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Subject[PATCH 13/13] tracing/uprobes: Add support for full argument access methods
Date
From: Namhyung Kim <namhyung.kim@lge.com>

Enable to fetch other types of argument for the uprobes. IOW, we can
access stack, memory, deref, bitfield and retval from uprobes now.

Original-patch-by: Hyeoncheol Lee <cheol.lee@lge.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: zhangwei(Jovi) <jovi.zhangwei@huawei.com>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
kernel/trace/trace_probe.c | 34 ++++++++++++++++++++--------------
1 file changed, 20 insertions(+), 14 deletions(-)

diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
index 70cd3bfde5a6..b68ceb7cad6e 100644
--- a/kernel/trace/trace_probe.c
+++ b/kernel/trace/trace_probe.c
@@ -253,7 +253,7 @@ fail:
}

/* Special function : only accept unsigned long */
-static __kprobes void fetch_stack_address(struct pt_regs *regs,
+static __kprobes void fetch_kernel_stack_address(struct pt_regs *regs,
void *dummy, void *dest, void *priv)
{
*(unsigned long *)dest = kernel_stack_pointer(regs);
@@ -303,7 +303,8 @@ int traceprobe_split_symbol_offset(char *symbol, unsigned long *offset)
#define PARAM_MAX_STACK (THREAD_SIZE / sizeof(unsigned long))

static int parse_probe_vars(char *arg, const struct fetch_type *t,
- struct fetch_param *f, bool is_return)
+ struct fetch_param *f, bool is_return,
+ bool is_kprobe)
{
int ret = 0;
unsigned long param;
@@ -315,13 +316,18 @@ static int parse_probe_vars(char *arg, const struct fetch_type *t,
ret = -EINVAL;
} else if (strncmp(arg, "stack", 5) == 0) {
if (arg[5] == '\0') {
- if (strcmp(t->name, DEFAULT_FETCH_TYPE_STR) == 0)
- f->fn = fetch_stack_address;
- else
- ret = -EINVAL;
+ if (strcmp(t->name, DEFAULT_FETCH_TYPE_STR))
+ return -EINVAL;
+
+ if (is_kprobe)
+ f->fn = fetch_kernel_stack_address;
+ else {
+ f->fn = t->fetch[FETCH_MTD_stack];
+ f->data = (void *)0;
+ }
} else if (isdigit(arg[5])) {
ret = kstrtoul(arg + 5, 10, &param);
- if (ret || param > PARAM_MAX_STACK)
+ if (ret || (is_kprobe && param > PARAM_MAX_STACK))
ret = -EINVAL;
else {
f->fn = t->fetch[FETCH_MTD_stack];
@@ -345,17 +351,13 @@ static int parse_probe_arg(char *arg, const struct fetch_type *t,
int ret;
const struct fetch_type *ttbl;

- ttbl = kprobes_fetch_type_table;
+ ttbl = is_kprobe ? kprobes_fetch_type_table : uprobes_fetch_type_table;

ret = 0;

- /* Until uprobe_events supports only reg arguments */
- if (!is_kprobe && arg[0] != '%')
- return -EINVAL;
-
switch (arg[0]) {
case '$':
- ret = parse_probe_vars(arg + 1, t, f, is_return);
+ ret = parse_probe_vars(arg + 1, t, f, is_return, is_kprobe);
break;

case '%': /* named register */
@@ -376,6 +378,10 @@ static int parse_probe_arg(char *arg, const struct fetch_type *t,
f->fn = t->fetch[FETCH_MTD_memory];
f->data = (void *)param;
} else {
+ /* uprobes don't support symbols */
+ if (!is_kprobe)
+ return -EINVAL;
+
ret = traceprobe_split_symbol_offset(arg + 1, &offset);
if (ret)
break;
@@ -482,7 +488,7 @@ int traceprobe_parse_probe_arg(char *arg, ssize_t *size,
int ret;
const struct fetch_type *ttbl;

- ttbl = kprobes_fetch_type_table;
+ ttbl = is_kprobe ? kprobes_fetch_type_table : uprobes_fetch_type_table;

if (strlen(arg) > MAX_ARGSTR_LEN) {
pr_info("Argument is too long.: %s\n", arg);
--
1.7.11.7


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