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/sg_pool.c | 180 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 180 insertions(+) create mode 100644 lib/sg_pool.c (limited to 'lib/sg_pool.c') diff --git a/lib/sg_pool.c b/lib/sg_pool.c new file mode 100644 index 000000000..9bfe60ca3 --- /dev/null +++ b/lib/sg_pool.c @@ -0,0 +1,180 @@ +// SPDX-License-Identifier: GPL-2.0-only +#include +#include +#include +#include + +#define SG_MEMPOOL_NR ARRAY_SIZE(sg_pools) +#define SG_MEMPOOL_SIZE 2 + +struct sg_pool { + size_t size; + char *name; + struct kmem_cache *slab; + mempool_t *pool; +}; + +#define SP(x) { .size = x, "sgpool-" __stringify(x) } +#if (SG_CHUNK_SIZE < 32) +#error SG_CHUNK_SIZE is too small (must be 32 or greater) +#endif +static struct sg_pool sg_pools[] = { + SP(8), + SP(16), +#if (SG_CHUNK_SIZE > 32) + SP(32), +#if (SG_CHUNK_SIZE > 64) + SP(64), +#if (SG_CHUNK_SIZE > 128) + SP(128), +#if (SG_CHUNK_SIZE > 256) +#error SG_CHUNK_SIZE is too large (256 MAX) +#endif +#endif +#endif +#endif + SP(SG_CHUNK_SIZE) +}; +#undef SP + +static inline unsigned int sg_pool_index(unsigned short nents) +{ + unsigned int index; + + BUG_ON(nents > SG_CHUNK_SIZE); + + if (nents <= 8) + index = 0; + else + index = get_count_order(nents) - 3; + + return index; +} + +static void sg_pool_free(struct scatterlist *sgl, unsigned int nents) +{ + struct sg_pool *sgp; + + sgp = sg_pools + sg_pool_index(nents); + mempool_free(sgl, sgp->pool); +} + +static struct scatterlist *sg_pool_alloc(unsigned int nents, gfp_t gfp_mask) +{ + struct sg_pool *sgp; + + sgp = sg_pools + sg_pool_index(nents); + return mempool_alloc(sgp->pool, gfp_mask); +} + +/** + * sg_free_table_chained - Free a previously mapped sg table + * @table: The sg table header to use + * @nents_first_chunk: size of the first_chunk SGL passed to + * sg_alloc_table_chained + * + * Description: + * Free an sg table previously allocated and setup with + * sg_alloc_table_chained(). + * + * @nents_first_chunk has to be same with that same parameter passed + * to sg_alloc_table_chained(). + * + **/ +void sg_free_table_chained(struct sg_table *table, + unsigned nents_first_chunk) +{ + if (table->orig_nents <= nents_first_chunk) + return; + + if (nents_first_chunk == 1) + nents_first_chunk = 0; + + __sg_free_table(table, SG_CHUNK_SIZE, nents_first_chunk, sg_pool_free, + table->orig_nents); +} +EXPORT_SYMBOL_GPL(sg_free_table_chained); + +/** + * sg_alloc_table_chained - Allocate and chain SGLs in an sg table + * @table: The sg table header to use + * @nents: Number of entries in sg list + * @first_chunk: first SGL + * @nents_first_chunk: number of the SGL of @first_chunk + * + * Description: + * Allocate and chain SGLs in an sg table. If @nents@ is larger than + * @nents_first_chunk a chained sg table will be setup. @first_chunk is + * ignored if nents_first_chunk <= 1 because user expects the SGL points + * non-chain SGL. + * + **/ +int sg_alloc_table_chained(struct sg_table *table, int nents, + struct scatterlist *first_chunk, unsigned nents_first_chunk) +{ + int ret; + + BUG_ON(!nents); + + if (first_chunk && nents_first_chunk) { + if (nents <= nents_first_chunk) { + table->nents = table->orig_nents = nents; + sg_init_table(table->sgl, nents); + return 0; + } + } + + /* User supposes that the 1st SGL includes real entry */ + if (nents_first_chunk <= 1) { + first_chunk = NULL; + nents_first_chunk = 0; + } + + ret = __sg_alloc_table(table, nents, SG_CHUNK_SIZE, + first_chunk, nents_first_chunk, + GFP_ATOMIC, sg_pool_alloc); + if (unlikely(ret)) + sg_free_table_chained(table, nents_first_chunk); + return ret; +} +EXPORT_SYMBOL_GPL(sg_alloc_table_chained); + +static __init int sg_pool_init(void) +{ + int i; + + for (i = 0; i < SG_MEMPOOL_NR; i++) { + struct sg_pool *sgp = sg_pools + i; + int size = sgp->size * sizeof(struct scatterlist); + + sgp->slab = kmem_cache_create(sgp->name, size, 0, + SLAB_HWCACHE_ALIGN, NULL); + if (!sgp->slab) { + printk(KERN_ERR "SG_POOL: can't init sg slab %s\n", + sgp->name); + goto cleanup_sdb; + } + + sgp->pool = mempool_create_slab_pool(SG_MEMPOOL_SIZE, + sgp->slab); + if (!sgp->pool) { + printk(KERN_ERR "SG_POOL: can't init sg mempool %s\n", + sgp->name); + goto cleanup_sdb; + } + } + + return 0; + +cleanup_sdb: + for (i = 0; i < SG_MEMPOOL_NR; i++) { + struct sg_pool *sgp = sg_pools + i; + + mempool_destroy(sgp->pool); + kmem_cache_destroy(sgp->slab); + } + + return -ENOMEM; +} + +subsys_initcall(sg_pool_init); -- cgit v1.3.1