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/test_dynamic_debug.c | 166 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 166 insertions(+) create mode 100644 lib/test_dynamic_debug.c (limited to 'lib/test_dynamic_debug.c') diff --git a/lib/test_dynamic_debug.c b/lib/test_dynamic_debug.c new file mode 100644 index 000000000..77c2a669b --- /dev/null +++ b/lib/test_dynamic_debug.c @@ -0,0 +1,166 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Kernel module for testing dynamic_debug + * + * Authors: + * Jim Cromie + */ + +#define pr_fmt(fmt) "test_dd: " fmt + +#include + +/* run tests by reading or writing sysfs node: do_prints */ + +static void do_prints(void); /* device under test */ +static int param_set_do_prints(const char *instr, const struct kernel_param *kp) +{ + do_prints(); + return 0; +} +static int param_get_do_prints(char *buffer, const struct kernel_param *kp) +{ + do_prints(); + return scnprintf(buffer, PAGE_SIZE, "did do_prints\n"); +} +static const struct kernel_param_ops param_ops_do_prints = { + .set = param_set_do_prints, + .get = param_get_do_prints, +}; +module_param_cb(do_prints, ¶m_ops_do_prints, NULL, 0600); + +/* + * Using the CLASSMAP api: + * - classmaps must have corresponding enum + * - enum symbols must match/correlate with class-name strings in the map. + * - base must equal enum's 1st value + * - multiple maps must set their base to share the 0-30 class_id space !! + * (build-bug-on tips welcome) + * Additionally, here: + * - tie together sysname, mapname, bitsname, flagsname + */ +#define DD_SYS_WRAP(_model, _flags) \ + static unsigned long bits_##_model; \ + static struct ddebug_class_param _flags##_model = { \ + .bits = &bits_##_model, \ + .flags = #_flags, \ + .map = &map_##_model, \ + }; \ + module_param_cb(_flags##_##_model, ¶m_ops_dyndbg_classes, &_flags##_model, 0600) + +/* numeric input, independent bits */ +enum cat_disjoint_bits { + D2_CORE = 0, + D2_DRIVER, + D2_KMS, + D2_PRIME, + D2_ATOMIC, + D2_VBL, + D2_STATE, + D2_LEASE, + D2_DP, + D2_DRMRES }; +DECLARE_DYNDBG_CLASSMAP(map_disjoint_bits, DD_CLASS_TYPE_DISJOINT_BITS, 0, + "D2_CORE", + "D2_DRIVER", + "D2_KMS", + "D2_PRIME", + "D2_ATOMIC", + "D2_VBL", + "D2_STATE", + "D2_LEASE", + "D2_DP", + "D2_DRMRES"); +DD_SYS_WRAP(disjoint_bits, p); +DD_SYS_WRAP(disjoint_bits, T); + +/* symbolic input, independent bits */ +enum cat_disjoint_names { LOW = 11, MID, HI }; +DECLARE_DYNDBG_CLASSMAP(map_disjoint_names, DD_CLASS_TYPE_DISJOINT_NAMES, 10, + "LOW", "MID", "HI"); +DD_SYS_WRAP(disjoint_names, p); +DD_SYS_WRAP(disjoint_names, T); + +/* numeric verbosity, V2 > V1 related */ +enum cat_level_num { V0 = 14, V1, V2, V3, V4, V5, V6, V7 }; +DECLARE_DYNDBG_CLASSMAP(map_level_num, DD_CLASS_TYPE_LEVEL_NUM, 14, + "V0", "V1", "V2", "V3", "V4", "V5", "V6", "V7"); +DD_SYS_WRAP(level_num, p); +DD_SYS_WRAP(level_num, T); + +/* symbolic verbosity */ +enum cat_level_names { L0 = 22, L1, L2, L3, L4, L5, L6, L7 }; +DECLARE_DYNDBG_CLASSMAP(map_level_names, DD_CLASS_TYPE_LEVEL_NAMES, 22, + "L0", "L1", "L2", "L3", "L4", "L5", "L6", "L7"); +DD_SYS_WRAP(level_names, p); +DD_SYS_WRAP(level_names, T); + +/* stand-in for all pr_debug etc */ +#define prdbg(SYM) __pr_debug_cls(SYM, #SYM " msg\n") + +static void do_cats(void) +{ + pr_debug("doing categories\n"); + + prdbg(LOW); + prdbg(MID); + prdbg(HI); + + prdbg(D2_CORE); + prdbg(D2_DRIVER); + prdbg(D2_KMS); + prdbg(D2_PRIME); + prdbg(D2_ATOMIC); + prdbg(D2_VBL); + prdbg(D2_STATE); + prdbg(D2_LEASE); + prdbg(D2_DP); + prdbg(D2_DRMRES); +} + +static void do_levels(void) +{ + pr_debug("doing levels\n"); + + prdbg(V1); + prdbg(V2); + prdbg(V3); + prdbg(V4); + prdbg(V5); + prdbg(V6); + prdbg(V7); + + prdbg(L1); + prdbg(L2); + prdbg(L3); + prdbg(L4); + prdbg(L5); + prdbg(L6); + prdbg(L7); +} + +static void do_prints(void) +{ + do_cats(); + do_levels(); +} + +static int __init test_dynamic_debug_init(void) +{ + pr_debug("init start\n"); + do_prints(); + pr_debug("init done\n"); + return 0; +} + +static void __exit test_dynamic_debug_exit(void) +{ + pr_debug("exited\n"); +} + +module_init(test_dynamic_debug_init); +module_exit(test_dynamic_debug_exit); + +MODULE_AUTHOR("Jim Cromie "); +MODULE_DESCRIPTION("Kernel module for testing dynamic_debug"); +MODULE_LICENSE("GPL"); -- cgit v1.3.1