On Fri, 2023-08-25 at 10:08 +0200, Benjamin Tissoires wrote:
On Tue, Aug 22, 2023 at 11:42 PM Justin Stitt justinstitt@google.com wrote:
Which kernel are you trying to test? I tested your 2 commands on v6.5-rc7 and it just works.
I'm also on v6.5-rc7 (706a741595047797872e669b3101429ab8d378ef)
I ran these exact commands:
$ make mrproper $ make LLVM=1 ARCH=x86_64 headers $ make LLVM=1 ARCH=x86_64 -j128 -C tools/testing/selftests
TARGETS=hid &> out
and here's the contents of `out` (still warnings/errors): https://gist.github.com/JustinStitt/d0c30180a2a2e046c32d5f0ce5f59c6d
I have a feeling I'm doing something fundamentally incorrectly. Any ideas?
Sigh... there is a high chance my Makefile is not correct and uses the installed headers (I was running the exact same commands, but on a v6.4-rc7+ kernel).
But sorry, it will have to wait for tomorrow if you want me to have a look at it. It's 11:35 PM here, and I need to go to bed
Take it easy. Thanks for the prompt responses here! I'd like to get the entire kselftest make target building with Clang so that we can close [1].
Sorry I got urgent matters to tackle yesterday.
It took me a while to understand what was going on, and I finally found it.
struct hid_bpf_ctx is internal to the kernel, and so is declared in vmlinux.h, that we generate through BTF. But to generate the vmlinux.h with the correct symbols, these need to be present in the running kernel. And that's where we had a fundamental difference: I was running my compilations on a kernel v6.3+ (6.4.11) with that symbol available, and you are probably not.
The bpf folks are using a clever trick to force the compilation[2]. And I think the following patch would work for you:
Hi Benjamin, Justin,
You might want to take a look at these two links: [1] https://nakryiko.com/posts/bpf-core-reference-guide/#handling-incompatible-f... [2] https://facebookmicrosites.github.io/bpf/blog/2020/02/19/bpf-portability-and...
The short version is: CO-RE relocation handling logic in libbpf ignores suffixes of form '___something' for type and field names.
So, the following should accomplish the same as the trick with #define/#undef:
#include "vmlinux.h" ... struct hid_bpf_ctx___local { __u32 index; const struct hid_device *hid; __u32 allocated_size; enum hid_report_type report_type; union { __s32 retval; __s32 size; };
}; ... extern __u8 *hid_bpf_get_data(struct hid_bpf_ctx___local *ctx, unsigned int offset, ...)
However, if the kernel does not have `hid_bpf_ctx` definition would the test `progs/hid.c` still make sense?
When I tried to build hid tests locally I run into similar errors:
... CLNG-BPF hid.bpf.o In file included from progs/hid.c:6: progs/hid_bpf_helpers.h:9:38: error: declaration of 'struct hid_bpf_ctx' \ will not be visible outside of this function [-Werror,-Wvisibility] extern __u8 *hid_bpf_get_data(struct hid_bpf_ctx *ctx, ...
And there is indeed no `hid_bpf_ctx` in my vmlinux.h. However, after enabling CONFIG_HID_BPF in kernel config the `hid_bpf_ctx` appears in vmlinux.h, and I can compile HID selftests w/o issues.
From bb9eccb7a896ba4b3a35ed12a248e6d6cfed2df6 Mon Sep 17 00:00:00 2001 From: Benjamin Tissoires bentiss@kernel.org Date: Fri, 25 Aug 2023 10:02:32 +0200 Subject: [PATCH] selftests/hid: ensure we can compile the tests on kernels pre-6.3
For the hid-bpf tests to compile, we need to have the definition of struct hid_bpf_ctx. This definition is an internal one from the kernel and it is supposed to be defined in the generated vmlinux.h.
This vmlinux.h header is generated based on the currently running kernel or if the kernel was already compiled in the tree. If you just compile the selftests without compiling the kernel beforehand and you are running on a 6.2 kernel, you'll end up with a vmlinux.h without the hid_bpf_ctx definition.
Use the clever trick from tools/testing/selftests/bpf/progs/bpf_iter.h to force the definition of that symbol in case we don't find it in the BTF.
Signed-off-by: Benjamin Tissoires bentiss@kernel.org
tools/testing/selftests/hid/progs/hid.c | 3 --- .../selftests/hid/progs/hid_bpf_helpers.h | 20 +++++++++++++++++++ 2 files changed, 20 insertions(+), 3 deletions(-)
diff --git a/tools/testing/selftests/hid/progs/hid.c b/tools/testing/selftests/hid/progs/hid.c index 88c593f753b5..1e558826b809 100644 --- a/tools/testing/selftests/hid/progs/hid.c +++ b/tools/testing/selftests/hid/progs/hid.c @@ -1,8 +1,5 @@ // SPDX-License-Identifier: GPL-2.0 /* Copyright (c) 2022 Red hat */ -#include "vmlinux.h" -#include <bpf/bpf_helpers.h> -#include <bpf/bpf_tracing.h> #include "hid_bpf_helpers.h" char _license[] SEC("license") = "GPL"; diff --git a/tools/testing/selftests/hid/progs/hid_bpf_helpers.h b/tools/testing/selftests/hid/progs/hid_bpf_helpers.h index 4fff31dbe0e7..749097f8f4d9 100644 --- a/tools/testing/selftests/hid/progs/hid_bpf_helpers.h +++ b/tools/testing/selftests/hid/progs/hid_bpf_helpers.h @@ -5,6 +5,26 @@ #ifndef __HID_BPF_HELPERS_H #define __HID_BPF_HELPERS_H +/* "undefine" structs in vmlinux.h, because we "override" them below */ +#define hid_bpf_ctx hid_bpf_ctx___not_used +#include "vmlinux.h" +#undef hid_bpf_ctx
+#include <bpf/bpf_helpers.h> +#include <bpf/bpf_tracing.h>
+struct hid_bpf_ctx {
- __u32 index;
- const struct hid_device *hid;
- __u32 allocated_size;
- enum hid_report_type report_type;
- union {
__s32 retval;__s32 size;- };
+};
- /* following are kfuncs exported by HID for HID-BPF */ extern __u8 *hid_bpf_get_data(struct hid_bpf_ctx *ctx, unsigned int offset,