Messages in this thread | | | Date | Fri, 21 Nov 2008 08:52:56 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH 1/1] function tracing: fix wrong position computing of stack_trace |
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* Liming Wang <liming.wang@windriver.com> wrote:
> Impact: make output of stack_trace complete if buffer overflow > > When read buffer overflows, the output of stack_trace isn't > complete. > > When printing records with seq_printf in t_show, if the read buffer > has overflowed 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 overflow 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 overflow and non > overflow. > > Signed-off-by: Liming Wang <liming.wang@windriver.com> > --- > kernel/trace/trace_stack.c | 24 +++++++++++++++--------- > 1 files changed, 15 insertions(+), 9 deletions(-)
applied to tip/tracing/urgent, thanks!
Note, i changed 'buffer overflow' to 'buffer overrun'. (buffer overflow is a term typically used in a security context)
> - i++; > + if (v == SEQ_START_TOKEN ) > + i = 0; > + else { > + i = *(long *)v; > + i++; > + }
i also fixed these two minor style problems pointed out by scripts/checkpatch.pl:
| ERROR: space prohibited before that close parenthesis ')' | #47: FILE: kernel/trace/trace_stack.c:187: | + if (v == SEQ_START_TOKEN ) | | ERROR: space prohibited before that close parenthesis ')' | #82: FILE: kernel/trace/trace_stack.c:245: | + if (v == SEQ_START_TOKEN ) { | | total: 2 errors, 0 warnings, 0 checks, 64 lines checked
Ingo
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