[PATCH bpf-next] selftests/bpf: Fix build of task_pt_regs tests for arm64

[Jean-Philippe Brucker <jean-philippe@linaro.org>]

struct pt_regs is not exported to userspace on all archs. arm64 and s390
export "user_pt_regs" instead, which causes build failure at the moment:

  progs/test_task_pt_regs.c:8:16: error: variable has incomplete type 'struct pt_regs'
  struct pt_regs current_regs = {};

Use the multi-arch macros defined by tools/lib/bpf/bpf_tracing.h to copy
the pt_regs into a locally-defined struct.

Copying the user_pt_regs struct on arm64 wouldn't work because the
struct is too large and the compiler complains about using too much
stack.

Fixes: 576d47bb1a92 ("bpf: selftests: Add bpf_task_pt_regs() selftest")
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
---
 .../selftests/bpf/bpf_pt_regs_helpers.h       | 30 +++++++++++++++++++
 .../selftests/bpf/prog_tests/task_pt_regs.c   |  1 +
 .../selftests/bpf/progs/test_task_pt_regs.c   | 10 ++++---
 3 files changed, 37 insertions(+), 4 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/bpf_pt_regs_helpers.h

diff --git a/tools/testing/selftests/bpf/bpf_pt_regs_helpers.h b/tools/testing/selftests/bpf/bpf_pt_regs_helpers.h
new file mode 100644
index 000000000000..7531f4824ead
--- /dev/null
+++ b/tools/testing/selftests/bpf/bpf_pt_regs_helpers.h
@@ -0,0 +1,30 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __BPF_PT_REGS_HELPERS
+#define __BPF_PT_REGS_HELPERS
+
+#include <bpf/bpf_tracing.h>
+
+struct bpf_pt_regs {
+	unsigned long long parm[5];
+	unsigned long long ret;
+	unsigned long long fp;
+	unsigned long long rc;
+	unsigned long long sp;
+	unsigned long long ip;
+};
+
+static inline void bpf_copy_pt_regs(struct bpf_pt_regs *dest, struct pt_regs *src)
+{
+	dest->parm[0]	= PT_REGS_PARM1(src);
+	dest->parm[1]	= PT_REGS_PARM2(src);
+	dest->parm[2]	= PT_REGS_PARM3(src);
+	dest->parm[3]	= PT_REGS_PARM4(src);
+	dest->parm[4]	= PT_REGS_PARM5(src);
+	dest->ret	= PT_REGS_RET(src);
+	dest->fp	= PT_REGS_FP(src);
+	dest->rc	= PT_REGS_RC(src);
+	dest->sp	= PT_REGS_SP(src);
+	dest->ip	= PT_REGS_IP(src);
+}
+
+#endif /* __BPF_PT_REGS_HELPERS */
diff --git a/tools/testing/selftests/bpf/prog_tests/task_pt_regs.c b/tools/testing/selftests/bpf/prog_tests/task_pt_regs.c
index 53f0e0fa1a53..196453b75937 100644
--- a/tools/testing/selftests/bpf/prog_tests/task_pt_regs.c
+++ b/tools/testing/selftests/bpf/prog_tests/task_pt_regs.c
@@ -2,6 +2,7 @@
 #define _GNU_SOURCE
 #include <test_progs.h>
 #include <linux/ptrace.h>
+#include "bpf_pt_regs_helpers.h"
 #include "test_task_pt_regs.skel.h"
 
 void test_task_pt_regs(void)
diff --git a/tools/testing/selftests/bpf/progs/test_task_pt_regs.c b/tools/testing/selftests/bpf/progs/test_task_pt_regs.c
index 6c059f1cfa1b..348da3509093 100644
--- a/tools/testing/selftests/bpf/progs/test_task_pt_regs.c
+++ b/tools/testing/selftests/bpf/progs/test_task_pt_regs.c
@@ -5,8 +5,10 @@
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_tracing.h>
 
-struct pt_regs current_regs = {};
-struct pt_regs ctx_regs = {};
+#include "bpf_pt_regs_helpers.h"
+
+struct bpf_pt_regs current_regs = {};
+struct bpf_pt_regs ctx_regs = {};
 int uprobe_res = 0;
 
 SEC("uprobe/trigger_func")
@@ -17,8 +19,8 @@ int handle_uprobe(struct pt_regs *ctx)
 
 	current = bpf_get_current_task_btf();
 	regs = (struct pt_regs *) bpf_task_pt_regs(current);
-	__builtin_memcpy(&current_regs, regs, sizeof(*regs));
-	__builtin_memcpy(&ctx_regs, ctx, sizeof(*ctx));
+	bpf_copy_pt_regs(&current_regs, regs);
+	bpf_copy_pt_regs(&ctx_regs, ctx);
 
 	/* Prove that uprobe was run */
 	uprobe_res = 1;
-- 
2.33.0