[sql] Import reference version of SQLite 3.17..

third_party/sqlite/sqlite-src-3170000/src/test_syscall.c

+/*
+** 2011 March 28
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+** The code in this file implements a Tcl interface used to test error
+** handling in the os_unix.c module. Wrapper functions that support fault
+** injection are registered as the low-level OS functions using the 
+** xSetSystemCall() method of the VFS. The Tcl interface is as follows:
+**
+**
+**   test_syscall install LIST
+**     Install wrapper functions for all system calls in argument LIST.
+**     LIST must be a list consisting of zero or more of the following
+**     literal values:
+**
+**         open        close      access   getcwd   stat      fstat    
+**         ftruncate   fcntl      read     pread    pread64   write
+**         pwrite      pwrite64   fchmod   fallocate mmap
+**
+**   test_syscall uninstall
+**     Uninstall all wrapper functions.
+**
+**   test_syscall fault ?COUNT PERSIST?
+**     If [test_syscall fault] is invoked without the two arguments, fault
+**     injection is disabled. Otherwise, fault injection is configured to
+**     cause a failure on the COUNT'th next call to a system call with a
+**     wrapper function installed. A COUNT value of 1 means fail the next
+**     system call. 
+** 
+**     Argument PERSIST is interpreted as a boolean. If true, the all
+**     system calls following the initial failure also fail. Otherwise, only
+**     the single transient failure is injected.
+**
+**   test_syscall errno CALL ERRNO
+**     Set the value that the global "errno" is set to following a fault
+**     in call CALL. Argument CALL must be one of the system call names
+**     listed above (under [test_syscall install]). ERRNO is a symbolic
+**     name (i.e. "EACCES"). Not all errno codes are supported. Add extra
+**     to the aErrno table in function test_syscall_errno() below as 
+**     required.
+**
+**   test_syscall reset ?SYSTEM-CALL?
+**     With no argument, this is an alias for the [uninstall] command. However,
+**     this command uses a VFS call of the form:
+**
+**       xSetSystemCall(pVfs, 0, 0);
+**
+**     To restore the default system calls. The [uninstall] command restores
+**     each system call individually by calling (i.e.):
+**
+**       xSetSystemCall(pVfs, "open", 0);
+**
+**     With an argument, this command attempts to reset the system call named
+**     by the parameter using the same method as [uninstall].
+**
+**   test_syscall exists SYSTEM-CALL
+**     Return true if the named system call exists. Or false otherwise.
+**
+**   test_syscall list
+**     Return a list of all system calls. The list is constructed using
+**     the xNextSystemCall() VFS method.
+**
+**   test_syscall pagesize PGSZ
+**     If PGSZ is a power of two greater than 256, install a wrapper around
+**     OS function getpagesize() that reports the system page size as PGSZ.
+**     Or, if PGSZ is less than zero, remove any wrapper already installed.
+*/
+
+#include "sqliteInt.h"
+#include "sqlite3.h"
+#if defined(INCLUDE_SQLITE_TCL_H)
+#  include "sqlite_tcl.h"
+#else
+#  include "tcl.h"
+#endif
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+
+#if SQLITE_OS_UNIX
+
+/* From main.c */
+extern const char *sqlite3ErrName(int);
+
+#include <sys/mman.h>
+#include <sys/types.h>
+#include <errno.h>
+
+static struct TestSyscallGlobal {
+  int bPersist;                   /* 1 for persistent errors, 0 for transient */
+  int nCount;                     /* Fail after this many more calls */
+  int nFail;                      /* Number of failures that have occurred */
+  int pgsz;
+  sqlite3_syscall_ptr orig_getpagesize;
+} gSyscall = { 0, 0, 0, 0, 0 };
+
+static int ts_open(const char *, int, int);
+static int ts_close(int fd);
+static int ts_access(const char *zPath, int mode);
+static char *ts_getcwd(char *zPath, size_t nPath);
+static int ts_stat(const char *zPath, struct stat *p);
+static int ts_fstat(int fd, struct stat *p);
+static int ts_ftruncate(int fd, off_t n);
+static int ts_fcntl(int fd, int cmd, ... );
+static int ts_read(int fd, void *aBuf, size_t nBuf);
+static int ts_pread(int fd, void *aBuf, size_t nBuf, off_t off);
+/* Note:  pread64() and pwrite64() actually use off64_t as the type on their
+** last parameter.  But that datatype is not defined on many systems 
+** (ex: Mac, OpenBSD).  So substitute a likely equivalent: sqlite3_uint64 */
+static int ts_pread64(int fd, void *aBuf, size_t nBuf, sqlite3_uint64 off);
+static int ts_write(int fd, const void *aBuf, size_t nBuf);
+static int ts_pwrite(int fd, const void *aBuf, size_t nBuf, off_t off);
+static int ts_pwrite64(int fd, const void *aBuf, size_t nBuf, sqlite3_uint64 off);
+static int ts_fchmod(int fd, mode_t mode);
+static int ts_fallocate(int fd, off_t off, off_t len);
+static void *ts_mmap(void *, size_t, int, int, int, off_t);
+static void *ts_mremap(void*, size_t, size_t, int, ...);
+
+struct TestSyscallArray {
+  const char *zName;
+  sqlite3_syscall_ptr xTest;
+  sqlite3_syscall_ptr xOrig;
+  int default_errno;              /* Default value for errno following errors */
+  int custom_errno;               /* Current value for errno if error */
+} aSyscall[] = {
+  /*  0 */ { "open",      (sqlite3_syscall_ptr)ts_open,      0, EACCES, 0 },
+  /*  1 */ { "close",     (sqlite3_syscall_ptr)ts_close,     0, 0, 0 },
+  /*  2 */ { "access",    (sqlite3_syscall_ptr)ts_access,    0, 0, 0 },
+  /*  3 */ { "getcwd",    (sqlite3_syscall_ptr)ts_getcwd,    0, 0, 0 },
+  /*  4 */ { "stat",      (sqlite3_syscall_ptr)ts_stat,      0, 0, 0 },
+  /*  5 */ { "fstat",     (sqlite3_syscall_ptr)ts_fstat,     0, 0, 0 },
+  /*  6 */ { "ftruncate", (sqlite3_syscall_ptr)ts_ftruncate, 0, EIO, 0 },
+  /*  7 */ { "fcntl",     (sqlite3_syscall_ptr)ts_fcntl,     0, EACCES, 0 },
+  /*  8 */ { "read",      (sqlite3_syscall_ptr)ts_read,      0, 0, 0 },
+  /*  9 */ { "pread",     (sqlite3_syscall_ptr)ts_pread,     0, 0, 0 },
+  /* 10 */ { "pread64",   (sqlite3_syscall_ptr)ts_pread64,   0, 0, 0 },
+  /* 11 */ { "write",     (sqlite3_syscall_ptr)ts_write,     0, 0, 0 },
+  /* 12 */ { "pwrite",    (sqlite3_syscall_ptr)ts_pwrite,    0, 0, 0 },
+  /* 13 */ { "pwrite64",  (sqlite3_syscall_ptr)ts_pwrite64,  0, 0, 0 },
+  /* 14 */ { "fchmod",    (sqlite3_syscall_ptr)ts_fchmod,    0, 0, 0 },
+  /* 15 */ { "fallocate", (sqlite3_syscall_ptr)ts_fallocate, 0, 0, 0 },
+  /* 16 */ { "mmap",      (sqlite3_syscall_ptr)ts_mmap,      0, 0, 0 },
+  /* 17 */ { "mremap",    (sqlite3_syscall_ptr)ts_mremap,    0, 0, 0 },
+           { 0, 0, 0, 0, 0 }
+};
+
+#define orig_open      ((int(*)(const char *, int, int))aSyscall[0].xOrig)
+#define orig_close     ((int(*)(int))aSyscall[1].xOrig)
+#define orig_access    ((int(*)(const char*,int))aSyscall[2].xOrig)
+#define orig_getcwd    ((char*(*)(char*,size_t))aSyscall[3].xOrig)
+#define orig_stat      ((int(*)(const char*,struct stat*))aSyscall[4].xOrig)
+#define orig_fstat     ((int(*)(int,struct stat*))aSyscall[5].xOrig)
+#define orig_ftruncate ((int(*)(int,off_t))aSyscall[6].xOrig)
+#define orig_fcntl     ((int(*)(int,int,...))aSyscall[7].xOrig)
+#define orig_read      ((ssize_t(*)(int,void*,size_t))aSyscall[8].xOrig)
+#define orig_pread     ((ssize_t(*)(int,void*,size_t,off_t))aSyscall[9].xOrig)
+#define orig_pread64   ((ssize_t(*)(int,void*,size_t,sqlite3_uint64))aSyscall[10].xOrig)
+#define orig_write     ((ssize_t(*)(int,const void*,size_t))aSyscall[11].xOrig)
+#define orig_pwrite    ((ssize_t(*)(int,const void*,size_t,off_t))\
+                       aSyscall[12].xOrig)
+#define orig_pwrite64  ((ssize_t(*)(int,const void*,size_t,sqlite3_uint64))\
+                       aSyscall[13].xOrig)
+#define orig_fchmod    ((int(*)(int,mode_t))aSyscall[14].xOrig)
+#define orig_fallocate ((int(*)(int,off_t,off_t))aSyscall[15].xOrig)
+#define orig_mmap      ((void*(*)(void*,size_t,int,int,int,off_t))aSyscall[16].xOrig)
+#define orig_mremap    ((void*(*)(void*,size_t,size_t,int,...))aSyscall[17].xOrig)
+
+/*
+** This function is called exactly once from within each invocation of a
+** system call wrapper in this file. It returns 1 if the function should
+** fail, or 0 if it should succeed.
+*/
+static int tsIsFail(void){
+  gSyscall.nCount--;
+  if( gSyscall.nCount==0 || (gSyscall.nFail && gSyscall.bPersist) ){
+    gSyscall.nFail++;
+    return 1;
+  }
+  return 0;
+}
+
+/*
+** Return the current error-number value for function zFunc. zFunc must be
+** the name of a system call in the aSyscall[] table.
+**
+** Usually, the current error-number is the value that errno should be set
+** to if the named system call fails. The exception is "fallocate". See 
+** comments above the implementation of ts_fallocate() for details.
+*/
+static int tsErrno(const char *zFunc){
+  int i;
+  int nFunc = strlen(zFunc);
+  for(i=0; aSyscall[i].zName; i++){
+    if( strlen(aSyscall[i].zName)!=nFunc ) continue;
+    if( memcmp(aSyscall[i].zName, zFunc, nFunc) ) continue;
+    return aSyscall[i].custom_errno;
+  }
+
+  assert(0);
+  return 0;
+}
+
+/*
+** A wrapper around tsIsFail(). If tsIsFail() returns non-zero, set the
+** value of errno before returning.
+*/ 
+static int tsIsFailErrno(const char *zFunc){
+  if( tsIsFail() ){
+    errno = tsErrno(zFunc);
+    return 1;
+  }
+  return 0;
+}
+
+/*
+** A wrapper around open().
+*/
+static int ts_open(const char *zFile, int flags, int mode){
+  if( tsIsFailErrno("open") ){
+    return -1;
+  }
+  return orig_open(zFile, flags, mode);
+}
+
+/*
+** A wrapper around close().
+*/
+static int ts_close(int fd){
+  if( tsIsFail() ){
+    /* Even if simulating an error, close the original file-descriptor. 
+    ** This is to stop the test process from running out of file-descriptors
+    ** when running a long test. If a call to close() appears to fail, SQLite
+    ** never attempts to use the file-descriptor afterwards (or even to close
+    ** it a second time).  */
+    orig_close(fd);
+    return -1;
+  }
+  return orig_close(fd);
+}
+
+/*
+** A wrapper around access().
+*/
+static int ts_access(const char *zPath, int mode){
+  if( tsIsFail() ){
+    return -1;
+  }
+  return orig_access(zPath, mode);
+}
+
+/*
+** A wrapper around getcwd().
+*/
+static char *ts_getcwd(char *zPath, size_t nPath){
+  if( tsIsFail() ){
+    return NULL;
+  }
+  return orig_getcwd(zPath, nPath);
+}
+
+/*
+** A wrapper around stat().
+*/
+static int ts_stat(const char *zPath, struct stat *p){
+  if( tsIsFail() ){
+    return -1;
+  }
+  return orig_stat(zPath, p);
+}
+
+/*
+** A wrapper around fstat().
+*/
+static int ts_fstat(int fd, struct stat *p){
+  if( tsIsFailErrno("fstat") ){
+    return -1;
+  }
+  return orig_fstat(fd, p);
+}
+
+/*
+** A wrapper around ftruncate().
+*/
+static int ts_ftruncate(int fd, off_t n){
+  if( tsIsFailErrno("ftruncate") ){
+    return -1;
+  }
+  return orig_ftruncate(fd, n);
+}
+
+/*
+** A wrapper around fcntl().
+*/
+static int ts_fcntl(int fd, int cmd, ... ){
+  va_list ap;
+  void *pArg;
+  if( tsIsFailErrno("fcntl") ){
+    return -1;
+  }
+  va_start(ap, cmd);
+  pArg = va_arg(ap, void *);
+  return orig_fcntl(fd, cmd, pArg);
+}
+
+/*
+** A wrapper around read().
+*/
+static int ts_read(int fd, void *aBuf, size_t nBuf){
+  if( tsIsFailErrno("read") ){
+    return -1;
+  }
+  return orig_read(fd, aBuf, nBuf);
+}
+
+/*
+** A wrapper around pread().
+*/
+static int ts_pread(int fd, void *aBuf, size_t nBuf, off_t off){
+  if( tsIsFailErrno("pread") ){
+    return -1;
+  }
+  return orig_pread(fd, aBuf, nBuf, off);
+}
+
+/*
+** A wrapper around pread64().
+*/
+static int ts_pread64(int fd, void *aBuf, size_t nBuf, sqlite3_uint64 off){
+  if( tsIsFailErrno("pread64") ){
+    return -1;
+  }
+  return orig_pread64(fd, aBuf, nBuf, off);
+}
+
+/*
+** A wrapper around write().
+*/
+static int ts_write(int fd, const void *aBuf, size_t nBuf){
+  if( tsIsFailErrno("write") ){
+    if( tsErrno("write")==EINTR ) orig_write(fd, aBuf, nBuf/2);
+    return -1;
+  }
+  return orig_write(fd, aBuf, nBuf);
+}
+
+/*
+** A wrapper around pwrite().
+*/
+static int ts_pwrite(int fd, const void *aBuf, size_t nBuf, off_t off){
+  if( tsIsFailErrno("pwrite") ){
+    return -1;
+  }
+  return orig_pwrite(fd, aBuf, nBuf, off);
+}
+
+/*
+** A wrapper around pwrite64().
+*/
+static int ts_pwrite64(int fd, const void *aBuf, size_t nBuf, sqlite3_uint64 off){
+  if( tsIsFailErrno("pwrite64") ){
+    return -1;
+  }
+  return orig_pwrite64(fd, aBuf, nBuf, off);
+}
+
+/*
+** A wrapper around fchmod().
+*/
+static int ts_fchmod(int fd, mode_t mode){
+  if( tsIsFail() ){
+    return -1;
+  }
+  return orig_fchmod(fd, mode);
+}
+
+/*
+** A wrapper around fallocate().
+**
+** SQLite assumes that the fallocate() function is compatible with
+** posix_fallocate(). According to the Linux man page (2009-09-30):
+**
+**   posix_fallocate() returns  zero on success, or an error number on
+**   failure. Note that errno is not set.
+*/
+static int ts_fallocate(int fd, off_t off, off_t len){
+  if( tsIsFail() ){
+    return tsErrno("fallocate");
+  }
+  return orig_fallocate(fd, off, len);
+}
+
+static void *ts_mmap(
+  void *pAddr, 
+  size_t nByte, 
+  int prot, 
+  int flags, 
+  int fd, 
+  off_t iOff
+){
+  if( tsIsFailErrno("mmap") ){
+    return MAP_FAILED;
+  }
+  return orig_mmap(pAddr, nByte, prot, flags, fd, iOff);
+}
+
+static void *ts_mremap(void *a, size_t b, size_t c, int d, ...){
+  va_list ap;
+  void *pArg;
+  if( tsIsFailErrno("mremap") ){
+    return MAP_FAILED;
+  }
+  va_start(ap, d);
+  pArg = va_arg(ap, void *);
+  return orig_mremap(a, b, c, d, pArg);
+}
+
+static int SQLITE_TCLAPI test_syscall_install(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_vfs *pVfs; 
+  int nElem;
+  int i;
+  Tcl_Obj **apElem;
+
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 2, objv, "SYSCALL-LIST");
+    return TCL_ERROR;
+  }
+  if( Tcl_ListObjGetElements(interp, objv[2], &nElem, &apElem) ){
+    return TCL_ERROR;
+  }
+  pVfs = sqlite3_vfs_find(0);
+
+  for(i=0; i<nElem; i++){
+    int iCall;
+    int rc = Tcl_GetIndexFromObjStruct(interp, 
+        apElem[i], aSyscall, sizeof(aSyscall[0]), "system-call", 0, &iCall
+    );
+    if( rc ) return rc;
+    if( aSyscall[iCall].xOrig==0 ){
+      aSyscall[iCall].xOrig = pVfs->xGetSystemCall(pVfs, aSyscall[iCall].zName);
+      pVfs->xSetSystemCall(pVfs, aSyscall[iCall].zName, aSyscall[iCall].xTest);
+    }
+    aSyscall[iCall].custom_errno = aSyscall[iCall].default_errno;
+  }
+
+  return TCL_OK;
+}
+
+static int SQLITE_TCLAPI test_syscall_uninstall(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_vfs *pVfs; 
+  int i;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 2, objv, "");
+    return TCL_ERROR;
+  }
+
+  pVfs = sqlite3_vfs_find(0);
+  for(i=0; aSyscall[i].zName; i++){
+    if( aSyscall[i].xOrig ){
+      pVfs->xSetSystemCall(pVfs, aSyscall[i].zName, 0);
+      aSyscall[i].xOrig = 0;
+    }
+  }
+  return TCL_OK;
+}
+
+static int SQLITE_TCLAPI test_syscall_reset(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_vfs *pVfs; 
+  int i;
+  int rc;
+
+  if( objc!=2 && objc!=3 ){
+    Tcl_WrongNumArgs(interp, 2, objv, "");
+    return TCL_ERROR;
+  }
+
+  pVfs = sqlite3_vfs_find(0);
+  if( objc==2 ){
+    rc = pVfs->xSetSystemCall(pVfs, 0, 0);
+    for(i=0; aSyscall[i].zName; i++) aSyscall[i].xOrig = 0;
+  }else{
+    int nFunc;
+    char *zFunc = Tcl_GetStringFromObj(objv[2], &nFunc);
+    rc = pVfs->xSetSystemCall(pVfs, Tcl_GetString(objv[2]), 0);
+    for(i=0; rc==SQLITE_OK && aSyscall[i].zName; i++){
+      if( strlen(aSyscall[i].zName)!=nFunc ) continue;
+      if( memcmp(aSyscall[i].zName, zFunc, nFunc) ) continue;
+      aSyscall[i].xOrig = 0;
+    }
+  }
+  if( rc!=SQLITE_OK ){
+    Tcl_SetObjResult(interp, Tcl_NewStringObj(sqlite3ErrName(rc), -1));
+    return TCL_ERROR;
+  }
+
+  Tcl_ResetResult(interp);
+  return TCL_OK;
+}
+
+static int SQLITE_TCLAPI test_syscall_exists(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_vfs *pVfs; 
+  sqlite3_syscall_ptr x;
+
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 2, objv, "");
+    return TCL_ERROR;
+  }
+
+  pVfs = sqlite3_vfs_find(0);
+  x = pVfs->xGetSystemCall(pVfs, Tcl_GetString(objv[2]));
+
+  Tcl_SetObjResult(interp, Tcl_NewBooleanObj(x!=0));
+  return TCL_OK;
+}
+
+static int SQLITE_TCLAPI test_syscall_fault(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int nCount = 0;
+  int bPersist = 0;
+
+  if( objc!=2 && objc!=4 ){
+    Tcl_WrongNumArgs(interp, 2, objv, "?COUNT PERSIST?");
+    return TCL_ERROR;
+  }
+
+  if( objc==4 ){
+    if( Tcl_GetIntFromObj(interp, objv[2], &nCount)
+     || Tcl_GetBooleanFromObj(interp, objv[3], &bPersist)
+    ){
+      return TCL_ERROR;
+    }
+  }
+
+  Tcl_SetObjResult(interp, Tcl_NewIntObj(gSyscall.nFail));
+  gSyscall.nCount = nCount;
+  gSyscall.bPersist = bPersist;
+  gSyscall.nFail = 0;
+  return TCL_OK;
+}
+
+static int SQLITE_TCLAPI test_syscall_errno(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int iCall;
+  int iErrno;
+  int rc;
+
+  struct Errno {
+    const char *z;
+    int i;
+  } aErrno[] = {
+    { "EACCES",    EACCES },
+    { "EINTR",     EINTR },
+    { "EIO",       EIO },
+    { "EOVERFLOW", EOVERFLOW },
+    { "ENOMEM",    ENOMEM },
+    { "EAGAIN",    EAGAIN },
+    { "ETIMEDOUT", ETIMEDOUT },
+    { "EBUSY",     EBUSY },
+    { "EPERM",     EPERM },
+    { "EDEADLK",   EDEADLK },
+    { "ENOLCK",    ENOLCK },
+    { 0, 0 }
+  };
+
+  if( objc!=4 ){
+    Tcl_WrongNumArgs(interp, 2, objv, "SYSCALL ERRNO");
+    return TCL_ERROR;
+  }
+
+  rc = Tcl_GetIndexFromObjStruct(interp, 
+      objv[2], aSyscall, sizeof(aSyscall[0]), "system-call", 0, &iCall
+  );
+  if( rc!=TCL_OK ) return rc;
+  rc = Tcl_GetIndexFromObjStruct(interp, 
+      objv[3], aErrno, sizeof(aErrno[0]), "errno", 0, &iErrno
+  );
+  if( rc!=TCL_OK ) return rc;
+
+  aSyscall[iCall].custom_errno = aErrno[iErrno].i;
+  return TCL_OK;
+}
+
+static int SQLITE_TCLAPI test_syscall_list(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  const char *zSys;
+  sqlite3_vfs *pVfs; 
+  Tcl_Obj *pList;
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 2, objv, "");
+    return TCL_ERROR;
+  }
+
+  pVfs = sqlite3_vfs_find(0);
+  pList = Tcl_NewObj();
+  Tcl_IncrRefCount(pList);
+  for(zSys = pVfs->xNextSystemCall(pVfs, 0); 
+      zSys!=0;
+      zSys = pVfs->xNextSystemCall(pVfs, zSys)
+  ){
+    Tcl_ListObjAppendElement(interp, pList, Tcl_NewStringObj(zSys, -1));
+  }
+
+  Tcl_SetObjResult(interp, pList);
+  Tcl_DecrRefCount(pList);
+  return TCL_OK;
+}
+
+static int SQLITE_TCLAPI test_syscall_defaultvfs(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_vfs *pVfs; 
+
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 2, objv, "");
+    return TCL_ERROR;
+  }
+
+  pVfs = sqlite3_vfs_find(0);
+  Tcl_SetObjResult(interp, Tcl_NewStringObj(pVfs->zName, -1));
+  return TCL_OK;
+}
+
+static int ts_getpagesize(void){
+  return gSyscall.pgsz;
+}
+
+static int SQLITE_TCLAPI test_syscall_pagesize(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  sqlite3_vfs *pVfs = sqlite3_vfs_find(0);
+  int pgsz;
+  if( objc!=3 ){
+    Tcl_WrongNumArgs(interp, 2, objv, "PGSZ");
+    return TCL_ERROR;
+  }
+  if( Tcl_GetIntFromObj(interp, objv[2], &pgsz) ){
+    return TCL_ERROR;
+  }
+
+  if( pgsz<0 ){
+    if( gSyscall.orig_getpagesize ){
+      pVfs->xSetSystemCall(pVfs, "getpagesize", gSyscall.orig_getpagesize);
+    }
+  }else{
+    if( pgsz<512 || (pgsz & (pgsz-1)) ){
+      Tcl_AppendResult(interp, "pgsz out of range", 0);
+      return TCL_ERROR;
+    }
+    gSyscall.orig_getpagesize = pVfs->xGetSystemCall(pVfs, "getpagesize");
+    gSyscall.pgsz = pgsz;
+    pVfs->xSetSystemCall(
+        pVfs, "getpagesize", (sqlite3_syscall_ptr)ts_getpagesize
+    );
+  }
+
+  return TCL_OK;
+}
+
+static int SQLITE_TCLAPI test_syscall(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  struct SyscallCmd {
+    const char *zName;
+    Tcl_ObjCmdProc *xCmd;
+  } aCmd[] = {
+    { "fault",      test_syscall_fault },
+    { "install",    test_syscall_install },
+    { "uninstall",  test_syscall_uninstall },
+    { "reset",      test_syscall_reset },
+    { "errno",      test_syscall_errno },
+    { "exists",     test_syscall_exists },
+    { "list",       test_syscall_list },
+    { "defaultvfs", test_syscall_defaultvfs },
+    { "pagesize",   test_syscall_pagesize },
+    { 0, 0 }
+  };
+  int iCmd;
+  int rc;
+  sqlite3_vfs *pVfs = sqlite3_vfs_find(0);
+
+  if( objc<2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "SUB-COMMAND ...");
+    return TCL_ERROR;
+  }
+  if( pVfs->iVersion<3 || pVfs->xSetSystemCall==0 ){
+    Tcl_AppendResult(interp, "VFS does not support xSetSystemCall", 0);
+    rc = TCL_ERROR;
+  }else{
+    rc = Tcl_GetIndexFromObjStruct(interp, 
+        objv[1], aCmd, sizeof(aCmd[0]), "sub-command", 0, &iCmd
+    );
+  }
+  if( rc!=TCL_OK ) return rc;
+  return aCmd[iCmd].xCmd(clientData, interp, objc, objv);
+}
+
+int SqlitetestSyscall_Init(Tcl_Interp *interp){
+  struct SyscallCmd {
+    const char *zName;
+    Tcl_ObjCmdProc *xCmd;
+  } aCmd[] = {
+    { "test_syscall",     test_syscall},
+  };
+  int i;
+
+  for(i=0; i<sizeof(aCmd)/sizeof(aCmd[0]); i++){
+    Tcl_CreateObjCommand(interp, aCmd[i].zName, aCmd[i].xCmd, 0, 0);
+  }
+  return TCL_OK;
+}
+#else
+int SqlitetestSyscall_Init(Tcl_Interp *interp){
+  return TCL_OK;
+}
+#endif