xref: /external/valgrind/main/coregrind/m_libcproc.c

/*--------------------------------------------------------------------*/
/*--- Process-related libc stuff.                     m_libcproc.c ---*/
/*--------------------------------------------------------------------*/

/*
   This file is part of Valgrind, a dynamic binary instrumentation
   framework.

   Copyright (C) 2000-2012 Julian Seward
      jseward@acm.org

   This program is free software; you can redistribute it and/or
   modify it under the terms of the GNU General Public License as
   published by the Free Software Foundation; either version 2 of the
   License, or (at your option) any later version.

   This program is distributed in the hope that it will be useful, but
   WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307, USA.

   The GNU General Public License is contained in the file COPYING.
*/

#include "pub_core_basics.h"
#include "pub_core_machine.h"    // For VG_(machine_get_VexArchInfo)
#include "pub_core_vki.h"
#include "pub_core_vkiscnums.h"
#include "pub_core_libcbase.h"
#include "pub_core_libcassert.h"
#include "pub_core_libcprint.h"
#include "pub_core_libcproc.h"
#include "pub_core_libcsignal.h"
#include "pub_core_seqmatch.h"
#include "pub_core_mallocfree.h"
#include "pub_core_syscall.h"
#include "pub_core_xarray.h"
#include "pub_core_clientstate.h"

#if defined(VGO_darwin)
/* --- !!! --- EXTERNAL HEADERS start --- !!! --- */
#include <mach/mach.h>   /* mach_thread_self */
/* --- !!! --- EXTERNAL HEADERS end --- !!! --- */
#endif

/* IMPORTANT: on Darwin it is essential to use the _nocancel versions
   of syscalls rather than the vanilla version, if a _nocancel version
   is available.  See docs/internals/Darwin-notes.txt for the reason
   why. */

/* ---------------------------------------------------------------------
   Command line and environment stuff
   ------------------------------------------------------------------ */

/* As deduced from sp_at_startup, the client's argc, argv[] and
   envp[] as extracted from the client's stack at startup-time. */
Char** VG_(client_envp) = NULL;

/* Path to library directory */
const Char *VG_(libdir) = VG_LIBDIR;

const Char *VG_(LD_PRELOAD_var_name) =
#if defined(VGO_linux)
   "LD_PRELOAD";
#elif defined(VGO_darwin)
   "DYLD_INSERT_LIBRARIES";
#else
#  error Unknown OS
#endif

/* We do getenv without libc's help by snooping around in
   VG_(client_envp) as determined at startup time. */
Char *VG_(getenv)(Char *varname)
{
   Int i, n;
   vg_assert( VG_(client_envp) );
   n = VG_(strlen)(varname);
   for (i = 0; VG_(client_envp)[i] != NULL; i++) {
      Char* s = VG_(client_envp)[i];
      if (VG_(strncmp)(varname, s, n) == 0 && s[n] == '=') {
         return & s[n+1];
      }
   }
   return NULL;
}

void  VG_(env_unsetenv) ( Char **env, const Char *varname )
{
   Char **from, **to;
   vg_assert(env);
   vg_assert(varname);
   to = NULL;
   Int len = VG_(strlen)(varname);

   for (from = to = env; from && *from; from++) {
      if (!(VG_(strncmp)(varname, *from, len) == 0 && (*from)[len] == '=')) {
	 *to = *from;
	 to++;
      }
   }
   *to = *from;
}

/* set the environment; returns the old env if a new one was allocated */
Char **VG_(env_setenv) ( Char ***envp, const Char* varname, const Char *val )
{
   Char **env = (*envp);
   Char **cpp;
   Int len = VG_(strlen)(varname);
   Char *valstr = VG_(arena_malloc)(VG_AR_CORE, "libcproc.es.1",
                                    len + VG_(strlen)(val) + 2);
   Char **oldenv = NULL;

   VG_(sprintf)(valstr, "%s=%s", varname, val);

   for (cpp = env; cpp && *cpp; cpp++) {
      if (VG_(strncmp)(varname, *cpp, len) == 0 && (*cpp)[len] == '=') {
	 *cpp = valstr;
	 return oldenv;
      }
   }

   if (env == NULL) {
      env = VG_(arena_malloc)(VG_AR_CORE, "libcproc.es.2", sizeof(Char **) * 2);
      env[0] = valstr;
      env[1] = NULL;

      *envp = env;

   }  else {
      Int envlen = (cpp-env) + 2;
      Char **newenv = VG_(arena_malloc)(VG_AR_CORE, "libcproc.es.3",
                                        envlen * sizeof(Char **));

      for (cpp = newenv; *env; )
	 *cpp++ = *env++;
      *cpp++ = valstr;
      *cpp++ = NULL;

      oldenv = *envp;

      *envp = newenv;
   }

   return oldenv;
}


/* Walk through a colon-separated environment variable, and remove the
   entries which match remove_pattern.  It slides everything down over
   the removed entries, and pads the remaining space with '\0'.  It
   modifies the entries in place (in the client address space), but it
   shouldn't matter too much, since we only do this just before an
   execve().

   This is also careful to mop up any excess ':'s, since empty strings
   delimited by ':' are considered to be '.' in a path.
*/
static void mash_colon_env(Char *varp, const Char *remove_pattern)
{
   Char *const start = varp;
   Char *entry_start = varp;
   Char *output = varp;

   if (varp == NULL)
      return;

   while(*varp) {
      if (*varp == ':') {
	 Char prev;
	 Bool match;

	 /* This is a bit subtle: we want to match against the entry
	    we just copied, because it may have overlapped with
	    itself, junking the original. */

	 prev = *output;
	 *output = '\0';

	 match = VG_(string_match)(remove_pattern, entry_start);

	 *output = prev;

	 if (match) {
	    output = entry_start;
	    varp++;			/* skip ':' after removed entry */
	 } else
	    entry_start = output+1;	/* entry starts after ':' */
      }

      if (*varp)
         *output++ = *varp++;
   }

   /* make sure last entry is nul terminated */
   *output = '\0';

   /* match against the last entry */
   if (VG_(string_match)(remove_pattern, entry_start)) {
      output = entry_start;
      if (output > start) {
	 /* remove trailing ':' */
	 output--;
	 vg_assert(*output == ':');
      }
   }

   /* pad out the left-overs with '\0' */
   while(output < varp)
      *output++ = '\0';
}


// Removes all the Valgrind-added stuff from the passed environment.  Used
// when starting child processes, so they don't see that added stuff.
void VG_(env_remove_valgrind_env_stuff)(Char** envp)
{

#if defined(VGO_darwin)

   // Environment cleanup is also handled during parent launch
   // in vg_preloaded.c:vg_cleanup_env().

#endif

   Int i;
   Char* ld_preload_str = NULL;
   Char* ld_library_path_str = NULL;
   Char* dyld_insert_libraries_str = NULL;
   Char* buf;

   // Find LD_* variables
   // DDD: should probably conditionally compiled some of this:
   // - LD_LIBRARY_PATH is universal?
   // - LD_PRELOAD is on Linux, not on Darwin, not sure about AIX
   // - DYLD_INSERT_LIBRARIES and DYLD_SHARED_REGION are Darwin-only
   for (i = 0; envp[i] != NULL; i++) {
      if (VG_(strncmp)(envp[i], "LD_PRELOAD=", 11) == 0) {
         envp[i] = VG_(arena_strdup)(VG_AR_CORE, "libcproc.erves.1", envp[i]);
         ld_preload_str = &envp[i][11];
      }
      if (VG_(strncmp)(envp[i], "LD_LIBRARY_PATH=", 16) == 0) {
         envp[i] = VG_(arena_strdup)(VG_AR_CORE, "libcproc.erves.2", envp[i]);
         ld_library_path_str = &envp[i][16];
      }
      if (VG_(strncmp)(envp[i], "DYLD_INSERT_LIBRARIES=", 22) == 0) {
         envp[i] = VG_(arena_strdup)(VG_AR_CORE, "libcproc.erves.3", envp[i]);
         dyld_insert_libraries_str = &envp[i][22];
      }
   }

   buf = VG_(arena_malloc)(VG_AR_CORE, "libcproc.erves.4",
                           VG_(strlen)(VG_(libdir)) + 20);

   // Remove Valgrind-specific entries from LD_*.
   VG_(sprintf)(buf, "%s*/vgpreload_*.so", VG_(libdir));
   mash_colon_env(ld_preload_str, buf);
   mash_colon_env(dyld_insert_libraries_str, buf);
   VG_(sprintf)(buf, "%s*", VG_(libdir));
   mash_colon_env(ld_library_path_str, buf);

   // Remove VALGRIND_LAUNCHER variable.
   VG_(env_unsetenv)(envp, VALGRIND_LAUNCHER);

   // Remove DYLD_SHARED_REGION variable.
   VG_(env_unsetenv)(envp, "DYLD_SHARED_REGION");

   // XXX if variable becomes empty, remove it completely?

   VG_(arena_free)(VG_AR_CORE, buf);
}

/* ---------------------------------------------------------------------
   Various important syscall wrappers
   ------------------------------------------------------------------ */

Int VG_(waitpid)(Int pid, Int *status, Int options)
{
#  if defined(VGO_linux)
   SysRes res = VG_(do_syscall4)(__NR_wait4,
                                 pid, (UWord)status, options, 0);
   return sr_isError(res) ? -1 : sr_Res(res);
#  elif defined(VGO_darwin)
   SysRes res = VG_(do_syscall4)(__NR_wait4_nocancel,
                                 pid, (UWord)status, options, 0);
   return sr_isError(res) ? -1 : sr_Res(res);
#  else
#    error Unknown OS
#  endif
}

/* clone the environment */
Char **VG_(env_clone) ( Char **oldenv )
{
   Char **oldenvp;
   Char **newenvp;
   Char **newenv;
   Int  envlen;

   vg_assert(oldenv);
   for (oldenvp = oldenv; oldenvp && *oldenvp; oldenvp++);

   envlen = oldenvp - oldenv + 1;

   newenv = VG_(arena_malloc)(VG_AR_CORE, "libcproc.ec.1",
                              envlen * sizeof(Char **));

   oldenvp = oldenv;
   newenvp = newenv;

   while (oldenvp && *oldenvp) {
      *newenvp++ = *oldenvp++;
   }

   *newenvp = *oldenvp;

   return newenv;
}

void VG_(execv) ( Char* filename, Char** argv )
{
   Char** envp;
   SysRes res;

   /* restore the DATA rlimit for the child */
   VG_(setrlimit)(VKI_RLIMIT_DATA, &VG_(client_rlimit_data));

   envp = VG_(env_clone)(VG_(client_envp));
   VG_(env_remove_valgrind_env_stuff)( envp );

   res = VG_(do_syscall3)(__NR_execve,
                          (UWord)filename, (UWord)argv, (UWord)envp);

   VG_(printf)("EXEC failed, errno = %lld\n", (Long)sr_Err(res));
}

/* Return -1 if error, else 0.  NOTE does not indicate return code of
   child! */
Int VG_(system) ( Char* cmd )
{
   Int pid;
   if (cmd == NULL)
      return 1;
   pid = VG_(fork)();
   if (pid < 0)
      return -1;
   if (pid == 0) {
      /* child */
      Char* argv[4] = { "/bin/sh", "-c", cmd, 0 };
      VG_(execv)(argv[0], argv);

      /* If we're still alive here, execve failed. */
      VG_(exit)(1);
   } else {
      /* parent */
      /* We have to set SIGCHLD to its default behaviour in order that
         VG_(waitpid) works (at least on AIX).  According to the Linux
         man page for waitpid:

         POSIX.1-2001 specifies that if the disposition of SIGCHLD is
         set to SIG_IGN or the SA_NOCLDWAIT flag is set for SIGCHLD
         (see sigaction(2)), then children that terminate do not
         become zombies and a call to wait() or waitpid() will block
         until all children have terminated, and then fail with errno
         set to ECHILD.  (The original POSIX standard left the
         behaviour of setting SIGCHLD to SIG_IGN unspecified.)
      */
      Int ir, zzz;
      vki_sigaction_toK_t sa, sa2;
      vki_sigaction_fromK_t saved_sa;
      VG_(memset)( &sa, 0, sizeof(sa) );
      VG_(sigemptyset)(&sa.sa_mask);
      sa.ksa_handler = VKI_SIG_DFL;
      sa.sa_flags    = 0;
      ir = VG_(sigaction)(VKI_SIGCHLD, &sa, &saved_sa);
      vg_assert(ir == 0);

      zzz = VG_(waitpid)(pid, NULL, 0);

      VG_(convert_sigaction_fromK_to_toK)( &saved_sa, &sa2 );
      ir = VG_(sigaction)(VKI_SIGCHLD, &sa2, NULL);
      vg_assert(ir == 0);
      return zzz == -1 ? -1 : 0;
   }
}

/* ---------------------------------------------------------------------
   Resource limits
   ------------------------------------------------------------------ */

/* Support for getrlimit. */
Int VG_(getrlimit) (Int resource, struct vki_rlimit *rlim)
{
   SysRes res = VG_(mk_SysRes_Error)(VKI_ENOSYS);
   /* res = getrlimit( resource, rlim ); */
#  ifdef __NR_ugetrlimit
   res = VG_(do_syscall2)(__NR_ugetrlimit, resource, (UWord)rlim);
#  endif
   if (sr_isError(res) && sr_Err(res) == VKI_ENOSYS)
      res = VG_(do_syscall2)(__NR_getrlimit, resource, (UWord)rlim);
   return sr_isError(res) ? -1 : sr_Res(res);
}


/* Support for setrlimit. */
Int VG_(setrlimit) (Int resource, const struct vki_rlimit *rlim)
{
   SysRes res;
   /* res = setrlimit( resource, rlim ); */
   res = VG_(do_syscall2)(__NR_setrlimit, resource, (UWord)rlim);
   return sr_isError(res) ? -1 : sr_Res(res);
}

/* Support for prctl. */
Int VG_(prctl) (Int option,
                ULong arg2, ULong arg3, ULong arg4, ULong arg5)
{
   SysRes res = VG_(mk_SysRes_Error)(VKI_ENOSYS);
#  if defined(VGO_linux)
   /* res = prctl( option, arg2, arg3, arg4, arg5 ); */
   res = VG_(do_syscall5)(__NR_prctl, (UWord) option,
                          (UWord) arg2, (UWord) arg3, (UWord) arg4,
                          (UWord) arg5);
#  endif

   return sr_isError(res) ? -1 : sr_Res(res);
}

/* ---------------------------------------------------------------------
   pids, etc
   ------------------------------------------------------------------ */

Int VG_(gettid)(void)
{
#  if defined(VGO_linux)
   SysRes res = VG_(do_syscall0)(__NR_gettid);

   if (sr_isError(res) && sr_Res(res) == VKI_ENOSYS) {
      Char pid[16];
      /*
       * The gettid system call does not exist. The obvious assumption
       * to make at this point would be that we are running on an older
       * system where the getpid system call actually returns the ID of
       * the current thread.
       *
       * Unfortunately it seems that there are some systems with a kernel
       * where getpid has been changed to return the ID of the thread group
       * leader but where the gettid system call has not yet been added.
       *
       * So instead of calling getpid here we use readlink to see where
       * the /proc/self link is pointing...
       */

      res = VG_(do_syscall3)(__NR_readlink, (UWord)"/proc/self",
                             (UWord)pid, sizeof(pid));
      if (!sr_isError(res) && sr_Res(res) > 0) {
         Char* s;
         pid[sr_Res(res)] = '\0';
         res = VG_(mk_SysRes_Success)(  VG_(strtoll10)(pid, &s) );
         if (*s != '\0') {
            VG_(message)(Vg_DebugMsg,
               "Warning: invalid file name linked to by /proc/self: %s\n",
               pid);
         }
      }
   }

   return sr_Res(res);

#  elif defined(VGO_darwin)
   // Darwin's gettid syscall is something else.
   // Use Mach thread ports for lwpid instead.
   return mach_thread_self();

#  else
#    error "Unknown OS"
#  endif
}

/* You'd be amazed how many places need to know the current pid. */
Int VG_(getpid) ( void )
{
   /* ASSUMES SYSCALL ALWAYS SUCCEEDS */
   return sr_Res( VG_(do_syscall0)(__NR_getpid) );
}

Int VG_(getpgrp) ( void )
{
   /* ASSUMES SYSCALL ALWAYS SUCCEEDS */
   return sr_Res( VG_(do_syscall0)(__NR_getpgrp) );
}

Int VG_(getppid) ( void )
{
   /* ASSUMES SYSCALL ALWAYS SUCCEEDS */
   return sr_Res( VG_(do_syscall0)(__NR_getppid) );
}

Int VG_(geteuid) ( void )
{
   /* ASSUMES SYSCALL ALWAYS SUCCEEDS */
#  if defined(__NR_geteuid32)
   // We use the 32-bit version if it's supported.  Otherwise, IDs greater
   // than 65536 cause problems, as bug #151209 showed.
   return sr_Res( VG_(do_syscall0)(__NR_geteuid32) );
#  else
   return sr_Res( VG_(do_syscall0)(__NR_geteuid) );
#  endif
}

Int VG_(getegid) ( void )
{
   /* ASSUMES SYSCALL ALWAYS SUCCEEDS */
#  if defined(__NR_getegid32)
   // We use the 32-bit version if it's supported.  Otherwise, IDs greater
   // than 65536 cause problems, as bug #151209 showed.
   return sr_Res( VG_(do_syscall0)(__NR_getegid32) );
#  else
   return sr_Res( VG_(do_syscall0)(__NR_getegid) );
#  endif
}

/* Get supplementary groups into list[0 .. size-1].  Returns the
   number of groups written, or -1 if error.  Note that in order to be
   portable, the groups are 32-bit unsigned ints regardless of the
   platform. */
Int VG_(getgroups)( Int size, UInt* list )
{
#  if defined(VGP_x86_linux) || defined(VGP_ppc32_linux)
   Int    i;
   SysRes sres;
   UShort list16[64];
   if (size < 0) return -1;
   if (size > 64) size = 64;
   sres = VG_(do_syscall2)(__NR_getgroups, size, (Addr)list16);
   if (sr_isError(sres))
      return -1;
   if (sr_Res(sres) > size)
      return -1;
   for (i = 0; i < sr_Res(sres); i++)
      list[i] = (UInt)list16[i];
   return sr_Res(sres);

#  elif defined(VGP_amd64_linux) || defined(VGP_ppc64_linux)  \
        || defined(VGP_arm_linux)                             \
        || defined(VGO_darwin) || defined(VGP_s390x_linux)    \
        || defined(VGP_mips32_linux)
   SysRes sres;
   sres = VG_(do_syscall2)(__NR_getgroups, size, (Addr)list);
   if (sr_isError(sres))
      return -1;
   return sr_Res(sres);

#  else
#     error "VG_(getgroups): needs implementation on this platform"
#  endif
}

/* ---------------------------------------------------------------------
   Process tracing
   ------------------------------------------------------------------ */

Int VG_(ptrace) ( Int request, Int pid, void *addr, void *data )
{
   SysRes res;
   res = VG_(do_syscall4)(__NR_ptrace, request, pid, (UWord)addr, (UWord)data);
   if (sr_isError(res))
      return -1;
   return sr_Res(res);
}

/* ---------------------------------------------------------------------
   Fork
   ------------------------------------------------------------------ */

Int VG_(fork) ( void )
{
#  if defined(VGO_linux)
   SysRes res;
   res = VG_(do_syscall0)(__NR_fork);
   if (sr_isError(res))
      return -1;
   return sr_Res(res);

#  elif defined(VGO_darwin)
   SysRes res;
   res = VG_(do_syscall0)(__NR_fork); /* __NR_fork is UX64 */
   if (sr_isError(res))
      return -1;
   /* on success: wLO = child pid; wHI = 1 for child, 0 for parent */
   if (sr_ResHI(res) != 0) {
      return 0;  /* this is child: return 0 instead of child pid */
   }
   return sr_Res(res);

#  else
#    error "Unknown OS"
#  endif
}

/* ---------------------------------------------------------------------
   Timing stuff
   ------------------------------------------------------------------ */

UInt VG_(read_millisecond_timer) ( void )
{
   /* 'now' and 'base' are in microseconds */
   static ULong base = 0;
   ULong  now;

#  if defined(VGO_linux)
   { SysRes res;
     struct vki_timespec ts_now;
     res = VG_(do_syscall2)(__NR_clock_gettime, VKI_CLOCK_MONOTONIC,
                            (UWord)&ts_now);
     if (sr_isError(res) == 0) {
        now = ts_now.tv_sec * 1000000ULL + ts_now.tv_nsec / 1000;
     } else {
       struct vki_timeval tv_now;
       res = VG_(do_syscall2)(__NR_gettimeofday, (UWord)&tv_now, (UWord)NULL);
       vg_assert(! sr_isError(res));
       now = tv_now.tv_sec * 1000000ULL + tv_now.tv_usec;
     }
   }

#  elif defined(VGO_darwin)
   // Weird: it seems that gettimeofday() doesn't fill in the timeval, but
   // rather returns the tv_sec as the low 32 bits of the result and the
   // tv_usec as the high 32 bits of the result.  (But the timeval cannot be
   // NULL!)  See bug 200990.
   { SysRes res;
     struct vki_timeval tv_now = { 0, 0 };
     res = VG_(do_syscall2)(__NR_gettimeofday, (UWord)&tv_now, (UWord)NULL);
     vg_assert(! sr_isError(res));
     now = sr_Res(res) * 1000000ULL + sr_ResHI(res);
   }

#  else
#    error "Unknown OS"
#  endif

   /* COMMON CODE */
   if (base == 0)
      base = now;

   return (now - base) / 1000;
}


/* ---------------------------------------------------------------------
   atfork()
   ------------------------------------------------------------------ */

struct atfork {
   vg_atfork_t  pre;
   vg_atfork_t  parent;
   vg_atfork_t  child;
};

#define VG_MAX_ATFORK 10

static struct atfork atforks[VG_MAX_ATFORK];
static Int n_atfork = 0;

void VG_(atfork)(vg_atfork_t pre, vg_atfork_t parent, vg_atfork_t child)
{
   Int i;

   for (i = 0; i < n_atfork; i++) {
      if (atforks[i].pre == pre &&
          atforks[i].parent == parent &&
          atforks[i].child == child)
         return;
   }

   if (n_atfork >= VG_MAX_ATFORK)
      VG_(core_panic)(
         "Too many VG_(atfork) handlers requested: raise VG_MAX_ATFORK");

   atforks[n_atfork].pre    = pre;
   atforks[n_atfork].parent = parent;
   atforks[n_atfork].child  = child;

   n_atfork++;
}

void VG_(do_atfork_pre)(ThreadId tid)
{
   Int i;

   for (i = 0; i < n_atfork; i++)
      if (atforks[i].pre != NULL)
         (*atforks[i].pre)(tid);
}

void VG_(do_atfork_parent)(ThreadId tid)
{
   Int i;

   for (i = 0; i < n_atfork; i++)
      if (atforks[i].parent != NULL)
         (*atforks[i].parent)(tid);
}

void VG_(do_atfork_child)(ThreadId tid)
{
   Int i;

   for (i = 0; i < n_atfork; i++)
      if (atforks[i].child != NULL)
         (*atforks[i].child)(tid);
}


/* ---------------------------------------------------------------------
   icache invalidation
   ------------------------------------------------------------------ */

void VG_(invalidate_icache) ( void *ptr, SizeT nbytes )
{
#  if defined(VGA_ppc32) || defined(VGA_ppc64)
   Addr startaddr = (Addr) ptr;
   Addr endaddr   = startaddr + nbytes;
   Addr cls;
   Addr addr;
   VexArchInfo vai;

   if (nbytes == 0) return;
   vg_assert(nbytes > 0);

   VG_(machine_get_VexArchInfo)( NULL, &vai );
   cls = vai.ppc_cache_line_szB;

   /* Stay sane .. */
   vg_assert(cls == 32 || cls == 64 || cls == 128);

   startaddr &= ~(cls - 1);
   for (addr = startaddr; addr < endaddr; addr += cls) {
      __asm__ __volatile__("dcbst 0,%0" : : "r" (addr));
   }
   __asm__ __volatile__("sync");
   for (addr = startaddr; addr < endaddr; addr += cls) {
      __asm__ __volatile__("icbi 0,%0" : : "r" (addr));
   }
   __asm__ __volatile__("sync; isync");

#  elif defined(VGA_x86)
   /* no need to do anything, hardware provides coherence */

#  elif defined(VGA_amd64)
   /* no need to do anything, hardware provides coherence */

#  elif defined(VGA_s390x)
   /* no need to do anything, hardware provides coherence */

#  elif defined(VGP_arm_linux)
   /* ARM cache flushes are privileged, so we must defer to the kernel. */
   Addr startaddr = (Addr) ptr;
   Addr endaddr   = startaddr + nbytes;
   VG_(do_syscall2)(__NR_ARM_cacheflush, startaddr, endaddr);

#  elif defined(VGA_mips32)
   SysRes sres = VG_(do_syscall3)(__NR_cacheflush, (UWord) ptr,
                                 (UWord) nbytes, (UWord) 3);
   vg_assert( sres._isError == 0 );

#  else
#    error "Unknown ARCH"
#  endif
}


/*--------------------------------------------------------------------*/
/*--- end                                                          ---*/
/*--------------------------------------------------------------------*/