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btrace: improve enable error messages 

Improve the error message when GDB fails to start recording branch trace.

This patch also removes a zero buffer size check for PT to align with BTS.  The
buffer size can not be configured to be zero.

gdb/
	* nat/linux-btrace.c (perf_event_pt_event_type): Improve error message.
	Remove parameter and change return type.  Update callers.  Move it.
	(linux_enable_bts, linux_enable_pt): Improve error message.
	(linux_enable_pt): Remove zero buffer size check.
	(linux_enable_btrace): Improve error messages.  Remove NULL return
	check.
This commit is contained in:
Markus Metzger 2018-01-19 13:56:32 +01:00
parent de6242d307
commit 17ad2a4f46
2 changed files with 39 additions and 41 deletions
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9
gdb/ChangeLog
View File

@ -1,3 +1,12 @@
2018-02-09 Markus Metzger <markus.t.metzger@intel.com>
* nat/linux-btrace.c (perf_event_pt_event_type): Improve error message.
Remove parameter and change return type. Update callers. Move it.
(linux_enable_bts, linux_enable_pt): Improve error message.
(linux_enable_pt): Remove zero buffer size check.
(linux_enable_btrace): Improve error messages. Remove NULL return
check.
2018-02-09 Markus Metzger <markus.t.metzger@intel.com> 2018-02-09 Markus Metzger <markus.t.metzger@intel.com>
* btrace.c (btrace_enable): Remove target_supports_btrace call. * btrace.c (btrace_enable): Remove target_supports_btrace call.

71
gdb/nat/linux-btrace.c
View File

@ -448,7 +448,7 @@ linux_enable_bts (ptid_t ptid, const struct btrace_config_bts *conf)
errno = 0; errno = 0;
scoped_fd fd (syscall (SYS_perf_event_open, &bts->attr, pid, -1, -1, 0)); scoped_fd fd (syscall (SYS_perf_event_open, &bts->attr, pid, -1, -1, 0));
if (fd.get () < 0) if (fd.get () < 0)
return nullptr; error (_("Failed to start recording: %s"), safe_strerror (errno));
/* Convert the requested size in bytes to pages (rounding up). */ /* Convert the requested size in bytes to pages (rounding up). */
pages = ((size_t) conf->size / PAGE_SIZE pages = ((size_t) conf->size / PAGE_SIZE
@ -484,6 +484,7 @@ linux_enable_bts (ptid_t ptid, const struct btrace_config_bts *conf)
if ((__u64) length != data_size + PAGE_SIZE) if ((__u64) length != data_size + PAGE_SIZE)
continue; continue;
errno = 0;
/* The number of pages we request needs to be a power of two. */ /* The number of pages we request needs to be a power of two. */
data.reset (nullptr, length, PROT_READ, MAP_SHARED, fd.get (), 0); data.reset (nullptr, length, PROT_READ, MAP_SHARED, fd.get (), 0);
if (data.get () != MAP_FAILED) if (data.get () != MAP_FAILED)
@ -491,7 +492,7 @@ linux_enable_bts (ptid_t ptid, const struct btrace_config_bts *conf)
} }
if (pages == 0) if (pages == 0)
return nullptr; error (_("Failed to map trace buffer: %s."), safe_strerror (errno));
struct perf_event_mmap_page *header = (struct perf_event_mmap_page *) struct perf_event_mmap_page *header = (struct perf_event_mmap_page *)
data.get (); data.get ();
@ -509,7 +510,7 @@ linux_enable_bts (ptid_t ptid, const struct btrace_config_bts *conf)
/* Check for overflows. */ /* Check for overflows. */
if ((__u64) size != data_size) if ((__u64) size != data_size)
return nullptr; error (_("Failed to determine trace buffer size."));
} }
#endif /* defined (PERF_ATTR_SIZE_VER5) */ #endif /* defined (PERF_ATTR_SIZE_VER5) */
@ -528,21 +529,23 @@ linux_enable_bts (ptid_t ptid, const struct btrace_config_bts *conf)
#if defined (PERF_ATTR_SIZE_VER5) #if defined (PERF_ATTR_SIZE_VER5)
/* Determine the event type. /* Determine the event type. */
Returns zero on success and fills in TYPE; returns -1 otherwise. */
static int static int
perf_event_pt_event_type (int *type) perf_event_pt_event_type ()
{ {
gdb_file_up file = static const char filename[] = "/sys/bus/event_source/devices/intel_pt/type";
gdb_fopen_cloexec ("/sys/bus/event_source/devices/intel_pt/type", "r");
if (file.get () == nullptr)
return -1;
int found = fscanf (file.get (), "%d", type); errno = 0;
if (found == 1) gdb_file_up file = gdb_fopen_cloexec (filename, "r");
return 0; if (file.get () == nullptr)
return -1; error (_("Failed to open %s: %s."), filename, safe_strerror (errno));
int type, found = fscanf (file.get (), "%d", &type);
if (found != 1)
error (_("Failed to read the PT event type from %s."), filename);
return type;
} }
/* Enable branch tracing in Intel Processor Trace format. */ /* Enable branch tracing in Intel Processor Trace format. */
@ -552,14 +555,7 @@ linux_enable_pt (ptid_t ptid, const struct btrace_config_pt *conf)
{ {
struct btrace_tinfo_pt *pt; struct btrace_tinfo_pt *pt;
size_t pages; size_t pages;
int pid, pg, errcode, type; int pid, pg;
if (conf->size == 0)
return NULL;
errcode = perf_event_pt_event_type (&type);
if (errcode != 0)
return NULL;
pid = ptid_get_lwp (ptid); pid = ptid_get_lwp (ptid);
if (pid == 0) if (pid == 0)
@ -573,7 +569,7 @@ linux_enable_pt (ptid_t ptid, const struct btrace_config_pt *conf)
pt = &tinfo->variant.pt; pt = &tinfo->variant.pt;
pt->attr.size = sizeof (pt->attr); pt->attr.size = sizeof (pt->attr);
pt->attr.type = type; pt->attr.type = perf_event_pt_event_type ();
pt->attr.exclude_kernel = 1; pt->attr.exclude_kernel = 1;
pt->attr.exclude_hv = 1; pt->attr.exclude_hv = 1;
@ -582,13 +578,13 @@ linux_enable_pt (ptid_t ptid, const struct btrace_config_pt *conf)
errno = 0; errno = 0;
scoped_fd fd (syscall (SYS_perf_event_open, &pt->attr, pid, -1, -1, 0)); scoped_fd fd (syscall (SYS_perf_event_open, &pt->attr, pid, -1, -1, 0));
if (fd.get () < 0) if (fd.get () < 0)
return nullptr; error (_("Failed to start recording: %s"), safe_strerror (errno));
/* Allocate the configuration page. */ /* Allocate the configuration page. */
scoped_mmap data (nullptr, PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, scoped_mmap data (nullptr, PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED,
fd.get (), 0); fd.get (), 0);
if (data.get () == MAP_FAILED) if (data.get () == MAP_FAILED)
return nullptr; error (_("Failed to map trace user page: %s."), safe_strerror (errno));
struct perf_event_mmap_page *header = (struct perf_event_mmap_page *) struct perf_event_mmap_page *header = (struct perf_event_mmap_page *)
data.get (); data.get ();
@ -630,6 +626,7 @@ linux_enable_pt (ptid_t ptid, const struct btrace_config_pt *conf)
header->aux_size = data_size; header->aux_size = data_size;
errno = 0;
aux.reset (nullptr, length, PROT_READ, MAP_SHARED, fd.get (), aux.reset (nullptr, length, PROT_READ, MAP_SHARED, fd.get (),
header->aux_offset); header->aux_offset);
if (aux.get () != MAP_FAILED) if (aux.get () != MAP_FAILED)
@ -637,7 +634,7 @@ linux_enable_pt (ptid_t ptid, const struct btrace_config_pt *conf)
} }
if (pages == 0) if (pages == 0)
return nullptr; error (_("Failed to map trace buffer: %s."), safe_strerror (errno));
pt->pt.size = aux.size (); pt->pt.size = aux.size ();
pt->pt.mem = (const uint8_t *) aux.release (); pt->pt.mem = (const uint8_t *) aux.release ();
@ -656,8 +653,7 @@ linux_enable_pt (ptid_t ptid, const struct btrace_config_pt *conf)
static struct btrace_target_info * static struct btrace_target_info *
linux_enable_pt (ptid_t ptid, const struct btrace_config_pt *conf) linux_enable_pt (ptid_t ptid, const struct btrace_config_pt *conf)
{ {
errno = EOPNOTSUPP; error (_("Intel Processor Trace support was disabled at compile time."));
return NULL;
} }
#endif /* !defined (PERF_ATTR_SIZE_VER5) */ #endif /* !defined (PERF_ATTR_SIZE_VER5) */
@ -667,27 +663,20 @@ linux_enable_pt (ptid_t ptid, const struct btrace_config_pt *conf)
struct btrace_target_info * struct btrace_target_info *
linux_enable_btrace (ptid_t ptid, const struct btrace_config *conf) linux_enable_btrace (ptid_t ptid, const struct btrace_config *conf)
{ {
struct btrace_target_info *tinfo;
tinfo = NULL;
switch (conf->format) switch (conf->format)
{ {
case BTRACE_FORMAT_NONE: case BTRACE_FORMAT_NONE:
break; error (_("Bad branch trace format."));
default:
error (_("Unknown branch trace format."));
case BTRACE_FORMAT_BTS: case BTRACE_FORMAT_BTS:
tinfo = linux_enable_bts (ptid, &conf->bts); return linux_enable_bts (ptid, &conf->bts);
break;
case BTRACE_FORMAT_PT: case BTRACE_FORMAT_PT:
tinfo = linux_enable_pt (ptid, &conf->pt); return linux_enable_pt (ptid, &conf->pt);
break;
} }
if (tinfo == NULL)
error (_("Unknown error."));
return tinfo;
} }
/* Disable BTS tracing. */ /* Disable BTS tracing. */