Support for dynamic PAGE_SIZE

This patch adds support for dynamic PAGE_SIZE values. It
is a little bit invasive in several aspects:

* it modifies the startup code. We need to know the position of
  the elf-info auxilary table which is located after 'environ'.
  We can not use 'environ' directly because it might be modified
  by the application.

  Hence, an additional __elfinfo variable is placed into .bss and
  filled in the startup code. Depending on platform, this adds
  4-8 instructions and an additional pointer to .bss.

  I tested only the i386 and x86_64 modifications; it would be
  nice when people with corresponding hardware would test the
  other ones. I am especially uncertain regarding the parisc
  changes.

  The elf-info stuff (which might be interesting e.g. for dynamic
  linking or sysconf(_SC_CLK_TCK)) can be enabled without the
  dynamic pagesize too.

* it removes the 'PAGE_SIZE' macro from <sys/shm.h>; this will
  break compilation of existing userspace application which are
  using this deprecated macro

* I added a new internal 'dietpagesize.h' header which defines

  | __DIET_PAGE_SIZE
  | __DIET_PAGE_SHIFT

  macros. These return either builtin constants (when
  WANT_DYN_PAGESIZE is not selected), or values derived from
  __libc_getpagesize().

  Every usage of PAGE_SIZE in dietlibc code was replaced by these
  macros.

* due to the previous point, the internal 'struct __dirstream'
  was modified. I replaced

  | getdents64(d->fd,(struct dirent64*)d->buf, sizeof (d->buf)-1);

  with

  | getdents64(d->fd,(struct dirent64*)d->buf,  __DIRSTREAM_BUF_SIZE-1);

  literally but I am not sure where the '-1' is coming from.
  There is one hunk, where this '-1' is missing so I think the
  '-1' should be removed from all calls to getdents64().

* changes affect the *alloc() functions too; on x86_64 around 64
  bytes were added to .text of alloc.o

* the new testprogramm requires a 'getconf' binary which returns
  the correct values for PAGE_SIZE and CLK_TCK

Patch seems to work fine on i386, x86_64, ppc and ppc64.  Things
went a little bit complicated with linux 2.6.25; previous kernels
exported a elf_addr_t type in <linux/elf.h> which is used in the
auxilary elf-info table. Now, this is not available anymore and I
use a type derived from __WORD_SIZE.

alpha/start.S

@@ -24,6 +24,15 @@ _start:
 
 	stq	$18, environ
 
+#ifdef WANT_ELFINFO
+#  warning "MAKE ME alpha ASSEMBLER!"
+1:	ldq	$19, $18	; load *envp into $19
+	addq	$18,  1,  $18	; increment *envp
+	orr	$19, $19, $19
+	jne	1b
+	stq	$18, __elfinfo
+#endif
+
 #ifdef WANT_DYNAMIC
 /* in v0 ($0) is the ld.so _fini pointer */
 	mov	 $0, $19	/* mov v0(dynload) to a3 */

arm/start.S

@@ -13,6 +13,17 @@ FUNC_START	_start
 	add	a3, a2, a1, lsl #2	@ &argv[argc]
 	add	a3, a3, #4		@ envp	
 	str	a3, [ip, #0]		@ environ = envp
+
+#ifdef WANT_ELFINFO
+	mov	r6, a3			@ work on a copy of a3 so that common
+					@ 'main(argc, argv, envp)' function
+					@ stays valid
+1:	ldr	r5, [r6], #4		@ load *envp and increment it
+	cmp	r5, #0			@ read value==0?
+	bne	1b
+	str	r6, [ip, #4]		@ __elfinfo = envp
+#endif
+
 	bl	main
 
 @
@@ -48,11 +59,25 @@ FUNC_START	_start
 #ifdef __DYN_LIB
 	ldr	sl, .L4
 1:	add	sl, pc, sl
-	str	a3, [sl, ip]		@ environ = envp
+	str	a3, [ip, sl]!		@ environ = envp; ip = GOT(environ)
 #else
 	str	a3, [ip, #0]		@ environ = envp
 #endif
 
+#ifdef WANT_ELFINFO
+	mov	r6, a3			@ work on a copy of a3 so that common
+					@ 'main(argc, argv, envp)' function
+					@ stays valid
+1:	ldr	r5, [r6], #4		@ load *envp and increment it
+	cmp	r5, #0			@ read value==0?
+	bne	1b
+#ifdef __DYN_LIB
+	str	r6, [ip, sl]		@ __elfinfo = envp
+#else
+	str	r6, [ip, #4]		@ __elfinfo = envp
+#endif
+#endif
+
 #ifdef PROFILING
 	stmdb	sp!, { r0 - r3 }
 	ldr	r0, .L5

dietdirent.h

@@ -1,11 +1,13 @@
 #include <sys/shm.h>
 
+#include "dietpagesize.h"
+
 struct __dirstream {
-  char buf[PAGE_SIZE-(sizeof (int)*3)];
   int fd;
   unsigned int num;
   unsigned int cur;
   unsigned char is_64;
+  char buf[] __attribute__((__aligned__(8)));
 };				/* stream data from opendir() */
 
 struct linux_dirent {
@@ -22,3 +24,5 @@ struct linux_dirent64 {
   unsigned char   d_type;
   char            d_name[0];
 };
+
+#define __DIRSTREAM_BUF_SIZE	(__DIET_PAGE_SIZE - offsetof(struct __dirstream, buf))

dietelfinfo.h

@@ -0,0 +1,20 @@
+#include "dietfeatures.h"
+
+#ifdef WANT_ELFINFO
+#include <elf.h>
+#include <endian.h>
+#include <stdint.h>
+
+/* TODO: exported interface from <linux/elf.h> has been changed in 2.6.25 so
+ * the 'elf_addr_t' type is not available anymore. Hence, derive it from
+ * __WORDSIZE__. */
+
+#if __WORDSIZE == 64
+typedef uint64_t	__diet_elf_addr_t;
+#elif __WORDSIZE == 32
+typedef uint32_t	__diet_elf_addr_t;
+#endif
+
+__diet_elf_addr_t const *	__get_elf_aux_value(unsigned int tag)
+	__attribute__((__visibility__("hidden"),__const__)) __pure;
+#endif

dietfeatures.h

@@ -142,6 +142,16 @@
 #define WANT_SSP
 #endif
 
+/* Some platforms like x86_64, ppc* or mips do not have a fixed PAGE_SIZE.
+ * Select WANT_DYN_PAGESIZE to detect the current PAGE_SIZE at runtime. Else,
+ * define WANT_STATIC_PAGESIZE to a proper value (must be a power of 2)
+ * matching the configured pagesize of the kernel where your binaries are
+ * running on.
+ *
+ * Selecting WANT_DYN_PAGESIZE enlarges the startup code by around 1-3
+ * instructions and might add an additional __elfinfo symbol */
+#define WANT_DYN_PAGESIZE
+/* #define WANT_STATIC_PAGESIZE 0x10000UL */
 
 
 /* stop uncommenting here ;-) */
@@ -176,4 +186,8 @@
 #undef WANT_LARGEFILE_BACKCOMPAT
 #endif
 
+#ifdef WANT_DYN_PAGESIZE
+#define WANT_ELFINFO
+#endif
+
 #endif

dietpagesize.h

@@ -0,0 +1,31 @@
+#ifndef H_DIETLIBC_DIETPAGESIZE_H
+#define H_DIETLIBC_DIETPAGESIZE_H
+
+#include <strings.h>
+#include "dietfeatures.h"
+
+extern size_t __libc_getpagesize(void) __attribute__((__const__)) __pure;
+
+#if defined(WANT_STATIC_PAGESIZE)
+#  define __DIET_PAGE_SIZE_PREDEF	(WANT_STATIC_PAGESIZE)
+#  define __DIET_PAGE_SHIFT_PREDEF	(ffs(__DIET_PAGE_SIZE_PREDEF)-1)
+#elif defined(__alpha__) || defined(__sparc__)
+#  define __DIET_PAGE_SIZE_PREDEF	(8192UL)
+#  define __DIET_PAGE_SHIFT_PREDEF	(13)
+#elif defined(__powerpc64__)
+#  define __DIET_PAGE_SIZE_PREDEF	(65536UL)
+#  define __DIET_PAGE_SHIFT_PREDEF	(16)
+#else
+#  define __DIET_PAGE_SIZE_PREDEF	(4096UL)
+#  define __DIET_PAGE_SHIFT_PREDEF	(12)
+#endif
+
+#ifdef WANT_DYN_PAGESIZE
+#  define __DIET_PAGE_SIZE	(__libc_getpagesize())
+#  define __DIET_PAGE_SHIFT	(ffs(__DIET_PAGE_SIZE)-1)
+#else
+#  define __DIET_PAGE_SIZE	__DIET_PAGE_SIZE_PREDEF
+#  define __DIET_PAGE_SHIFT	__DIET_PAGE_SHIFT_PREDEF
+#endif
+
+#endif	/* H_DIETLIBC_DIETPAGESIZE_H */

dynlinker/ldso_start.S

@@ -86,6 +86,15 @@ __environ:
 	.long 0
 #endif
 
+/* __elfinfo must follow __environ immediately */
+.global __elfinfo
+__elfinfo:
+#if __WORDSIZE == 64
+	.quad 0
+#else
+	.long 0
+#endif
+
 .global fini_entry
 fini_entry:
 	.long 0

i386/start.S

@@ -20,12 +20,18 @@ _start:
 	PIC_INIT			/* non-PIC: this is an empty line */
 	PUT_VAR %esi, environ, %ecx	/* non-PIC: movl %esi,environ */
 
-#ifdef WANT_SYSENTER
+#if defined(WANT_ELFINFO) || defined(WANT_SYSENTER)
 /* skip environment, scan for NULL */
 1:
 	lodsl
 	testl	%eax,%eax
 	jnz	1b
+#  ifdef WANT_ELFINFO
+	PUT_VAR %esi, __elfinfo, %ecx
+#  endif
+#endif
+
+#ifdef WANT_SYSENTER
 /* The ELF auxvec follows the environment, consists of key/value pairs.
    We are looking for key 32, which stands for the vsyscall page */
 1:

ia64/start.S

@@ -40,6 +40,16 @@ _start:
 	;;
 	st8  [r14] = out2           /* store envp in environ */
 
+#ifdef WANT_ELFINFO
+#  warning "MAKE ME IE64 CODE!"
+1:	ld8	r9 = [out2], 8	    /* load *envp and increment it */
+	orr	r9 = r9, r9	    /* test for NULL */
+	bne	1b
+
+	adds r14 = 8, r14	    /* __elfinfo = environ + 8 */
+	st8  [r14] = out2           /* store envp in __elfinfo */
+#endif
+
 #ifdef WANT_DYNAMIC
 /* FIXME: dl_init parameter ??? */
 	br.call.sptk.few rp = _dyn_start

include/sys/shm.h

@@ -60,15 +60,6 @@ struct shm_info {
   unsigned long swap_successes;
 };
 
-#if defined(__i386__) || defined(__mips__) || defined(__arm__) || defined(__powerpc__) || defined (__powerpc64__) || defined(__s390__) || defined(__hppa__) || defined(__x86_64__) || defined(__ia64__)
-#define PAGE_SIZE 4096UL
-#define PAGE_SHIFT 12
-#elif defined(__alpha__) || defined(__sparc__)
-/* sun4* has 4k except sun4 architecture, sparc64 has 8k */
-#define PAGE_SIZE 8192UL
-#define PAGE_SHIFT 13
-#endif
-
 extern int shmget(key_t key, int size, int shmflg) __THROW;
 extern void *shmat(int shmid, const void *shmaddr, int shmflg) __THROW;
 extern int shmdt (const void *shmaddr) __THROW;

lib/__get_elf_aux_value.c

@@ -0,0 +1,19 @@
+#include "dietfeatures.h"
+
+#ifdef WANT_ELFINFO
+#include <stdlib.h>
+#include "../dietelfinfo.h"
+
+__diet_elf_addr_t const *__get_elf_aux_value(unsigned int tag)
+{
+  extern __diet_elf_addr_t const * const	__elfinfo;
+  __diet_elf_addr_t const			*aux_ptr;
+
+  for (aux_ptr = __elfinfo; aux_ptr[0]!=AT_NULL; aux_ptr += 2)
+    if (aux_ptr[0]==tag)
+      return aux_ptr+1;
+
+  return NULL;
+}
+
+#endif

lib/alloc.c

@@ -18,8 +18,7 @@
 #include <stdlib.h>
 #include <string.h>
 
-#include <sys/shm.h>	/* for PAGE_SIZE */
-
+#include "../dietpagesize.h"
 
 /* -- HELPER CODE --------------------------------------------------------- */
 
@@ -39,7 +38,7 @@ typedef struct {
 #define BLOCK_START(b)	(((void*)(b))-sizeof(__alloc_t))
 #define BLOCK_RET(b)	(((void*)(b))+sizeof(__alloc_t))
 
-#define MEM_BLOCK_SIZE	PAGE_SIZE
+#define MEM_BLOCK_SIZE	__DIET_PAGE_SIZE
 #define PAGE_ALIGN(s)	(((s)+MEM_BLOCK_SIZE-1)&(unsigned long)(~(MEM_BLOCK_SIZE-1)))
 
 /* a simple mmap :) */
@@ -66,7 +65,9 @@ static __alloc_t* __small_mem[8];
 
 #define FIRST_SMALL(p)		(((unsigned long)(p))&(~(MEM_BLOCK_SIZE-1)))
 
-static inline int __ind_shift() { return (MEM_BLOCK_SIZE==4096)?4:5; }
+static inline int __ind_shift() {
+	return __DIET_PAGE_SHIFT - sizeof(__small_mem)/sizeof(__small_mem[0]);
+}
 
 static size_t REGPARM(1) get_index(size_t _size) {
   register size_t idx=0;

lib/closedir.c

@@ -4,8 +4,10 @@
 #include <dirent.h>
 #include <stdlib.h>
 
+#include "../dietpagesize.h"
+
 int closedir (DIR* d) {
   int res=close(d->fd);
-  munmap (d, PAGE_SIZE);
+  munmap (d, __DIET_PAGE_SIZE);
   return res;
 }

lib/fdopendir.c

@@ -1,4 +1,5 @@
 #include "dietdirent.h"
+#include "dietpagesize.h"
 #include <sys/mman.h>
 #include <unistd.h>
 #include <dirent.h>
@@ -9,7 +10,7 @@ DIR*  fdopendir ( int fd ) {
   DIR*  t  = NULL;
 
   if ( fd >= 0 ) {
-    t = (DIR *) mmap (NULL, PAGE_SIZE, PROT_READ | PROT_WRITE, 
+    t = (DIR *) mmap (NULL, __DIET_PAGE_SIZE, PROT_READ | PROT_WRITE,
 		MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
     if (t != MAP_FAILED)
       t->fd = fd;

lib/mmap64.c

@@ -4,16 +4,18 @@
 #include <syscalls.h>
 #include <errno.h>
 
+#include "../dietpagesize.h"
+
 #ifdef __NR_mmap2
 void*__mmap2(void*start,size_t length,int prot,int flags,int fd,off_t pgoffset);
 
 void*__libc_mmap64(void*addr,size_t len,int prot,int flags,int fd,off64_t offset);
 void*__libc_mmap64(void*addr,size_t len,int prot,int flags,int fd,off64_t offset) {
-  if (offset&(PAGE_SIZE-1)) {
+  if (offset&(__DIET_PAGE_SIZE)) {
     errno=-EINVAL;
     return MAP_FAILED;
   }
-  return __mmap2(addr,len,prot,flags,fd,offset>>PAGE_SHIFT);
+  return __mmap2(addr,len,prot,flags,fd,offset>>__DIET_PAGE_SHIFT);
 }
 
 void*mmap64(void*addr,size_t len,int prot,int flags,int fd,off64_t offset)

lib/opendir.c

@@ -5,14 +5,16 @@
 #include <stdlib.h>
 #include <fcntl.h>
 
+#include "../dietpagesize.h"
+
 DIR*  opendir ( const char* name ) {
   int   fd = open (name, O_RDONLY | O_DIRECTORY);
   DIR*  t  = NULL;
 
   if ( fd >= 0 ) {
     if (fcntl (fd, F_SETFD, FD_CLOEXEC) < 0)
       goto lose;
-    t = (DIR *) mmap (NULL, PAGE_SIZE, PROT_READ | PROT_WRITE, 
+    t = (DIR *) mmap (NULL, __DIET_PAGE_SIZE, PROT_READ | PROT_WRITE,
 		MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
     if (t == MAP_FAILED)
 lose:

lib/readdir64.c

@@ -15,7 +15,7 @@
 struct dirent64* readdir64(DIR *d) {
   struct linux_dirent64 *ld = d->num ? (struct linux_dirent64*)(d->buf+d->cur) : NULL;
   if (!d->num || (d->cur += ld->d_reclen)>=d->num) {
-    int res=getdents64(d->fd,(struct linux_dirent64*)d->buf, sizeof (d->buf)-1);
+    int res=getdents64(d->fd,(struct linux_dirent64*)d->buf, __DIRSTREAM_BUF_SIZE-1);
     if (res<=0) return 0;
     d->num=res; d->cur=0; d->is_64=1;
   }
@@ -34,7 +34,7 @@ struct dirent64* readdir64(DIR *d) {
 #endif
     struct linux_dirent *ld = d->num ? (struct linux_dirent*)(d->buf+d->cur) : NULL;
     if (!d->num || (d->cur += ld->d_reclen)>=d->num) {
-      int res=getdents(d->fd,(struct linux_dirent*)d->buf, sizeof (d->buf)-1);
+      int res=getdents(d->fd,(struct linux_dirent*)d->buf, __DIRSTREAM_BUF_SIZE-1);
       if (res<=0) return 0;
       d->num=res; d->cur=0;d->is_64=0;
       ld=(struct linux_dirent*)(d->buf+d->cur);
@@ -50,7 +50,7 @@ struct dirent64* readdir64(DIR *d) {
   {
   struct linux_dirent64 *ld = d->num ? (struct linux_dirent64*)(d->buf+d->cur) : NULL;
   if (!d->num || (d->cur += ld->d_reclen)>=d->num) {
-    int res=getdents64(d->fd,(struct linux_dirent64*)d->buf,sizeof (d->buf));
+    int res=getdents64(d->fd,(struct linux_dirent64*)d->buf,__DIRSTREAM_BUF_SIZE);
     if (res<=0) {
       if (errno==ENOSYS) {
 	trygetdents64=0;

lib/readdir_r.c

@@ -8,7 +8,7 @@ int readdir_r(DIR *d,struct dirent* entry, struct dirent** result) {
   struct linux_dirent* ld = d->num ? (struct linux_dirent*)(d->buf+d->cur) : NULL;
   *result=0;
   if (!d->num || d->cur >= d->num || (d->cur += ld->d_reclen)>=d->num) {
-    int res=getdents(d->fd,(struct linux_dirent*)d->buf,sizeof (d->buf)-1);
+    int res=getdents(d->fd,(struct linux_dirent*)d->buf,__DIRSTREAM_BUF_SIZE-1);
     if (res<=0)
       return res<0;
     d->num=res; d->cur=0; d->is_64=0;