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 --- Documentation/admin-guide/device-mapper/dm-ebs.rst | 51 ++++++++++++++++++++++ 1 file changed, 51 insertions(+) create mode 100644 Documentation/admin-guide/device-mapper/dm-ebs.rst (limited to 'Documentation/admin-guide/device-mapper/dm-ebs.rst') diff --git a/Documentation/admin-guide/device-mapper/dm-ebs.rst b/Documentation/admin-guide/device-mapper/dm-ebs.rst new file mode 100644 index 000000000..c09f66db5 --- /dev/null +++ b/Documentation/admin-guide/device-mapper/dm-ebs.rst @@ -0,0 +1,51 @@ +====== +dm-ebs +====== + + +This target is similar to the linear target except that it emulates +a smaller logical block size on a device with a larger logical block +size. Its main purpose is to provide emulation of 512 byte sectors on +devices that do not provide this emulation (i.e. 4K native disks). + +Supported emulated logical block sizes 512, 1024, 2048 and 4096. + +Underlying block size can be set to > 4K to test buffering larger units. + + +Table parameters +---------------- + [] + +Mandatory parameters: + + : + Full pathname to the underlying block-device, + or a "major:minor" device-number. + : + Starting sector within the device; + has to be a multiple of . + : + Number of sectors defining the logical block size to be emulated; + 1, 2, 4, 8 sectors of 512 bytes supported. + +Optional parameter: + + : + Number of sectors defining the logical block size of . + 2^N supported, e.g. 8 = emulate 8 sectors of 512 bytes = 4KiB. + If not provided, the logical block size of will be used. + + +Examples: + +Emulate 1 sector = 512 bytes logical block size on /dev/sda starting at +offset 1024 sectors with underlying devices block size automatically set: + +ebs /dev/sda 1024 1 + +Emulate 2 sector = 1KiB logical block size on /dev/sda starting at +offset 128 sectors, enforce 2KiB underlying device block size. +This presumes 2KiB logical blocksize on /dev/sda or less to work: + +ebs /dev/sda 128 2 4 -- cgit v1.3.1