+ if (!ds)
+ return -ENXIO;
+
+ end = ds_get_bts_index(ds);
+ if (end <= 0)
+ return end;
+
+ for (i = 0; i < end; i++, out++) {
+ struct bts_struct ret;
+ int retval;
+
+ retval = ds_read_bts(ds, i, &ret);
+ if (retval < 0)
+ return retval;
+
+ if (copy_to_user(out, &ret, sizeof(ret)))
+ return -EFAULT;
+ }
+
+ ds_clear(ds);
+
+ return i;
+}
+
+static int ptrace_bts_config(struct task_struct *child,
+ const struct ptrace_bts_config __user *ucfg)
+{
+ struct ptrace_bts_config cfg;
+ unsigned long debugctl_mask;
+ int bts_size, ret;
+ void *ds;
+
+ if (copy_from_user(&cfg, ucfg, sizeof(cfg)))
+ return -EFAULT;
+
+ bts_size = 0;
+ ds = (void *)child->thread.ds_area_msr;
+ if (ds) {
+ bts_size = ds_get_bts_size(ds);
+ if (bts_size < 0)
+ return bts_size;
+ }
+
+ if (bts_size != cfg.size) {
+ ret = ds_free((void **)&child->thread.ds_area_msr);
+ if (ret < 0)
+ return ret;
+
+ if (cfg.size > 0)
+ ret = ds_allocate((void **)&child->thread.ds_area_msr,
+ cfg.size);
+ ds = (void *)child->thread.ds_area_msr;
+ if (ds)
+ set_tsk_thread_flag(child, TIF_DS_AREA_MSR);
+ else
+ clear_tsk_thread_flag(child, TIF_DS_AREA_MSR);
+
+ if (ret < 0)
+ return ret;
+
+ bts_size = ds_get_bts_size(ds);
+ if (bts_size <= 0)
+ return bts_size;
+ }
+
+ if (ds) {
+ if (cfg.flags & PTRACE_BTS_O_SIGNAL) {
+ ret = ds_set_overflow(ds, DS_O_SIGNAL);
+ } else {
+ ret = ds_set_overflow(ds, DS_O_WRAP);
+ }
+ if (ret < 0)
+ return ret;
+ }
+
+ debugctl_mask = ds_debugctl_mask();
+ if (ds && (cfg.flags & PTRACE_BTS_O_TRACE)) {
child->thread.debugctlmsr |= debugctl_mask;
set_tsk_thread_flag(child, TIF_DEBUGCTLMSR);
} else {
@@ -555,7 +622,7 @@
clear_tsk_thread_flag(child, TIF_DEBUGCTLMSR);
}
- if (options & PTRACE_BTS_O_TIMESTAMPS)
+ if (ds && (cfg.flags & PTRACE_BTS_O_SCHED))
set_tsk_thread_flag(child, TIF_BTS_TRACE_TS);
else
clear_tsk_thread_flag(child, TIF_BTS_TRACE_TS);
@@ -563,59 +630,32 @@
return 0;
}
-static int ptrace_bts_status(struct task_struct *child)
+static int ptrace_bts_status(struct task_struct *child,
+ struct ptrace_bts_config __user *ucfg)
{
- unsigned long debugctl_mask = ds_debugctl_mask();
- int retval, status = 0;
+ void *ds = (void *)child->thread.ds_area_msr;
+ struct ptrace_bts_config cfg;
- retval = ptrace_bts_get_buffer_size(child);
- if (retval < 0)
- return retval;
- if (retval == 0)
- return -ENXIO;
+ memset(&cfg, 0, sizeof(cfg));
- if (ptrace_bts_get_buffer_size(child) <= 0)
- return -ENXIO;
+ if (ds) {
+ cfg.size = ds_get_bts_size(ds);
- if (test_tsk_thread_flag(child, TIF_DEBUGCTLMSR) &&
- child->thread.debugctlmsr & debugctl_mask)
- status |= PTRACE_BTS_O_TRACE_TASK;
- if (test_tsk_thread_flag(child, TIF_BTS_TRACE_TS))
- status |= PTRACE_BTS_O_TIMESTAMPS;
+ if (ds_get_overflow(ds) == DS_O_SIGNAL)
+ cfg.flags |= PTRACE_BTS_O_SIGNAL;
- return status;
-}
+ if (test_tsk_thread_flag(child, TIF_DEBUGCTLMSR) &&
+ child->thread.debugctlmsr & ds_debugctl_mask())
+ cfg.flags |= PTRACE_BTS_O_TRACE;
-static int ptrace_bts_allocate_bts(struct task_struct *child,
- int size_in_records)
-{
- int retval = 0;
- void *ds;
-
- if (size_in_records < 0)
- return -EINVAL;
-
- if (size_in_records > ptrace_bts_max_buffer_size())
- return -EINVAL;
-
- if (size_in_records == 0) {
- ptrace_bts_config(child, /* options = */ 0);
- } else {
- retval = ds_allocate(&ds, size_in_records);
- if (retval)
- return retval;
+ if (test_tsk_thread_flag(child, TIF_BTS_TRACE_TS))
+ cfg.flags |= PTRACE_BTS_O_SCHED;
}
- if (child->thread.ds_area_msr)
- ds_free((void **)&child->thread.ds_area_msr);
+ if (copy_to_user(ucfg, &cfg, sizeof(cfg)))
+ return -EFAULT;
- child->thread.ds_area_msr = (unsigned long)ds;
- if (child->thread.ds_area_msr)
- set_tsk_thread_flag(child, TIF_DS_AREA_MSR);
- else
- clear_tsk_thread_flag(child, TIF_DS_AREA_MSR);
-
- return retval;
+ return sizeof(cfg);
}
void ptrace_bts_take_timestamp(struct task_struct *tsk,
@@ -626,9 +666,6 @@
.variant.jiffies = jiffies
};
- if (ptrace_bts_get_buffer_size(tsk) <= 0)
- return;
-
ptrace_bts_write_record(tsk, &rec);
}
@@ -808,30 +845,32 @@
break;
#endif
- case PTRACE_BTS_MAX_BUFFER_SIZE:
- ret = ptrace_bts_max_buffer_size();
- 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_READ_RECORD:
- ret = ptrace_bts_read_record
- (child, data,
- (struct bts_struct __user *) addr);
- break;
-
case PTRACE_BTS_CONFIG:
- ret = ptrace_bts_config(child, data);
+ ret = ptrace_bts_config
+ (child, (struct ptrace_bts_config __user *)addr);
break;
case PTRACE_BTS_STATUS:
- ret = ptrace_bts_status(child);
+ ret = ptrace_bts_status
+ (child, (struct ptrace_bts_config __user *)addr);
+ break;
+
+ case PTRACE_BTS_SIZE:
+ ret = ptrace_bts_get_size(child);
+ break;
+
+ case PTRACE_BTS_GET:
+ ret = ptrace_bts_read_record
+ (child, data, (struct bts_struct __user *) addr);
+ break;
+
+ case PTRACE_BTS_CLEAR:
+ ret = ptrace_bts_clear(child);
+ break;
+
+ case PTRACE_BTS_DRAIN:
+ ret = ptrace_bts_drain
+ (child, (struct bts_struct __user *) addr);
break;
default:
@@ -1017,12 +1056,12 @@
case PTRACE_SETOPTIONS:
case PTRACE_SET_THREAD_AREA:
case PTRACE_GET_THREAD_AREA:
- case PTRACE_BTS_MAX_BUFFER_SIZE:
- case PTRACE_BTS_ALLOCATE_BUFFER:
- case PTRACE_BTS_GET_BUFFER_SIZE:
- case PTRACE_BTS_READ_RECORD:
case PTRACE_BTS_CONFIG:
case PTRACE_BTS_STATUS:
+ case PTRACE_BTS_SIZE:
+ case PTRACE_BTS_GET:
+ case PTRACE_BTS_CLEAR:
+ case PTRACE_BTS_DRAIN:
return sys_ptrace(request, pid, addr, data);
default:
diff --git a/include/asm-x86/ds.h b/include/asm-x86/ds.h
index c9e1538..b84040a 100644
--- a/include/asm-x86/ds.h
+++ b/include/asm-x86/ds.h
@@ -52,11 +52,18 @@
} variant;
};
+/* Overflow handling mechanisms */
+#define DS_O_SIGNAL 1 /* send overflow signal */
+#define DS_O_WRAP 2 /* wrap around */
extern int ds_allocate(void **, size_t);
extern int ds_free(void **);
extern int ds_get_bts_size(void *);
+extern int ds_get_bts_end(void *);
extern int ds_get_bts_index(void *);
+extern int ds_set_overflow(void *, int);
+extern int ds_get_overflow(void *);
+extern int ds_clear(void *);
extern int ds_read_bts(void *, size_t, struct bts_struct *);
extern int ds_write_bts(void *, const struct bts_struct *);
extern unsigned long ds_debugctl_mask(void);
diff --git a/include/asm-x86/ptrace-abi.h b/include/asm-x86/ptrace-abi.h
index b473ad4..cf2fe46 100644
--- a/include/asm-x86/ptrace-abi.h
+++ b/include/asm-x86/ptrace-abi.h
@@ -80,51 +80,53 @@
#define PTRACE_SINGLEBLOCK 33 /* resume execution until next branch */
-/* Return maximal BTS buffer size in number of records,
- if successuf; -1, otherwise.
- EOPNOTSUPP...processor does not support bts tracing */
-#define PTRACE_BTS_MAX_BUFFER_SIZE 40
+/* configuration/status structure used in PTRACE_BTS_CONFIG and
+ PTRACE_BTS_STATUS commands.
+*/
+struct ptrace_bts_config {
+ /* requested or actual size of BTS buffer in bytes */
+ unsigned long size;
+ /* bitmask of below flags */
+ unsigned long flags;
+};
-/* Allocate new bts buffer (free old one, if exists) of size DATA bts records;
- parameter ADDR is ignored.
- Return 0, if successful; -1, otherwise.
- EOPNOTSUPP...processor does not support bts tracing
- EINVAL.......invalid size in records
- ENOMEM.......out of memory */
-#define PTRACE_BTS_ALLOCATE_BUFFER 41
+#define PTRACE_BTS_O_TRACE 0x1 /* branch trace */
+#define PTRACE_BTS_O_SCHED 0x2 /* scheduling events w/ jiffies */
+#define PTRACE_BTS_O_SIGNAL 0x4 /* send SIG? on buffer overflow
+ instead of wrapping around */
+#define PTRACE_BTS_O_CUT_SIZE 0x8 /* cut requested size to max available
+ instead of failing */
-/* Return the size of the bts buffer in number of bts records,
- if successful; -1, otherwise.
- EOPNOTSUPP...processor does not support bts tracing
- ENXIO........no buffer allocated */
-#define PTRACE_BTS_GET_BUFFER_SIZE 42
-
-/* Read the DATA'th bts record into a ptrace_bts_record buffer
- provided in ADDR.
- Records are ordered from newest to oldest.
- Return 0, if successful; -1, otherwise
- EOPNOTSUPP...processor does not support bts tracing
- ENXIO........no buffer allocated
- EINVAL.......invalid index */
-#define PTRACE_BTS_READ_RECORD 43
-
-/* Configure last branch trace; the configuration is given as a bit-mask of
- PTRACE_BTS_O_* options in DATA; parameter ADDR is ignored.
- Return 0, if successful; -1, otherwise
- EOPNOTSUPP...processor does not support bts tracing
- ENXIO........no buffer allocated */
-#define PTRACE_BTS_CONFIG 44
-
-/* Return the configuration as bit-mask of PTRACE_BTS_O_* options
- if successful; -1, otherwise.
- EOPNOTSUPP...processor does not support bts tracing
- ENXIO........no buffer allocated */
-#define PTRACE_BTS_STATUS 45
-
-/* 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
+#define PTRACE_BTS_CONFIG 40
+/* Configure branch trace recording.
+ DATA is ignored, ADDR points to a struct ptrace_bts_config.
+ A new buffer is allocated, iff the size changes.
+*/
+#define PTRACE_BTS_STATUS 41
+/* Return the current configuration.
+ DATA is ignored, ADDR points to a struct ptrace_bts_config
+ that will contain the result.
+*/
+#define PTRACE_BTS_SIZE 42
+/* Return the number of available BTS records.
+ DATA and ADDR are ignored.
+*/
+#define PTRACE_BTS_GET 43
+/* Get a single BTS record.
+ DATA defines the index into the BTS array, where 0 is the newest
+ entry, and higher indices refer to older entries.
+ ADDR is pointing to struct bts_struct (see asm/ds.h).
+*/
+#define PTRACE_BTS_CLEAR 44
+/* Clear the BTS buffer.
+ DATA and ADDR are ignored.
+*/
+#define PTRACE_BTS_DRAIN 45
+/* Read all available BTS records and clear the buffer.
+ DATA is ignored. ADDR points to an array of struct bts_struct of
+ suitable size.
+ BTS records are read from oldest to newest.
+ Returns number of BTS records drained.
+*/
#endif
diff --git a/include/asm-x86/ptrace.h b/include/asm-x86/ptrace.h
index a9a1bab..61946fe 100644
--- a/include/asm-x86/ptrace.h
+++ b/include/asm-x86/ptrace.h
@@ -9,6 +9,7 @@
#ifdef __KERNEL__
+/* the DS BTS struct is used for ptrace as well */
#include <asm/ds.h>
struct task_struct;