linux-kernel - Re: [PATCH 3/7] objtool: Mark __ubsan_handle_builtin

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Message-ID: <YpTD6k95/4dShUl1@elver.google.com>
Date:   Mon, 30 May 2022 15:17:30 +0200
From:   Marco Elver <elver@...gle.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     x86@...nel.org, jpoimboe@...hat.com, linux-kernel@...r.kernel.org,
        jbaron@...mai.com, rostedt@...dmis.org, ardb@...nel.org,
        mark.rutland@....com, kernel test robot <lkp@...el.com>
Subject: Re: [PATCH 3/7] objtool: Mark __ubsan_handle_builtin_unreachable()
 as noreturn

On Thu, May 26, 2022 at 12:52PM +0200, Peter Zijlstra wrote:
>   fs/ntfs3/ntfs3.prelink.o: warning: objtool: ni_read_frame() falls through to next function ni_readpage_cmpr.cold()
> 
> That is in fact:
> 
> 000000000000124a <ni_read_frame.cold>:
>     124a:       44 89 e0                mov    %r12d,%eax
>     124d:       0f b6 55 98             movzbl -0x68(%rbp),%edx
>     1251:       48 c7 c7 00 00 00 00    mov    $0x0,%rdi        1254: R_X86_64_32S      .data+0x1380
>     1258:       48 89 c6                mov    %rax,%rsi
>     125b:       e8 00 00 00 00          call   1260 <ni_read_frame.cold+0x16>   125c: R_X86_64_PLT32    __ubsan_handle_shift_out_of_bounds-0x4
>     1260:       48 8d 7d cc             lea    -0x34(%rbp),%rdi
>     1264:       e8 00 00 00 00          call   1269 <ni_read_frame.cold+0x1f>   1265: R_X86_64_PLT32    __tsan_read4-0x4
>     1269:       8b 45 cc                mov    -0x34(%rbp),%eax
>     126c:       e9 00 00 00 00          jmp    1271 <ni_read_frame.cold+0x27>   126d: R_X86_64_PC32     .text+0x19109
>     1271:       48 8b 75 a0             mov    -0x60(%rbp),%rsi
>     1275:       48 63 d0                movslq %eax,%rdx
>     1278:       48 c7 c7 00 00 00 00    mov    $0x0,%rdi        127b: R_X86_64_32S      .data+0x13a0
>     127f:       89 45 88                mov    %eax,-0x78(%rbp)
>     1282:       e8 00 00 00 00          call   1287 <ni_read_frame.cold+0x3d>   1283: R_X86_64_PLT32    __ubsan_handle_shift_out_of_bounds-0x4
>     1287:       8b 45 88                mov    -0x78(%rbp),%eax
>     128a:       e9 00 00 00 00          jmp    128f <ni_read_frame.cold+0x45>   128b: R_X86_64_PC32     .text+0x19098
>     128f:       48 c7 c7 00 00 00 00    mov    $0x0,%rdi        1292: R_X86_64_32S      .data+0x11f0
>     1296:       e8 00 00 00 00          call   129b <ni_readpage_cmpr.cold>     1297: R_X86_64_PLT32    __ubsan_handle_builtin_unreachable-0x4
> 
> 000000000000129b <ni_readpage_cmpr.cold>:
> 
> Tell objtool that __ubsan_handle_builtin_unreachable() is a noreturn.
> 
> Reported-by: kernel test robot <lkp@...el.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> Link: https://lkml.kernel.org/r/20220502091514.GB479834@worktop.programming.kicks-ass.net

Acked-by: Marco Elver <elver@...gle.com>

> ---
>  tools/objtool/check.c |    1 +
>  1 file changed, 1 insertion(+)
> 
> --- a/tools/objtool/check.c
> +++ b/tools/objtool/check.c
> @@ -185,6 +185,7 @@ static bool __dead_end_function(struct o
>  		"stop_this_cpu",
>  		"__invalid_creds",
>                 "cpu_startup_entry",
> +		"__ubsan_handle_builtin_unreachable",
>  	};
>  
>  	if (!func)
> 
>