samples: bpf: enable trace samples for s390x

The trace bpf samples do not compile on s390x because they use x86
specific fields from the "pt_regs" structure.

Fix this and access the fields via new PT_REGS macros.
Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Acked-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

samples/bpf/bpf_helpers.h

@@ -60,4 +60,29 @@ static int (*bpf_l3_csum_replace)(void *ctx, int off, int from, int to, int flag
 static int (*bpf_l4_csum_replace)(void *ctx, int off, int from, int to, int flags) =
 	(void *) BPF_FUNC_l4_csum_replace;
 
+#if defined(__x86_64__)
+
+#define PT_REGS_PARM1(x) ((x)->di)
+#define PT_REGS_PARM2(x) ((x)->si)
+#define PT_REGS_PARM3(x) ((x)->dx)
+#define PT_REGS_PARM4(x) ((x)->cx)
+#define PT_REGS_PARM5(x) ((x)->r8)
+#define PT_REGS_RET(x) ((x)->sp)
+#define PT_REGS_FP(x) ((x)->bp)
+#define PT_REGS_RC(x) ((x)->ax)
+#define PT_REGS_SP(x) ((x)->sp)
+
+#elif defined(__s390x__)
+
+#define PT_REGS_PARM1(x) ((x)->gprs[2])
+#define PT_REGS_PARM2(x) ((x)->gprs[3])
+#define PT_REGS_PARM3(x) ((x)->gprs[4])
+#define PT_REGS_PARM4(x) ((x)->gprs[5])
+#define PT_REGS_PARM5(x) ((x)->gprs[6])
+#define PT_REGS_RET(x) ((x)->gprs[14])
+#define PT_REGS_FP(x) ((x)->gprs[11]) /* Works only with CONFIG_FRAME_POINTER */
+#define PT_REGS_RC(x) ((x)->gprs[2])
+#define PT_REGS_SP(x) ((x)->gprs[15])
+
+#endif
 #endif

samples/bpf/tracex1_kern.c

@@ -29,7 +29,7 @@ int bpf_prog1(struct pt_regs *ctx)
 	int len;
 
 	/* non-portable! works for the given kernel only */
-	skb = (struct sk_buff *) ctx->di;
+	skb = (struct sk_buff *) PT_REGS_PARM1(ctx);
 
 	dev = _(skb->dev);
 

samples/bpf/tracex2_kern.c

@@ -27,10 +27,10 @@ int bpf_prog2(struct pt_regs *ctx)
 	long init_val = 1;
 	long *value;
 
-	/* x64 specific: read ip of kfree_skb caller.
+	/* x64/s390x specific: read ip of kfree_skb caller.
 	 * non-portable version of __builtin_return_address(0)
 	 */
-	bpf_probe_read(&loc, sizeof(loc), (void *)ctx->sp);
+	bpf_probe_read(&loc, sizeof(loc), (void *)PT_REGS_RET(ctx));
 
 	value = bpf_map_lookup_elem(&my_map, &loc);
 	if (value)
@@ -79,7 +79,7 @@ struct bpf_map_def SEC("maps") my_hist_map = {
 SEC("kprobe/sys_write")
 int bpf_prog3(struct pt_regs *ctx)
 {
-	long write_size = ctx->dx; /* arg3 */
+	long write_size = PT_REGS_PARM3(ctx);
 	long init_val = 1;
 	long *value;
 	struct hist_key key = {};

samples/bpf/tracex3_kern.c

@@ -23,7 +23,7 @@ struct bpf_map_def SEC("maps") my_map = {
 SEC("kprobe/blk_mq_start_request")
 int bpf_prog1(struct pt_regs *ctx)
 {
-	long rq = ctx->di;
+	long rq = PT_REGS_PARM1(ctx);
 	u64 val = bpf_ktime_get_ns();
 
 	bpf_map_update_elem(&my_map, &rq, &val, BPF_ANY);
@@ -51,7 +51,7 @@ struct bpf_map_def SEC("maps") lat_map = {
 SEC("kprobe/blk_update_request")
 int bpf_prog2(struct pt_regs *ctx)
 {
-	long rq = ctx->di;
+	long rq = PT_REGS_PARM1(ctx);
 	u64 *value, l, base;
 	u32 index;
 

samples/bpf/tracex4_kern.c

@@ -27,7 +27,7 @@ struct bpf_map_def SEC("maps") my_map = {
 SEC("kprobe/kmem_cache_free")
 int bpf_prog1(struct pt_regs *ctx)
 {
-	long ptr = ctx->si;
+	long ptr = PT_REGS_PARM2(ctx);
 
 	bpf_map_delete_elem(&my_map, &ptr);
 	return 0;
@@ -36,11 +36,11 @@ int bpf_prog1(struct pt_regs *ctx)
 SEC("kretprobe/kmem_cache_alloc_node")
 int bpf_prog2(struct pt_regs *ctx)
 {
-	long ptr = ctx->ax;
+	long ptr = PT_REGS_RC(ctx);
 	long ip = 0;
 
 	/* get ip address of kmem_cache_alloc_node() caller */
-	bpf_probe_read(&ip, sizeof(ip), (void *)(ctx->bp + sizeof(ip)));
+	bpf_probe_read(&ip, sizeof(ip), (void *)(PT_REGS_FP(ctx) + sizeof(ip)));
 
 	struct pair v = {
 		.val = bpf_ktime_get_ns(),

samples/bpf/tracex5_kern.c

@@ -24,7 +24,7 @@ int bpf_prog1(struct pt_regs *ctx)
 {
 	struct seccomp_data sd = {};
 
-	bpf_probe_read(&sd, sizeof(sd), (void *)ctx->di);
+	bpf_probe_read(&sd, sizeof(sd), (void *)PT_REGS_PARM1(ctx));
 
 	/* dispatch into next BPF program depending on syscall number */
 	bpf_tail_call(ctx, &progs, sd.nr);
@@ -42,7 +42,7 @@ PROG(__NR_write)(struct pt_regs *ctx)
 {
 	struct seccomp_data sd = {};
 
-	bpf_probe_read(&sd, sizeof(sd), (void *)ctx->di);
+	bpf_probe_read(&sd, sizeof(sd), (void *)PT_REGS_PARM1(ctx));
 	if (sd.args[2] == 512) {
 		char fmt[] = "write(fd=%d, buf=%p, size=%d)\n";
 		bpf_trace_printk(fmt, sizeof(fmt),
@@ -55,7 +55,7 @@ PROG(__NR_read)(struct pt_regs *ctx)
 {
 	struct seccomp_data sd = {};
 
-	bpf_probe_read(&sd, sizeof(sd), (void *)ctx->di);
+	bpf_probe_read(&sd, sizeof(sd), (void *)PT_REGS_PARM1(ctx));
 	if (sd.args[2] > 128 && sd.args[2] <= 1024) {
 		char fmt[] = "read(fd=%d, buf=%p, size=%d)\n";
 		bpf_trace_printk(fmt, sizeof(fmt),