[PATCH] D76900: Enable IBT(Indirect Branch Tracking) in JIT with CET(Control-flow Enforcement Technology)

[H.J Lu via Phabricator via llvm-commits]

hjl.tools added a comment.

In D76900#1953937 <https://reviews.llvm.org/D76900#1953937>, @xiangzhangllvm wrote:

> I find your patch will not deal with internal function. 
>  I tested GCC, It really will generate endbr for static functions:
>
>   gcc version 9.3.1 20200317 (Red Hat 9.3.1-1) (GCC)
>    [xiangzh1 at gnu-tgl-1 ~/tmp]$cat t.c
>   extern int foo2(int a);
>  
>   extern int foo2(int a)
>   {
>     return a*6;
>   }
>  
>   static int foo3(int a)
>   {
>     return a*7;
>   }
>  
>   int foo(int a){
>   //  int (*pf3)(int) = foo;
>   //  int b = foo2(a) +foo3(a) + pf3(a);
>     int b = foo2(a) +foo3(a);
>     return b;
>   }
>    [xiangzh1 at gnu-tgl-1 ~/tmp]$
>   [xiangzh1 at gnu-tgl-1 ~/tmp]$gcc -fcf-protection t.c -S -o t.s


You need -O2 to turn on optimization:

  [hjl at gnu-cfl-2 tmp]$ cat y.c
  __attribute__ ((noclone, noinline))
  static int foo3(int a)
  {
    return a*7;
  }
  
  extern int b;
  
  void
  foo(int a)
  {
    b = foo3(a);
  }
  [hjl at gnu-cfl-2 tmp]$ gcc  -fcf-protection -O2 -S y.c
  [hjl at gnu-cfl-2 tmp]$ cat y.s
  	.file	"y.c"
  	.text
  	.p2align 4
  	.type	foo3, @function
  foo3:
  .LFB0:
  	.cfi_startproc
  	leal	0(,%rdi,8), %eax
  	subl	%edi, %eax
  	ret
  	.cfi_endproc
  .LFE0:
  	.size	foo3, .-foo3
  	.p2align 4
  	.globl	foo
  	.type	foo, @function
  foo:
  .LFB1:
  	.cfi_startproc
  	endbr64
  	call	foo3
  	movl	%eax, b(%rip)
  	ret
  	.cfi_endproc
  .LFE1:
  	.size	foo, .-foo
  	.ident	"GCC: (GNU) 9.3.1 20200317 (Red Hat 9.3.1-1)"
  	.section	.note.GNU-stack,"", at progbits
  	.section	.note.gnu.property,"a"
  	.align 8
  	.long	 1f - 0f
  	.long	 4f - 1f
  	.long	 5
  0:
  	.string	 "GNU"
  1:
  	.align 8
  	.long	 0xc0000002
  	.long	 3f - 2f
  2:
  	.long	 0x3
  3:
  	.align 8
  4:
  [hjl at gnu-cfl-2 tmp]$ 


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