[PATCH v2 bpf-next 3/4] selftests/bpf: make PT_REGS_* work in userspace

[Ilya Leoshkevich <iii@linux.ibm.com>]

Right now, at least on s390 and x86_64, these macros are usable only
with kernel headers. This patch makes it possible to use them with
userspace headers and, as a consequence, in BPF selftests.

On s390, provide the forward declaration of struct pt_regs and cast it
to user_pt_regs in PT_REGS_* macros. This is necessary, because instead
of the full struct pt_regs, s390 exposes only its first member
user_pt_regs to userspace, and bpf_helpers.h is used with both userspace
(in selftests) and kernel (in samples) headers. It was added in commit
466698e654e8 ("s390/bpf: correct broken uapi for
BPF_PROG_TYPE_PERF_EVENT program type").

On x86, provide userspace versions of PT_REGS_* macros. Unlike s390, x86
provides struct pt_regs to both userspace and kernel, however, with
different member names.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 tools/testing/selftests/bpf/bpf_helpers.h | 36 ++++++++++++++++-------
 1 file changed, 26 insertions(+), 10 deletions(-)

diff --git a/tools/testing/selftests/bpf/bpf_helpers.h b/tools/testing/selftests/bpf/bpf_helpers.h
index 622dc4af0c65..faf86d83301a 100644
--- a/tools/testing/selftests/bpf/bpf_helpers.h
+++ b/tools/testing/selftests/bpf/bpf_helpers.h
@@ -355,6 +355,7 @@ static int (*bpf_skb_adjust_room)(void *ctx, __s32 len_diff, __u32 mode,
 
 #if defined(bpf_target_x86)
 
+#ifdef __KERNEL__
 #define PT_REGS_PARM1(x) ((x)->di)
 #define PT_REGS_PARM2(x) ((x)->si)
 #define PT_REGS_PARM3(x) ((x)->dx)
@@ -365,19 +366,34 @@ static int (*bpf_skb_adjust_room)(void *ctx, __s32 len_diff, __u32 mode,
 #define PT_REGS_RC(x) ((x)->ax)
 #define PT_REGS_SP(x) ((x)->sp)
 #define PT_REGS_IP(x) ((x)->ip)
+#else
+#define PT_REGS_PARM1(x) ((x)->rdi)
+#define PT_REGS_PARM2(x) ((x)->rsi)
+#define PT_REGS_PARM3(x) ((x)->rdx)
+#define PT_REGS_PARM4(x) ((x)->rcx)
+#define PT_REGS_PARM5(x) ((x)->r8)
+#define PT_REGS_RET(x) ((x)->rsp)
+#define PT_REGS_FP(x) ((x)->rbp)
+#define PT_REGS_RC(x) ((x)->rax)
+#define PT_REGS_SP(x) ((x)->rsp)
+#define PT_REGS_IP(x) ((x)->rip)
+#endif
 
 #elif defined(bpf_target_s390)
 
-#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])
-#define PT_REGS_IP(x) ((x)->psw.addr)
+/* s390 provides user_pt_regs instead of struct pt_regs to userspace */
+struct pt_regs;
+#define PT_REGS_PARM1(x) (((const volatile user_pt_regs *)(x))->gprs[2])
+#define PT_REGS_PARM2(x) (((const volatile user_pt_regs *)(x))->gprs[3])
+#define PT_REGS_PARM3(x) (((const volatile user_pt_regs *)(x))->gprs[4])
+#define PT_REGS_PARM4(x) (((const volatile user_pt_regs *)(x))->gprs[5])
+#define PT_REGS_PARM5(x) (((const volatile user_pt_regs *)(x))->gprs[6])
+#define PT_REGS_RET(x) (((const volatile user_pt_regs *)(x))->gprs[14])
+/* Works only with CONFIG_FRAME_POINTER */
+#define PT_REGS_FP(x) (((const volatile user_pt_regs *)(x))->gprs[11])
+#define PT_REGS_RC(x) (((const volatile user_pt_regs *)(x))->gprs[2])
+#define PT_REGS_SP(x) (((const volatile user_pt_regs *)(x))->gprs[15])
+#define PT_REGS_IP(x) (((const volatile user_pt_regs *)(x))->psw.addr)
 
 #elif defined(bpf_target_arm)
 
-- 
2.21.0