Messages in this thread | | | Date | Fri, 21 Nov 2008 16:13:22 +0800 | From | Wang Liming <> | Subject | Re: [PATCH 1/1] function tracing: fix wrong position computing of stack_trace |
| |
Ingo Molnar wrote: > * 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) OK.
> >> - 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 It's my fault, thanks a lot!
walimis > > Ingo >
| |