Re: [tip:objtool/core 8/12] vmlinux.o: warning: objtool: rust_begin_unwind+0x5c: rust_helper_BUG() is missing a __noreturn annotation
From: Josh Poimboeuf
Date: Tue Jun 06 2023 - 17:52:20 EST
Hi Miguel, Wedson,
Objtool detected that rust_helper_BUG() doesn't return, and seems to be
missing a __noreturn. But it actually *does* have __noreturn. The
problem is actually that its rust callees don't seem to know that, i.e.
they assume it returns.
After a little digging I found this comment in rust panic():
unsafe { bindings::BUG() };
// Bindgen currently does not recognize `__noreturn` so `BUG` returns `()`
// instead of `!`. See <https://github.com/rust-lang/rust-bindgen/issues/2094>.
loop {}
So it seems to be an issue with bindgen, though that github issue has
been resolved. Any idea when this will show up in a toolchain?
In the meantime we may have to get objtool to manually silence the
warning, unless you have any better ideas.
On Wed, Jun 07, 2023 at 04:57:42AM +0800, kernel test robot wrote:
> tree: https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git objtool/core
> head: ff9a6459bbec06df7da2545020d7383aba13b3fb
> commit: fedb724c3db5490234ddde0103811c28c2fedae0 [8/12] objtool: Detect missing __noreturn annotations
> config: x86_64-randconfig-a012-20230606 (https://download.01.org/0day-ci/archive/20230607/202306070408.EFxuDoRs-lkp@xxxxxxxxx/config)
> compiler: clang version 15.0.7 (https://github.com/llvm/llvm-project.git 8dfdcc7b7bf66834a761bd8de445840ef68e4d1a)
> reproduce (this is a W=1 build):
> mkdir -p ~/bin
> wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> chmod +x ~/bin/make.cross
> # https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit/?id=fedb724c3db5490234ddde0103811c28c2fedae0
> git remote add tip https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git
> git fetch --no-tags tip objtool/core
> git checkout fedb724c3db5490234ddde0103811c28c2fedae0
> # save the config file
> mkdir build_dir && cp config build_dir/.config
> COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang ~/bin/make.cross W=1 O=build_dir ARCH=x86_64 olddefconfig
> COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang ~/bin/make.cross W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash
>
> If you fix the issue, kindly add following tag where applicable
> | Reported-by: kernel test robot <lkp@xxxxxxxxx>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202306070408.EFxuDoRs-lkp@xxxxxxxxx/
>
> All warnings (new ones prefixed by >>):
>
> >> vmlinux.o: warning: objtool: rust_begin_unwind+0x5c: rust_helper_BUG() is missing a __noreturn annotation
>
>
> objdump-func vmlinux.o rust_begin_unwind:
> 0000 00000000000b9e69 <rust_begin_unwind>:
> 0000 b9e69: 48 83 ec 48 sub $0x48,%rsp
> 0004 b9e6d: 48 89 e0 mov %rsp,%rax
> 0007 b9e70: 48 89 38 mov %rdi,(%rax)
> 000a b9e73: 48 8d 4c 24 08 lea 0x8(%rsp),%rcx
> 000f b9e78: 48 89 01 mov %rax,(%rcx)
> 0012 b9e7b: 48 c7 41 08 00 00 00 00 movq $0x0,0x8(%rcx) b9e7f: R_X86_64_32S _RNvXsR_NtCs3yuwAp0waWO_4core3fmtRNtNtNtB7_5panic10panic_info9PanicInfoNtB5_7Display3fmtCsfATHBUcknU9_6kernel
> 001a b9e83: 48 8d 54 24 18 lea 0x18(%rsp),%rdx
> 001f b9e88: 48 c7 02 00 00 00 00 movq $0x0,(%rdx) b9e8b: R_X86_64_32S .rodata+0x137d8
> 0026 b9e8f: 48 c7 42 08 02 00 00 00 movq $0x2,0x8(%rdx)
> 002e b9e97: 48 c7 42 10 00 00 00 00 movq $0x0,0x10(%rdx)
> 0036 b9e9f: 48 89 4a 20 mov %rcx,0x20(%rdx)
> 003a b9ea3: 48 c7 42 28 01 00 00 00 movq $0x1,0x28(%rdx)
> 0042 b9eab: 48 c7 c7 00 00 00 00 mov $0x0,%rdi b9eae: R_X86_64_32S _RNvNtNtCsfATHBUcknU9_6kernel5print14format_strings5EMERG
> 0049 b9eb2: 48 c7 c6 00 00 00 00 mov $0x0,%rsi b9eb5: R_X86_64_32S .rodata+0x13568
> 0050 b9eb9: 31 c0 xor %eax,%eax
> 0052 b9ebb: e8 00 00 00 00 call b9ec0 <rust_begin_unwind+0x57> b9ebc: R_X86_64_PLT32 _printk-0x4
> 0057 b9ec0: e8 00 00 00 00 call b9ec5 <rust_begin_unwind+0x5c> b9ec1: R_X86_64_PLT32 rust_helper_BUG-0x4
> 005c b9ec5: eb fe jmp b9ec5 <rust_begin_unwind+0x5c>
>
> --
> 0-DAY CI Kernel Test Service
> https://github.com/intel/lkp-tests/wiki
--
Josh