Messages in this thread | | | Date | Tue, 7 Jul 2009 23:29:12 +0200 | From | Frederic Weisbecker <> | Subject | Re: [PATCH 2/8] ksym_tracer: Rewrite ksym_trace_filter_read() |
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On Tue, Jul 07, 2009 at 01:52:52PM +0800, Li Zefan wrote: > Reading ksym_trace_filter gave me some arbitrary characters, > when it should show nothing. It's because buf is not initialized > when there's no filter. > > Also reduce stack usage by about 512 bytes. > > Signed-off-by: Li Zefan <lizf@cn.fujitsu.com> > --- > kernel/trace/trace_ksym.c | 29 ++++++++++++++++++----------- > 1 files changed, 18 insertions(+), 11 deletions(-) > > diff --git a/kernel/trace/trace_ksym.c b/kernel/trace/trace_ksym.c > index 085ff05..b6710d3 100644 > --- a/kernel/trace/trace_ksym.c > +++ b/kernel/trace/trace_ksym.c > @@ -35,7 +35,6 @@ > #define KSYM_TRACER_MAX HBP_NUM > > #define KSYM_TRACER_OP_LEN 3 /* rw- */ > -#define KSYM_FILTER_ENTRY_LEN (KSYM_NAME_LEN + KSYM_TRACER_OP_LEN + 1) > > struct trace_ksym { > struct hw_breakpoint *ksym_hbp; > @@ -230,25 +229,33 @@ static ssize_t ksym_trace_filter_read(struct file *filp, char __user *ubuf, > { > struct trace_ksym *entry; > struct hlist_node *node; > - char buf[KSYM_FILTER_ENTRY_LEN * KSYM_TRACER_MAX]; > - ssize_t ret, cnt = 0; > + struct trace_seq *s;
Hehe, this trace_seq type is very convenient :)
> + ssize_t cnt = 0; > + int ret; > + > + s = kmalloc(sizeof(*s), GFP_KERNEL); > + if (!s) > + return -ENOMEM; > + trace_seq_init(s); > > mutex_lock(&ksym_tracer_mutex); > > hlist_for_each_entry(entry, node, &ksym_filter_head, ksym_hlist) { > - cnt += snprintf(&buf[cnt], KSYM_FILTER_ENTRY_LEN - cnt, "%s:", > - entry->ksym_hbp->info.name); > + ret = trace_seq_printf(s, "%s:", entry->ksym_hbp->info.name); > if (entry->ksym_hbp->info.type == HW_BREAKPOINT_WRITE) > - cnt += snprintf(&buf[cnt], KSYM_FILTER_ENTRY_LEN - cnt, > - "-w-\n"); > + ret = trace_seq_puts(s, "-w-\n"); > else if (entry->ksym_hbp->info.type == HW_BREAKPOINT_RW) > - cnt += snprintf(&buf[cnt], KSYM_FILTER_ENTRY_LEN - cnt, > - "rw-\n"); > + ret = trace_seq_puts(s, "rw-\n"); > + WARN_ON_ONCE(!ret); > } > - ret = simple_read_from_buffer(ubuf, count, ppos, buf, strlen(buf)); > + > + cnt = simple_read_from_buffer(ubuf, count, ppos, s->buffer, s->len); > + > mutex_unlock(&ksym_tracer_mutex); > > - return ret; > + kfree(s); > + > + return cnt; > } > > static ssize_t ksym_trace_filter_write(struct file *file,
Looks good too.
Ack.
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