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 --- fs/jffs2/compr_rtime.c | 136 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 136 insertions(+) create mode 100644 fs/jffs2/compr_rtime.c (limited to 'fs/jffs2/compr_rtime.c') diff --git a/fs/jffs2/compr_rtime.c b/fs/jffs2/compr_rtime.c new file mode 100644 index 000000000..3bd9d2f3b --- /dev/null +++ b/fs/jffs2/compr_rtime.c @@ -0,0 +1,136 @@ +/* + * JFFS2 -- Journalling Flash File System, Version 2. + * + * Copyright © 2001-2007 Red Hat, Inc. + * Copyright © 2004-2010 David Woodhouse + * + * Created by Arjan van de Ven + * + * For licensing information, see the file 'LICENCE' in this directory. + * + * + * + * Very simple lz77-ish encoder. + * + * Theory of operation: Both encoder and decoder have a list of "last + * occurrences" for every possible source-value; after sending the + * first source-byte, the second byte indicated the "run" length of + * matches + * + * The algorithm is intended to only send "whole bytes", no bit-messing. + * + */ + +#include +#include +#include +#include +#include +#include "compr.h" + +/* _compress returns the compressed size, -1 if bigger */ +static int jffs2_rtime_compress(unsigned char *data_in, + unsigned char *cpage_out, + uint32_t *sourcelen, uint32_t *dstlen) +{ + unsigned short positions[256]; + int outpos = 0; + int pos=0; + + if (*dstlen <= 3) + return -1; + + memset(positions,0,sizeof(positions)); + + while (pos < (*sourcelen) && outpos <= (*dstlen)-2) { + int backpos, runlen=0; + unsigned char value; + + value = data_in[pos]; + + cpage_out[outpos++] = data_in[pos++]; + + backpos = positions[value]; + positions[value]=pos; + + while ((backpos < pos) && (pos < (*sourcelen)) && + (data_in[pos]==data_in[backpos++]) && (runlen<255)) { + pos++; + runlen++; + } + cpage_out[outpos++] = runlen; + } + + if (outpos >= pos) { + /* We failed */ + return -1; + } + + /* Tell the caller how much we managed to compress, and how much space it took */ + *sourcelen = pos; + *dstlen = outpos; + return 0; +} + + +static int jffs2_rtime_decompress(unsigned char *data_in, + unsigned char *cpage_out, + uint32_t srclen, uint32_t destlen) +{ + unsigned short positions[256]; + int outpos = 0; + int pos=0; + + memset(positions,0,sizeof(positions)); + + while (outpos destlen) { + return 1; + } + if (backoffs + repeat >= outpos) { + while(repeat) { + cpage_out[outpos++] = cpage_out[backoffs++]; + repeat--; + } + } else { + memcpy(&cpage_out[outpos],&cpage_out[backoffs],repeat); + outpos+=repeat; + } + } + } + return 0; +} + +static struct jffs2_compressor jffs2_rtime_comp = { + .priority = JFFS2_RTIME_PRIORITY, + .name = "rtime", + .compr = JFFS2_COMPR_RTIME, + .compress = &jffs2_rtime_compress, + .decompress = &jffs2_rtime_decompress, +#ifdef JFFS2_RTIME_DISABLED + .disabled = 1, +#else + .disabled = 0, +#endif +}; + +int jffs2_rtime_init(void) +{ + return jffs2_register_compressor(&jffs2_rtime_comp); +} + +void jffs2_rtime_exit(void) +{ + jffs2_unregister_compressor(&jffs2_rtime_comp); +} -- cgit v1.3.1