samples/bpf: Enable powerpc support

Add the necessary definitions for building bpf samples on ppc.

Since ppc doesn't store function return address on the stack, modify how
PT_REGS_RET() and PT_REGS_FP() work.

Also, introduce PT_REGS_IP() to access the instruction pointer.

Cc: Alexei Starovoitov <ast@fb.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: David S. Miller <davem@davemloft.net>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

samples/bpf/bpf_helpers.h

@@ -82,6 +82,7 @@ static int (*bpf_l4_csum_replace)(void *ctx, int off, int from, int to, int flag
 #define PT_REGS_FP(x) ((x)->bp)
 #define PT_REGS_RC(x) ((x)->ax)
 #define PT_REGS_SP(x) ((x)->sp)
+#define PT_REGS_IP(x) ((x)->ip)
 
 #elif defined(__s390x__)
 
@@ -94,6 +95,7 @@ static int (*bpf_l4_csum_replace)(void *ctx, int off, int from, int to, int flag
 #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])
+#define PT_REGS_IP(x) ((x)->ip)
 
 #elif defined(__aarch64__)
 
@@ -106,6 +108,30 @@ static int (*bpf_l4_csum_replace)(void *ctx, int off, int from, int to, int flag
 #define PT_REGS_FP(x) ((x)->regs[29]) /* Works only with CONFIG_FRAME_POINTER */
 #define PT_REGS_RC(x) ((x)->regs[0])
 #define PT_REGS_SP(x) ((x)->sp)
+#define PT_REGS_IP(x) ((x)->pc)
+
+#elif defined(__powerpc__)
+
+#define PT_REGS_PARM1(x) ((x)->gpr[3])
+#define PT_REGS_PARM2(x) ((x)->gpr[4])
+#define PT_REGS_PARM3(x) ((x)->gpr[5])
+#define PT_REGS_PARM4(x) ((x)->gpr[6])
+#define PT_REGS_PARM5(x) ((x)->gpr[7])
+#define PT_REGS_RC(x) ((x)->gpr[3])
+#define PT_REGS_SP(x) ((x)->sp)
+#define PT_REGS_IP(x) ((x)->nip)
 
 #endif
+
+#ifdef __powerpc__
+#define BPF_KPROBE_READ_RET_IP(ip, ctx)		({ (ip) = (ctx)->link; })
+#define BPF_KRETPROBE_READ_RET_IP		BPF_KPROBE_READ_RET_IP
+#else
+#define BPF_KPROBE_READ_RET_IP(ip, ctx)		({				\
+		bpf_probe_read(&(ip), sizeof(ip), (void *)PT_REGS_RET(ctx)); })
+#define BPF_KRETPROBE_READ_RET_IP(ip, ctx)	({				\
+		bpf_probe_read(&(ip), sizeof(ip),				\
+				(void *)(PT_REGS_FP(ctx) + sizeof(ip))); })
+#endif
+
 #endif

samples/bpf/spintest_kern.c

@@ -34,7 +34,7 @@ struct bpf_map_def SEC("maps") stackmap = {
 #define PROG(foo) \
 int foo(struct pt_regs *ctx) \
 { \
-	long v = ctx->ip, *val; \
+	long v = PT_REGS_IP(ctx), *val; \
 \
 	val = bpf_map_lookup_elem(&my_map, &v); \
 	bpf_map_update_elem(&my_map, &v, &v, BPF_ANY); \

samples/bpf/tracex2_kern.c

@@ -27,10 +27,10 @@ int bpf_prog2(struct pt_regs *ctx)
 	long init_val = 1;
 	long *value;
 
-	/* x64/s390x specific: read ip of kfree_skb caller.
+	/* read ip of kfree_skb caller.
 	 * non-portable version of __builtin_return_address(0)
 	 */
-	bpf_probe_read(&loc, sizeof(loc), (void *)PT_REGS_RET(ctx));
+	BPF_KPROBE_READ_RET_IP(loc, ctx);
 
 	value = bpf_map_lookup_elem(&my_map, &loc);
 	if (value)

samples/bpf/tracex4_kern.c

@@ -40,7 +40,7 @@ int bpf_prog2(struct pt_regs *ctx)
 	long ip = 0;
 
 	/* get ip address of kmem_cache_alloc_node() caller */
-	bpf_probe_read(&ip, sizeof(ip), (void *)(PT_REGS_FP(ctx) + sizeof(ip)));
+	BPF_KRETPROBE_READ_RET_IP(ip, ctx);
 
 	struct pair v = {
 		.val = bpf_ktime_get_ns(),