From 5febf432df1cfa5b25d99b54c32103fafbdd0eb9 Mon Sep 17 00:00:00 2001 From: Miguel Ojeda Date: Sun, 16 Aug 2026 15:32:33 +0200 Subject: kbuild: rust: keep Rust objects out of Clang LTO with inline helpers Under `CONFIG_LTO_CLANG` + `CONFIG_RUST_INLINE_HELPERS`, one may hit `objtool` errors such as: vmlinux.o: error: objtool: _R..._3Gsp4boot+0xd6a: can't find jump dest instruction at .text._R..._3Gsp4boot+0x1dfd The reason is that in such builds, the Clang invocation that compiles the combined Rust plus helpers bitcode emits LLVM bitcode (again) -- the final code generation happens in the linker's LTO step, which the `-mllvm` trap options passed to Clang do not reach. This, in turn, means that unreachable traps are missing, and the impossible paths do not merely fallthrough to the next symbol, but past the end of their own section, since LTO builds place each function in its own section. Thus filter `CC_FLAGS_LTO` out of the Clang invocation, so that it always emits machine code directly, with the traps in place. Assisted-by: LLM Cc: Gary Guo Cc: Boqun Feng Cc: Alice Ryhl Cc: Matthew Maurer Cc: Josh Poimboeuf Cc: Peter Zijlstra Cc: stable@vger.kernel.org Fixes: 3a2486cc1da5 ("kbuild: rust: provide an option to inline C helpers into Rust") Acked-by: Gary Guo Link: https://patch.msgid.link/20260816133233.197500-2-ojeda@kernel.org Signed-off-by: Miguel Ojeda --- io_uring/bpf-ops.c | 275 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 275 insertions(+) create mode 100644 io_uring/bpf-ops.c (limited to 'io_uring/bpf-ops.c') diff --git a/io_uring/bpf-ops.c b/io_uring/bpf-ops.c new file mode 100644 index 000000000..cf2bd068e --- /dev/null +++ b/io_uring/bpf-ops.c @@ -0,0 +1,275 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#include +#include +#include + +#include "io_uring.h" +#include "register.h" +#include "loop.h" +#include "memmap.h" +#include "bpf-ops.h" + +static DEFINE_MUTEX(io_bpf_ctrl_mutex); +static const struct btf_type *loop_params_type; + +__bpf_kfunc_start_defs(); + +__bpf_kfunc int bpf_io_uring_submit_sqes(struct iou_ctx *loop_ctx, u32 nr) +{ + struct io_ring_ctx *ctx = io_loop_demangle_ctx(loop_ctx); + + return io_submit_sqes(ctx, nr); +} + +__bpf_kfunc +__u8 *bpf_io_uring_get_region(struct iou_ctx *loop_ctx, __u32 region_id, + const size_t rdwr_buf_size) +{ + struct io_ring_ctx *ctx = io_loop_demangle_ctx(loop_ctx); + struct io_mapped_region *r; + + lockdep_assert_held(&ctx->uring_lock); + + switch (region_id) { + case IOU_REGION_MEM: + r = &ctx->param_region; + break; + case IOU_REGION_CQ: + r = &ctx->ring_region; + break; + case IOU_REGION_SQ: + r = &ctx->sq_region; + break; + default: + return NULL; + } + + if (unlikely(rdwr_buf_size > io_region_size(r))) + return NULL; + return io_region_get_ptr(r); +} + +__bpf_kfunc_end_defs(); + +BTF_KFUNCS_START(io_uring_kfunc_set) +BTF_ID_FLAGS(func, bpf_io_uring_submit_sqes, KF_SLEEPABLE); +BTF_ID_FLAGS(func, bpf_io_uring_get_region, KF_RET_NULL); +BTF_KFUNCS_END(io_uring_kfunc_set) + +static const struct btf_kfunc_id_set bpf_io_uring_kfunc_set = { + .owner = THIS_MODULE, + .set = &io_uring_kfunc_set, +}; + +static int io_bpf_ops__loop_step(struct iou_ctx *ctx, + struct iou_loop_params *lp) +{ + return IOU_LOOP_STOP; +} + +static struct io_uring_bpf_ops io_bpf_ops_stubs = { + .loop_step = io_bpf_ops__loop_step, +}; + +static bool bpf_io_is_valid_access(int off, int size, + enum bpf_access_type type, + const struct bpf_prog *prog, + struct bpf_insn_access_aux *info) +{ + if (type != BPF_READ) + return false; + if (off < 0 || off >= sizeof(__u64) * MAX_BPF_FUNC_ARGS) + return false; + if (off % size != 0) + return false; + + return btf_ctx_access(off, size, type, prog, info); +} + +static int bpf_io_btf_struct_access(struct bpf_verifier_log *log, + const struct bpf_reg_state *reg, int off, + int size) +{ + const struct btf_type *t = btf_type_by_id(reg->btf, reg->btf_id); + + if (t == loop_params_type) { + if (off + size <= offsetofend(struct iou_loop_params, cq_wait_idx)) + return SCALAR_VALUE; + } + + return -EACCES; +} + +static const struct bpf_verifier_ops bpf_io_verifier_ops = { + .get_func_proto = bpf_base_func_proto, + .is_valid_access = bpf_io_is_valid_access, + .btf_struct_access = bpf_io_btf_struct_access, +}; + +static const struct btf_type * +io_lookup_struct_type(struct btf *btf, const char *name) +{ + s32 type_id; + + type_id = btf_find_by_name_kind(btf, name, BTF_KIND_STRUCT); + if (type_id < 0) + return NULL; + return btf_type_by_id(btf, type_id); +} + +static int bpf_io_init(struct btf *btf) +{ + int ret; + + loop_params_type = io_lookup_struct_type(btf, "iou_loop_params"); + if (!loop_params_type) { + pr_err("io_uring: Failed to locate iou_loop_params\n"); + return -EINVAL; + } + + ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_STRUCT_OPS, + &bpf_io_uring_kfunc_set); + if (ret) { + pr_err("io_uring: Failed to register kfuncs (%d)\n", ret); + return ret; + } + return 0; +} + +static int bpf_io_check_member(const struct btf_type *t, + const struct btf_member *member, + const struct bpf_prog *prog) +{ + return 0; +} + +static int bpf_io_init_member(const struct btf_type *t, + const struct btf_member *member, + void *kdata, const void *udata) +{ + u32 moff = __btf_member_bit_offset(t, member) / 8; + const struct io_uring_bpf_ops *uops = udata; + struct io_uring_bpf_ops *ops = kdata; + + switch (moff) { + case offsetof(struct io_uring_bpf_ops, ring_fd): + ops->ring_fd = uops->ring_fd; + return 1; + } + return 0; +} + +static int io_install_bpf(struct io_ring_ctx *ctx, struct io_uring_bpf_ops *ops) +{ + if (ctx->flags & (IORING_SETUP_SQPOLL | IORING_SETUP_IOPOLL)) + return -EOPNOTSUPP; + if (!(ctx->flags & IORING_SETUP_DEFER_TASKRUN)) + return -EOPNOTSUPP; + + if (ctx->bpf_ops) + return -EBUSY; + if (ops->priv) + return -EBUSY; + if (WARN_ON_ONCE(!ops->loop_step)) + return -EINVAL; + + ops->priv = ctx; + ctx->bpf_ops = ops; + ctx->loop_step = ops->loop_step; + return 0; +} + +static int bpf_io_reg(void *kdata, struct bpf_link *link) +{ + struct io_uring_bpf_ops *ops = kdata; + struct io_ring_ctx *ctx; + struct file *file; + int ret = -EBUSY; + + file = io_uring_ctx_get_file(ops->ring_fd, false); + if (IS_ERR(file)) + return PTR_ERR(file); + ctx = file->private_data; + + scoped_guard(mutex, &io_bpf_ctrl_mutex) { + guard(mutex)(&ctx->uring_lock); + ret = io_install_bpf(ctx, ops); + } + + fput(file); + return ret; +} + +static void io_eject_bpf(struct io_ring_ctx *ctx) +{ + struct io_uring_bpf_ops *ops = ctx->bpf_ops; + + if (WARN_ON_ONCE(!ops)) + return; + if (WARN_ON_ONCE(ops->priv != ctx)) + return; + + ops->priv = NULL; + ctx->bpf_ops = NULL; + ctx->loop_step = NULL; +} + +static void bpf_io_unreg(void *kdata, struct bpf_link *link) +{ + struct io_uring_bpf_ops *ops = kdata; + struct io_ring_ctx *ctx; + + guard(mutex)(&io_bpf_ctrl_mutex); + ctx = ops->priv; + if (ctx) { + guard(mutex)(&ctx->uring_lock); + if (WARN_ON_ONCE(ctx->bpf_ops != ops)) + return; + + io_eject_bpf(ctx); + } +} + +void io_unregister_bpf_ops(struct io_ring_ctx *ctx) +{ + /* + * ->bpf_ops is write protected by io_bpf_ctrl_mutex and uring_lock, + * and read protected by either. Try to avoid taking the global lock + * for rings that never had any bpf installed. + */ + scoped_guard(mutex, &ctx->uring_lock) { + if (!ctx->bpf_ops) + return; + } + + guard(mutex)(&io_bpf_ctrl_mutex); + guard(mutex)(&ctx->uring_lock); + if (ctx->bpf_ops) + io_eject_bpf(ctx); +} + +static struct bpf_struct_ops bpf_ring_ops = { + .verifier_ops = &bpf_io_verifier_ops, + .reg = bpf_io_reg, + .unreg = bpf_io_unreg, + .check_member = bpf_io_check_member, + .init_member = bpf_io_init_member, + .init = bpf_io_init, + .cfi_stubs = &io_bpf_ops_stubs, + .name = "io_uring_bpf_ops", + .owner = THIS_MODULE, +}; + +static int __init io_uring_bpf_init(void) +{ + int ret; + + ret = register_bpf_struct_ops(&bpf_ring_ops, io_uring_bpf_ops); + if (ret) { + pr_err("io_uring: Failed to register struct_ops (%d)\n", ret); + return ret; + } + + return 0; +} +__initcall(io_uring_bpf_init); -- cgit v1.3.1