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 --- drivers/base/regmap/regmap-raw-ram.c | 144 +++++++++++++++++++++++++++++++++++ 1 file changed, 144 insertions(+) create mode 100644 drivers/base/regmap/regmap-raw-ram.c (limited to 'drivers/base/regmap/regmap-raw-ram.c') diff --git a/drivers/base/regmap/regmap-raw-ram.c b/drivers/base/regmap/regmap-raw-ram.c new file mode 100644 index 000000000..60d6e95cd --- /dev/null +++ b/drivers/base/regmap/regmap-raw-ram.c @@ -0,0 +1,144 @@ +// SPDX-License-Identifier: GPL-2.0 +// +// Register map access API - Memory region with raw access +// +// This is intended for testing only +// +// Copyright (c) 2023, Arm Ltd + +#include +#include +#include +#include +#include +#include +#include + +#include "internal.h" + +static unsigned int decode_reg(enum regmap_endian endian, const void *reg) +{ + const u16 *r = reg; + + if (endian == REGMAP_ENDIAN_BIG) + return be16_to_cpu(*r); + else + return le16_to_cpu(*r); +} + +static int regmap_raw_ram_gather_write(void *context, + const void *reg, size_t reg_len, + const void *val, size_t val_len) +{ + struct regmap_ram_data *data = context; + unsigned int r; + u16 *our_buf = (u16 *)data->vals; + int i; + + if (reg_len != 2) + return -EINVAL; + if (val_len % 2) + return -EINVAL; + + r = decode_reg(data->reg_endian, reg); + if (data->noinc_reg && data->noinc_reg(data, r)) { + memcpy(&our_buf[r], val + val_len - 2, 2); + data->written[r] = true; + } else { + memcpy(&our_buf[r], val, val_len); + + for (i = 0; i < val_len / 2; i++) + data->written[r + i] = true; + } + + return 0; +} + +static int regmap_raw_ram_write(void *context, const void *data, size_t count) +{ + return regmap_raw_ram_gather_write(context, data, 2, + data + 2, count - 2); +} + +static int regmap_raw_ram_read(void *context, + const void *reg, size_t reg_len, + void *val, size_t val_len) +{ + struct regmap_ram_data *data = context; + unsigned int r; + u16 *our_buf = (u16 *)data->vals; + int i; + + if (reg_len != 2) + return -EINVAL; + if (val_len % 2) + return -EINVAL; + + r = decode_reg(data->reg_endian, reg); + if (data->noinc_reg && data->noinc_reg(data, r)) { + for (i = 0; i < val_len; i += 2) + memcpy(val + i, &our_buf[r], 2); + data->read[r] = true; + } else { + memcpy(val, &our_buf[r], val_len); + + for (i = 0; i < val_len / 2; i++) + data->read[r + i] = true; + } + + return 0; +} + +static void regmap_raw_ram_free_context(void *context) +{ + struct regmap_ram_data *data = context; + + kfree(data->vals); + kfree(data->read); + kfree(data->written); + kfree(data); +} + +static const struct regmap_bus regmap_raw_ram = { + .fast_io = true, + .write = regmap_raw_ram_write, + .gather_write = regmap_raw_ram_gather_write, + .read = regmap_raw_ram_read, + .free_context = regmap_raw_ram_free_context, +}; + +struct regmap *__regmap_init_raw_ram(struct device *dev, + const struct regmap_config *config, + struct regmap_ram_data *data, + struct lock_class_key *lock_key, + const char *lock_name) +{ + struct regmap *map; + + if (config->reg_bits != 16) + return ERR_PTR(-EINVAL); + + if (!config->max_register) { + pr_crit("No max_register specified for RAM regmap\n"); + return ERR_PTR(-EINVAL); + } + + data->read = kzalloc_objs(bool, config->max_register + 1); + if (!data->read) + return ERR_PTR(-ENOMEM); + + data->written = kzalloc_objs(bool, config->max_register + 1); + if (!data->written) + return ERR_PTR(-ENOMEM); + + data->reg_endian = config->reg_format_endian; + + map = __regmap_init(dev, ®map_raw_ram, data, config, + lock_key, lock_name); + + return map; +} +EXPORT_SYMBOL_GPL(__regmap_init_raw_ram); + +MODULE_DESCRIPTION("Register map access API - Memory region with raw access"); +MODULE_LICENSE("GPL v2"); -- cgit v1.3.1