Backport of upstream commit db7d62c8d5:

Avoid attempting to mmap memory from an offset that is not a multiple of

the system page size on systems with page sizes larger than 32KB.

https://www.sqlite.org/src/info/db7d62c8d58eb1e8654a762c9b199ae4e2759038

Index: src/os_unix.c

==================================================================

--- src/os_unix.c

+++ src/os_unix.c

@@ -321,10 +321,11 @@

   return geteuid() ? 0 : fchown(fd,uid,gid);

 }

 /* Forward reference */

 static int openDirectory(const char*, int*);

+static int unixGetpagesize(void);

 /*

 ** Many system calls are accessed through pointer-to-functions so that

 ** they may be overridden at runtime to facilitate fault injection during

 ** testing and sandboxing.  The following array holds the names and pointers

@@ -443,10 +444,13 @@

   { "mremap",       (sqlite3_syscall_ptr)mremap,          0 },

 #else

   { "mremap",       (sqlite3_syscall_ptr)0,               0 },

 #endif

 #define osMremap ((void*(*)(void*,size_t,size_t,int,...))aSyscall[23].pCurrent)

+

+  { "getpagesize",  (sqlite3_syscall_ptr)unixGetpagesize, 0 },

+#define osGetpagesize ((int(*)(void))aSyscall[24].pCurrent)

 }; /* End of the overrideable system calls */

 /*

 ** This is the xSetSystemCall() method of sqlite3_vfs for all of the

@@ -4103,10 +4107,40 @@

 #endif

   return rc;        

 }

+/*

+** Return the system page size.

+**

+** This function should not be called directly by other code in this file. 

+** Instead, it should be called via macro osGetpagesize().

+*/

+static int unixGetpagesize(void){

+#if defined(_BSD_SOURCE)

+  return getpagesize();

+#else

+  return (int)sysconf(_SC_PAGESIZE);

+#endif

+}

+

+/*

+** Return the minimum number of 32KB shm regions that should be mapped at

+** a time, assuming that each mapping must be an integer multiple of the

+** current system page-size.

+**

+** Usually, this is 1. The exception seems to be systems that are configured

+** to use 64KB pages - in this case each mapping must cover at least two

+** shm regions.

+*/

+static int unixShmRegionPerMap(void){

+  int shmsz = 32*1024;            /* SHM region size */

+  int pgsz = osGetpagesize();   /* System page size */

+  assert( ((pgsz-1)&pgsz)==0 );   /* Page size must be a power of 2 */

+  if( pgsz

+  return pgsz/shmsz;

+}

 /*

 ** Purge the unixShmNodeList list of all entries with unixShmNode.nRef==0.

 **

 ** This is not a VFS shared-memory method; it is a utility function called

@@ -4114,14 +4148,15 @@

 */

 static void unixShmPurge(unixFile *pFd){

   unixShmNode *p = pFd->pInode->pShmNode;

   assert( unixMutexHeld() );

   if( p && p->nRef==0 ){

+    int nShmPerMap = unixShmRegionPerMap();

     int i;

     assert( p->pInode==pFd->pInode );

     sqlite3_mutex_free(p->mutex);

-    for(i=0; i<p->nRegion; i++){

+    for(i=0; i<p->nRegion; i+=nShmPerMap){

       if( p->h>=0 ){

         osMunmap(p->apRegion[i], p->szRegion);

       }else{

         sqlite3_free(p->apRegion[i]);

       }

@@ -4324,10 +4359,12 @@

 ){

   unixFile *pDbFd = (unixFile*)fd;

   unixShm *p;

   unixShmNode *pShmNode;

   int rc = SQLITE_OK;

+  int nShmPerMap = unixShmRegionPerMap();

+  int nReqRegion;

   /* If the shared-memory file has not yet been opened, open it now. */

   if( pDbFd->pShm==0 ){

     rc = unixOpenSharedMemory(pDbFd);

     if( rc!=SQLITE_OK ) return rc;

@@ -4339,13 +4376,16 @@

   assert( szRegion==pShmNode->szRegion || pShmNode->nRegion==0 );

   assert( pShmNode->pInode==pDbFd->pInode );

   assert( pShmNode->h>=0 || pDbFd->pInode->bProcessLock==1 );

   assert( pShmNode->h<0 || pDbFd->pInode->bProcessLock==0 );

-  if( pShmNode->nRegion<=iRegion ){

+  /* Minimum number of regions required to be mapped. */

+  nReqRegion = ((iRegion+nShmPerMap) / nShmPerMap) * nShmPerMap;

+

+  if( pShmNode->nRegion

     char **apNew;                      /* New apRegion[] array */

-    int nByte = (iRegion+1)*szRegion;  /* Minimum required file size */

+    int nByte = nReqRegion*szRegion;   /* Minimum required file size */

     struct stat sStat;                 /* Used by fstat() */

     pShmNode->szRegion = szRegion;

     if( pShmNode->h>=0 ){

@@ -4390,21 +4430,23 @@

       }

     }

     /* Map the requested memory region into this processes address space. */

     apNew = (char **)sqlite3_realloc(

-        pShmNode->apRegion, (iRegion+1)*sizeof(char *)

+        pShmNode->apRegion, nReqRegion*sizeof(char *)

     );

     if( !apNew ){

       rc = SQLITE_IOERR_NOMEM;

       goto shmpage_out;

     }

     pShmNode->apRegion = apNew;

-    while(pShmNode->nRegion<=iRegion){

+    while( pShmNode->nRegion

+      int nMap = szRegion*nShmPerMap;

+      int i;

       void *pMem;

       if( pShmNode->h>=0 ){

-        pMem = osMmap(0, szRegion,

+        pMem = osMmap(0, nMap,

             pShmNode->isReadonly ? PROT_READ : PROT_READ|PROT_WRITE, 

             MAP_SHARED, pShmNode->h, szRegion*(i64)pShmNode->nRegion

         );

         if( pMem==MAP_FAILED ){

           rc = unixLogError(SQLITE_IOERR_SHMMAP, "mmap", pShmNode->zFilename);

@@ -4416,12 +4458,15 @@

           rc = SQLITE_NOMEM;

           goto shmpage_out;

         }

         memset(pMem, 0, szRegion);

       }

-      pShmNode->apRegion[pShmNode->nRegion] = pMem;

-      pShmNode->nRegion++;

+

+      for(i=0; i

+        pShmNode->apRegion[pShmNode->nRegion+i] = &((char*)pMem)[szRegion*i];

+      }

+      pShmNode->nRegion += nShmPerMap;

     }

   }

 shmpage_out:

   if( pShmNode->nRegion>iRegion ){

@@ -4631,25 +4676,10 @@

 #endif

 }

 #if SQLITE_MAX_MMAP_SIZE>0

 /*

-** Return the system page size.

-*/

-static int unixGetPagesize(void){

-#if HAVE_MREMAP

-  return 512;

-#elif defined(_BSD_SOURCE)

-  return getpagesize();

-#else

-  return (int)sysconf(_SC_PAGESIZE);

-#endif

-}

-#endif /* SQLITE_MAX_MMAP_SIZE>0 */

-

-#if SQLITE_MAX_MMAP_SIZE>0

-/*

 ** Attempt to set the size of the memory mapping maintained by file 

 ** descriptor pFd to nNew bytes. Any existing mapping is discarded.

 **

 ** If successful, this function sets the following variables:

 **

@@ -4680,12 +4712,16 @@

   assert( MAP_FAILED!=0 );

   if( (pFd->ctrlFlags & UNIXFILE_RDONLY)==0 ) flags |= PROT_WRITE;

   if( pOrig ){

-    const int szSyspage = unixGetPagesize();

+#if HAVE_MREMAP

+    i64 nReuse = pFd->mmapSize;

+#else

+    const int szSyspage = osGetpagesize();

     i64 nReuse = (pFd->mmapSize & ~(szSyspage-1));

+#endif

     u8 *pReq = &pOrig[nReuse];

     /* Unmap any pages of the existing mapping that cannot be reused. */

     if( nReuse!=nOrig ){

       osMunmap(pReq, nOrig-nReuse);

@@ -7427,11 +7463,11 @@

   };

   unsigned int i;          /* Loop counter */

   /* Double-check that the aSyscall[] array has been constructed

   ** correctly.  See ticket [bb3a86e890c8e96ab] */

-  assert( ArraySize(aSyscall)==24 );

+  assert( ArraySize(aSyscall)==25 );

   /* Register all VFSes defined in the aVfs[] array */

   for(i=0; i<(sizeof(aVfs)/sizeof(sqlite3_vfs)); i++){

     sqlite3_vfs_register(&aVfs[i], i==0);

   }

Index: src/test_syscall.c

==================================================================

--- src/test_syscall.c

+++ src/test_syscall.c

@@ -65,10 +65,15 @@

 **     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"

 #include "tcl.h"

@@ -87,11 +92,13 @@

 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 */

-} gSyscall = { 0, 0 };

+  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);

@@ -647,10 +654,49 @@

   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 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 test_syscall(

   void * clientData,

   Tcl_Interp *interp,

   int objc,

@@ -666,10 +712,11 @@

     { "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;

Index: test/syscall.test

==================================================================

--- test/syscall.test

+++ test/syscall.test

@@ -59,10 +59,11 @@

 foreach s {

     open close access getcwd stat fstat ftruncate

     fcntl read pread write pwrite fchmod fallocate

     pread64 pwrite64 unlink openDirectory mkdir rmdir 

     statvfs fchown umask mmap munmap mremap

+    getpagesize

 } {

   if {[test_syscall exists $s]} {lappend syscall_list $s}

 }

 do_test 3.1 { lsort [test_syscall list] } [lsort $syscall_list]

ADDED   test/wal64k.test

Index: test/wal64k.test

==================================================================

--- test/wal64k.test

+++ test/wal64k.test

@@ -0,0 +1,47 @@

+# 2010 April 13

+#

+# 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.

+#

+#***********************************************************************

+# This file implements regression tests for SQLite library.  The

+# focus of this file is testing the operation of the library in

+# "PRAGMA journal_mode=WAL" mode.

+#

+

+set testdir [file dirname $argv0]

+source $testdir/tester.tcl

+set testprefix wal64k

+

+ifcapable !wal {finish_test ; return }

+

+db close

+test_syscall pagesize 65536

+sqlite3 db test.db

+

+do_execsql_test 1.0 { 

+  PRAGMA journal_mode = WAL;

+  CREATE TABLE t1(x);

+  CREATE INDEX i1 ON t1(x);

+} {wal}

+do_test 1.1 { file size test.db-shm } {65536}

+

+do_test 1.2 {

+  execsql BEGIN

+  while {[file size test.db-shm]==65536} {

+    execsql { INSERT INTO t1 VALUES( randstr(900,1100) ) }

+  }

+  execsql COMMIT

+  file size test.db-shm

+} {131072}

+

+integrity_check 1.3

+

+db close

+test_syscall pagesize -1

+finish_test

+