selftests/bpf: Fix an endianness issue in bpf_syscall_macro test

bpf_syscall_macro reads a long argument into an int variable, which
produces a wrong value on big-endian systems. Fix by reading the
argument into an intermediate long variable first.

Fixes: 77fc0330dfe5 ("selftests/bpf: Add a test to confirm PT_REGS_PARM4_SYSCALL")
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220209021745.2215452-2-iii@linux.ibm.com

diff --git a/tools/testing/selftests/bpf/progs/bpf_syscall_macro.c b/tools/testing/selftests/bpf/progs/bpf_syscall_macro.c
index c8e60220cda855ed62bd09f8b978533bbf4f2931..f5c6ef2ff6d18867ed20c213792373f6426d0ebd 100644 (file)
--- a/tools/testing/selftests/bpf/progs/bpf_syscall_macro.c
+++ b/tools/testing/selftests/bpf/progs/bpf_syscall_macro.c
@@ -28,6 +28,7 @@ int BPF_KPROBE(handle_sys_prctl)
 {
        struct pt_regs *real_regs;
        pid_t pid = bpf_get_current_pid_tgid() >> 32;
+       unsigned long tmp;
 
        if (pid != filter_pid)
                return 0;
@@ -35,7 +36,9 @@ int BPF_KPROBE(handle_sys_prctl)
        real_regs = (struct pt_regs *)PT_REGS_PARM1(ctx);
 
        /* test for PT_REGS_PARM */
-       bpf_probe_read_kernel(&arg1, sizeof(arg1), &PT_REGS_PARM1_SYSCALL(real_regs));
+
+       bpf_probe_read_kernel(&tmp, sizeof(tmp), &PT_REGS_PARM1_SYSCALL(real_regs));
+       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));