[1/2] Improve error reporting when handling SystemTap SDT probes
Commit Message
This patch improves the error reporting when handling SystemTap SDT
probes. "Handling", in this case, mostly means "parsing".
On gdb/probe.h, only trivial changes on functions' comments in order
to explicitly mention that some of them can throw exceptions. This is
just to make the API a bit more clear.
On gdb/stap-probe.c, I have s/internal_error/error/ on two functions
that are responsible for parsing specific bits of the probes'
arguments: stap_get_opcode and stap_get_expected_argument_type. It is
not correct to call internal_error on such situations because it is
not really GDB's fault if the probes have malformed arguments. I also
improved the error reported on stap_get_expected_argument_type by also
including the probe name on it.
Aside from that, and perhaps most importantly, I added a check on
stap_get_arg to make sure that we don't try to extract an argument
from a probe that has no arguments. This check issues an
internal_error, because it really means that GDB is doing something it
shouldn't.
Although it can be considered almost trivial, and despite the fact
that I am the maintainer for this part of the code, I am posting this
patch for review. I will wait a few days, and if nobody has anything
to say, I will go ahead and push it.
gdb/ChangeLog:
2015-08-21 Sergio Durigan Junior <sergiodj@redhat.com>
* probe.h (struct probe_ops) <get_probe_argument_count,
evaluate_probe_argument, enable_probe, disable_probe>: Mention in
the comment that the function can throw an exception.
(get_probe_argument_count): Likewise.
(evaluate_probe_argument): Likewise.
* stap-probe.c (stap_get_opcode): Call error instead of
internal_error.
(stap_get_expected_argument_type): Likewise. Add argument
'probe'. Improve error message by mentioning the probe's name.
(stap_parse_probe_arguments): Adjust call to
stap_get_expected_argument_type.
(stap_get_arg): Add comment. Assert that 'probe->args_parsed' is
not zero. Call internal_error if GDB requests an argument but the
probe has no arguments.
---
gdb/probe.h | 20 ++++++++++++++------
gdb/stap-probe.c | 29 ++++++++++++++++++++++-------
2 files changed, 36 insertions(+), 13 deletions(-)
Comments
On Friday, August 21 2015, I wrote:
> This patch improves the error reporting when handling SystemTap SDT
> probes. "Handling", in this case, mostly means "parsing".
Pushed.
https://sourceware.org/ml/gdb-cvs/2015-09/msg00001.html
@@ -72,7 +72,8 @@ struct probe_ops
CORE_ADDR (*get_probe_address) (struct probe *probe,
struct objfile *objfile);
- /* Return the number of arguments of PROBE. */
+ /* Return the number of arguments of PROBE. This function can
+ throw an exception. */
unsigned (*get_probe_argument_count) (struct probe *probe,
struct frame_info *frame);
@@ -84,7 +85,8 @@ struct probe_ops
int (*can_evaluate_probe_arguments) (struct probe *probe);
/* Evaluate the Nth argument from the PROBE, returning a value
- corresponding to it. The argument number is represented N. */
+ corresponding to it. The argument number is represented N.
+ This function can throw an exception. */
struct value *(*evaluate_probe_argument) (struct probe *probe,
unsigned n,
@@ -143,13 +145,15 @@ struct probe_ops
/* Enable a probe. The semantics of "enabling" a probe depend on
the specific backend and the field can be NULL in case enabling
- probes is not supported. */
+ probes is not supported. This function can throw an
+ exception. */
void (*enable_probe) (struct probe *probe);
/* Disable a probe. The semantics of "disabling" a probe depend
on the specific backend and the field can be NULL in case
- disabling probes is not supported. */
+ disabling probes is not supported. This function can throw an
+ exception. */
void (*disable_probe) (struct probe *probe);
};
@@ -266,7 +270,9 @@ extern struct cmd_list_element **info_probes_cmdlist_get (void);
extern CORE_ADDR get_probe_address (struct probe *probe,
struct objfile *objfile);
-/* Return the argument count of the specified probe. */
+/* Return the argument count of the specified probe.
+
+ This function can throw an exception. */
extern unsigned get_probe_argument_count (struct probe *probe,
struct frame_info *frame);
@@ -278,7 +284,9 @@ extern unsigned get_probe_argument_count (struct probe *probe,
extern int can_evaluate_probe_arguments (struct probe *probe);
/* Evaluate argument N of the specified probe. N must be between 0
- inclusive and get_probe_argument_count exclusive. */
+ inclusive and get_probe_argument_count exclusive.
+
+ This function can throw an exception. */
extern struct value *evaluate_probe_argument (struct probe *probe,
unsigned n,
@@ -313,9 +313,8 @@ stap_get_opcode (const char **s)
break;
default:
- internal_error (__FILE__, __LINE__,
- _("Invalid opcode in expression `%s' for SystemTap"
- "probe"), *s);
+ error (_("Invalid opcode in expression `%s' for SystemTap"
+ "probe"), *s);
}
return op;
@@ -326,7 +325,8 @@ stap_get_opcode (const char **s)
static struct type *
stap_get_expected_argument_type (struct gdbarch *gdbarch,
- enum stap_arg_bitness b)
+ enum stap_arg_bitness b,
+ const struct stap_probe *probe)
{
switch (b)
{
@@ -361,8 +361,8 @@ stap_get_expected_argument_type (struct gdbarch *gdbarch,
return builtin_type (gdbarch)->builtin_uint64;
default:
- internal_error (__FILE__, __LINE__,
- _("Undefined bitness for probe."));
+ error (_("Undefined bitness for probe '%s'."),
+ probe->p.name);
break;
}
}
@@ -1172,7 +1172,8 @@ stap_parse_probe_arguments (struct stap_probe *probe, struct gdbarch *gdbarch)
else
arg.bitness = STAP_ARG_BITNESS_UNDEFINED;
- arg.atype = stap_get_expected_argument_type (gdbarch, arg.bitness);
+ arg.atype = stap_get_expected_argument_type (gdbarch, arg.bitness,
+ probe);
expr = stap_parse_argument (&cur, arg.atype, gdbarch);
@@ -1278,12 +1279,26 @@ stap_is_operator (const char *op)
return ret;
}
+/* Return argument N of probe PROBE.
+
+ If the probe's arguments have not been parsed yet, parse them. If
+ there are no arguments, throw an exception (error). Otherwise,
+ return the requested argument. */
+
static struct stap_probe_arg *
stap_get_arg (struct stap_probe *probe, unsigned n, struct gdbarch *gdbarch)
{
if (!probe->args_parsed)
stap_parse_probe_arguments (probe, gdbarch);
+ gdb_assert (probe->args_parsed);
+ if (probe->args_u.vec == NULL)
+ internal_error (__FILE__, __LINE__,
+ _("Probe '%s' apparently does not have arguments, but \n"
+ "GDB is requesting its argument number %u anyway. "
+ "This should not happen. Please report this bug."),
+ probe->p.name, n);
+
return VEC_index (stap_probe_arg_s, probe->args_u.vec, n);
}