On Thu, Sep 2, 2021 at 2:08 AM Jean-Philippe Brucker
<jean-philippe@xxxxxxxxxx> wrote:
>
> 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 = {};
Right, which is 'bpf_user_pt_regs_t'.
It's defined for all archs and arm64/s390/ppc/risv define it
differently from pt_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.
That's a different issue.
I think the cleaner fix would be to make the test use
bpf_user_pt_regs_t instead.
> Fixes: 576d47bb1a92 ("bpf: selftests: Add bpf_task_pt_regs() selftest")
> Signed-off-by: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx>
> ---
> .../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(¤t_regs, regs, sizeof(*regs));
> - __builtin_memcpy(&ctx_regs, ctx, sizeof(*ctx));
> + bpf_copy_pt_regs(¤t_regs, regs);
> + bpf_copy_pt_regs(&ctx_regs, ctx);
>
> /* Prove that uprobe was run */
> uprobe_res = 1;
> --
> 2.33.0
>
