[bpf-next v3 5/6] samples/bpf: use BPF_KSYSCALL macro in syscall tracing programs

Daniel T. Lee
2022-12-24T07:16:10Z

This commit enhances the syscall tracing programs by using the
BPF_SYSCALL macro to reduce the inconvenience of parsing arguments from
pt_regs. By simplifying argument extraction, bpf program will become
clear to understand.

Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
---
samples/bpf/map_perf_test.bpf.c | 26 ++++++++-----------
.../bpf/test_current_task_under_cgroup.bpf.c | 4 ++-
samples/bpf/test_probe_write_user.bpf.c | 12 ++++-----
3 files changed, 19 insertions(+), 23 deletions(-)

diff --git a/samples/bpf/map_perf_test.bpf.c b/samples/bpf/map_perf_test.bpf.c
index 0c7885057ffe..3cdeba2afe12 100644
--- a/samples/bpf/map_perf_test.bpf.c
+++ b/samples/bpf/map_perf_test.bpf.c
@@ -101,7 +101,7 @@ struct {
} lru_hash_lookup_map SEC(".maps");

SEC("ksyscall/getuid")
-int stress_hmap(struct pt_regs *ctx)
+int BPF_KSYSCALL(stress_hmap)
{
u32 key = bpf_get_current_pid_tgid();
long init_val = 1;
@@ -119,7 +119,7 @@ int stress_hmap(struct pt_regs *ctx)
}

SEC("ksyscall/geteuid")
-int stress_percpu_hmap(struct pt_regs *ctx)
+int BPF_KSYSCALL(stress_percpu_hmap)
{
u32 key = bpf_get_current_pid_tgid();
long init_val = 1;
@@ -136,7 +136,7 @@ int stress_percpu_hmap(struct pt_regs *ctx)
}

SEC("ksyscall/getgid")
-int stress_hmap_alloc(struct pt_regs *ctx)
+int BPF_KSYSCALL(stress_hmap_alloc)
{
u32 key = bpf_get_current_pid_tgid();
long init_val = 1;
@@ -153,7 +153,7 @@ int stress_hmap_alloc(struct pt_regs *ctx)
}

SEC("ksyscall/getegid")
-int stress_percpu_hmap_alloc(struct pt_regs *ctx)
+int BPF_KSYSCALL(stress_percpu_hmap_alloc)
{
u32 key = bpf_get_current_pid_tgid();
long init_val = 1;
@@ -168,11 +168,10 @@ int stress_percpu_hmap_alloc(struct pt_regs *ctx)
}
return 0;
}
-
SEC("ksyscall/connect")
-int stress_lru_hmap_alloc(struct pt_regs *ctx)
+int BPF_KSYSCALL(stress_lru_hmap_alloc, int fd, struct sockaddr_in *uservaddr,
+ int addrlen)
{
- struct pt_regs *real_regs = (struct pt_regs *)PT_REGS_PARM1_CORE(ctx);
char fmt[] = "Failed at stress_lru_hmap_alloc. ret:%dn";
union {
u16 dst6[8];
@@ -185,14 +184,11 @@ int stress_lru_hmap_alloc(struct pt_regs *ctx)
u32 key;
};
} test_params;
- struct sockaddr_in6 *in6;
+ struct sockaddr_in6 *in6 = (struct sockaddr_in6 *)uservaddr;
u16 test_case;
- int addrlen, ret;
long val = 1;
u32 key = 0;
-
- in6 = (struct sockaddr_in6 *)PT_REGS_PARM2_CORE(real_regs);
- addrlen = (int)PT_REGS_PARM3_CORE(real_regs);
+ int ret;

if (addrlen != sizeof(*in6))
return 0;
@@ -250,7 +246,7 @@ int stress_lru_hmap_alloc(struct pt_regs *ctx)
}

SEC("ksyscall/gettid")
-int stress_lpm_trie_map_alloc(struct pt_regs *ctx)
+int BPF_KSYSCALL(stress_lpm_trie_map_alloc)
{
union {
u32 b32[2];
@@ -272,7 +268,7 @@ int stress_lpm_trie_map_alloc(struct pt_regs *ctx)
}

SEC("ksyscall/getpgid")
-int stress_hash_map_lookup(struct pt_regs *ctx)
+int BPF_KSYSCALL(stress_hash_map_lookup)
{
u32 key = 1, i;
long *value;
@@ -285,7 +281,7 @@ int stress_hash_map_lookup(struct pt_regs *ctx)
}

SEC("ksyscall/getppid")
-int stress_array_map_lookup(struct pt_regs *ctx)
+int BPF_KSYSCALL(stress_array_map_lookup)
{
u32 key = 1, i;
long *value;
diff --git a/samples/bpf/test_current_task_under_cgroup.bpf.c b/samples/bpf/test_current_task_under_cgroup.bpf.c
index 0b059cee3cba..58b9cf7ed659 100644
--- a/samples/bpf/test_current_task_under_cgroup.bpf.c
+++ b/samples/bpf/test_current_task_under_cgroup.bpf.c
@@ -8,6 +8,8 @@
#include "vmlinux.h"
#include <linux/version.h>
#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_core_read.h>

struct {
__uint(type, BPF_MAP_TYPE_CGROUP_ARRAY);
@@ -25,7 +27,7 @@ struct {

/* Writes the last PID that called sync to a map at index 0 */
SEC("ksyscall/sync")
-int bpf_prog1(struct pt_regs *ctx)
+int BPF_KSYSCALL(bpf_prog1)
{
u64 pid = bpf_get_current_pid_tgid();
int idx = 0;
diff --git a/samples/bpf/test_probe_write_user.bpf.c b/samples/bpf/test_probe_write_user.bpf.c
index a0f10c5ca273..a4f3798b7fb0 100644
--- a/samples/bpf/test_probe_write_user.bpf.c
+++ b/samples/bpf/test_probe_write_user.bpf.c
@@ -27,24 +27,22 @@ struct {
* of course, across platforms, and over time, the ABI may change.
*/
SEC("ksyscall/connect")
-int bpf_prog1(struct pt_regs *ctx)
+int BPF_KSYSCALL(bpf_prog1, int fd, struct sockaddr_in *uservaddr,
+ int addrlen)
{
- struct pt_regs *real_regs = (struct pt_regs *)PT_REGS_PARM1_CORE(ctx);
- void *sockaddr_arg = (void *)PT_REGS_PARM2_CORE(real_regs);
- int sockaddr_len = (int)PT_REGS_PARM3_CORE(real_regs);
struct sockaddr_in new_addr, orig_addr = {};
struct sockaddr_in *mapped_addr;

- if (sockaddr_len > sizeof(orig_addr))
+ if (addrlen > sizeof(orig_addr))
return 0;

- if (bpf_probe_read_user(&orig_addr, sizeof(orig_addr), sockaddr_arg) != 0)
+ if (bpf_probe_read_user(&orig_addr, sizeof(orig_addr), uservaddr) != 0)
return 0;

mapped_addr = bpf_map_lookup_elem(&dnat_map, &orig_addr);
if (mapped_addr != NULL) {
memcpy(&new_addr, mapped_addr, sizeof(new_addr));
- bpf_probe_write_user(sockaddr_arg, &new_addr,
+ bpf_probe_write_user(uservaddr, &new_addr,
sizeof(new_addr));
}
return 0;
--
2.34.1