[PATCH v5 0/3] Fix the incorrect register read for syscalls on x86_64

[PATCH v5 0/3] Fix the incorrect register read for syscalls on x86_64

[Kenta Tada]

Currently, rcx is read as the fourth parameter of syscall on x86_64.
But x86_64 Linux System Call convention uses r10 actually.
This commit adds the wrapper for users who want to access to
syscall params to analyze the user space.

Changelog:
----------
v1 -> v2:
- Rebase to current bpf-next
https://lore.kernel.org/bpf/20211222213924.1869758-1-andrii@kernel.org/

v2 -> v3:
- Modify the definition of SYSCALL macros for only targeted archs.
- Define __BPF_TARGET_MISSING variants for completeness.
- Remove CORE variants. These macros will not be used.
- Add a selftest.

v3 -> v4:
- Modify a selftest not to use serial tests.
- Modify a selftest to use ASSERT_EQ().
- Extract syscall wrapper for all the other tests.
- Add CORE variants.

v4 -> v5:
- Modify the CORE variant macro not to read memory directly.
- Remove the unnecessary comment.
- Add a selftest for the CORE variant.

Kenta Tada (3):
  libbpf: Extract syscall wrapper
  libbpf: Fix the incorrect register read for syscalls on x86_64
  libbpf: Add a test to confirm PT_REGS_PARM4_SYSCALL

 tools/lib/bpf/bpf_tracing.h                   | 34 ++++++++++
 .../bpf/prog_tests/test_bpf_syscall_macro.c   | 63 ++++++++++++++++++
 tools/testing/selftests/bpf/progs/bpf_misc.h  | 19 ++++++
 .../selftests/bpf/progs/bpf_syscall_macro.c   | 64 +++++++++++++++++++
 .../selftests/bpf/progs/test_probe_user.c     | 15 +----
 5 files changed, 181 insertions(+), 14 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/test_bpf_syscall_macro.c
 create mode 100644 tools/testing/selftests/bpf/progs/bpf_misc.h
 create mode 100644 tools/testing/selftests/bpf/progs/bpf_syscall_macro.c

-- 
2.32.0

[PATCH v5 1/3] libbpf: Extract syscall wrapper

[Kenta Tada]

Extract the helper to set up SYS_PREFIX for fentry and kprobe selftests
that use __x86_sys_* attach functions.

Signed-off-by: Kenta Tada <Kenta.Tada@sony.com>
Suggested-by: Andrii Nakryiko <andrii@kernel.org>
---
 tools/testing/selftests/bpf/progs/bpf_misc.h  | 19 +++++++++++++++++++
 .../selftests/bpf/progs/test_probe_user.c     | 15 +--------------
 2 files changed, 20 insertions(+), 14 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/progs/bpf_misc.h

diff --git a/tools/testing/selftests/bpf/progs/bpf_misc.h b/tools/testing/selftests/bpf/progs/bpf_misc.h
new file mode 100644
index 000000000000..0b78bc9b1b4c
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/bpf_misc.h
@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __BPF_MISC_H__
+#define __BPF_MISC_H__
+
+#if defined(__TARGET_ARCH_x86)
+#define SYSCALL_WRAPPER 1
+#define SYS_PREFIX "__x64_"
+#elif defined(__TARGET_ARCH_s390)
+#define SYSCALL_WRAPPER 1
+#define SYS_PREFIX "__s390x_"
+#elif defined(__TARGET_ARCH_arm64)
+#define SYSCALL_WRAPPER 1
+#define SYS_PREFIX "__arm64_"
+#else
+#define SYSCALL_WRAPPER 0
+#define SYS_PREFIX ""
+#endif
+
+#endif
diff --git a/tools/testing/selftests/bpf/progs/test_probe_user.c b/tools/testing/selftests/bpf/progs/test_probe_user.c
index 8812a90da4eb..702578a5e496 100644
--- a/tools/testing/selftests/bpf/progs/test_probe_user.c
+++ b/tools/testing/selftests/bpf/progs/test_probe_user.c
@@ -7,20 +7,7 @@
 
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_tracing.h>
-
-#if defined(__TARGET_ARCH_x86)
-#define SYSCALL_WRAPPER 1
-#define SYS_PREFIX "__x64_"
-#elif defined(__TARGET_ARCH_s390)
-#define SYSCALL_WRAPPER 1
-#define SYS_PREFIX "__s390x_"
-#elif defined(__TARGET_ARCH_arm64)
-#define SYSCALL_WRAPPER 1
-#define SYS_PREFIX "__arm64_"
-#else
-#define SYSCALL_WRAPPER 0
-#define SYS_PREFIX ""
-#endif
+#include "bpf_misc.h"
 
 static struct sockaddr_in old;
 
-- 
2.32.0

[PATCH v5 2/3] libbpf: Fix the incorrect register read for syscalls on x86_64

[Kenta Tada]

Currently, rcx is read as the fourth parameter of syscall on x86_64.
But x86_64 Linux System Call convention uses r10 actually.
This commit adds the wrapper for users who want to access to
syscall params to analyze the user space.

Signed-off-by: Kenta Tada <Kenta.Tada@sony.com>
---
 tools/lib/bpf/bpf_tracing.h | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/tools/lib/bpf/bpf_tracing.h b/tools/lib/bpf/bpf_tracing.h
index 90f56b0f585f..032ba809f3e5 100644
--- a/tools/lib/bpf/bpf_tracing.h
+++ b/tools/lib/bpf/bpf_tracing.h
@@ -70,6 +70,7 @@
 #define __PT_PARM2_REG si
 #define __PT_PARM3_REG dx
 #define __PT_PARM4_REG cx
+#define __PT_PARM4_REG_SYSCALL r10 /* syscall uses r10 */
 #define __PT_PARM5_REG r8
 #define __PT_RET_REG sp
 #define __PT_FP_REG bp
@@ -99,6 +100,7 @@
 #define __PT_PARM2_REG rsi
 #define __PT_PARM3_REG rdx
 #define __PT_PARM4_REG rcx
+#define __PT_PARM4_REG_SYSCALL r10 /* syscall uses r10 */
 #define __PT_PARM5_REG r8
 #define __PT_RET_REG rsp
 #define __PT_FP_REG rbp
@@ -263,6 +265,26 @@ struct pt_regs;
 
 #endif
 
+#define PT_REGS_PARM1_SYSCALL(x) PT_REGS_PARM1(x)
+#define PT_REGS_PARM2_SYSCALL(x) PT_REGS_PARM2(x)
+#define PT_REGS_PARM3_SYSCALL(x) PT_REGS_PARM3(x)
+#ifdef __PT_PARM4_REG_SYSCALL
+#define PT_REGS_PARM4_SYSCALL(x) (__PT_REGS_CAST(x)->__PT_PARM4_REG_SYSCALL)
+#else /* __PT_PARM4_REG_SYSCALL */
+#define PT_REGS_PARM4_SYSCALL(x) PT_REGS_PARM4(x)
+#endif
+#define PT_REGS_PARM5_SYSCALL(x) PT_REGS_PARM5(x)
+
+#define PT_REGS_PARM1_CORE_SYSCALL(x) PT_REGS_PARM1_CORE(x)
+#define PT_REGS_PARM2_CORE_SYSCALL(x) PT_REGS_PARM2_CORE(x)
+#define PT_REGS_PARM3_CORE_SYSCALL(x) PT_REGS_PARM3_CORE(x)
+#ifdef __PT_PARM4_REG_SYSCALL
+#define PT_REGS_PARM4_CORE_SYSCALL(x) BPF_CORE_READ(__PT_REGS_CAST(x), __PT_PARM4_REG_SYSCALL)
+#else /* __PT_PARM4_REG_SYSCALL */
+#define PT_REGS_PARM4_CORE_SYSCALL(x) PT_REGS_PARM4_CORE(x)
+#endif
+#define PT_REGS_PARM5_CORE_SYSCALL(x) PT_REGS_PARM5_CORE(x)
+
 #else /* defined(bpf_target_defined) */
 
 #define PT_REGS_PARM1(x) ({ _Pragma(__BPF_TARGET_MISSING); 0l; })
@@ -290,6 +312,18 @@ struct pt_regs;
 #define BPF_KPROBE_READ_RET_IP(ip, ctx) ({ _Pragma(__BPF_TARGET_MISSING); 0l; })
 #define BPF_KRETPROBE_READ_RET_IP(ip, ctx) ({ _Pragma(__BPF_TARGET_MISSING); 0l; })
 
+#define PT_REGS_PARM1_SYSCALL(x) ({ _Pragma(__BPF_TARGET_MISSING); 0l; })
+#define PT_REGS_PARM2_SYSCALL(x) ({ _Pragma(__BPF_TARGET_MISSING); 0l; })
+#define PT_REGS_PARM3_SYSCALL(x) ({ _Pragma(__BPF_TARGET_MISSING); 0l; })
+#define PT_REGS_PARM4_SYSCALL(x) ({ _Pragma(__BPF_TARGET_MISSING); 0l; })
+#define PT_REGS_PARM5_SYSCALL(x) ({ _Pragma(__BPF_TARGET_MISSING); 0l; })
+
+#define PT_REGS_PARM1_CORE_SYSCALL(x) ({ _Pragma(__BPF_TARGET_MISSING); 0l; })
+#define PT_REGS_PARM2_CORE_SYSCALL(x) ({ _Pragma(__BPF_TARGET_MISSING); 0l; })
+#define PT_REGS_PARM3_CORE_SYSCALL(x) ({ _Pragma(__BPF_TARGET_MISSING); 0l; })
+#define PT_REGS_PARM4_CORE_SYSCALL(x) ({ _Pragma(__BPF_TARGET_MISSING); 0l; })
+#define PT_REGS_PARM5_CORE_SYSCALL(x) ({ _Pragma(__BPF_TARGET_MISSING); 0l; })
+
 #endif /* defined(bpf_target_defined) */
 
 #ifndef ___bpf_concat
-- 
2.32.0

[PATCH v5 3/3] libbpf: Add a test to confirm PT_REGS_PARM4_SYSCALL

[Kenta Tada]

Add a selftest to verify the behavior of PT_REGS_xxx
and the CORE variant.

Signed-off-by: Kenta Tada <Kenta.Tada@sony.com>
---
 .../bpf/prog_tests/test_bpf_syscall_macro.c   | 63 ++++++++++++++++++
 .../selftests/bpf/progs/bpf_syscall_macro.c   | 64 +++++++++++++++++++
 2 files changed, 127 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/test_bpf_syscall_macro.c
 create mode 100644 tools/testing/selftests/bpf/progs/bpf_syscall_macro.c

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
new file mode 100644
index 000000000000..f5f4c8adf539
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/test_bpf_syscall_macro.c
@@ -0,0 +1,63 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright 2022 Sony Group Corporation */
+#include <sys/prctl.h>
+#include <test_progs.h>
+#include "bpf_syscall_macro.skel.h"
+
+void test_bpf_syscall_macro(void)
+{
+	struct bpf_syscall_macro *skel = NULL;
+	int err;
+	int exp_arg1 = 1001;
+	unsigned long exp_arg2 = 12;
+	unsigned long exp_arg3 = 13;
+	unsigned long exp_arg4 = 14;
+	unsigned long exp_arg5 = 15;
+
+	/* check whether it can open program */
+	skel = bpf_syscall_macro__open();
+	if (!ASSERT_OK_PTR(skel, "bpf_syscall_macro__open"))
+		return;
+
+	skel->rodata->filter_pid = getpid();
+
+	/* check whether it can load program */
+	err = bpf_syscall_macro__load(skel);
+	if (!ASSERT_OK(err, "bpf_syscall_macro__load"))
+		goto cleanup;
+
+	/* check whether it can attach kprobe */
+	err = bpf_syscall_macro__attach(skel);
+	if (!ASSERT_OK(err, "bpf_syscall_macro__attach"))
+		goto cleanup;
+
+	/* check whether args of syscall are copied correctly */
+	prctl(exp_arg1, exp_arg2, exp_arg3, exp_arg4, exp_arg5);
+	ASSERT_EQ(skel->bss->arg1, exp_arg1, "syscall_arg1");
+	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 */
+#ifdef __x86_64__
+	ASSERT_NEQ(skel->bss->arg4_cx, exp_arg4, "syscall_arg4_from_cx");
+#else
+	ASSERT_EQ(skel->bss->arg4_cx, exp_arg4, "syscall_arg4_from_cx");
+#endif
+	ASSERT_EQ(skel->bss->arg4, exp_arg4, "syscall_arg4");
+	ASSERT_EQ(skel->bss->arg5, exp_arg5, "syscall_arg5");
+
+	/* check whether args of syscall are copied correctly for CORE variants */
+	ASSERT_EQ(skel->bss->arg1_core, exp_arg1, "syscall_arg1_core_variant");
+	ASSERT_EQ(skel->bss->arg2_core, exp_arg2, "syscall_arg2_core_variant");
+	ASSERT_EQ(skel->bss->arg3_core, exp_arg3, "syscall_arg3_core_variant");
+	/* it cannot copy arg4 when uses PT_REGS_PARM4_CORE on x86_64 */
+#ifdef __x86_64__
+	ASSERT_NEQ(skel->bss->arg4_core_cx, exp_arg4, "syscall_arg4_from_cx_core_variant");
+#else
+	ASSERT_EQ(skel->bss->arg4_core_cx, exp_arg4, "syscall_arg4_from_cx_core_variant");
+#endif
+	ASSERT_EQ(skel->bss->arg4_core, exp_arg4, "syscall_arg4_core_variant");
+	ASSERT_EQ(skel->bss->arg5_core, exp_arg5, "syscall_arg5_core_variant");
+
+cleanup:
+	bpf_syscall_macro__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/progs/bpf_syscall_macro.c b/tools/testing/selftests/bpf/progs/bpf_syscall_macro.c
new file mode 100644
index 000000000000..cfeccd85f40e
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/bpf_syscall_macro.c
@@ -0,0 +1,64 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright 2022 Sony Group Corporation */
+#include <vmlinux.h>
+
+#include <bpf/bpf_core_read.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include "bpf_misc.h"
+
+int arg1 = 0;
+unsigned long arg2 = 0;
+unsigned long arg3 = 0;
+unsigned long arg4_cx = 0;
+unsigned long arg4 = 0;
+unsigned long arg5 = 0;
+
+int arg1_core = 0;
+unsigned long arg2_core = 0;
+unsigned long arg3_core = 0;
+unsigned long arg4_core_cx = 0;
+unsigned long arg4_core = 0;
+unsigned long arg5_core = 0;
+
+const volatile pid_t filter_pid = 0;
+
+SEC("kprobe/" SYS_PREFIX "sys_prctl")
+int BPF_KPROBE(handle_sys_prctl)
+{
+	struct pt_regs *real_regs;
+	int orig_arg1;
+	unsigned long orig_arg2, orig_arg3, orig_arg4_cx, orig_arg4, orig_arg5;
+	pid_t pid = bpf_get_current_pid_tgid() >> 32;
+
+	if (pid != filter_pid)
+		return 0;
+
+	/* test for PT_REGS_PARM */
+	real_regs = (struct pt_regs *)PT_REGS_PARM1(ctx);
+	bpf_probe_read_kernel(&orig_arg1, sizeof(orig_arg1), &PT_REGS_PARM1_SYSCALL(real_regs));
+	bpf_probe_read_kernel(&orig_arg2, sizeof(orig_arg2), &PT_REGS_PARM2_SYSCALL(real_regs));
+	bpf_probe_read_kernel(&orig_arg3, sizeof(orig_arg3), &PT_REGS_PARM3_SYSCALL(real_regs));
+	bpf_probe_read_kernel(&orig_arg4_cx, sizeof(orig_arg4_cx), &PT_REGS_PARM4(real_regs));
+	bpf_probe_read_kernel(&orig_arg4, sizeof(orig_arg4), &PT_REGS_PARM4_SYSCALL(real_regs));
+	bpf_probe_read_kernel(&orig_arg5, sizeof(orig_arg5), &PT_REGS_PARM5_SYSCALL(real_regs));
+	/* copy all actual args and the wrong arg4 on x86_64 */
+	arg1 = orig_arg1;
+	arg2 = orig_arg2;
+	arg3 = orig_arg3;
+	arg4_cx = orig_arg4_cx;
+	arg4 = orig_arg4;
+	arg5 = orig_arg5;
+
+	/* test for the CORE variant of PT_REGS_PARM */
+	arg1_core = PT_REGS_PARM1_CORE_SYSCALL(real_regs);
+	arg2_core = PT_REGS_PARM2_CORE_SYSCALL(real_regs);
+	arg3_core = PT_REGS_PARM3_CORE_SYSCALL(real_regs);
+	arg4_core_cx = PT_REGS_PARM4_CORE(real_regs);
+	arg4_core = PT_REGS_PARM4_CORE_SYSCALL(real_regs);
+	arg5_core = PT_REGS_PARM5_CORE_SYSCALL(real_regs);
+
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";
-- 
2.32.0

Re: [PATCH v5 3/3] libbpf: Add a test to confirm PT_REGS_PARM4_SYSCALL

[Andrii Nakryiko]

+cc Hengqi

On Mon, Jan 24, 2022 at 6:20 AM Kenta Tada <Kenta.Tada@sony.com> wrote:
>
> Add a selftest to verify the behavior of PT_REGS_xxx
> and the CORE variant.
>
> Signed-off-by: Kenta Tada <Kenta.Tada@sony.com>
> ---
>  .../bpf/prog_tests/test_bpf_syscall_macro.c   | 63 ++++++++++++++++++
>  .../selftests/bpf/progs/bpf_syscall_macro.c   | 64 +++++++++++++++++++
>  2 files changed, 127 insertions(+)
>  create mode 100644 tools/testing/selftests/bpf/prog_tests/test_bpf_syscall_macro.c
>  create mode 100644 tools/testing/selftests/bpf/progs/bpf_syscall_macro.c
>

[...]

> diff --git a/tools/testing/selftests/bpf/progs/bpf_syscall_macro.c b/tools/testing/selftests/bpf/progs/bpf_syscall_macro.c
> new file mode 100644
> index 000000000000..cfeccd85f40e
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/bpf_syscall_macro.c
> @@ -0,0 +1,64 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright 2022 Sony Group Corporation */
> +#include <vmlinux.h>
> +
> +#include <bpf/bpf_core_read.h>
> +#include <bpf/bpf_helpers.h>
> +#include <bpf/bpf_tracing.h>
> +#include "bpf_misc.h"
> +
> +int arg1 = 0;
> +unsigned long arg2 = 0;
> +unsigned long arg3 = 0;
> +unsigned long arg4_cx = 0;
> +unsigned long arg4 = 0;
> +unsigned long arg5 = 0;
> +
> +int arg1_core = 0;
> +unsigned long arg2_core = 0;
> +unsigned long arg3_core = 0;
> +unsigned long arg4_core_cx = 0;
> +unsigned long arg4_core = 0;
> +unsigned long arg5_core = 0;
> +
> +const volatile pid_t filter_pid = 0;
> +
> +SEC("kprobe/" SYS_PREFIX "sys_prctl")
> +int BPF_KPROBE(handle_sys_prctl)
> +{
> +       struct pt_regs *real_regs;
> +       int orig_arg1;
> +       unsigned long orig_arg2, orig_arg3, orig_arg4_cx, orig_arg4, orig_arg5;
> +       pid_t pid = bpf_get_current_pid_tgid() >> 32;
> +
> +       if (pid != filter_pid)
> +               return 0;
> +
> +       /* test for PT_REGS_PARM */
> +       real_regs = (struct pt_regs *)PT_REGS_PARM1(ctx);
> +       bpf_probe_read_kernel(&orig_arg1, sizeof(orig_arg1), &PT_REGS_PARM1_SYSCALL(real_regs));
> +       bpf_probe_read_kernel(&orig_arg2, sizeof(orig_arg2), &PT_REGS_PARM2_SYSCALL(real_regs));
> +       bpf_probe_read_kernel(&orig_arg3, sizeof(orig_arg3), &PT_REGS_PARM3_SYSCALL(real_regs));
> +       bpf_probe_read_kernel(&orig_arg4_cx, sizeof(orig_arg4_cx), &PT_REGS_PARM4(real_regs));
> +       bpf_probe_read_kernel(&orig_arg4, sizeof(orig_arg4), &PT_REGS_PARM4_SYSCALL(real_regs));
> +       bpf_probe_read_kernel(&orig_arg5, sizeof(orig_arg5), &PT_REGS_PARM5_SYSCALL(real_regs));
> +       /* copy all actual args and the wrong arg4 on x86_64 */
> +       arg1 = orig_arg1;
> +       arg2 = orig_arg2;
> +       arg3 = orig_arg3;
> +       arg4_cx = orig_arg4_cx;
> +       arg4 = orig_arg4;
> +       arg5 = orig_arg5;

I don't get why you needed orig_argX variables and then copying them
into argX variables. I changed this to read directly into argX. I
suspect arg1 handling might break on big-endian arches due to int vs
long differences, please check that and send a follow up fix.

Also keep in mind that selftest changes should come with
"selftests/bpf:" subject prefix, not "libbpf:". Fixed that up as well.

Applied to bpf-next, thanks.

Hopefully Hengqi will build his SYSCALL prog wrapper macros on top of
this as a follow up as well.

> +
> +       /* test for the CORE variant of PT_REGS_PARM */
> +       arg1_core = PT_REGS_PARM1_CORE_SYSCALL(real_regs);
> +       arg2_core = PT_REGS_PARM2_CORE_SYSCALL(real_regs);
> +       arg3_core = PT_REGS_PARM3_CORE_SYSCALL(real_regs);
> +       arg4_core_cx = PT_REGS_PARM4_CORE(real_regs);
> +       arg4_core = PT_REGS_PARM4_CORE_SYSCALL(real_regs);
> +       arg5_core = PT_REGS_PARM5_CORE_SYSCALL(real_regs);
> +
> +       return 0;
> +}
> +
> +char _license[] SEC("license") = "GPL";
> --
> 2.32.0
>

Re: [PATCH v5 3/3] libbpf: Add a test to confirm PT_REGS_PARM4_SYSCALL

[Andrii Nakryiko]

+cc Ilya


On Mon, Jan 24, 2022 at 9:05 PM Andrii Nakryiko
<andrii.nakryiko@gmail.com> wrote:
>
> +cc Hengqi
>
> On Mon, Jan 24, 2022 at 6:20 AM Kenta Tada <Kenta.Tada@sony.com> wrote:
> >
> > Add a selftest to verify the behavior of PT_REGS_xxx
> > and the CORE variant.
> >
> > Signed-off-by: Kenta Tada <Kenta.Tada@sony.com>
> > ---
> >  .../bpf/prog_tests/test_bpf_syscall_macro.c   | 63 ++++++++++++++++++
> >  .../selftests/bpf/progs/bpf_syscall_macro.c   | 64 +++++++++++++++++++
> >  2 files changed, 127 insertions(+)
> >  create mode 100644 tools/testing/selftests/bpf/prog_tests/test_bpf_syscall_macro.c
> >  create mode 100644 tools/testing/selftests/bpf/progs/bpf_syscall_macro.c
> >
>
> [...]
>
> > diff --git a/tools/testing/selftests/bpf/progs/bpf_syscall_macro.c b/tools/testing/selftests/bpf/progs/bpf_syscall_macro.c
> > new file mode 100644
> > index 000000000000..cfeccd85f40e
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/progs/bpf_syscall_macro.c
> > @@ -0,0 +1,64 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/* Copyright 2022 Sony Group Corporation */
> > +#include <vmlinux.h>
> > +
> > +#include <bpf/bpf_core_read.h>
> > +#include <bpf/bpf_helpers.h>
> > +#include <bpf/bpf_tracing.h>
> > +#include "bpf_misc.h"
> > +
> > +int arg1 = 0;
> > +unsigned long arg2 = 0;
> > +unsigned long arg3 = 0;
> > +unsigned long arg4_cx = 0;
> > +unsigned long arg4 = 0;
> > +unsigned long arg5 = 0;
> > +
> > +int arg1_core = 0;
> > +unsigned long arg2_core = 0;
> > +unsigned long arg3_core = 0;
> > +unsigned long arg4_core_cx = 0;
> > +unsigned long arg4_core = 0;
> > +unsigned long arg5_core = 0;
> > +
> > +const volatile pid_t filter_pid = 0;
> > +
> > +SEC("kprobe/" SYS_PREFIX "sys_prctl")
> > +int BPF_KPROBE(handle_sys_prctl)
> > +{
> > +       struct pt_regs *real_regs;
> > +       int orig_arg1;
> > +       unsigned long orig_arg2, orig_arg3, orig_arg4_cx, orig_arg4, orig_arg5;
> > +       pid_t pid = bpf_get_current_pid_tgid() >> 32;
> > +
> > +       if (pid != filter_pid)
> > +               return 0;
> > +
> > +       /* test for PT_REGS_PARM */
> > +       real_regs = (struct pt_regs *)PT_REGS_PARM1(ctx);
> > +       bpf_probe_read_kernel(&orig_arg1, sizeof(orig_arg1), &PT_REGS_PARM1_SYSCALL(real_regs));
> > +       bpf_probe_read_kernel(&orig_arg2, sizeof(orig_arg2), &PT_REGS_PARM2_SYSCALL(real_regs));
> > +       bpf_probe_read_kernel(&orig_arg3, sizeof(orig_arg3), &PT_REGS_PARM3_SYSCALL(real_regs));
> > +       bpf_probe_read_kernel(&orig_arg4_cx, sizeof(orig_arg4_cx), &PT_REGS_PARM4(real_regs));
> > +       bpf_probe_read_kernel(&orig_arg4, sizeof(orig_arg4), &PT_REGS_PARM4_SYSCALL(real_regs));
> > +       bpf_probe_read_kernel(&orig_arg5, sizeof(orig_arg5), &PT_REGS_PARM5_SYSCALL(real_regs));
> > +       /* copy all actual args and the wrong arg4 on x86_64 */
> > +       arg1 = orig_arg1;
> > +       arg2 = orig_arg2;
> > +       arg3 = orig_arg3;
> > +       arg4_cx = orig_arg4_cx;
> > +       arg4 = orig_arg4;
> > +       arg5 = orig_arg5;
>
> I don't get why you needed orig_argX variables and then copying them
> into argX variables. I changed this to read directly into argX. I
> suspect arg1 handling might break on big-endian arches due to int vs
> long differences, please check that and send a follow up fix.
>
> Also keep in mind that selftest changes should come with
> "selftests/bpf:" subject prefix, not "libbpf:". Fixed that up as well.
>
> Applied to bpf-next, thanks.

This selftest is failing on s390x (see [0]). Ilya, do you know if
something special needs to be done for s390x for this case?

Here are the two failures:

test_bpf_syscall_macro:FAIL:syscall_arg1 unexpected syscall_arg1:
actual -1 != expected 1001
test_bpf_syscall_macro:FAIL:syscall_arg1_core_variant unexpected
syscall_arg1_core_variant: actual -38 != expected 1001

  [0] https://github.com/libbpf/libbpf/runs/5025905587?check_suite_focus=true

>
> Hopefully Hengqi will build his SYSCALL prog wrapper macros on top of
> this as a follow up as well.
>
> > +
> > +       /* test for the CORE variant of PT_REGS_PARM */
> > +       arg1_core = PT_REGS_PARM1_CORE_SYSCALL(real_regs);
> > +       arg2_core = PT_REGS_PARM2_CORE_SYSCALL(real_regs);
> > +       arg3_core = PT_REGS_PARM3_CORE_SYSCALL(real_regs);
> > +       arg4_core_cx = PT_REGS_PARM4_CORE(real_regs);
> > +       arg4_core = PT_REGS_PARM4_CORE_SYSCALL(real_regs);
> > +       arg5_core = PT_REGS_PARM5_CORE_SYSCALL(real_regs);
> > +
> > +       return 0;
> > +}
> > +
> > +char _license[] SEC("license") = "GPL";
> > --
> > 2.32.0
> >

Re: [PATCH v5 3/3] libbpf: Add a test to confirm PT_REGS_PARM4_SYSCALL

[Ilya Leoshkevich]

On Tue, 2022-02-01 at 11:36 -0800, Andrii Nakryiko wrote:
> +cc Ilya
> 
> 
> On Mon, Jan 24, 2022 at 9:05 PM Andrii Nakryiko
> <andrii.nakryiko@gmail.com> wrote:
> > 
> > +cc Hengqi
> > 
> > On Mon, Jan 24, 2022 at 6:20 AM Kenta Tada <Kenta.Tada@sony.com>
> > wrote:
> > > 
> > > Add a selftest to verify the behavior of PT_REGS_xxx
> > > and the CORE variant.
> > > 
> > > Signed-off-by: Kenta Tada <Kenta.Tada@sony.com>
> > > ---
> > >  .../bpf/prog_tests/test_bpf_syscall_macro.c   | 63
> > > ++++++++++++++++++
> > >  .../selftests/bpf/progs/bpf_syscall_macro.c   | 64
> > > +++++++++++++++++++
> > >  2 files changed, 127 insertions(+)
> > >  create mode 100644
> > > tools/testing/selftests/bpf/prog_tests/test_bpf_syscall_macro.c
> > >  create mode 100644
> > > tools/testing/selftests/bpf/progs/bpf_syscall_macro.c
> > > 
> > 
> > [...]
> > 
> > > diff --git
> > > a/tools/testing/selftests/bpf/progs/bpf_syscall_macro.c
> > > b/tools/testing/selftests/bpf/progs/bpf_syscall_macro.c
> > > new file mode 100644
> > > index 000000000000..cfeccd85f40e
> > > --- /dev/null
> > > +++ b/tools/testing/selftests/bpf/progs/bpf_syscall_macro.c
> > > @@ -0,0 +1,64 @@
> > > +// SPDX-License-Identifier: GPL-2.0
> > > +/* Copyright 2022 Sony Group Corporation */
> > > +#include <vmlinux.h>
> > > +
> > > +#include <bpf/bpf_core_read.h>
> > > +#include <bpf/bpf_helpers.h>
> > > +#include <bpf/bpf_tracing.h>
> > > +#include "bpf_misc.h"
> > > +
> > > +int arg1 = 0;
> > > +unsigned long arg2 = 0;
> > > +unsigned long arg3 = 0;
> > > +unsigned long arg4_cx = 0;
> > > +unsigned long arg4 = 0;
> > > +unsigned long arg5 = 0;
> > > +
> > > +int arg1_core = 0;
> > > +unsigned long arg2_core = 0;
> > > +unsigned long arg3_core = 0;
> > > +unsigned long arg4_core_cx = 0;
> > > +unsigned long arg4_core = 0;
> > > +unsigned long arg5_core = 0;
> > > +
> > > +const volatile pid_t filter_pid = 0;
> > > +
> > > +SEC("kprobe/" SYS_PREFIX "sys_prctl")
> > > +int BPF_KPROBE(handle_sys_prctl)
> > > +{
> > > +       struct pt_regs *real_regs;
> > > +       int orig_arg1;
> > > +       unsigned long orig_arg2, orig_arg3, orig_arg4_cx,
> > > orig_arg4, orig_arg5;
> > > +       pid_t pid = bpf_get_current_pid_tgid() >> 32;
> > > +
> > > +       if (pid != filter_pid)
> > > +               return 0;
> > > +
> > > +       /* test for PT_REGS_PARM */
> > > +       real_regs = (struct pt_regs *)PT_REGS_PARM1(ctx);
> > > +       bpf_probe_read_kernel(&orig_arg1, sizeof(orig_arg1),
> > > &PT_REGS_PARM1_SYSCALL(real_regs));
> > > +       bpf_probe_read_kernel(&orig_arg2, sizeof(orig_arg2),
> > > &PT_REGS_PARM2_SYSCALL(real_regs));
> > > +       bpf_probe_read_kernel(&orig_arg3, sizeof(orig_arg3),
> > > &PT_REGS_PARM3_SYSCALL(real_regs));
> > > +       bpf_probe_read_kernel(&orig_arg4_cx,
> > > sizeof(orig_arg4_cx), &PT_REGS_PARM4(real_regs));
> > > +       bpf_probe_read_kernel(&orig_arg4, sizeof(orig_arg4),
> > > &PT_REGS_PARM4_SYSCALL(real_regs));
> > > +       bpf_probe_read_kernel(&orig_arg5, sizeof(orig_arg5),
> > > &PT_REGS_PARM5_SYSCALL(real_regs));
> > > +       /* copy all actual args and the wrong arg4 on x86_64 */
> > > +       arg1 = orig_arg1;
> > > +       arg2 = orig_arg2;
> > > +       arg3 = orig_arg3;
> > > +       arg4_cx = orig_arg4_cx;
> > > +       arg4 = orig_arg4;
> > > +       arg5 = orig_arg5;
> > 
> > I don't get why you needed orig_argX variables and then copying
> > them
> > into argX variables. I changed this to read directly into argX. I
> > suspect arg1 handling might break on big-endian arches due to int
> > vs
> > long differences, please check that and send a follow up fix.
> > 
> > Also keep in mind that selftest changes should come with
> > "selftests/bpf:" subject prefix, not "libbpf:". Fixed that up as
> > well.
> > 
> > Applied to bpf-next, thanks.
> 
> This selftest is failing on s390x (see [0]). Ilya, do you know if
> something special needs to be done for s390x for this case?
> 
> Here are the two failures:
> 
> test_bpf_syscall_macro:FAIL:syscall_arg1 unexpected syscall_arg1:
> actual -1 != expected 1001
> test_bpf_syscall_macro:FAIL:syscall_arg1_core_variant unexpected
> syscall_arg1_core_variant: actual -38 != expected 1001
> 
>   [0]
> https://github.com/libbpf/libbpf/runs/5025905587?check_suite_focus=true
> 

I think we need to use orig_gpr2 for the first syscall argument
(see arch/s390/include/asm/syscall.h). I'll test it and send a patch.
>