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-rw-r--r--gdb/common/btrace-common.h27
-rw-r--r--gdb/common/linux-btrace.c97
-rw-r--r--gdb/common/linux-btrace.h15
3 files changed, 101 insertions, 38 deletions
diff --git a/gdb/common/btrace-common.h b/gdb/common/btrace-common.h
index 1d389af..25617bb 100644
--- a/gdb/common/btrace-common.h
+++ b/gdb/common/btrace-common.h
@@ -42,7 +42,9 @@
asynchronous, e.g. interrupts. */
struct btrace_block
{
- /* The address of the first byte of the first instruction in the block. */
+ /* The address of the first byte of the first instruction in the block.
+ The address may be zero if we do not know the beginning of this block,
+ such as for the first block in a delta trace. */
CORE_ADDR begin;
/* The address of the first byte of the last instruction in the block. */
@@ -67,7 +69,28 @@ enum btrace_read_type
BTRACE_READ_ALL,
/* Send all available trace, if it changed. */
- BTRACE_READ_NEW
+ BTRACE_READ_NEW,
+
+ /* Send the trace since the last request. This will fail if the trace
+ buffer overflowed. */
+ BTRACE_READ_DELTA
+};
+
+/* Enumeration of btrace errors. */
+
+enum btrace_error
+{
+ /* No error. Everything is OK. */
+ BTRACE_ERR_NONE,
+
+ /* An unknown error. */
+ BTRACE_ERR_UNKNOWN,
+
+ /* Branch tracing is not supported on this system. */
+ BTRACE_ERR_NOT_SUPPORTED,
+
+ /* The branch trace buffer overflowed; no delta read possible. */
+ BTRACE_ERR_OVERFLOW
};
#endif /* BTRACE_COMMON_H */
diff --git a/gdb/common/linux-btrace.c b/gdb/common/linux-btrace.c
index e469900..218e0ce 100644
--- a/gdb/common/linux-btrace.c
+++ b/gdb/common/linux-btrace.c
@@ -172,11 +172,11 @@ perf_event_sample_ok (const struct perf_event_sample *sample)
static VEC (btrace_block_s) *
perf_event_read_bts (struct btrace_target_info* tinfo, const uint8_t *begin,
- const uint8_t *end, const uint8_t *start)
+ const uint8_t *end, const uint8_t *start, size_t size)
{
VEC (btrace_block_s) *btrace = NULL;
struct perf_event_sample sample;
- size_t read = 0, size = (end - begin);
+ size_t read = 0;
struct btrace_block block = { 0, 0 };
struct regcache *regcache;
@@ -252,6 +252,13 @@ perf_event_read_bts (struct btrace_target_info* tinfo, const uint8_t *begin,
block.end = psample->bts.from;
}
+ /* Push the last block (i.e. the first one of inferior execution), as well.
+ We don't know where it ends, but we know where it starts. If we're
+ reading delta trace, we can fill in the start address later on.
+ Otherwise we will prune it. */
+ block.begin = 0;
+ VEC_safe_push (btrace_block_s, btrace, &block);
+
return btrace;
}
@@ -476,7 +483,7 @@ linux_enable_btrace (ptid_t ptid)
/* See linux-btrace.h. */
-int
+enum btrace_error
linux_disable_btrace (struct btrace_target_info *tinfo)
{
int errcode;
@@ -484,12 +491,12 @@ linux_disable_btrace (struct btrace_target_info *tinfo)
errno = 0;
errcode = munmap (tinfo->buffer, perf_event_mmap_size (tinfo));
if (errcode != 0)
- return errno;
+ return BTRACE_ERR_UNKNOWN;
close (tinfo->file);
xfree (tinfo);
- return 0;
+ return BTRACE_ERR_NONE;
}
/* Check whether the branch trace has changed. */
@@ -504,21 +511,24 @@ linux_btrace_has_changed (struct btrace_target_info *tinfo)
/* See linux-btrace.h. */
-VEC (btrace_block_s) *
-linux_read_btrace (struct btrace_target_info *tinfo,
+enum btrace_error
+linux_read_btrace (VEC (btrace_block_s) **btrace,
+ struct btrace_target_info *tinfo,
enum btrace_read_type type)
{
- VEC (btrace_block_s) *btrace = NULL;
volatile struct perf_event_mmap_page *header;
const uint8_t *begin, *end, *start;
- unsigned long data_head, retries = 5;
- size_t buffer_size;
+ unsigned long data_head, data_tail, retries = 5;
+ size_t buffer_size, size;
+ /* For delta reads, we return at least the partial last block containing
+ the current PC. */
if (type == BTRACE_READ_NEW && !linux_btrace_has_changed (tinfo))
- return NULL;
+ return BTRACE_ERR_NONE;
header = perf_event_header (tinfo);
buffer_size = perf_event_buffer_size (tinfo);
+ data_tail = tinfo->data_head;
/* We may need to retry reading the trace. See below. */
while (retries--)
@@ -526,23 +536,45 @@ linux_read_btrace (struct btrace_target_info *tinfo,
data_head = header->data_head;
/* Delete any leftover trace from the previous iteration. */
- VEC_free (btrace_block_s, btrace);
+ VEC_free (btrace_block_s, *btrace);
- /* If there's new trace, let's read it. */
- if (data_head != tinfo->data_head)
+ if (type == BTRACE_READ_DELTA)
{
- /* Data_head keeps growing; the buffer itself is circular. */
- begin = perf_event_buffer_begin (tinfo);
- start = begin + data_head % buffer_size;
-
- if (data_head <= buffer_size)
- end = start;
- else
- end = perf_event_buffer_end (tinfo);
+ /* Determine the number of bytes to read and check for buffer
+ overflows. */
+
+ /* Check for data head overflows. We might be able to recover from
+ those but they are very unlikely and it's not really worth the
+ effort, I think. */
+ if (data_head < data_tail)
+ return BTRACE_ERR_OVERFLOW;
+
+ /* If the buffer is smaller than the trace delta, we overflowed. */
+ size = data_head - data_tail;
+ if (buffer_size < size)
+ return BTRACE_ERR_OVERFLOW;
+ }
+ else
+ {
+ /* Read the entire buffer. */
+ size = buffer_size;
- btrace = perf_event_read_bts (tinfo, begin, end, start);
+ /* Adjust the size if the buffer has not overflowed, yet. */
+ if (data_head < size)
+ size = data_head;
}
+ /* Data_head keeps growing; the buffer itself is circular. */
+ begin = perf_event_buffer_begin (tinfo);
+ start = begin + data_head % buffer_size;
+
+ if (data_head <= buffer_size)
+ end = start;
+ else
+ end = perf_event_buffer_end (tinfo);
+
+ *btrace = perf_event_read_bts (tinfo, begin, end, start, size);
+
/* The stopping thread notifies its ptracer before it is scheduled out.
On multi-core systems, the debugger might therefore run while the
kernel might be writing the last branch trace records.
@@ -554,7 +586,13 @@ linux_read_btrace (struct btrace_target_info *tinfo,
tinfo->data_head = data_head;
- return btrace;
+ /* Prune the incomplete last block (i.e. the first one of inferior execution)
+ if we're not doing a delta read. There is no way of filling in its zeroed
+ BEGIN element. */
+ if (!VEC_empty (btrace_block_s, *btrace) && type != BTRACE_READ_DELTA)
+ VEC_pop (btrace_block_s, *btrace);
+
+ return BTRACE_ERR_NONE;
}
#else /* !HAVE_LINUX_PERF_EVENT_H */
@@ -577,19 +615,20 @@ linux_enable_btrace (ptid_t ptid)
/* See linux-btrace.h. */
-int
+enum btrace_error
linux_disable_btrace (struct btrace_target_info *tinfo)
{
- return ENOSYS;
+ return BTRACE_ERR_NOT_SUPPORTED;
}
/* See linux-btrace.h. */
-VEC (btrace_block_s) *
-linux_read_btrace (struct btrace_target_info *tinfo,
+enum btrace_error
+linux_read_btrace (VEC (btrace_block_s) **btrace,
+ struct btrace_target_info *tinfo,
enum btrace_read_type type)
{
- return NULL;
+ return BTRACE_ERR_NOT_SUPPORTED;
}
#endif /* !HAVE_LINUX_PERF_EVENT_H */
diff --git a/gdb/common/linux-btrace.h b/gdb/common/linux-btrace.h
index 32a0403..a97b697 100644
--- a/gdb/common/linux-btrace.h
+++ b/gdb/common/linux-btrace.h
@@ -61,17 +61,18 @@ struct btrace_target_info
int ptr_bits;
};
-/* Check whether branch tracing is supported. */
+/* See to_supports_btrace in target.h. */
extern int linux_supports_btrace (void);
-/* Enable branch tracing for @ptid. */
+/* See to_enable_btrace in target.h. */
extern struct btrace_target_info *linux_enable_btrace (ptid_t ptid);
-/* Disable branch tracing and deallocate @tinfo. */
-extern int linux_disable_btrace (struct btrace_target_info *tinfo);
+/* See to_disable_btrace in target.h. */
+extern enum btrace_error linux_disable_btrace (struct btrace_target_info *ti);
-/* Read branch trace data. */
-extern VEC (btrace_block_s) *linux_read_btrace (struct btrace_target_info *,
- enum btrace_read_type);
+/* See to_read_btrace in target.h. */
+extern enum btrace_error linux_read_btrace (VEC (btrace_block_s) **btrace,
+ struct btrace_target_info *btinfo,
+ enum btrace_read_type type);
#endif /* LINUX_BTRACE_H */
generated by cgit v1.1 at 2025-04-08 05:09:11 +0000