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Commit 6821a2b

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requested changes
- remove obsolete comments - use `pr_fmt` to clean kprintf - remove clang-format comments - `static` declarations - fix ignored return value warning
1 parent 7486076 commit 6821a2b

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1 file changed

+24
-24
lines changed

1 file changed

+24
-24
lines changed

‎examples/syscall-ftrace.c‎

Lines changed: 24 additions & 24 deletions
Original file line numberDiff line numberDiff line change
@@ -20,13 +20,15 @@
2020
#include <linux/sched.h>
2121
#include <linux/uaccess.h>
2222
#include <linux/slab.h>
23-
/** This is what we're using here. */
2423
#include <linux/ftrace.h>
2524

2625
MODULE_LICENSE("GPL");
2726

2827
#define MAX_FILENAME_SIZE 200
2928

29+
#undef pr_fmt
30+
#define pr_fmt(fmt) "[syscall-ftrace] " fmt
31+
3032
/* UID we want to spy on - will be filled from the command line. */
3133
static int uid = 0;
3234
module_param(uid, int, 0644);
@@ -48,14 +50,12 @@ typedef struct ftrace_hook {
4850
struct ftrace_ops ops; // ftrace structure
4951
} ftrace_hook_t;
5052

51-
// clang-format off
52-
#define PREPARE_HOOK(_nr, _hook, _orig) \
53-
{ \
54-
.nr = (_nr), .new = (_hook), .orig = (_orig) \
53+
#define PREPARE_HOOK(_nr, _hook, _orig) \
54+
{ \
55+
.nr = (_nr), .new = (_hook), .orig = (_orig) \
5556
}
5657

57-
unsigned long **sys_call_table;
58-
// clang-format on
58+
static unsigned long **sys_call_table;
5959

6060
/**
6161
* For the sake of simplicity, only the kprobe method is included.
@@ -71,19 +71,19 @@ static int resolve_address(ftrace_hook_t *hook)
7171
unregister_kprobe(&kp);
7272

7373
if (kallsyms_lookup_name)
74-
pr_info("[syscall-ftrace] kallsyms_lookup_name is found at 0x%lx\n",
74+
pr_info("kallsyms_lookup_name is found at 0x%lx\n",
7575
(unsigned long)kallsyms_lookup_name);
7676
else {
77-
pr_err("[syscall-ftrace] kallsyms_lookup_name is not found!\n");
77+
pr_err("kallsyms_lookup_name is not found!\n");
7878
return -1;
7979
}
8080

8181
sys_call_table = (unsigned long **)kallsyms_lookup_name("sys_call_table");
8282
if (sys_call_table)
83-
pr_info("[syscall-ftrace] sys_call_table is found at 0x%lx\n",
83+
pr_info("sys_call_table is found at 0x%lx\n",
8484
(unsigned long)sys_call_table);
8585
else {
86-
pr_err("[syscall-ftrace] sys_call_table is not found!\n");
86+
pr_err("sys_call_table is not found!\n");
8787
return -1;
8888
}
8989

@@ -127,7 +127,7 @@ static void notrace ftrace_thunk(unsigned long ip, unsigned long parent_ip,
127127

128128
#endif /** Version >= v5.11 */
129129

130-
int install_hook(ftrace_hook_t *hook)
130+
staticint install_hook(ftrace_hook_t *hook)
131131
{
132132
int err;
133133
err = resolve_address(hook);
@@ -141,38 +141,38 @@ int install_hook(ftrace_hook_t *hook)
141141
/** Only sys_openat should be traced */
142142
err = ftrace_set_filter_ip(&hook->ops, hook->address, 0, 0);
143143
if (err) {
144-
pr_err("[syscall-ftrace] ftrace_set_filter_ip() failed: %d\n", err);
144+
pr_err("ftrace_set_filter_ip() failed: %d\n", err);
145145
return err;
146146
}
147147

148148
err = register_ftrace_function(&hook->ops);
149149
if (err) {
150-
pr_err("[syscall-ftrace] register_ftrace_function() failed: %d\n", err);
150+
pr_err("register_ftrace_function() failed: %d\n", err);
151151
return err;
152152
}
153153

154154
return 0;
155155
}
156156

157-
void remove_hook(ftrace_hook_t *hook)
157+
staticvoid remove_hook(ftrace_hook_t *hook)
158158
{
159159
int err;
160160
err = unregister_ftrace_function(&hook->ops);
161161
if (err)
162-
pr_err("[syscall-ftrace] unregister_ftrace_function() failed: %d\n",
163-
err);
162+
pr_err("unregister_ftrace_function() failed: %d\n", err);
164163

165164
/** Disable the trace by setting remove to 1 */
166165
err = ftrace_set_filter_ip(&hook->ops, hook->address, 1, 0);
167166
if (err)
168-
pr_err("[syscall-ftrace] ftrace_set_filter_ip() failed: %d\n", err);
167+
pr_err("ftrace_set_filter_ip() failed: %d\n", err);
169168
}
170169

171170
/** For some reason the kernel segfaults when the parameters are expanded. */
172171
static asmlinkage long (*original_call)(struct pt_regs *regs);
173172
static asmlinkage long our_sys_openat(struct pt_regs *regs)
174173
{
175174
char *kfilename;
175+
int errcode = 0;
176176
if (current->cred->uid.val != uid)
177177
return original_call(regs);
178178
kfilename = kmalloc(GFP_KERNEL, MAX_FILENAME_SIZE * sizeof(char));
@@ -186,14 +186,14 @@ static asmlinkage long our_sys_openat(struct pt_regs *regs)
186186
* Change regs->si to appropriate registers
187187
* if you are trying on different architecture.
188188
*/
189-
// clang-format off
190-
if (copy_from_user(kfilename, (char __user *)regs->si, MAX_FILENAME_SIZE) < 0) {
189+
errcode =
190+
copy_from_user(kfilename, (char __user *)regs->si, MAX_FILENAME_SIZE);
191+
if (errcode < 0) {
191192
kfree(kfilename);
192193
return original_call(regs);
193194
}
194-
// clang-format on
195195

196-
pr_info("[syscall-ftrace] File opened by UID %d: %s\n", uid, kfilename);
196+
pr_info("File opened by UID %d: %s\n", uid, kfilename);
197197
kfree(kfilename);
198198

199199
return original_call(regs);
@@ -208,14 +208,14 @@ static int __init syscall_ftrace_start(void)
208208
err = install_hook(&sys_openat_hook);
209209
if (err)
210210
return err;
211-
pr_info("[syscall-ftrace] hooked, spying on uid %d\n", uid);
211+
pr_info("hooked, spying on uid %d\n", uid);
212212
return 0;
213213
}
214214

215215
static void __exit syscall_ftrace_end(void)
216216
{
217217
remove_hook(&sys_openat_hook);
218-
pr_info("[syscall-ftrace] removed\n");
218+
pr_info("removed\n");
219219
}
220220

221221
module_init(syscall_ftrace_start);

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