Merge branch 'Fix accessing syscall arguments'

Ilya Leoshkevich says:

====================

libbpf now has macros to access syscall arguments in an
architecture-agnostic manner, but unfortunately they have a number of
issues on non-Intel arches, which this series aims to fix.

v1: https://lore.kernel.org/bpf/20220201234200.1836443-1-iii@linux.ibm.com/
v1 -> v2:
* Put orig_gpr2 in place of args[1] on s390 (Vasily).
* Fix arm64, powerpc and riscv (Heiko).

v2: https://lore.kernel.org/bpf/20220204041955.1958263-1-iii@linux.ibm.com/
v2 -> v3:
* Undo args[1] change (Andrii).
* Rename PT_REGS_SYSCALL to PT_REGS_SYSCALL_REGS (Andrii).
* Split the riscv patch (Andrii).

v3: https://lore.kernel.org/bpf/20220204145018.1983773-1-iii@linux.ibm.com/
v3 -> v4:
* Undo arm64's and s390's user_pt_regs changes.
* Use struct pt_regs when vmlinux.h is available (Andrii).
* Use offsetofend for accessing orig_gpr2 and orig_x0 (Andrii).
* Move libbpf's copy of offsetofend to a new header.
* Fix riscv's __PT_FP_REG.
* Use PT_REGS_SYSCALL_REGS in test_probe_user.c.
* Test bpf_syscall_macro with userspace headers.
* Use Naveen's suggestions and code in patches 5 and 6.
* Add warnings to arm64's and s390's ptrace.h (Andrii).

v4: https://lore.kernel.org/bpf/20220208051635.2160304-1-iii@linux.ibm.com/
v4 -> v5:
* Go back to v3.
* Do not touch arch headers.
* Use CO-RE struct flavors to access orig_x0 and orig_gpr2.
* Fail compilation if non-CO-RE macros are used to access the first
  syscall parameter on arm64 and s390.
* Fix accessing frame pointer on riscv.
====================

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

2 files changed, 11 insertions, 2 deletions

diff --git a/tools/testing/selftests/bpf/prog_tests/test_bpf_syscall_macro.c b/tools/testing/selftests/bpf/prog_tests/test_bpf_syscall_macro.c
index f5f4c8adf539..8bc58bda500d 100644
--- a/tools/testing/selftests/bpf/prog_tests/test_bpf_syscall_macro.c
+++ b/tools/testing/selftests/bpf/prog_tests/test_bpf_syscall_macro.c
@@ -33,7 +33,11 @@ void test_bpf_syscall_macro(void)
 
 	/* check whether args of syscall are copied correctly */
 	prctl(exp_arg1, exp_arg2, exp_arg3, exp_arg4, exp_arg5);
+#if defined(__aarch64__) || defined(__s390__)
+	ASSERT_NEQ(skel->bss->arg1, exp_arg1, "syscall_arg1");
+#else
 	ASSERT_EQ(skel->bss->arg1, exp_arg1, "syscall_arg1");
+#endif
 	ASSERT_EQ(skel->bss->arg2, exp_arg2, "syscall_arg2");
 	ASSERT_EQ(skel->bss->arg3, exp_arg3, "syscall_arg3");
 	/* it cannot copy arg4 when uses PT_REGS_PARM4 on x86_64 */
diff --git a/tools/testing/selftests/bpf/progs/bpf_syscall_macro.c b/tools/testing/selftests/bpf/progs/bpf_syscall_macro.c
index c8e60220cda8..496e54d0ac22 100644
--- a/tools/testing/selftests/bpf/progs/bpf_syscall_macro.c
+++ b/tools/testing/selftests/bpf/progs/bpf_syscall_macro.c
@@ -28,14 +28,19 @@ int BPF_KPROBE(handle_sys_prctl)
 {
 	struct pt_regs *real_regs;
 	pid_t pid = bpf_get_current_pid_tgid() >> 32;
+	unsigned long tmp = 0;
 
 	if (pid != filter_pid)
 		return 0;
 
-	real_regs = (struct pt_regs *)PT_REGS_PARM1(ctx);
+	real_regs = PT_REGS_SYSCALL_REGS(ctx);
 
 	/* test for PT_REGS_PARM */
-	bpf_probe_read_kernel(&arg1, sizeof(arg1), &PT_REGS_PARM1_SYSCALL(real_regs));
+
+#if !defined(bpf_target_arm64) && !defined(bpf_target_s390)
+	bpf_probe_read_kernel(&tmp, sizeof(tmp), &PT_REGS_PARM1_SYSCALL(real_regs));
+#endif
+	arg1 = tmp;
 	bpf_probe_read_kernel(&arg2, sizeof(arg2), &PT_REGS_PARM2_SYSCALL(real_regs));
 	bpf_probe_read_kernel(&arg3, sizeof(arg3), &PT_REGS_PARM3_SYSCALL(real_regs));
 	bpf_probe_read_kernel(&arg4_cx, sizeof(arg4_cx), &PT_REGS_PARM4(real_regs));