[PATCH 1/4] ksym_tracer: Fix to make the tracer work

From: Li Zefan
Date: Wed Dec 30 2009 - 01:22:39 EST


ksym tracer doesn't work:

# echo tasklist_lock:rw- > ksym_trace_filter
-bash: echo: write error: No such device

It's because we pass to perf_event_create_kernel_counter()
a cpu number which is not present.

Signed-off-by: Li Zefan <lizf@xxxxxxxxxxxxxx>
---
kernel/hw_breakpoint.c | 10 +++++++---
kernel/trace/trace_ksym.c | 1 -
2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/kernel/hw_breakpoint.c b/kernel/hw_breakpoint.c
index dbcbf6a..50dbd59 100644
--- a/kernel/hw_breakpoint.c
+++ b/kernel/hw_breakpoint.c
@@ -40,6 +40,7 @@
#include <linux/percpu.h>
#include <linux/sched.h>
#include <linux/init.h>
+#include <linux/cpu.h>
#include <linux/smp.h>

#include <linux/hw_breakpoint.h>
@@ -388,7 +389,8 @@ register_wide_hw_breakpoint(struct perf_event_attr *attr,
if (!cpu_events)
return ERR_PTR(-ENOMEM);

- for_each_possible_cpu(cpu) {
+ get_online_cpus();
+ for_each_online_cpu(cpu) {
pevent = per_cpu_ptr(cpu_events, cpu);
bp = perf_event_create_kernel_counter(attr, cpu, -1, triggered);

@@ -399,18 +401,20 @@ register_wide_hw_breakpoint(struct perf_event_attr *attr,
goto fail;
}
}
+ put_online_cpus();

return cpu_events;

fail:
- for_each_possible_cpu(cpu) {
+ for_each_online_cpu(cpu) {
pevent = per_cpu_ptr(cpu_events, cpu);
if (IS_ERR(*pevent))
break;
unregister_hw_breakpoint(*pevent);
}
+ put_online_cpus();
+
free_percpu(cpu_events);
- /* return the error if any */
return ERR_PTR(err);
}
EXPORT_SYMBOL_GPL(register_wide_hw_breakpoint);
diff --git a/kernel/trace/trace_ksym.c b/kernel/trace/trace_ksym.c
index faf37fa..340b6ff 100644
--- a/kernel/trace/trace_ksym.c
+++ b/kernel/trace/trace_ksym.c
@@ -197,7 +197,6 @@ int process_new_ksym_entry(char *ksymname, int op, unsigned long addr)
entry->attr.bp_addr = addr;
entry->attr.bp_len = HW_BREAKPOINT_LEN_4;

- ret = -EAGAIN;
entry->ksym_hbp = register_wide_hw_breakpoint(&entry->attr,
ksym_hbp_handler);

--
1.6.3

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