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 --- lib/generic-radix-tree.c | 230 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 230 insertions(+) create mode 100644 lib/generic-radix-tree.c (limited to 'lib/generic-radix-tree.c') diff --git a/lib/generic-radix-tree.c b/lib/generic-radix-tree.c new file mode 100644 index 000000000..79e067b51 --- /dev/null +++ b/lib/generic-radix-tree.c @@ -0,0 +1,230 @@ + +#include +#include +#include +#include +#include + +/* + * Returns pointer to the specified byte @offset within @radix, or NULL if not + * allocated + */ +void *__genradix_ptr(struct __genradix *radix, size_t offset) +{ + return __genradix_ptr_inlined(radix, offset); +} +EXPORT_SYMBOL(__genradix_ptr); + +/* + * Returns pointer to the specified byte @offset within @radix, allocating it if + * necessary - newly allocated slots are always zeroed out: + */ +void *__genradix_ptr_alloc(struct __genradix *radix, size_t offset, + struct genradix_node **preallocated, + gfp_t gfp_mask) +{ + struct genradix_root *v = READ_ONCE(radix->root); + struct genradix_node *n, *new_node = NULL; + unsigned level; + + if (preallocated) + swap(new_node, *preallocated); + + /* Increase tree depth if necessary: */ + while (1) { + struct genradix_root *r = v, *new_root; + + n = genradix_root_to_node(r); + level = genradix_root_to_depth(r); + + if (n && ilog2(offset) < genradix_depth_shift(level)) + break; + + if (!new_node) { + new_node = genradix_alloc_node(gfp_mask); + if (!new_node) + return NULL; + } + + new_node->children[0] = n; + new_root = ((struct genradix_root *) + ((unsigned long) new_node | (n ? level + 1 : 0))); + + if ((v = cmpxchg_release(&radix->root, r, new_root)) == r) { + v = new_root; + new_node = NULL; + } else { + new_node->children[0] = NULL; + } + } + + while (level--) { + struct genradix_node **p = + &n->children[offset >> genradix_depth_shift(level)]; + offset &= genradix_depth_size(level) - 1; + + n = READ_ONCE(*p); + if (!n) { + if (!new_node) { + new_node = genradix_alloc_node(gfp_mask); + if (!new_node) + return NULL; + } + + if (!(n = cmpxchg_release(p, NULL, new_node))) + swap(n, new_node); + } + } + + if (new_node) + genradix_free_node(new_node); + + return &n->data[offset]; +} +EXPORT_SYMBOL(__genradix_ptr_alloc); + +void *__genradix_iter_peek(struct genradix_iter *iter, + struct __genradix *radix, + size_t objs_per_page) +{ + struct genradix_root *r; + struct genradix_node *n; + unsigned level, i; + + if (iter->offset == SIZE_MAX) + return NULL; + +restart: + r = READ_ONCE(radix->root); + if (!r) + return NULL; + + n = genradix_root_to_node(r); + level = genradix_root_to_depth(r); + + if (ilog2(iter->offset) >= genradix_depth_shift(level)) + return NULL; + + while (level) { + level--; + + i = (iter->offset >> genradix_depth_shift(level)) & + (GENRADIX_ARY - 1); + + while (!n->children[i]) { + size_t objs_per_ptr = genradix_depth_size(level); + + if (iter->offset + objs_per_ptr < iter->offset) { + iter->offset = SIZE_MAX; + iter->pos = SIZE_MAX; + return NULL; + } + + i++; + iter->offset = round_down(iter->offset + objs_per_ptr, + objs_per_ptr); + iter->pos = (iter->offset >> GENRADIX_NODE_SHIFT) * + objs_per_page; + if (i == GENRADIX_ARY) + goto restart; + } + + n = n->children[i]; + } + + return &n->data[iter->offset & (GENRADIX_NODE_SIZE - 1)]; +} +EXPORT_SYMBOL(__genradix_iter_peek); + +void *__genradix_iter_peek_prev(struct genradix_iter *iter, + struct __genradix *radix, + size_t objs_per_page, + size_t obj_size_plus_page_remainder) +{ + struct genradix_root *r; + struct genradix_node *n; + unsigned level, i; + + if (iter->offset == SIZE_MAX) + return NULL; + +restart: + r = READ_ONCE(radix->root); + if (!r) + return NULL; + + n = genradix_root_to_node(r); + level = genradix_root_to_depth(r); + + if (ilog2(iter->offset) >= genradix_depth_shift(level)) { + iter->offset = genradix_depth_size(level); + iter->pos = (iter->offset >> GENRADIX_NODE_SHIFT) * objs_per_page; + + iter->offset -= obj_size_plus_page_remainder; + iter->pos--; + } + + while (level) { + level--; + + i = (iter->offset >> genradix_depth_shift(level)) & + (GENRADIX_ARY - 1); + + while (!n->children[i]) { + size_t objs_per_ptr = genradix_depth_size(level); + + iter->offset = round_down(iter->offset, objs_per_ptr); + iter->pos = (iter->offset >> GENRADIX_NODE_SHIFT) * objs_per_page; + + if (!iter->offset) + return NULL; + + iter->offset -= obj_size_plus_page_remainder; + iter->pos--; + + if (!i) + goto restart; + --i; + } + + n = n->children[i]; + } + + return &n->data[iter->offset & (GENRADIX_NODE_SIZE - 1)]; +} +EXPORT_SYMBOL(__genradix_iter_peek_prev); + +static void genradix_free_recurse(struct genradix_node *n, unsigned level) +{ + if (level) { + unsigned i; + + for (i = 0; i < GENRADIX_ARY; i++) + if (n->children[i]) + genradix_free_recurse(n->children[i], level - 1); + } + + genradix_free_node(n); +} + +int __genradix_prealloc(struct __genradix *radix, size_t size, + gfp_t gfp_mask) +{ + size_t offset; + + for (offset = 0; offset < size; offset += GENRADIX_NODE_SIZE) + if (!__genradix_ptr_alloc(radix, offset, NULL, gfp_mask)) + return -ENOMEM; + + return 0; +} +EXPORT_SYMBOL(__genradix_prealloc); + +void __genradix_free(struct __genradix *radix) +{ + struct genradix_root *r = xchg(&radix->root, NULL); + + genradix_free_recurse(genradix_root_to_node(r), + genradix_root_to_depth(r)); +} +EXPORT_SYMBOL(__genradix_free); -- cgit v1.3.1