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.
This fixes the parser to get minus offset correctly.

Signed-off-by: Masami Hiramatsu <[email protected]>
---
 kernel/trace/trace_kprobe.c |    2 +-
 kernel/trace/trace_probe.c  |   10 +++++-----
 kernel/trace/trace_probe.h  |    2 +-
 3 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 5ce9b8cf7be3..dab4a5b54269 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -754,7 +754,7 @@ static int create_trace_kprobe(int argc, char **argv)
                /* a symbol specified */
                symbol = argv[1];
                /* TODO: support .init module functions */
-               ret = traceprobe_split_symbol_offset(symbol, &offset);
+               ret = traceprobe_split_symbol_offset(symbol, (long *)&offset);
                if (ret) {
                        pr_info("Failed to parse either an address or a 
symbol.\n");
                        return ret;
diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
index d59357308677..3e291a754862 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 +328,13 @@ 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 = kstrtoul(tmp + 1, 0, (unsigned long *)offset);
                if (ret)
                        return ret;
-
+               if (*tmp == '-')
+                       *offset = -(*offset);
                *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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