[PATCH 0/2] nptl: Update struct pthread_unwind_buf

[Florian Weimer]

On 02/09/2018 03:13 PM, H.J. Lu wrote:
> I built glibc master with gcc-8.0.1 -mcet -fcf-protection.  Some object
> files do get CET marker as expected.  But static executable isn't:

I said static libraries.  If I compile this code (based on the example 
from the manual page) on Fedora rawhide:

#include <pthread.h>
#include <stdio.h>

static int done = 0;
static int cleanup_pop_arg = 0;
static int cnt = 0;

static void
cleanup_handler(void *arg)
{
   printf("Called clean-up handler\n");
   cnt = 0;
}

void *
thread_start(void *arg)
{
   time_t start, curr;

   printf("New thread started\n");

   pthread_cleanup_push(cleanup_handler, NULL);

   curr = start = time(NULL);

   while (!done) {
     pthread_testcancel();           /* A cancellation point */
     if (curr < time(NULL)) {
       curr = time(NULL);
       printf("cnt = %d\n", cnt);  /* A cancellation point */
       cnt++;
     }
   }

   pthread_cleanup_pop(cleanup_pop_arg);
   return NULL;
}

the small jump buffer is used:

0000000000000030 <thread_start>:
   30:   f3 0f 1e fa             endbr64
   34:   53                      push   %rbx
   35:   bf 00 00 00 00          mov    $0x0,%edi
                         36: R_X86_64_32 .rodata.str1.1+0x18
   3a:   48 83 ec 70             sub    $0x70,%rsp
   3e:   e8 00 00 00 00          callq  43 <thread_start+0x13>
                         3f: R_X86_64_PC32       puts-0x4
   43:   31 f6                   xor    %esi,%esi
   45:   48 89 e7                mov    %rsp,%rdi
   48:   e8 00 00 00 00          callq  4d <thread_start+0x1d>
                         49: R_X86_64_PC32       __sigsetjmp-0x4
   4d:   f3 0f 1e fa             endbr64
   51:   85 c0                   test   %eax,%eax
   53:   75 51                   jne    a6 <thread_start+0x76>
   55:   48 89 e7                mov    %rsp,%rdi
   58:   e8 00 00 00 00          callq  5d <thread_start+0x2d>
                         59: R_X86_64_PC32  __pthread_register_cancel-0x4

And it looks to me that readelf says the object file is compatible with CET:

Displaying notes found in: .note.gnu.property
   Owner                 Data size       Description
   GNU                  0x00000010       NT_GNU_PROPERTY_TYPE_0
       Properties: x86 feature: IBT, SHSTK

Thanks,
Florian