On 10/18, Xu Kuohai wrote:
From: Xu Kuohai <xukuohai@xxxxxxxxxx>
The reg_name in parse_usdt_arg() is used to hold register name, which
is short enough to be held in a 16-byte array, so we could define
reg_name as char reg_name[16] to avoid dynamically allocating reg_name
with sscanf.
Suggested-by: Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx>
Signed-off-by: Xu Kuohai <xukuohai@xxxxxxxxxx>
Addresses Andrii's suggestion from the following:
https://lore.kernel.org/bpf/86c88c01-22eb-b7f8-9c65-0faf97b4096b@xxxxxxxxxx/
Acked-by: Stanislav Fomichev <sdf@xxxxxxxxxx>
---
tools/lib/bpf/usdt.c | 16 ++++++----------
1 file changed, 6 insertions(+), 10 deletions(-)
diff --git a/tools/lib/bpf/usdt.c b/tools/lib/bpf/usdt.c
index 49f3c3b7f609..28fa1b2283de 100644
--- a/tools/lib/bpf/usdt.c
+++ b/tools/lib/bpf/usdt.c
@@ -1225,26 +1225,24 @@ static int calc_pt_regs_off(const char *reg_name)
static int parse_usdt_arg(const char *arg_str, int arg_num, struct
usdt_arg_spec *arg)
{
- char *reg_name = NULL;
+ char reg_name[16];
int arg_sz, len, reg_off;
long off;
- if (sscanf(arg_str, " %d @ %ld ( %%%m[^)] ) %n", &arg_sz, &off,
®_name, &len) == 3) {
+ if (sscanf(arg_str, " %d @ %ld ( %%%15[^)] ) %n", &arg_sz, &off,
reg_name, &len) == 3) {
/* Memory dereference case, e.g., -4@-20(%rbp) */
arg->arg_type = USDT_ARG_REG_DEREF;
arg->val_off = off;
reg_off = calc_pt_regs_off(reg_name);
- free(reg_name);
if (reg_off < 0)
return reg_off;
arg->reg_off = reg_off;
- } else if (sscanf(arg_str, " %d @ %%%ms %n", &arg_sz, ®_name, &len)
== 2) {
+ } else if (sscanf(arg_str, " %d @ %%%15s %n", &arg_sz, reg_name, &len)
== 2) {
/* Register read case, e.g., -4@%eax */
arg->arg_type = USDT_ARG_REG;
arg->val_off = 0;
reg_off = calc_pt_regs_off(reg_name);
- free(reg_name);
if (reg_off < 0)
return reg_off;
arg->reg_off = reg_off;
@@ -1456,16 +1454,15 @@ static int calc_pt_regs_off(const char *reg_name)
static int parse_usdt_arg(const char *arg_str, int arg_num, struct
usdt_arg_spec *arg)
{
- char *reg_name = NULL;
+ char reg_name[16];
int arg_sz, len, reg_off;
long off;
- if (sscanf(arg_str, " %d @ %ld ( %m[a-z0-9] ) %n", &arg_sz, &off,
®_name, &len) == 3) {
+ if (sscanf(arg_str, " %d @ %ld ( %15[a-z0-9] ) %n", &arg_sz, &off,
reg_name, &len) == 3) {
/* Memory dereference case, e.g., -8@-88(s0) */
arg->arg_type = USDT_ARG_REG_DEREF;
arg->val_off = off;
reg_off = calc_pt_regs_off(reg_name);
- free(reg_name);
if (reg_off < 0)
return reg_off;
arg->reg_off = reg_off;
@@ -1474,12 +1471,11 @@ static int parse_usdt_arg(const char *arg_str,
int arg_num, struct usdt_arg_spec
arg->arg_type = USDT_ARG_CONST;
arg->val_off = off;
arg->reg_off = 0;
- } else if (sscanf(arg_str, " %d @ %m[a-z0-9] %n", &arg_sz, ®_name,
&len) == 2) {
+ } else if (sscanf(arg_str, " %d @ %15[a-z0-9] %n", &arg_sz, reg_name,
&len) == 2) {
/* Register read case, e.g., -8@a1 */
arg->arg_type = USDT_ARG_REG;
arg->val_off = 0;
reg_off = calc_pt_regs_off(reg_name);
- free(reg_name);
if (reg_off < 0)
return reg_off;
arg->reg_off = reg_off;
--
2.30.2
