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 <markus.t.metzger@intel.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 429 insertions, 0 deletions

diff --git a/arch/x86/kernel/ds.c b/arch/x86/kernel/ds.c
new file mode 100644
index 0000000..996a7c4
--- /dev/null
+++ b/arch/x86/kernel/ds.c
@@ -0,0 +1,429 @@
+/*
+ * Debug Store support
+ *
+ * This provides a low-level interface to the hardware's Debug Store
+ * feature that is used for last branch recording (LBR) and
+ * precise-event based sampling (PEBS).
+ *
+ * Different architectures use a different DS layout/pointer size.
+ * The below functions therefore work on a void*.
+ *
+ *
+ * Since there is no user for PEBS, yet, only LBR (or branch
+ * trace store, BTS) is supported.
+ *
+ *
+ * Copyright (C) 2007 Intel Corporation.
+ * Markus Metzger <markus.t.metzger@intel.com>, Dec 2007
+ */
+
+#include <asm/ds.h>
+
+#include <linux/errno.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+
+
+/*
+ * Debug Store (DS) save area configuration (see Intel64 and IA32
+ * Architectures Software Developer's Manual, section 18.5)
+ *
+ * The DS configuration consists of the following fields; different
+ * architetures 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
+ *
+ * Netburst supported a predicated bit that had been dropped in later
+ * architectures. We do not suppor it.
+ *
+ *
+ * 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 (mostly a pointer type) and we expect the
+ * field to be at least as big as that type.
+ */
+
+/*
+ * A special from_ip address to indicate that the BTS record is an
+ * info record that needs to be interpreted or skipped.
+ */
+#define BTS_ESCAPE_ADDRESS (-1)
+
+/*
+ * A field access descriptor
+ */
+struct access_desc {
+	unsigned char offset;
+	unsigned char size;
+};
+
+/*
+ * The configuration for a particular DS/BTS hardware implementation.
+ */
+struct ds_configuration {
+	/* the DS configuration */
+	unsigned char  sizeof_ds;
+	struct access_desc bts_buffer_base;
+	struct access_desc bts_index;
+	struct access_desc bts_absolute_maximum;
+	struct access_desc bts_interrupt_threshold;
+	/* the BTS configuration */
+	unsigned char  sizeof_bts;
+	struct access_desc from_ip;
+	struct access_desc to_ip;
+	/* BTS variants used to store additional information like
+	   timestamps */
+	struct access_desc info_type;
+	struct access_desc info_data;
+	unsigned long debugctl_mask;
+};
+
+/*
+ * The global configuration used by the below accessor functions
+ */
+static struct ds_configuration ds_cfg;
+
+/*
+ * Accessor functions for some DS and BTS fields using the above
+ * global ptrace_bts_cfg.
+ */
+static inline void *get_bts_buffer_base(char *base)
+{
+	return *(void **)(base + ds_cfg.bts_buffer_base.offset);
+}
+static inline void set_bts_buffer_base(char *base, void *value)
+{
+	(*(void **)(base + ds_cfg.bts_buffer_base.offset)) = value;
+}
+static inline void *get_bts_index(char *base)
+{
+	return *(void **)(base + ds_cfg.bts_index.offset);
+}
+static inline void set_bts_index(char *base, void *value)
+{
+	(*(void **)(base + ds_cfg.bts_index.offset)) = value;
+}
+static inline void *get_bts_absolute_maximum(char *base)
+{
+	return *(void **)(base + ds_cfg.bts_absolute_maximum.offset);
+}
+static inline void set_bts_absolute_maximum(char *base, void *value)
+{
+	(*(void **)(base + ds_cfg.bts_absolute_maximum.offset)) = value;
+}
+static inline void *get_bts_interrupt_threshold(char *base)
+{
+	return *(void **)(base + ds_cfg.bts_interrupt_threshold.offset);
+}
+static inline void set_bts_interrupt_threshold(char *base, void *value)
+{
+	(*(void **)(base + ds_cfg.bts_interrupt_threshold.offset)) = value;
+}
+static inline long get_from_ip(char *base)
+{
+	return *(long *)(base + ds_cfg.from_ip.offset);
+}
+static inline void set_from_ip(char *base, long value)
+{
+	(*(long *)(base + ds_cfg.from_ip.offset)) = value;
+}
+static inline long get_to_ip(char *base)
+{
+	return *(long *)(base + ds_cfg.to_ip.offset);
+}
+static inline void set_to_ip(char *base, long value)
+{
+	(*(long *)(base + ds_cfg.to_ip.offset)) = value;
+}
+static inline unsigned char get_info_type(char *base)
+{
+	return *(unsigned char *)(base + ds_cfg.info_type.offset);
+}
+static inline void set_info_type(char *base, unsigned char value)
+{
+	(*(unsigned char *)(base + ds_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 get_info_data(char *base)
+{
+	unsigned long long value = 0;
+	memcpy(&value,
+	       base + ds_cfg.info_data.offset,
+	       ds_cfg.info_data.size);
+	return value;
+}
+static inline void set_info_data(char *base, unsigned long long value)
+{
+	memcpy(base + ds_cfg.info_data.offset,
+	       &value,
+	       ds_cfg.info_data.size);
+}
+
+
+int ds_allocate(void **dsp, size_t bts_size_in_records)
+{
+	size_t bts_size_in_bytes = 0;
+	void *bts = 0;
+	void *ds = 0;
+
+	if (!ds_cfg.sizeof_ds || !ds_cfg.sizeof_bts)
+		return -EOPNOTSUPP;
+
+	if (bts_size_in_records < 0)
+		return -EINVAL;
+
+	bts_size_in_bytes =
+		bts_size_in_records * ds_cfg.sizeof_bts;
+
+	if (bts_size_in_bytes <= 0)
+		return -EINVAL;
+
+	bts = kzalloc(bts_size_in_bytes, GFP_KERNEL);
+
+	if (!bts)
+		return -ENOMEM;
+
+	ds = kzalloc(ds_cfg.sizeof_ds, GFP_KERNEL);
+
+	if (!ds) {
+		kfree(bts);
+		return -ENOMEM;
+	}
+
+	set_bts_buffer_base(ds, bts);
+	set_bts_index(ds, bts);
+	set_bts_absolute_maximum(ds, bts + bts_size_in_bytes);
+	set_bts_interrupt_threshold(ds, bts + bts_size_in_bytes + 1);
+
+	*dsp = ds;
+	return 0;
+}
+
+int ds_free(void **dsp)
+{
+	if (*dsp)
+		kfree(get_bts_buffer_base(*dsp));
+	kfree(*dsp);
+	*dsp = 0;
+
+	return 0;
+}
+
+int ds_get_bts_size(void *ds)
+{
+	size_t size_in_bytes;
+
+	if (!ds_cfg.sizeof_ds || !ds_cfg.sizeof_bts)
+		return -EOPNOTSUPP;
+
+	size_in_bytes =
+		get_bts_absolute_maximum(ds) -
+		get_bts_buffer_base(ds);
+
+	return size_in_bytes / ds_cfg.sizeof_bts;
+}
+
+int ds_get_bts_index(void *ds)
+{
+	size_t index_offset_in_bytes;
+
+	if (!ds_cfg.sizeof_ds || !ds_cfg.sizeof_bts)
+		return -EOPNOTSUPP;
+
+	index_offset_in_bytes =
+		get_bts_index(ds) -
+		get_bts_buffer_base(ds);
+
+	return index_offset_in_bytes / ds_cfg.sizeof_bts;
+}
+
+int ds_read_bts(void *ds, size_t index, struct bts_struct *out)
+{
+	void *bts;
+
+	if (!ds_cfg.sizeof_ds || !ds_cfg.sizeof_bts)
+		return -EOPNOTSUPP;
+
+	if (index < 0)
+		return -EINVAL;
+
+	if (index >= ds_get_bts_size(ds))
+		return -EINVAL;
+
+	bts = get_bts_buffer_base(ds);
+	bts = (char *)bts + (index * ds_cfg.sizeof_bts);
+
+	memset(out, 0, sizeof(*out));
+	if (get_from_ip(bts) == BTS_ESCAPE_ADDRESS) {
+		out->qualifier         = get_info_type(bts);
+		out->variant.timestamp = get_info_data(bts);
+	} else {
+		out->qualifier = BTS_BRANCH;
+		out->variant.lbr.from_ip = get_from_ip(bts);
+		out->variant.lbr.to_ip   = get_to_ip(bts);
+	}
+
+	return 0;
+}
+
+int ds_write_bts(void *ds, const struct bts_struct *in)
+{
+	void *bts;
+
+	if (!ds_cfg.sizeof_ds || !ds_cfg.sizeof_bts)
+		return -EOPNOTSUPP;
+
+	if (ds_get_bts_size(ds) <= 0)
+		return -ENXIO;
+
+	bts = get_bts_index(ds);
+
+	memset(bts, 0, ds_cfg.sizeof_bts);
+	switch (in->qualifier) {
+	case BTS_INVALID:
+		break;
+
+	case BTS_BRANCH:
+		set_from_ip(bts, in->variant.lbr.from_ip);
+		set_to_ip(bts, in->variant.lbr.to_ip);
+		break;
+
+	case BTS_TASK_ARRIVES:
+	case BTS_TASK_DEPARTS:
+		set_from_ip(bts, BTS_ESCAPE_ADDRESS);
+		set_info_type(bts, in->qualifier);
+		set_info_data(bts, in->variant.timestamp);
+		break;
+
+	default:
+		return -EINVAL;
+	}
+
+	bts = (char *)bts + ds_cfg.sizeof_bts;
+	if (bts >= get_bts_absolute_maximum(ds))
+		bts = get_bts_buffer_base(ds);
+	set_bts_index(ds, bts);
+
+	return 0;
+}
+
+unsigned long ds_debugctl_mask(void)
+{
+	return ds_cfg.debugctl_mask;
+}
+
+#ifdef __i386__
+static const struct ds_configuration ds_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 },
+	.debugctl_mask = (1<<2)|(1<<3)
+};
+
+static const struct ds_configuration ds_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 },
+	.debugctl_mask = (1<<6)|(1<<7)
+};
+#endif /* _i386_ */
+
+static const struct ds_configuration ds_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 },
+	.debugctl_mask = (1<<6)|(1<<7)|(1<<9)
+};
+
+static inline void
+ds_configure(const struct ds_configuration *cfg)
+{
+	ds_cfg = *cfg;
+}
+
+void __cpuinit ds_init_intel(struct cpuinfo_x86 *c)
+{
+	switch (c->x86) {
+	case 0x6:
+		switch (c->x86_model) {
+#ifdef __i386__
+		case 0xD:
+		case 0xE: /* Pentium M */
+			ds_configure(&ds_cfg_pentium_m);
+			break;
+#endif /* _i386_ */
+		case 0xF: /* Core2 */
+			ds_configure(&ds_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 */
+			ds_configure(&ds_cfg_netburst);
+			break;
+#endif /* _i386_ */
+		default:
+			/* sorry, don't know about them */
+			break;
+		}
+		break;
+	default:
+		/* sorry, don't know about them */
+		break;
+	}
+}