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Date: Mon, 14 Nov 2022 19:02:01 -0800
From: Stanislav Fomichev <sdf@...gle.com>
To: bpf@...r.kernel.org
Cc: ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
martin.lau@...ux.dev, song@...nel.org, yhs@...com,
john.fastabend@...il.com, kpsingh@...nel.org, sdf@...gle.com,
haoluo@...gle.com, jolsa@...nel.org,
David Ahern <dsahern@...il.com>,
Jakub Kicinski <kuba@...nel.org>,
Willem de Bruijn <willemb@...gle.com>,
Jesper Dangaard Brouer <brouer@...hat.com>,
Anatoly Burakov <anatoly.burakov@...el.com>,
Alexander Lobakin <alexandr.lobakin@...el.com>,
Magnus Karlsson <magnus.karlsson@...il.com>,
Maryam Tahhan <mtahhan@...hat.com>, xdp-hints@...-project.net,
netdev@...r.kernel.org
Subject: [PATCH bpf-next 02/11] bpf: Introduce bpf_patch
A simple abstraction around a series of instructions that transparently
handles resizing.
Currently, we have insn_buf[16] in convert_ctx_accesses which might
not be enough for xdp kfuncs.
If we find this abstraction helpful, we might convert existing
insn_buf[16] to it in the future.
Cc: John Fastabend <john.fastabend@...il.com>
Cc: David Ahern <dsahern@...il.com>
Cc: Martin KaFai Lau <martin.lau@...ux.dev>
Cc: Jakub Kicinski <kuba@...nel.org>
Cc: Willem de Bruijn <willemb@...gle.com>
Cc: Jesper Dangaard Brouer <brouer@...hat.com>
Cc: Anatoly Burakov <anatoly.burakov@...el.com>
Cc: Alexander Lobakin <alexandr.lobakin@...el.com>
Cc: Magnus Karlsson <magnus.karlsson@...il.com>
Cc: Maryam Tahhan <mtahhan@...hat.com>
Cc: xdp-hints@...-project.net
Cc: netdev@...r.kernel.org
Signed-off-by: Stanislav Fomichev <sdf@...gle.com>
---
include/linux/bpf_patch.h | 29 +++++++++++++++
kernel/bpf/Makefile | 2 +-
kernel/bpf/bpf_patch.c | 77 +++++++++++++++++++++++++++++++++++++++
3 files changed, 107 insertions(+), 1 deletion(-)
create mode 100644 include/linux/bpf_patch.h
create mode 100644 kernel/bpf/bpf_patch.c
diff --git a/include/linux/bpf_patch.h b/include/linux/bpf_patch.h
new file mode 100644
index 000000000000..359c165ad68b
--- /dev/null
+++ b/include/linux/bpf_patch.h
@@ -0,0 +1,29 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef _LINUX_BPF_PATCH_H
+#define _LINUX_BPF_PATCH_H 1
+
+#include <linux/bpf.h>
+
+struct bpf_patch {
+ struct bpf_insn *insn;
+ size_t capacity;
+ size_t len;
+ int err;
+};
+
+void bpf_patch_free(struct bpf_patch *patch);
+size_t bpf_patch_len(const struct bpf_patch *patch);
+int bpf_patch_err(const struct bpf_patch *patch);
+void __bpf_patch_append(struct bpf_patch *patch, struct bpf_insn insn);
+struct bpf_insn *bpf_patch_data(const struct bpf_patch *patch);
+void bpf_patch_resolve_jmp(struct bpf_patch *patch);
+u32 bpf_patch_magles_registers(const struct bpf_patch *patch);
+
+#define bpf_patch_append(patch, ...) ({ \
+ struct bpf_insn insn[] = { __VA_ARGS__ }; \
+ int i; \
+ for (i = 0; i < ARRAY_SIZE(insn); i++) \
+ __bpf_patch_append(patch, insn[i]); \
+})
+
+#endif
diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile
index 3a12e6b400a2..5724f36292a5 100644
--- a/kernel/bpf/Makefile
+++ b/kernel/bpf/Makefile
@@ -13,7 +13,7 @@ obj-$(CONFIG_BPF_SYSCALL) += bpf_local_storage.o bpf_task_storage.o
obj-${CONFIG_BPF_LSM} += bpf_inode_storage.o
obj-$(CONFIG_BPF_SYSCALL) += disasm.o
obj-$(CONFIG_BPF_JIT) += trampoline.o
-obj-$(CONFIG_BPF_SYSCALL) += btf.o memalloc.o
+obj-$(CONFIG_BPF_SYSCALL) += btf.o memalloc.o bpf_patch.o
obj-$(CONFIG_BPF_JIT) += dispatcher.o
ifeq ($(CONFIG_NET),y)
obj-$(CONFIG_BPF_SYSCALL) += devmap.o
diff --git a/kernel/bpf/bpf_patch.c b/kernel/bpf/bpf_patch.c
new file mode 100644
index 000000000000..eb768398fd8f
--- /dev/null
+++ b/kernel/bpf/bpf_patch.c
@@ -0,0 +1,77 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/bpf_patch.h>
+
+void bpf_patch_free(struct bpf_patch *patch)
+{
+ kfree(patch->insn);
+}
+
+size_t bpf_patch_len(const struct bpf_patch *patch)
+{
+ return patch->len;
+}
+
+int bpf_patch_err(const struct bpf_patch *patch)
+{
+ return patch->err;
+}
+
+void __bpf_patch_append(struct bpf_patch *patch, struct bpf_insn insn)
+{
+ void *arr;
+
+ if (patch->err)
+ return;
+
+ if (patch->len + 1 > patch->capacity) {
+ if (!patch->capacity)
+ patch->capacity = 16;
+ else
+ patch->capacity *= 2;
+
+ arr = krealloc_array(patch->insn, patch->capacity, sizeof(insn), GFP_KERNEL);
+ if (!arr) {
+ patch->err = -ENOMEM;
+ kfree(patch->insn);
+ return;
+ }
+
+ patch->insn = arr;
+ patch->capacity *= 2;
+ }
+
+ patch->insn[patch->len++] = insn;
+}
+EXPORT_SYMBOL(__bpf_patch_append);
+
+struct bpf_insn *bpf_patch_data(const struct bpf_patch *patch)
+{
+ return patch->insn;
+}
+
+void bpf_patch_resolve_jmp(struct bpf_patch *patch)
+{
+ int i;
+
+ for (i = 0; i < patch->len; i++) {
+ if (BPF_CLASS(patch->insn[i].code) != BPF_JMP)
+ continue;
+
+ if (patch->insn[i].off != S16_MAX)
+ continue;
+
+ patch->insn[i].off = patch->len - i - 1;
+ }
+}
+
+u32 bpf_patch_magles_registers(const struct bpf_patch *patch)
+{
+ u32 mask = 0;
+ int i;
+
+ for (i = 0; i < patch->len; i++)
+ mask |= 1 << patch->insn[i].dst_reg;
+
+ return mask;
+}
--
2.38.1.431.g37b22c650d-goog
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