Line data    Source code

       1             : #define _GNU_SOURCE
       2             : #include "fd_tile.h"
       3             : 
       4             : #include <errno.h>
       5             : #include <unistd.h>
       6             : #include <sys/syscall.h>
       7             : 
       8             : /* glibc>=2.35 (and RHEL 9's 2.34 backport) registers rseq on every
       9             :    thread and exports the area through <sys/rseq.h>.  Older glibc and
      10             :    musl register nothing, so there is nothing to unregister. */
      11             : #if defined(__has_include)
      12             : #if __has_include(<sys/rseq.h>)
      13             : #include <sys/rseq.h>
      14             : #define FD_TILE_HAS_GLIBC_RSEQ 1
      15             : #endif
      16             : #endif
      17             : #ifndef FD_TILE_HAS_GLIBC_RSEQ
      18             : #define FD_TILE_HAS_GLIBC_RSEQ 0
      19             : #endif
      20             : 
      21             : int
      22           0 : fd_tile_rseq_unregister( void ) {
      23           0 : #if FD_HAS_X86 && FD_TILE_HAS_GLIBC_RSEQ
      24           0 :   if( FD_UNLIKELY( !__rseq_size ) ) return 0; /* glibc did not register rseq */
      25             : 
      26           0 :   ulong tp; __asm__( "mov %%fs:0, %0" : "=r"(tp) ); /* x86-64 thread pointer */
      27           0 :   struct rseq * rs = (struct rseq *)( tp + (ulong)__rseq_offset );
      28           0 :   if( FD_UNLIKELY( (int)FD_VOLATILE_CONST( rs->cpu_id )<0 ) ) return 0; /* unregistered or registration failed */
      29             : 
      30             :   /* The kernel requires the exact registered length to unregister.
      31             :      glibc registers max(__rseq_size,32) bytes, where __rseq_size is the
      32             :      used feature size (32 or 20 for glibc<2.41; AT_RSEQ_FEATURE_SIZE for
      33             :      glibc>=2.41, e.g. 28, or 33 on Linux>=7.0).  The length is not
      34             :      rounded up to the area alignment. */
      35           0 :   uint len = fd_uint_max( __rseq_size, 32U );
      36           0 :   if( FD_UNLIKELY( syscall( SYS_rseq, rs, len, RSEQ_FLAG_UNREGISTER, 0x53053053U /* x86 RSEQ_SIG */ ) ) ) {
      37           0 :     FD_LOG_WARNING(( "rseq(RSEQ_FLAG_UNREGISTER) failed (%i-%s)", errno, fd_io_strerror( errno ) ));
      38           0 :     return 0;
      39           0 :   }
      40           0 :   return 1;
      41             : #else
      42             :   return 0; /* no glibc rseq area, or not x86-64 */
      43             : #endif
      44           0 : }