Hi Geert,
see attached for the 2.4.30 version of kmap.c.
Cheers,
Michael
Am 23.05.2018 um 19:44 schrieb Geert Uytterhoeven:
Hi Michael,
On Tue, May 22, 2018 at 12:51 PM, Michael Schmitz <schmitzmic@xxxxxxxxx> wrote:
Am 22.05.2018 um 20:18 schrieb Geert Uytterhoeven:
On Mon, May 14, 2018 at 1:10 PM, Michael Schmitz <schmitzmic@xxxxxxxxx> wrote:
Comment on whether the gap size should be considered in looking for a
suitable address to place the next mapping in get_io_area() would be welcome.
At first sight (and looking in full-history-linux git history), I see no
reason for the gap. I'd assume having a block with address and size aligned
to 256 KiB (which the caller already takes care of: IO_SIZE is 256 KiB if
020/030 support is enabled) should be sufficient to use early termination
tables.
My guess is that someone wanted to catch out of bounds accesses by
leaving the unmapped areas in between ioremapped 256 kB chunks. The
unmapped gaps must 256 kB as well to avoid disturbing the alignment.
The adjustment for gap size was dropped sometime between 2.4.30 and
2.6.18. At the same time, a comment in get_io_area was removed that
stated 'leave a gap of IO_SIZE'. I haven't looked at the full history to
find out who removed that comment (and the adjustment).
I can't seem to find the addition/removal of that comment (checked
full-history-linux and the old m68k-linux CVS)?
Gr{oetje,eeting}s,
Geert
/*
* linux/arch/m68k/mm/kmap.c
*
* Copyright (C) 1997 Roman Hodek
*
* 10/01/99 cleaned up the code and changing to the same interface
* used by other architectures /Roman Zippel
*/
#include <linux/config.h>
#include <linux/mm.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <asm/setup.h>
#include <asm/segment.h>
#include <asm/page.h>
#include <asm/pgalloc.h>
#include <asm/io.h>
#include <asm/system.h>
#undef DEBUG
#define PTRTREESIZE (256*1024)
/*
* For 040/060 we can use the virtual memory area like other architectures,
* but for 020/030 we want to use early termination page descriptor and we
* can't mix this with normal page descriptors, so we have to copy that code
* (mm/vmalloc.c) and return appriorate aligned addresses.
*/
#ifdef CPU_M68040_OR_M68060_ONLY
#define IO_SIZE PAGE_SIZE
static inline struct vm_struct *get_io_area(unsigned long size)
{
return get_vm_area(size, VM_IOREMAP);
}
static inline void free_io_area(void *addr)
{
return vfree((void *)(PAGE_MASK & (unsigned long)addr));
}
#else
#define IO_SIZE (256*1024)
static struct vm_struct *iolist = NULL;
static struct vm_struct *get_io_area(unsigned long size)
{
unsigned long addr;
struct vm_struct **p, *tmp, *area;
area = (struct vm_struct *)kmalloc(sizeof(*area), GFP_KERNEL);
if (!area)
return NULL;
addr = KMAP_START;
for (p = &iolist; (tmp = *p) ; p = &tmp->next) {
if (size + addr < (unsigned long)tmp->addr)
break;
if (addr > KMAP_END-size)
return NULL;
addr = tmp->size + (unsigned long)tmp->addr;
}
area->addr = (void *)addr;
area->size = size + IO_SIZE; /* leave a gap between */
area->next = *p;
*p = area;
return area;
}
static inline void free_io_area(void *addr)
{
struct vm_struct **p, *tmp;
if (!addr)
return;
addr = (void *)((unsigned long)addr & -IO_SIZE);
for (p = &iolist ; (tmp = *p) ; p = &tmp->next) {
if (tmp->addr == addr) {
*p = tmp->next;
if ( tmp->size > IO_SIZE )
__iounmap(tmp->addr, tmp->size - IO_SIZE);
else
printk("free_io_area: Invalid I/O area size %lu\n", tmp->size);
kfree(tmp);
return;
}
}
}
#endif
/*
* Map some physical address range into the kernel address space. The
* code is copied and adapted from map_chunk().
*/
/* Rewritten by Andreas Schwab to remove all races. */
void *__ioremap(unsigned long physaddr, unsigned long size, int cacheflag)
{
struct vm_struct *area;
unsigned long virtaddr, retaddr;
long offset;
pgd_t *pgd_dir;
pmd_t *pmd_dir;
pte_t *pte_dir;
/*
* Don't allow mappings that wrap..
*/
if (!size || size > physaddr + size)
return NULL;
#ifdef CONFIG_AMIGA
if (MACH_IS_AMIGA) {
if ((physaddr >= 0x40000000) && (physaddr + size < 0x60000000)
&& (cacheflag == IOMAP_NOCACHE_SER))
return (void *)physaddr;
}
#endif
#ifdef DEBUG
printk("ioremap: 0x%lx,0x%lx(%d) - ", physaddr, size, cacheflag);
#endif
/*
* Mappings have to be aligned
*/
offset = physaddr & (IO_SIZE - 1);
physaddr &= -IO_SIZE;
size = (size + offset + IO_SIZE - 1) & -IO_SIZE;
/*
* Ok, go for it..
*/
area = get_io_area(size);
if (!area)
return NULL;
virtaddr = (unsigned long)area->addr;
retaddr = virtaddr + offset;
#ifdef DEBUG
printk("0x%lx,0x%lx,0x%lx", physaddr, virtaddr, retaddr);
#endif
/*
* add cache and table flags to physical address
*/
if (CPU_IS_040_OR_060) {
physaddr |= (_PAGE_PRESENT | _PAGE_GLOBAL040 |
_PAGE_ACCESSED | _PAGE_DIRTY);
switch (cacheflag) {
case IOMAP_FULL_CACHING:
physaddr |= _PAGE_CACHE040;
break;
case IOMAP_NOCACHE_SER:
default:
physaddr |= _PAGE_NOCACHE_S;
break;
case IOMAP_NOCACHE_NONSER:
physaddr |= _PAGE_NOCACHE;
break;
case IOMAP_WRITETHROUGH:
physaddr |= _PAGE_CACHE040W;
break;
}
} else {
physaddr |= (_PAGE_PRESENT | _PAGE_ACCESSED | _PAGE_DIRTY);
switch (cacheflag) {
case IOMAP_NOCACHE_SER:
case IOMAP_NOCACHE_NONSER:
default:
physaddr |= _PAGE_NOCACHE030;
break;
case IOMAP_FULL_CACHING:
case IOMAP_WRITETHROUGH:
break;
}
}
while ((long)size > 0) {
#ifdef DEBUG
if (!(virtaddr & (PTRTREESIZE-1)))
printk ("\npa=%#lx va=%#lx ", physaddr, virtaddr);
#endif
pgd_dir = pgd_offset_k(virtaddr);
pmd_dir = pmd_alloc_kernel(pgd_dir, virtaddr);
if (!pmd_dir) {
printk("ioremap: no mem for pmd_dir\n");
return NULL;
}
if (CPU_IS_020_OR_030) {
pmd_dir->pmd[(virtaddr/PTRTREESIZE) & 15] = physaddr;
physaddr += PTRTREESIZE;
virtaddr += PTRTREESIZE;
size -= PTRTREESIZE;
} else {
pte_dir = pte_alloc_kernel(pmd_dir, virtaddr);
if (!pte_dir) {
printk("ioremap: no mem for pte_dir\n");
return NULL;
}
pte_val(*pte_dir) = physaddr;
virtaddr += PAGE_SIZE;
physaddr += PAGE_SIZE;
size -= PAGE_SIZE;
}
}
#ifdef DEBUG
printk("\n");
#endif
flush_tlb_all();
return (void *)retaddr;
}
/*
* Unmap a ioremap()ed region again
*/
void iounmap(void *addr)
{
#ifdef CONFIG_AMIGA
if ((!MACH_IS_AMIGA) ||
(((unsigned long)addr < 0x40000000) ||
((unsigned long)addr > 0x60000000)))
free_io_area(addr);
#else
free_io_area(addr);
#endif
}
/*
* __iounmap unmaps nearly everything, so be careful
* it doesn't free currently pointer/page tables anymore but it
* wans't used anyway and might be added later.
*/
void __iounmap(void *addr, unsigned long size)
{
unsigned long virtaddr = (unsigned long)addr;
pgd_t *pgd_dir;
pmd_t *pmd_dir;
pte_t *pte_dir;
while ((long)size > 0) {
pgd_dir = pgd_offset_k(virtaddr);
if (pgd_bad(*pgd_dir)) {
printk("iounmap: bad pgd(%08lx)\n", pgd_val(*pgd_dir));
pgd_clear(pgd_dir);
return;
}
pmd_dir = pmd_offset(pgd_dir, virtaddr);
if (CPU_IS_020_OR_030) {
int pmd_off = (virtaddr/PTRTREESIZE) & 15;
if ((pmd_dir->pmd[pmd_off] & _DESCTYPE_MASK) == _PAGE_PRESENT) {
pmd_dir->pmd[pmd_off] = 0;
virtaddr += PTRTREESIZE;
size -= PTRTREESIZE;
continue;
}
}
if (pmd_bad(*pmd_dir)) {
printk("iounmap: bad pmd (%08lx)\n", pmd_val(*pmd_dir));
pmd_clear(pmd_dir);
return;
}
pte_dir = pte_offset(pmd_dir, virtaddr);
pte_val(*pte_dir) = 0;
virtaddr += PAGE_SIZE;
size -= PAGE_SIZE;
}
flush_tlb_all();
}
/*
* Set new cache mode for some kernel address space.
* The caller must push data for that range itself, if such data may already
* be in the cache.
*/
void kernel_set_cachemode(void *addr, unsigned long size, int cmode)
{
unsigned long virtaddr = (unsigned long)addr;
pgd_t *pgd_dir;
pmd_t *pmd_dir;
pte_t *pte_dir;
if (CPU_IS_040_OR_060) {
switch (cmode) {
case IOMAP_FULL_CACHING:
cmode = _PAGE_CACHE040;
break;
case IOMAP_NOCACHE_SER:
default:
cmode = _PAGE_NOCACHE_S;
break;
case IOMAP_NOCACHE_NONSER:
cmode = _PAGE_NOCACHE;
break;
case IOMAP_WRITETHROUGH:
cmode = _PAGE_CACHE040W;
break;
}
} else {
switch (cmode) {
case IOMAP_NOCACHE_SER:
case IOMAP_NOCACHE_NONSER:
default:
cmode = _PAGE_NOCACHE030;
break;
case IOMAP_FULL_CACHING:
case IOMAP_WRITETHROUGH:
cmode = 0;
}
}
while ((long)size > 0) {
pgd_dir = pgd_offset_k(virtaddr);
if (pgd_bad(*pgd_dir)) {
printk("iocachemode: bad pgd(%08lx)\n", pgd_val(*pgd_dir));
pgd_clear(pgd_dir);
return;
}
pmd_dir = pmd_offset(pgd_dir, virtaddr);
if (CPU_IS_020_OR_030) {
int pmd_off = (virtaddr/PTRTREESIZE) & 15;
if ((pmd_dir->pmd[pmd_off] & _DESCTYPE_MASK) == _PAGE_PRESENT) {
pmd_dir->pmd[pmd_off] = (pmd_dir->pmd[pmd_off] &
_CACHEMASK040) | cmode;
virtaddr += PTRTREESIZE;
size -= PTRTREESIZE;
continue;
}
}
if (pmd_bad(*pmd_dir)) {
printk("iocachemode: bad pmd (%08lx)\n", pmd_val(*pmd_dir));
pmd_clear(pmd_dir);
return;
}
pte_dir = pte_offset(pmd_dir, virtaddr);
pte_val(*pte_dir) = (pte_val(*pte_dir) & _CACHEMASK040) | cmode;
virtaddr += PAGE_SIZE;
size -= PAGE_SIZE;
}
flush_tlb_all();
}
