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authorLiming Wang <liming.wang@windriver.com>2008-11-20 22:00:18 -0500
committerIngo Molnar <mingo@elte.hu>2008-11-21 02:49:52 -0500
commit522a110b42b306d696cf84e34c677ed0e7080194 (patch)
treea77d238aed14185cb5662daae5f01f0da405a834 /kernel
parented313489badef16d700f5a3be50e8fd8f8294bc8 (diff)
function tracing: fix wrong position computing of stack_trace
Impact: make output of stack_trace complete if buffer overruns When read buffer overruns, the output of stack_trace isn't complete. When printing records with seq_printf in t_show, if the read buffer has overruned by the current record, then this record won't be printed to user space through read buffer, it will just be dropped in this printing. When next printing, t_start should return the "*pos"th record, which is the one dropped by previous printing, but it just returns (m->private + *pos)th record. Here we use a more sane method to implement seq_operations which can be found in kernel code. Thus we needn't initialize m->private. About testing, it's not easy to overrun read buffer, but we can use seq_printf to print more padding bytes in t_show, then it's easy to check whether or not records are lost. This commit has been tested on both condition of overrun and non overrun. Signed-off-by: Liming Wang <liming.wang@windriver.com> Acked-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/trace/trace_stack.c24
1 files changed, 15 insertions, 9 deletions
diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c
index be682b62fe58..3bdb44bde4b7 100644
--- a/kernel/trace/trace_stack.c
+++ b/kernel/trace/trace_stack.c
@@ -184,11 +184,16 @@ static struct file_operations stack_max_size_fops = {
184static void * 184static void *
185t_next(struct seq_file *m, void *v, loff_t *pos) 185t_next(struct seq_file *m, void *v, loff_t *pos)
186{ 186{
187 long i = (long)m->private; 187 long i;
188 188
189 (*pos)++; 189 (*pos)++;
190 190
191 i++; 191 if (v == SEQ_START_TOKEN)
192 i = 0;
193 else {
194 i = *(long *)v;
195 i++;
196 }
192 197
193 if (i >= max_stack_trace.nr_entries || 198 if (i >= max_stack_trace.nr_entries ||
194 stack_dump_trace[i] == ULONG_MAX) 199 stack_dump_trace[i] == ULONG_MAX)
@@ -201,12 +206,15 @@ t_next(struct seq_file *m, void *v, loff_t *pos)
201 206
202static void *t_start(struct seq_file *m, loff_t *pos) 207static void *t_start(struct seq_file *m, loff_t *pos)
203{ 208{
204 void *t = &m->private; 209 void *t = SEQ_START_TOKEN;
205 loff_t l = 0; 210 loff_t l = 0;
206 211
207 local_irq_disable(); 212 local_irq_disable();
208 __raw_spin_lock(&max_stack_lock); 213 __raw_spin_lock(&max_stack_lock);
209 214
215 if (*pos == 0)
216 return SEQ_START_TOKEN;
217
210 for (; t && l < *pos; t = t_next(m, t, &l)) 218 for (; t && l < *pos; t = t_next(m, t, &l))
211 ; 219 ;
212 220
@@ -235,10 +243,10 @@ static int trace_lookup_stack(struct seq_file *m, long i)
235 243
236static int t_show(struct seq_file *m, void *v) 244static int t_show(struct seq_file *m, void *v)
237{ 245{
238 long i = *(long *)v; 246 long i;
239 int size; 247 int size;
240 248
241 if (i < 0) { 249 if (v == SEQ_START_TOKEN) {
242 seq_printf(m, " Depth Size Location" 250 seq_printf(m, " Depth Size Location"
243 " (%d entries)\n" 251 " (%d entries)\n"
244 " ----- ---- --------\n", 252 " ----- ---- --------\n",
@@ -246,6 +254,8 @@ static int t_show(struct seq_file *m, void *v)
246 return 0; 254 return 0;
247 } 255 }
248 256
257 i = *(long *)v;
258
249 if (i >= max_stack_trace.nr_entries || 259 if (i >= max_stack_trace.nr_entries ||
250 stack_dump_trace[i] == ULONG_MAX) 260 stack_dump_trace[i] == ULONG_MAX)
251 return 0; 261 return 0;
@@ -275,10 +285,6 @@ static int stack_trace_open(struct inode *inode, struct file *file)
275 int ret; 285 int ret;
276 286
277 ret = seq_open(file, &stack_trace_seq_ops); 287 ret = seq_open(file, &stack_trace_seq_ops);
278 if (!ret) {
279 struct seq_file *m = file->private_data;
280 m->private = (void *)-1;
281 }
282 288
283 return ret; 289 return ret;
284} 290}