Re: [PATCH v4 01/19] [BUGFIX] tracing: probeevent: Fix to support minus offset from symbol

Hi Masami,

On Wed, Feb 28, 2018 at 12:19:53PM +0900, Masami Hiramatsu wrote:

In Documentation/trace/kprobetrace.txt, it says

@SYM[+|-offs] : Fetch memory at SYM +|- offs (SYM should be a data symbol)

However, the parser doesn't parse minus offset correctly, since commit 2fba0c8867af ("tracing/kprobes: Fix probe offset to be unsigned") drops minus ("-") offset support for kprobe probe address usage.

This fixes the traceprobe_split_symbol_offset() to parse minus offset again with checking the offset range, and add a minus offset check in kprobe probe address usage.

It now parses a minus offset but doesn't allow it, right? Then I still think it's better to fix the documentation.

Fixes: 2fba0c8867af ("tracing/kprobes: Fix probe offset to be unsigned") Signed-off-by: Masami Hiramatsu mhiramat@kernel.org

---

Changes in v3:

• Use kstrtol instead of kstrtoul. (Thanks Namhyung!)

Changes in v4:

• Fix to decode sign. (Thanks Namhyung!)
• Fix to check UINT_MAX for kprobe offset.

---

kernel/trace/trace_kprobe.c | 4 ++-- kernel/trace/trace_probe.c | 8 +++----- kernel/trace/trace_probe.h | 2 +- 3 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c index 5ce9b8cf7be3..1cd3fb4d70f8 100644 --- a/kernel/trace/trace_kprobe.c +++ b/kernel/trace/trace_kprobe.c @@ -667,7 +667,7 @@ static int create_trace_kprobe(int argc, char **argv) char *symbol = NULL, *event = NULL, *group = NULL; int maxactive = 0; char *arg;

• unsigned long offset = 0;

• long offset = 0; void *addr = NULL; char buf[MAX_EVENT_NAME_LEN];

@@ -755,7 +755,7 @@ static int create_trace_kprobe(int argc, char **argv) symbol = argv[1]; /* TODO: support .init module functions */ ret = traceprobe_split_symbol_offset(symbol, &offset);

• if (ret) {
  

• if (ret || offset < 0 || offset > UINT_MAX) {
  pr_info("Failed to parse either an address or a symbol.\n");
  return ret;
  

Wouldn't it be confusing if it returns 0 for an invalid input?

Thanks, Namhyung

}

diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c index d59357308677..daf54bda4dc8 100644 --- a/kernel/trace/trace_probe.c +++ b/kernel/trace/trace_probe.c @@ -320,7 +320,7 @@ static fetch_func_t get_fetch_size_function(const struct fetch_type *type, } /* Split symbol and offset. */ -int traceprobe_split_symbol_offset(char *symbol, unsigned long *offset) +int traceprobe_split_symbol_offset(char *symbol, long *offset) { char *tmp; int ret; @@ -328,13 +328,11 @@ int traceprobe_split_symbol_offset(char *symbol, unsigned long *offset) if (!offset) return -EINVAL;

• tmp = strchr(symbol, '+');

• tmp = strpbrk(symbol, "+-"); if (tmp) {

• /* skip sign because kstrtoul doesn't accept '+' */
  

• ret = kstrtoul(tmp + 1, 0, offset);
  

• ret = kstrtol(tmp, 0, offset);
  

  if (ret) return ret;

• *tmp = '\0'; } else *offset = 0;

diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h index 0745f895f780..75daff22ccea 100644 --- a/kernel/trace/trace_probe.h +++ b/kernel/trace/trace_probe.h @@ -365,7 +365,7 @@ extern int traceprobe_conflict_field_name(const char *name, extern void traceprobe_update_arg(struct probe_arg *arg); extern void traceprobe_free_probe_arg(struct probe_arg *arg); -extern int traceprobe_split_symbol_offset(char *symbol, unsigned long *offset); +extern int traceprobe_split_symbol_offset(char *symbol, long *offset); /* Sum up total data length for dynamic arraies (strings) */ static nokprobe_inline int

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