Re: [PATCH v6 00/30] objtool: Function validation tracing

[Alexandre Chartre]

On 11/24/25 12:04, Borislav Petkov wrote:
> On Fri, Nov 21, 2025 at 10:53:10AM +0100, Alexandre Chartre wrote:
> > Notes:
> > ======
>
> So those examples below look very useful and cool. Can you pls document them
> so that I can find the breadcrumbs next time and use them?
>
> :-)
>
> Thx.

Sure. I will add a doc in tools/objtool/Documentation/ in followup patches.

Rgds,

alex.

> > Disassembly can show default alternative jumping to .altinstr_aux
> > -----------------------------------------------------------------
> > Disassembly can show a default alternative jumping to .altinstr_aux. This
> > happens when the _static_cpu_has() function is used. Its default code
> > jumps to .altinstr_aux where a test sequence is executed (test; jnz; jmp).
> >
> > At runtime, this sequence is not used because the _static_cpu_has()
> > an alternative with the X86_FEATURE_ALWAYS feature.
> >
> >
> >    debc:  perf_get_x86_pmu_capability+0xc      jmpq   0xdec1 <.altinstr_aux+0xfc> | NOP5  (X86_FEATURE_HYBRID_CPU) | jmpq   0x61a <perf_get_x86_pmu_capability+0x37>  (X86_FEATURE_ALWAYS)   # <alternative.debc>
> >    dec1:  perf_get_x86_pmu_capability+0x11     ud2
> >
> >
> > Disassembly can show alternative jumping to the next instruction
> > ----------------------------------------------------------------
> >
> > The disassembly can show jump tables with an alternative which jumps
> > to the next instruction.
> >
> > For example:
> >
> > def9:  perf_get_x86_pmu_capability+0x49    NOP2 | jmp    defb <perf_get_x86_pmu_capability+0x4b>  (JUMP)   # <alternative.def9>
> > defb:  perf_get_x86_pmu_capability+0x4b	   mov    0x0(%rip),%rdi        # 0xdf02 <x86_pmu+0xd8>
> >
> > This disassembly is correct. These instructions come from:
> >
> >          cap->num_counters_gp = x86_pmu_num_counters(NULL)):
> >
> > which will end up executing this statement:
> >
> >          if (static_branch_unlikely(&perf_is_hybrid) && NULL)
> > 	        <do something>;
> >
> > This statement is optimized to do nothing because the condition is
> > always false. But static_branch_unlikely() is implemented with a jump
> > table inside an "asm goto" statement, and "asm goto" statements are
> > not optimized.
> >
> > So basically the code is optimized like this:
> >
> >          if (static_branch_unlikely(&perf_is_hybrid))
> > 	        ;
> >
> > And this translates to the assembly code above.
> >
> >
> > Examples:
> > =========
> >
> > Example 1 (--trace option): Trace the validation of the os_save() function
> > --------------------------------------------------------------------------
> >
> > $ ./tools/objtool/objtool --hacks=jump_label --hacks=noinstr --hacks=skylake --ibt --orc --retpoline --rethunk --sls --static-call --uaccess --prefix=16 --link --trace os_xsave -v vmlinux.o
> > os_xsave: validation begin
> >   59be0:  os_xsave+0x0                  push   %r12                                          - state: cfa=rsp+16 r12=(cfa-16) stack_size=16
> >   59be2:  os_xsave+0x2		       mov    0x0(%rip),%eax        # 0x59be8 <alternatives_patched>
> >   59be8:  os_xsave+0x8		       push   %rbp                                          - state: cfa=rsp+24 rbp=(cfa-24) stack_size=24
> >   59be9:  os_xsave+0x9		       mov    %rdi,%rbp
> >   59bec:  os_xsave+0xc		       push   %rbx					     - state: cfa=rsp+32 rbx=(cfa-32) stack_size=32
> >   59bed:  os_xsave+0xd		       mov    0x8(%rdi),%rbx
> >   59bf1:  os_xsave+0x11		       mov    %rbx,%r12
> >   59bf4:  os_xsave+0x14		       shr    $0x20,%r12
> >   59bf8:  os_xsave+0x18		       test   %eax,%eax
> >   59bfa:  os_xsave+0x1a		       je     0x59c22 <os_xsave+0x42>                        - jump taken
> >   59c22:  os_xsave+0x42		       | ud2
> >   59c24:  os_xsave+0x44		       | jmp    0x59bfc <os_xsave+0x1c>                      - unconditional jump
> >   59bfc:  os_xsave+0x1c		       | | xor    %edx,%edx
> >   59bfe:  os_xsave+0x1e		       | | mov    %rbx,%rsi
> >   59c01:  os_xsave+0x21		       | | mov    %rbp,%rdi
> >   59c04:  os_xsave+0x24		       | | callq  0x59c09 <xfd_validate_state>               - call
> >   59c09:  os_xsave+0x29		       | | mov    %ebx,%eax
> >   59c0b:  os_xsave+0x2b		       | | mov    %r12d,%edx
> >   	 			       | | / <alternative.59c0e> X86_FEATURE_XSAVEOPT
> >    1b29:  .altinstr_replacement+0x1b29  | | | xsaveopt64 0x40(%rbp)
> >   59c13:  os_xsave+0x33		       | | | xor    %ebx,%ebx
> >   59c15:  os_xsave+0x35		       | | | test   %ebx,%ebx
> >   59c17:  os_xsave+0x37		       | | | jne    0x59c26 <os_xsave+0x46>                  - jump taken
> >   59c26:  os_xsave+0x46		       | | | | ud2
> >   59c28:  os_xsave+0x48		       | | | | pop    %rbx                                   - state: cfa=rsp+24 rbx=<undef> stack_size=24
> >   59c29:  os_xsave+0x49		       | | | | pop    %rbp				     - state: cfa=rsp+16 rbp=<undef> stack_size=16
> >   59c2a:  os_xsave+0x4a		       | | | | pop    %r12				     - state: cfa=rsp+8 r12=<undef> stack_size=8
> >   59c2c:  os_xsave+0x4c		       | | | | jmpq   0x59c31 <__x86_return_thunk>	     - return
> >   59c17:  os_xsave+0x37		       | | | jne    0x59c26 <os_xsave+0x46>		     - jump not taken
> >   59c19:  os_xsave+0x39		       | | | pop    %rbx    				     - state: cfa=rsp+24 rbx=<undef> stack_size=24
> >   59c1a:  os_xsave+0x3a		       | | | pop    %rbp				     - state: cfa=rsp+16 rbp=<undef> stack_size=16
> >   59c1b:  os_xsave+0x3b		       | | | pop    %r12				     - state: cfa=rsp+8 r12=<undef> stack_size=8
> >   59c1d:  os_xsave+0x3d		       | | | jmpq   0x59c22 <__x86_return_thunk>	     - return
> >   	 			       | | \ <alternative.59c0e> X86_FEATURE_XSAVEOPT
> > 				       | | / <alternative.59c0e> X86_FEATURE_XSAVEC
> >    1b2e:  .altinstr_replacement+0x1b2e  | | | xsavec64 0x40(%rbp)
> >   59c13:  os_xsave+0x33		       | | | xor    %ebx,%ebx                                - already visited
> >   	 			       | | \ <alternative.59c0e> X86_FEATURE_XSAVEC
> > 				       | | / <alternative.59c0e> X86_FEATURE_XSAVES
> >    1b33:  .altinstr_replacement+0x1b33  | | | xsaves64 0x40(%rbp)
> >   59c13:  os_xsave+0x33		       | | | xor    %ebx,%ebx                                - already visited
> >   	 			       | | \ <alternative.59c0e> X86_FEATURE_XSAVES
> > 				       | | / <alternative.59c0e> EXCEPTION for instruction at 0x59c0e <os_xsave+0x2e>
> >   59c15:  os_xsave+0x35		       | | | test   %ebx,%ebx                                - already visited
> >   	 			       | | \ <alternative.59c0e> EXCEPTION
> > 				       | | / <alternative.59c0e> DEFAULT
> >   59c0e:  os_xsave+0x2e		       | | xsave64 0x40(%rbp)
> >   59c13:  os_xsave+0x33		       | | xor    %ebx,%ebx                                  - already visited
> >   59bfa:  os_xsave+0x1a		       je     0x59c22 <os_xsave+0x42>                        - jump not taken
> >   59bfc:  os_xsave+0x1c		       xor    %edx,%edx                                      - already visited
> > os_xsave: validation end
> >
> >
> > Example 2 (--disas option): Single Instruction Alternatives
> > -----------------------------------------------------------
> >
> > Compact Output (default):
> >
> > Alternatives with single instructions are displayed each on one line,
> > with the instruction and a description of the alternative.
> >
> > $ ./tools/objtool/objtool --disas=perf_get_x86_pmu_capability --link vmlinux.o
> > perf_get_x86_pmu_capability:
> >    deb0:  perf_get_x86_pmu_capability+0x0     endbr64
> >    deb4:  perf_get_x86_pmu_capability+0x4     callq  0xdeb9 <__fentry__>
> >    deb9:  perf_get_x86_pmu_capability+0x9     mov    %rdi,%rdx
> >    debc:  perf_get_x86_pmu_capability+0xc     <alternative.debc>
> >    	 				     = jmpq   0xdec1 <.altinstr_aux+0xfc>                 (if DEFAULT)
> > 					     = jmpq   0x622 <perf_get_x86_pmu_capability+0x37>    (if X86_FEATURE_ALWAYS)
> > 					     = nop5                                               (if X86_FEATURE_HYBRID_CPU)
> >    dec1:  perf_get_x86_pmu_capability+0x11    ud2
> >    dec3:  perf_get_x86_pmu_capability+0x13    movq   $0x0,(%rdx)
> >    deca:  perf_get_x86_pmu_capability+0x1a    movq   $0x0,0x8(%rdx)
> >    ded2:  perf_get_x86_pmu_capability+0x22    movq   $0x0,0x10(%rdx)
> >    deda:  perf_get_x86_pmu_capability+0x2a    movq   $0x0,0x18(%rdx)
> >    dee2:  perf_get_x86_pmu_capability+0x32    jmpq   0xdee7 <__x86_return_thunk>
> >    dee7:  perf_get_x86_pmu_capability+0x37    cmpq   $0x0,0x0(%rip)        # 0xdeef <x86_pmu+0x10>
> >    deef:  perf_get_x86_pmu_capability+0x3f    je     0xdec3 <perf_get_x86_pmu_capability+0x13>
> >    def1:  perf_get_x86_pmu_capability+0x41    mov    0x0(%rip),%eax        # 0xdef7 <x86_pmu+0x8>
> >    def7:  perf_get_x86_pmu_capability+0x47    mov    %eax,(%rdi)
> >    def9:  perf_get_x86_pmu_capability+0x49    <jump_table.def9>
> >    	 				     = nop2                                              (if DEFAULT)
> > 					     = jmp    defb <perf_get_x86_pmu_capability+0x4b>    (if JUMP)
> >    defb:  perf_get_x86_pmu_capability+0x4b    mov    0x0(%rip),%rdi        # 0xdf02 <x86_pmu+0xd8>
> >    df02:  perf_get_x86_pmu_capability+0x52    <alternative.df02>
> >    	 				     = callq  0xdf07 <__sw_hweight64>    (if DEFAULT)
> > 					     = popcnt %rdi,%rax                  (if X86_FEATURE_POPCNT)
> >    df07:  perf_get_x86_pmu_capability+0x57    mov    %eax,0x4(%rdx)
> >    df0a:  perf_get_x86_pmu_capability+0x5a    <jump_table.df0a>
> >    	 				     = nop2                                              (if DEFAULT)
> > 					     = jmp    df0c <perf_get_x86_pmu_capability+0x5c>    (if JUMP)
> >    df0c:  perf_get_x86_pmu_capability+0x5c    mov    0x0(%rip),%rdi        # 0xdf13 <x86_pmu+0xe0>
> >    df13:  perf_get_x86_pmu_capability+0x63    <alternative.df13>
> >    	 				     = callq  0xdf18 <__sw_hweight64>    (if DEFAULT)
> > 					     = popcnt %rdi,%rax                  (if X86_FEATURE_POPCNT)
> >    df18:  perf_get_x86_pmu_capability+0x68    mov    %eax,0x8(%rdx)
> >    df1b:  perf_get_x86_pmu_capability+0x6b    mov    0x0(%rip),%eax        # 0xdf21 <x86_pmu+0xf8>
> >    df21:  perf_get_x86_pmu_capability+0x71    mov    %eax,0xc(%rdx)
> >    df24:  perf_get_x86_pmu_capability+0x74    mov    %eax,0x10(%rdx)
> >    df27:  perf_get_x86_pmu_capability+0x77    mov    0x0(%rip),%rax        # 0xdf2e <x86_pmu+0x108>
> >    df2e:  perf_get_x86_pmu_capability+0x7e    mov    %eax,0x14(%rdx)
> >    df31:  perf_get_x86_pmu_capability+0x81    mov    0x0(%rip),%eax        # 0xdf37 <x86_pmu+0x110>
> >    df37:  perf_get_x86_pmu_capability+0x87    mov    %eax,0x18(%rdx)
> >    df3a:  perf_get_x86_pmu_capability+0x8a    movzbl 0x0(%rip),%ecx        # 0xdf41 <x86_pmu+0x1d1>
> >    df41:  perf_get_x86_pmu_capability+0x91    movzbl 0x1c(%rdx),%eax
> >    df45:  perf_get_x86_pmu_capability+0x95    shr    %cl
> >    df47:  perf_get_x86_pmu_capability+0x97    and    $0x1,%ecx
> >    df4a:  perf_get_x86_pmu_capability+0x9a    and    $0xfffffffe,%eax
> >    df4d:  perf_get_x86_pmu_capability+0x9d    or     %ecx,%eax
> >    df4f:  perf_get_x86_pmu_capability+0x9f    mov    %al,0x1c(%rdx)
> >    df52:  perf_get_x86_pmu_capability+0xa2    jmpq   0xdf57 <__x86_return_thunk>
> >
> >
> > Wide Output (--wide option):
> >
> > Alternatives with single instructions are displayed side-by-side,
> > with an header.
> >
> > $ ./tools/objtool/objtool --disas=perf_get_x86_pmu_capability --wide --link vmlinux.o
> > perf_get_x86_pmu_capability:
> >    deb0:  perf_get_x86_pmu_capability+0x0       endbr64
> >    deb4:  perf_get_x86_pmu_capability+0x4       callq  0xdeb9 <__fentry__>
> >    deb9:  perf_get_x86_pmu_capability+0x9       mov    %rdi,%rdx
> >    debc:  perf_get_x86_pmu_capability+0xc     | <alternative.debc>                 | X86_FEATURE_ALWAYS                              | X86_FEATURE_HYBRID_CPU
> >    debc:  perf_get_x86_pmu_capability+0xc     | jmpq   0xdec1 <.altinstr_aux+0xfc> | jmpq   0x622 <perf_get_x86_pmu_capability+0x37> | nop5
> >    dec1:  perf_get_x86_pmu_capability+0x11      ud2
> >    dec3:  perf_get_x86_pmu_capability+0x13      movq   $0x0,(%rdx)
> >    deca:  perf_get_x86_pmu_capability+0x1a      movq   $0x0,0x8(%rdx)
> >    ded2:  perf_get_x86_pmu_capability+0x22      movq   $0x0,0x10(%rdx)
> >    deda:  perf_get_x86_pmu_capability+0x2a      movq   $0x0,0x18(%rdx)
> >    dee2:  perf_get_x86_pmu_capability+0x32      jmpq   0xdee7 <__x86_return_thunk>
> >    dee7:  perf_get_x86_pmu_capability+0x37      cmpq   $0x0,0x0(%rip)        # 0xdeef <x86_pmu+0x10>
> >    deef:  perf_get_x86_pmu_capability+0x3f      je     0xdec3 <perf_get_x86_pmu_capability+0x13>
> >    def1:  perf_get_x86_pmu_capability+0x41      mov    0x0(%rip),%eax        # 0xdef7 <x86_pmu+0x8>
> >    def7:  perf_get_x86_pmu_capability+0x47      mov    %eax,(%rdi)
> >    def9:  perf_get_x86_pmu_capability+0x49    | <jump_table.def9> | JUMP
> >    def9:  perf_get_x86_pmu_capability+0x49    | nop2              | jmp    defb <perf_get_x86_pmu_capability+0x4b>
> >    defb:  perf_get_x86_pmu_capability+0x4b      mov    0x0(%rip),%rdi        # 0xdf02 <x86_pmu+0xd8>
> >    df02:  perf_get_x86_pmu_capability+0x52    | <alternative.df02>             | X86_FEATURE_POPCNT
> >    df02:  perf_get_x86_pmu_capability+0x52    | callq  0xdf07 <__sw_hweight64> | popcnt %rdi,%rax
> >    df07:  perf_get_x86_pmu_capability+0x57      mov    %eax,0x4(%rdx)
> >    df0a:  perf_get_x86_pmu_capability+0x5a    | <jump_table.df0a> | JUMP
> >    df0a:  perf_get_x86_pmu_capability+0x5a    | nop2              | jmp    df0c <perf_get_x86_pmu_capability+0x5c>
> >    df0c:  perf_get_x86_pmu_capability+0x5c      mov    0x0(%rip),%rdi        # 0xdf13 <x86_pmu+0xe0>
> >    df13:  perf_get_x86_pmu_capability+0x63    | <alternative.df13>             | X86_FEATURE_POPCNT
> >    df13:  perf_get_x86_pmu_capability+0x63    | callq  0xdf18 <__sw_hweight64> | popcnt %rdi,%rax
> >    df18:  perf_get_x86_pmu_capability+0x68      mov    %eax,0x8(%rdx)
> >    df1b:  perf_get_x86_pmu_capability+0x6b      mov    0x0(%rip),%eax        # 0xdf21 <x86_pmu+0xf8>
> >    df21:  perf_get_x86_pmu_capability+0x71      mov    %eax,0xc(%rdx)
> >    df24:  perf_get_x86_pmu_capability+0x74      mov    %eax,0x10(%rdx)
> >    df27:  perf_get_x86_pmu_capability+0x77      mov    0x0(%rip),%rax        # 0xdf2e <x86_pmu+0x108>
> >    df2e:  perf_get_x86_pmu_capability+0x7e      mov    %eax,0x14(%rdx)
> >    df31:  perf_get_x86_pmu_capability+0x81      mov    0x0(%rip),%eax        # 0xdf37 <x86_pmu+0x110>
> >    df37:  perf_get_x86_pmu_capability+0x87      mov    %eax,0x18(%rdx)
> >    df3a:  perf_get_x86_pmu_capability+0x8a      movzbl 0x0(%rip),%ecx        # 0xdf41 <x86_pmu+0x1d1>
> >    df41:  perf_get_x86_pmu_capability+0x91      movzbl 0x1c(%rdx),%eax
> >    df45:  perf_get_x86_pmu_capability+0x95      shr    %cl
> >    df47:  perf_get_x86_pmu_capability+0x97      and    $0x1,%ecx
> >    df4a:  perf_get_x86_pmu_capability+0x9a      and    $0xfffffffe,%eax
> >    df4d:  perf_get_x86_pmu_capability+0x9d      or     %ecx,%eax
> >    df4f:  perf_get_x86_pmu_capability+0x9f      mov    %al,0x1c(%rdx)
> >    df52:  perf_get_x86_pmu_capability+0xa2      jmpq   0xdf57 <__x86_return_thunk>
> >
> >
> > Example 3 (--disas option): Alternatives with multiple instructions
> > -------------------------------------------------------------------
> >
> > Compact Output (default):
> >
> > Alternatives with multiple instructions are displayed one above the other,
> > with an header describing the alternative.
> >
> > $ ./tools/objtool/objtool --disas=__switch_to_asm --link vmlinux.o
> > __switch_to_asm:
> >    82c0:  __switch_to_asm+0x0       push   %rbp
> >    82c1:  __switch_to_asm+0x1	   push   %rbx
> >    82c2:  __switch_to_asm+0x2	   push   %r12
> >    82c4:  __switch_to_asm+0x4	   push   %r13
> >    82c6:  __switch_to_asm+0x6	   push   %r14
> >    82c8:  __switch_to_asm+0x8	   push   %r15
> >    82ca:  __switch_to_asm+0xa	   mov    %rsp,0x1670(%rdi)
> >    82d1:  __switch_to_asm+0x11	   mov    0x1670(%rsi),%rsp
> >    82d8:  __switch_to_asm+0x18	   mov    0xad8(%rsi),%rbx
> >    82df:  __switch_to_asm+0x1f	   mov    %rbx,%gs:0x0(%rip)        # 0x82e7 <__stack_chk_guard>
> >    82e7:  __switch_to_asm+0x27	   <alternative.82e7>
> >    	 			   = DEFAULT
> >    82e7:  __switch_to_asm+0x27	   | jmp    0x8312 <__switch_to_asm+0x52>
> >    82e9:  __switch_to_asm+0x29	   | nop*41
> >    	 			   |
> > 				   = X86_FEATURE_RSB_CTXSW
> >    82e7:  __switch_to_asm+0x27	   | mov    $0x10,%r12
> >    82ee:  __switch_to_asm+0x2e	   | callq  0x82f4 <__switch_to_asm+0x34>
> >    82f3:  __switch_to_asm+0x33	   | int3
> >    82f4:  __switch_to_asm+0x34	   | callq  0x82fa <__switch_to_asm+0x3a>
> >    82f9:  __switch_to_asm+0x39	   | int3
> >    82fa:  __switch_to_asm+0x3a	   | add    $0x10,%rsp
> >    82fe:  __switch_to_asm+0x3e	   | dec    %r12
> >    8301:  __switch_to_asm+0x41	   | jne    0x82ee <__switch_to_asm+0x2e>
> >    8303:  __switch_to_asm+0x43	   | lfence
> >    8306:  __switch_to_asm+0x46	   | movq   $0xffffffffffffffff,%gs:0x0(%rip)        # 0x20b <__x86_call_depth>
> >    	 			   |
> > 				   = !X86_FEATURE_ALWAYS
> >    82e7:  __switch_to_asm+0x27	   | nop1
> >    82e8:  __switch_to_asm+0x28	   | nop1
> >    82e9:  __switch_to_asm+0x29	   | callq  0x82ef <__switch_to_asm+0x2f>
> >    82ee:  __switch_to_asm+0x2e	   | int3
> >    82ef:  __switch_to_asm+0x2f	   | add    $0x8,%rsp
> >    82f3:  __switch_to_asm+0x33	   | lfence
> >    	 			   |
> >    8312:  __switch_to_asm+0x52	   pop    %r15
> >    8314:  __switch_to_asm+0x54	   pop    %r14
> >    8316:  __switch_to_asm+0x56	   pop    %r13
> >    8318:  __switch_to_asm+0x58	   pop    %r12
> >    831a:  __switch_to_asm+0x5a	   pop    %rbx
> >    831b:  __switch_to_asm+0x5b	   pop    %rbp
> >    831c:  __switch_to_asm+0x5c	   jmpq   0x8321 <__switch_to>
> >
> >
> > Wide Output (--wide option):
> >
> > Alternatives with multiple instructions are displayed side-by-side, with
> > an header describing the alternative. The code in the first column is the
> > default code of the alternative.
> >
> > $ ./tools/objtool/objtool --disas=__switch_to_asm --wide  --link vmlinux.o
> > __switch_to_asm:
> >    82c0:  __switch_to_asm+0x0       push   %rbp
> >    82c1:  __switch_to_asm+0x1	   push   %rbx
> >    82c2:  __switch_to_asm+0x2	   push   %r12
> >    82c4:  __switch_to_asm+0x4	   push   %r13
> >    82c6:  __switch_to_asm+0x6	   push   %r14
> >    82c8:  __switch_to_asm+0x8	   push   %r15
> >    82ca:  __switch_to_asm+0xa	   mov    %rsp,0x1670(%rdi)
> >    82d1:  __switch_to_asm+0x11	   mov    0x1670(%rsi),%rsp
> >    82d8:  __switch_to_asm+0x18	   mov    0xad8(%rsi),%rbx
> >    82df:  __switch_to_asm+0x1f	   mov    %rbx,%gs:0x0(%rip)        # 0x82e7 <__stack_chk_guard>
> >    82e7:  __switch_to_asm+0x27	 | <alternative.82e7>                   | X86_FEATURE_RSB_CTXSW                                               | !X86_FEATURE_ALWAYS
> >    82e7:  __switch_to_asm+0x27	 | jmp    0x8312 <__switch_to_asm+0x52> | mov    $0x10,%r12						      | nop1
> >    82e8:  __switch_to_asm+0x28	 |                                      | 	 							      | nop1
> >    82e9:  __switch_to_asm+0x29	 | nop*41                               |                                                                     | callq  0x82ef <__switch_to_asm+0x2f>
> >    82ee:  __switch_to_asm+0x2e	 |                                      | callq  0x82f4 <__switch_to_asm+0x34>                                | int3
> >    82ef:  __switch_to_asm+0x2f	 |                                      |                                                                     | add    $0x8,%rsp
> >    82f3:  __switch_to_asm+0x33	 |                                      | int3                                                                | lfence
> >    82f4:  __switch_to_asm+0x34	 |                                      | callq  0x82fa <__switch_to_asm+0x3a>                                |
> >    82f9:  __switch_to_asm+0x39	 |                                      | int3                                                                |
> >    82fa:  __switch_to_asm+0x3a	 |                                      | add    $0x10,%rsp                                                   |
> >    82fe:  __switch_to_asm+0x3e	 |                                      | dec    %r12                                                         |
> >    8301:  __switch_to_asm+0x41	 |                                      | jne    0x82ee <__switch_to_asm+0x2e>                                |
> >    8303:  __switch_to_asm+0x43	 |                                      | lfence                                                              |
> >    8306:  __switch_to_asm+0x46	 |                                      | movq   $0xffffffffffffffff,%gs:0x0(%rip) # 0x20b <__x86_call_depth> |
> >    8312:  __switch_to_asm+0x52	   pop    %r15
> >    8314:  __switch_to_asm+0x54	   pop    %r14
> >    8316:  __switch_to_asm+0x56	   pop    %r13
> >    8318:  __switch_to_asm+0x58	   pop    %r12
> >    831a:  __switch_to_asm+0x5a	   pop    %rbx
> >    831b:  __switch_to_asm+0x5b	   pop    %rbp
> >    831c:  __switch_to_asm+0x5c	   jmpq   0x8321 <__switch_to>
> >    
> > -----
> >
> > Alexandre Chartre (30):
> >    objtool: Move disassembly functions to a separated file
> >    objtool: Create disassembly context
> >    objtool: Disassemble code with libopcodes instead of running objdump
> >    tool build: Remove annoying newline in build output
> >    objtool: Print symbol during disassembly
> >    objtool: Store instruction disassembly result
> >    objtool: Disassemble instruction on warning or backtrace
> >    objtool: Extract code to validate instruction from the validate branch
> >      loop
> >    objtool: Record symbol name max length
> >    objtool: Add option to trace function validation
> >    objtool: Trace instruction state changes during function validation
> >    objtool: Improve register reporting during function validation
> >    objtool: Identify the different types of alternatives
> >    objtool: Add functions to better name alternatives
> >    objtool: Improve tracing of alternative instructions
> >    objtool: Do not validate IBT for .return_sites and .call_sites
> >    objtool: Add the --disas=<function-pattern> action
> >    objtool: Preserve alternatives order
> >    objtool: Print headers for alternatives
> >    objtool: Disassemble group alternatives
> >    objtool: Print addresses with alternative instructions
> >    objtool: Disassemble exception table alternatives
> >    objtool: Disassemble jump table alternatives
> >    objtool: Fix address references in alternatives
> >    objtool: Provide access to feature and flags of group alternatives
> >    objtool: Function to get the name of a CPU feature
> >    objtool: Improve naming of group alternatives
> >    objtool: Compact output for alternatives with one instruction
> >    objtool: Add wide output for disassembly
> >    objtool: Trim trailing NOPs in alternative
> >
> >   .../x86/tools/gen-cpu-feature-names-x86.awk   |   33 +
> >   tools/build/Makefile.feature                  |    4 +-
> >   tools/objtool/.gitignore                      |    3 +
> >   tools/objtool/Build                           |    3 +
> >   tools/objtool/Makefile                        |   26 +
> >   tools/objtool/arch/loongarch/decode.c         |   23 +
> >   tools/objtool/arch/loongarch/special.c        |    5 +
> >   tools/objtool/arch/powerpc/decode.c           |   24 +
> >   tools/objtool/arch/powerpc/special.c          |    5 +
> >   tools/objtool/arch/x86/Build                  |    8 +
> >   tools/objtool/arch/x86/decode.c               |   20 +
> >   tools/objtool/arch/x86/special.c              |   10 +
> >   tools/objtool/builtin-check.c                 |    4 +
> >   tools/objtool/check.c                         |  648 +++++----
> >   tools/objtool/disas.c                         | 1245 +++++++++++++++++
> >   tools/objtool/include/objtool/arch.h          |   11 +
> >   tools/objtool/include/objtool/builtin.h       |    3 +
> >   tools/objtool/include/objtool/check.h         |   35 +-
> >   tools/objtool/include/objtool/disas.h         |   81 ++
> >   tools/objtool/include/objtool/special.h       |    4 +-
> >   tools/objtool/include/objtool/trace.h         |  141 ++
> >   tools/objtool/include/objtool/warn.h          |   17 +-
> >   tools/objtool/special.c                       |    2 +
> >   tools/objtool/trace.c                         |  203 +++
> >   24 files changed, 2259 insertions(+), 299 deletions(-)
> >   create mode 100644 tools/arch/x86/tools/gen-cpu-feature-names-x86.awk
> >   create mode 100644 tools/objtool/disas.c
> >   create mode 100644 tools/objtool/include/objtool/disas.h
> >   create mode 100644 tools/objtool/include/objtool/trace.h
> >   create mode 100644 tools/objtool/trace.c
> >
> > --
> > 2.43.5