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 --- tools/perf/util/strbuf.c | 170 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 170 insertions(+) create mode 100644 tools/perf/util/strbuf.c (limited to 'tools/perf/util/strbuf.c') diff --git a/tools/perf/util/strbuf.c b/tools/perf/util/strbuf.c new file mode 100644 index 000000000..a64a37628 --- /dev/null +++ b/tools/perf/util/strbuf.c @@ -0,0 +1,170 @@ +// SPDX-License-Identifier: GPL-2.0 +#include "cache.h" +#include "debug.h" +#include "strbuf.h" +#include +#include +#include +#include +#include +#include +#include + +/* + * Used as the default ->buf value, so that people can always assume + * buf is non NULL and ->buf is NUL terminated even for a freshly + * initialized strbuf. + */ +char strbuf_slopbuf[1]; + +int strbuf_init(struct strbuf *sb, ssize_t hint) +{ + sb->alloc = sb->len = 0; + sb->buf = strbuf_slopbuf; + if (hint) + return strbuf_grow(sb, hint); + return 0; +} + +void strbuf_release(struct strbuf *sb) +{ + if (sb->alloc) { + zfree(&sb->buf); + strbuf_init(sb, 0); + } +} + +char *strbuf_detach(struct strbuf *sb, size_t *sz) +{ + char *res = sb->alloc ? sb->buf : NULL; + if (sz) + *sz = sb->len; + strbuf_init(sb, 0); + return res; +} + +int strbuf_grow(struct strbuf *sb, size_t extra) +{ + char *buf; + size_t nr = sb->len + extra + 1; + + if (nr < sb->alloc) + return 0; + + if (nr <= sb->len) + return -E2BIG; + + if (alloc_nr(sb->alloc) > nr) + nr = alloc_nr(sb->alloc); + + /* + * Note that sb->buf == strbuf_slopbuf if sb->alloc == 0, and it is + * a static variable. Thus we have to avoid passing it to realloc. + */ + buf = realloc(sb->alloc ? sb->buf : NULL, nr * sizeof(*buf)); + if (!buf) + return -ENOMEM; + + sb->buf = buf; + sb->alloc = nr; + return 0; +} + +int strbuf_addch(struct strbuf *sb, int c) +{ + int ret = strbuf_grow(sb, 1); + if (ret) + return ret; + + sb->buf[sb->len++] = c; + sb->buf[sb->len] = '\0'; + return 0; +} + +int strbuf_add(struct strbuf *sb, const void *data, size_t len) +{ + int ret = strbuf_grow(sb, len); + if (ret) + return ret; + + memcpy(sb->buf + sb->len, data, len); + return strbuf_setlen(sb, sb->len + len); +} + +static int strbuf_addv(struct strbuf *sb, const char *fmt, va_list ap) +{ + int len, ret; + va_list ap_saved; + + if (!strbuf_avail(sb)) { + ret = strbuf_grow(sb, 64); + if (ret) + return ret; + } + + va_copy(ap_saved, ap); + len = vsnprintf(sb->buf + sb->len, sb->alloc - sb->len, fmt, ap); + if (len < 0) { + va_end(ap_saved); + return len; + } + if (len > strbuf_avail(sb)) { + ret = strbuf_grow(sb, len); + if (ret) { + va_end(ap_saved); + return ret; + } + len = vsnprintf(sb->buf + sb->len, sb->alloc - sb->len, fmt, ap_saved); + if (len > strbuf_avail(sb)) { + pr_debug("this should not happen, your vsnprintf is broken"); + va_end(ap_saved); + return -EINVAL; + } + } + va_end(ap_saved); + return strbuf_setlen(sb, sb->len + len); +} + +int strbuf_addf(struct strbuf *sb, const char *fmt, ...) +{ + va_list ap; + int ret; + + va_start(ap, fmt); + ret = strbuf_addv(sb, fmt, ap); + va_end(ap); + return ret; +} + +ssize_t strbuf_read(struct strbuf *sb, int fd, ssize_t hint) +{ + size_t oldlen = sb->len; + size_t oldalloc = sb->alloc; + int ret; + + ret = strbuf_grow(sb, hint ? hint : 8192); + if (ret) + return ret; + + for (;;) { + ssize_t cnt; + + cnt = read(fd, sb->buf + sb->len, sb->alloc - sb->len - 1); + if (cnt < 0) { + if (oldalloc == 0) + strbuf_release(sb); + else + strbuf_setlen(sb, oldlen); + return cnt; + } + if (!cnt) + break; + sb->len += cnt; + ret = strbuf_grow(sb, 8192); + if (ret) + return ret; + } + + sb->buf[sb->len] = '\0'; + return sb->len - oldlen; +} -- cgit v1.3.1