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From: Kumar Kartikeya Dwivedi <memxor@gmail.com>
To: bpf@vger.kernel.org
Cc: Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andrii@kernel.org>, Yonghong Song <yhs@fb.com>,
	Pavel Emelyanov <ovzxemul@gmail.com>,
	Alexander Mikhalitsyn <alexander@mihalicyn.com>,
	Andrei Vagin <avagin@gmail.com>,
	criu@openvz.org, io-uring@vger.kernel.org,
	linux-fsdevel@vger.kernel.org
Subject: [PATCH bpf-next v3 02/10] bpf: Add bpf_page_to_pfn helper
Date: Wed,  1 Dec 2021 09:53:25 +0530	[thread overview]
Message-ID: <20211201042333.2035153-3-memxor@gmail.com> (raw)
In-Reply-To: <20211201042333.2035153-1-memxor@gmail.com>

In CRIU, we need to be able to determine whether the page pinned by
io_uring is still present in the same range in the process VMA.
/proc/<pid>/pagemap gives us the PFN, hence using this helper we can
establish this mapping easily from the iterator side.

It is a simple wrapper over the in-kernel page_to_pfn macro, and ensures
the passed in pointer is a struct page PTR_TO_BTF_ID. This is obtained
from the bvec of io_uring_ubuf for the CRIU usecase.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 include/linux/bpf.h            |  1 +
 include/uapi/linux/bpf.h       |  9 +++++++++
 kernel/trace/bpf_trace.c       | 19 +++++++++++++++++++
 scripts/bpf_doc.py             |  2 ++
 tools/include/uapi/linux/bpf.h |  9 +++++++++
 5 files changed, 40 insertions(+)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 967842881024..e44503158d76 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2176,6 +2176,7 @@ extern const struct bpf_func_proto bpf_sk_setsockopt_proto;
 extern const struct bpf_func_proto bpf_sk_getsockopt_proto;
 extern const struct bpf_func_proto bpf_kallsyms_lookup_name_proto;
 extern const struct bpf_func_proto bpf_find_vma_proto;
+extern const struct bpf_func_proto bpf_page_to_pfn_proto;
 
 const struct bpf_func_proto *tracing_prog_func_proto(
   enum bpf_func_id func_id, const struct bpf_prog *prog);
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 1ad1ae85743c..885d9293c147 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -4960,6 +4960,14 @@ union bpf_attr {
  *		**-ENOENT** if *task->mm* is NULL, or no vma contains *addr*.
  *		**-EBUSY** if failed to try lock mmap_lock.
  *		**-EINVAL** for invalid **flags**.
+ *
+ * long bpf_page_to_pfn(struct page *page)
+ *	Description
+ *		Obtain the page frame number (PFN) for the given *struct page*
+ *		pointer.
+ *	Return
+ *		Page Frame Number corresponding to the page pointed to by the
+ *		*struct page* pointer, or U64_MAX if pointer is NULL.
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -5143,6 +5151,7 @@ union bpf_attr {
 	FN(skc_to_unix_sock),		\
 	FN(kallsyms_lookup_name),	\
 	FN(find_vma),			\
+	FN(page_to_pfn),		\
 	/* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 25ea521fb8f1..2a6488f14e58 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1091,6 +1091,23 @@ static const struct bpf_func_proto bpf_get_branch_snapshot_proto = {
 	.arg2_type	= ARG_CONST_SIZE_OR_ZERO,
 };
 
+BPF_CALL_1(bpf_page_to_pfn, struct page *, page)
+{
+	/* PTR_TO_BTF_ID can be NULL */
+	if (!page)
+		return U64_MAX;
+	return page_to_pfn(page);
+}
+
+BTF_ID_LIST_SINGLE(btf_page_to_pfn_ids, struct, page)
+
+const struct bpf_func_proto bpf_page_to_pfn_proto = {
+	.func		= bpf_page_to_pfn,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_BTF_ID,
+	.arg1_btf_id	= &btf_page_to_pfn_ids[0],
+};
+
 static const struct bpf_func_proto *
 bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 {
@@ -1212,6 +1229,8 @@ bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return &bpf_find_vma_proto;
 	case BPF_FUNC_trace_vprintk:
 		return bpf_get_trace_vprintk_proto();
+	case BPF_FUNC_page_to_pfn:
+		return &bpf_page_to_pfn_proto;
 	default:
 		return bpf_base_func_proto(func_id);
 	}
diff --git a/scripts/bpf_doc.py b/scripts/bpf_doc.py
index a6403ddf5de7..ae68ca794980 100755
--- a/scripts/bpf_doc.py
+++ b/scripts/bpf_doc.py
@@ -549,6 +549,7 @@ class PrinterHelpers(Printer):
             'struct socket',
             'struct file',
             'struct bpf_timer',
+            'struct page',
     ]
     known_types = {
             '...',
@@ -598,6 +599,7 @@ class PrinterHelpers(Printer):
             'struct socket',
             'struct file',
             'struct bpf_timer',
+            'struct page',
     }
     mapped_types = {
             'u8': '__u8',
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 1ad1ae85743c..885d9293c147 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -4960,6 +4960,14 @@ union bpf_attr {
  *		**-ENOENT** if *task->mm* is NULL, or no vma contains *addr*.
  *		**-EBUSY** if failed to try lock mmap_lock.
  *		**-EINVAL** for invalid **flags**.
+ *
+ * long bpf_page_to_pfn(struct page *page)
+ *	Description
+ *		Obtain the page frame number (PFN) for the given *struct page*
+ *		pointer.
+ *	Return
+ *		Page Frame Number corresponding to the page pointed to by the
+ *		*struct page* pointer, or U64_MAX if pointer is NULL.
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -5143,6 +5151,7 @@ union bpf_attr {
 	FN(skc_to_unix_sock),		\
 	FN(kallsyms_lookup_name),	\
 	FN(find_vma),			\
+	FN(page_to_pfn),		\
 	/* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
-- 
2.34.1


  parent reply	other threads:[~2021-12-01  4:23 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-01  4:23 [PATCH bpf-next v3 00/10] Introduce BPF iterators for io_uring and epoll Kumar Kartikeya Dwivedi
2021-12-01  4:23 ` [PATCH bpf-next v3 01/10] io_uring: Implement eBPF iterator for registered buffers Kumar Kartikeya Dwivedi
2021-12-01  4:23 ` Kumar Kartikeya Dwivedi [this message]
2021-12-01  4:23 ` [PATCH bpf-next v3 03/10] io_uring: Implement eBPF iterator for registered files Kumar Kartikeya Dwivedi
2021-12-01  4:23 ` [PATCH bpf-next v3 04/10] epoll: Implement eBPF iterator for registered items Kumar Kartikeya Dwivedi
2021-12-01  4:23 ` [PATCH bpf-next v3 05/10] bpftool: Output io_uring iterator info Kumar Kartikeya Dwivedi
2021-12-01  4:23 ` [PATCH bpf-next v3 06/10] selftests/bpf: Add test for io_uring BPF iterators Kumar Kartikeya Dwivedi
2021-12-01  4:23 ` [PATCH bpf-next v3 07/10] selftests/bpf: Add test for epoll BPF iterator Kumar Kartikeya Dwivedi
2021-12-01  4:23 ` [PATCH bpf-next v3 08/10] selftests/bpf: Test partial reads for io_uring, epoll iterators Kumar Kartikeya Dwivedi
2021-12-01  4:23 ` [PATCH bpf-next v3 09/10] selftests/bpf: Fix btf_dump test for bpf_iter_link_info Kumar Kartikeya Dwivedi
2021-12-01  4:23 ` [PATCH RFC bpf-next v3 10/10] samples/bpf: Add example to checkpoint/restore io_uring Kumar Kartikeya Dwivedi

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