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hw-breakpoints: ftrace plugin for kernel symbol tracing using HW Breakpoint interfaces

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This patch adds an ftrace plugin to detect and profile memory access over kernel
variables. It uses HW Breakpoint interfaces to 'watch memory addresses.

Signed-off-by: K.Prasad <prasad@linux.vnet.ibm.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
This commit is contained in:
K.Prasad
2009-06-01 23:46:40 +05:30
committed by Frederic Weisbecker
parent 432039933a
commit 0722db015c
5 changed files with 623 additions and 0 deletions
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53
kernel/trace/trace_selftest.c
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@ -17,6 +17,7 @@ static inline int trace_valid_entry(struct trace_entry *entry)
case TRACE_GRAPH_ENT:
case TRACE_GRAPH_RET:
case TRACE_HW_BRANCHES:
case TRACE_KSYM:
return 1;
}
return 0;
@ -807,3 +808,55 @@ trace_selftest_startup_hw_branches(struct tracer *trace,
return ret;
}
#endif /* CONFIG_HW_BRANCH_TRACER */
#ifdef CONFIG_KSYM_TRACER
static int ksym_selftest_dummy;
int
trace_selftest_startup_ksym(struct tracer *trace, struct trace_array *tr)
{
unsigned long count;
int ret;
/* start the tracing */
ret = tracer_init(trace, tr);
if (ret) {
warn_failed_init_tracer(trace, ret);
return ret;
}
ksym_selftest_dummy = 0;
/* Register the read-write tracing request */
ret = process_new_ksym_entry(KSYM_SELFTEST_ENTRY, HW_BREAKPOINT_RW,
(unsigned long)(&ksym_selftest_dummy));
if (ret < 0) {
printk(KERN_CONT "ksym_trace read-write startup test failed\n");
goto ret_path;
}
/* Perform a read and a write operation over the dummy variable to
* trigger the tracer
*/
if (ksym_selftest_dummy == 0)
ksym_selftest_dummy++;
/* stop the tracing. */
tracing_stop();
/* check the trace buffer */
ret = trace_test_buffer(tr, &count);
trace->reset(tr);
tracing_start();
/* read & write operations - one each is performed on the dummy variable
* triggering two entries in the trace buffer
*/
if (!ret && count != 2) {
printk(KERN_CONT "Ksym tracer startup test failed");
ret = -1;
}
ret_path:
return ret;
}
#endif /* CONFIG_KSYM_TRACER */