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x86: CPA, fix alias checks
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c_p_a() did not discover all aliases correctly. (such as when called
on vmalloc()-ed areas or ioremap()-ed areas)

Push the alias checks to the lower, physical level and consistently
discover all aliases that might exist: the low direct mappings and
the high linear kernel-text mappings (on 64-bit).

Thanks to Andi Kleen for pointing out that this was buggy.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Thomas Gleixner committed Feb 18, 2008
1 parent 1309d4e commit c31c7d4
Showing 1 changed file with 92 additions and 100 deletions.
192 changes: 92 additions & 100 deletions arch/x86/mm/pageattr.c
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,7 @@
#include <asm/sections.h>
#include <asm/uaccess.h>
#include <asm/pgalloc.h>
#include <asm/proto.h>

/*
* The current flushing context - we pass it instead of 5 arguments:
Expand All @@ -26,8 +27,23 @@ struct cpa_data {
pgprot_t mask_clr;
int numpages;
int flushtlb;
unsigned long pfn;
};

#ifdef CONFIG_X86_64

static inline unsigned long highmap_start_pfn(void)
{
return __pa(_text) >> PAGE_SHIFT;
}

static inline unsigned long highmap_end_pfn(void)
{
return __pa(round_up((unsigned long)_end, PMD_SIZE)) >> PAGE_SHIFT;
}

#endif

static inline int
within(unsigned long addr, unsigned long start, unsigned long end)
{
Expand Down Expand Up @@ -123,60 +139,38 @@ static void cpa_flush_range(unsigned long start, int numpages, int cache)
}
}

#define HIGH_MAP_START __START_KERNEL_map
#define HIGH_MAP_END (__START_KERNEL_map + KERNEL_TEXT_SIZE)


/*
* Converts a virtual address to a X86-64 highmap address
*/
static unsigned long virt_to_highmap(void *address)
{
#ifdef CONFIG_X86_64
return __pa((unsigned long)address) + HIGH_MAP_START - phys_base;
#else
return (unsigned long)address;
#endif
}

/*
* Certain areas of memory on x86 require very specific protection flags,
* for example the BIOS area or kernel text. Callers don't always get this
* right (again, ioremap() on BIOS memory is not uncommon) so this function
* checks and fixes these known static required protection bits.
*/
static inline pgprot_t static_protections(pgprot_t prot, unsigned long address)
static inline pgprot_t static_protections(pgprot_t prot, unsigned long address,
unsigned long pfn)
{
pgprot_t forbidden = __pgprot(0);

/*
* The BIOS area between 640k and 1Mb needs to be executable for
* PCI BIOS based config access (CONFIG_PCI_GOBIOS) support.
*/
if (within(__pa(address), BIOS_BEGIN, BIOS_END))
if (within(pfn, BIOS_BEGIN >> PAGE_SHIFT, BIOS_END >> PAGE_SHIFT))
pgprot_val(forbidden) |= _PAGE_NX;

/*
* The kernel text needs to be executable for obvious reasons
* Does not cover __inittext since that is gone later on
* Does not cover __inittext since that is gone later on. On
* 64bit we do not enforce !NX on the low mapping
*/
if (within(address, (unsigned long)_text, (unsigned long)_etext))
pgprot_val(forbidden) |= _PAGE_NX;
/*
* Do the same for the x86-64 high kernel mapping
*/
if (within(address, virt_to_highmap(_text), virt_to_highmap(_etext)))
pgprot_val(forbidden) |= _PAGE_NX;

/* The .rodata section needs to be read-only */
if (within(address, (unsigned long)__start_rodata,
(unsigned long)__end_rodata))
pgprot_val(forbidden) |= _PAGE_RW;
/*
* Do the same for the x86-64 high kernel mapping
* The .rodata section needs to be read-only. Using the pfn
* catches all aliases.
*/
if (within(address, virt_to_highmap(__start_rodata),
virt_to_highmap(__end_rodata)))
if (within(pfn, __pa((unsigned long)__start_rodata) >> PAGE_SHIFT,
__pa((unsigned long)__end_rodata) >> PAGE_SHIFT))
pgprot_val(forbidden) |= _PAGE_RW;

prot = __pgprot(pgprot_val(prot) & ~pgprot_val(forbidden));
Expand Down Expand Up @@ -253,7 +247,7 @@ static int
try_preserve_large_page(pte_t *kpte, unsigned long address,
struct cpa_data *cpa)
{
unsigned long nextpage_addr, numpages, pmask, psize, flags, addr;
unsigned long nextpage_addr, numpages, pmask, psize, flags, addr, pfn;
pte_t new_pte, old_pte, *tmp;
pgprot_t old_prot, new_prot;
int i, do_split = 1;
Expand Down Expand Up @@ -301,16 +295,25 @@ try_preserve_large_page(pte_t *kpte, unsigned long address,

pgprot_val(new_prot) &= ~pgprot_val(cpa->mask_clr);
pgprot_val(new_prot) |= pgprot_val(cpa->mask_set);
new_prot = static_protections(new_prot, address);

/*
* old_pte points to the large page base address. So we need
* to add the offset of the virtual address:
*/
pfn = pte_pfn(old_pte) + ((address & (psize - 1)) >> PAGE_SHIFT);
cpa->pfn = pfn;

new_prot = static_protections(new_prot, address, pfn);

/*
* We need to check the full range, whether
* static_protection() requires a different pgprot for one of
* the pages in the range we try to preserve:
*/
addr = address + PAGE_SIZE;
for (i = 1; i < cpa->numpages; i++, addr += PAGE_SIZE) {
pgprot_t chk_prot = static_protections(new_prot, addr);
pfn++;
for (i = 1; i < cpa->numpages; i++, addr += PAGE_SIZE, pfn++) {
pgprot_t chk_prot = static_protections(new_prot, addr, pfn);

if (pgprot_val(chk_prot) != pgprot_val(new_prot))
goto out_unlock;
Expand Down Expand Up @@ -505,46 +508,51 @@ static int split_large_page(pte_t *kpte, unsigned long address)
return 0;
}

static int __change_page_attr(unsigned long address, struct cpa_data *cpa)
static int __change_page_attr(struct cpa_data *cpa, int primary)
{
unsigned long address = cpa->vaddr;
int do_split, err;
unsigned int level;
struct page *kpte_page;
pte_t *kpte;
pte_t *kpte, old_pte;

repeat:
kpte = lookup_address(address, &level);
if (!kpte)
return primary ? -EINVAL : 0;

old_pte = *kpte;
if (!pte_val(old_pte)) {
if (!primary)
return 0;
printk(KERN_WARNING "CPA: called for zero pte. "
"vaddr = %lx cpa->vaddr = %lx\n", address,
cpa->vaddr);
WARN_ON(1);
return -EINVAL;
}

kpte_page = virt_to_page(kpte);
BUG_ON(PageLRU(kpte_page));
BUG_ON(PageCompound(kpte_page));

if (level == PG_LEVEL_4K) {
pte_t new_pte, old_pte = *kpte;
pte_t new_pte;
pgprot_t new_prot = pte_pgprot(old_pte);

if(!pte_val(old_pte)) {
printk(KERN_WARNING "CPA: called for zero pte. "
"vaddr = %lx cpa->vaddr = %lx\n", address,
cpa->vaddr);
WARN_ON(1);
return -EINVAL;
}
unsigned long pfn = pte_pfn(old_pte);

pgprot_val(new_prot) &= ~pgprot_val(cpa->mask_clr);
pgprot_val(new_prot) |= pgprot_val(cpa->mask_set);

new_prot = static_protections(new_prot, address);
new_prot = static_protections(new_prot, address, pfn);

/*
* We need to keep the pfn from the existing PTE,
* after all we're only going to change it's attributes
* not the memory it points to
*/
new_pte = pfn_pte(pte_pfn(old_pte), canon_pgprot(new_prot));

new_pte = pfn_pte(pfn, canon_pgprot(new_prot));
cpa->pfn = pfn;
/*
* Do we really change anything ?
*/
Expand Down Expand Up @@ -581,67 +589,44 @@ static int __change_page_attr(unsigned long address, struct cpa_data *cpa)
return err;
}

/**
* change_page_attr_addr - Change page table attributes in linear mapping
* @address: Virtual address in linear mapping.
* @prot: New page table attribute (PAGE_*)
*
* Change page attributes of a page in the direct mapping. This is a variant
* of change_page_attr() that also works on memory holes that do not have
* mem_map entry (pfn_valid() is false).
*
* See change_page_attr() documentation for more details.
*
* Modules and drivers should use the set_memory_* APIs instead.
*/
static int change_page_attr_addr(struct cpa_data *cpa)
static int __change_page_attr_set_clr(struct cpa_data *cpa, int checkalias);

static int cpa_process_alias(struct cpa_data *cpa)
{
int err;
unsigned long address = cpa->vaddr;
struct cpa_data alias_cpa;
int ret;

#ifdef CONFIG_X86_64
unsigned long phys_addr = __pa(address);
if (cpa->pfn > max_pfn_mapped)
return 0;

/*
* If we are inside the high mapped kernel range, then we
* fixup the low mapping first. __va() returns the virtual
* address in the linear mapping:
*/
if (within(address, HIGH_MAP_START, HIGH_MAP_END))
address = (unsigned long) __va(phys_addr);
#endif
alias_cpa = *cpa;
alias_cpa.vaddr = (unsigned long) __va(cpa->pfn << PAGE_SHIFT);

err = __change_page_attr(address, cpa);
if (err)
return err;
ret = __change_page_attr_set_clr(&alias_cpa, 0);

#ifdef CONFIG_X86_64
if (ret)
return ret;
/*
* If the physical address is inside the kernel map, we need
* to touch the high mapped kernel as well:
*/
if (within(phys_addr, 0, KERNEL_TEXT_SIZE)) {
/*
* Calc the high mapping address. See __phys_addr()
* for the non obvious details.
*
* Note that NX and other required permissions are
* checked in static_protections().
*/
address = phys_addr + HIGH_MAP_START - phys_base;
if (!within(cpa->pfn, highmap_start_pfn(), highmap_end_pfn()))
return 0;

/*
* Our high aliases are imprecise, because we check
* everything between 0 and KERNEL_TEXT_SIZE, so do
* not propagate lookup failures back to users:
*/
__change_page_attr(address, cpa);
}
alias_cpa = *cpa;
alias_cpa.vaddr =
(cpa->pfn << PAGE_SHIFT) + __START_KERNEL_map - phys_base;

/*
* The high mapping range is imprecise, so ignore the return value.
*/
__change_page_attr_set_clr(&alias_cpa, 0);
#endif
return err;
return ret;
}

static int __change_page_attr_set_clr(struct cpa_data *cpa)
static int __change_page_attr_set_clr(struct cpa_data *cpa, int checkalias)
{
int ret, numpages = cpa->numpages;

Expand All @@ -651,10 +636,17 @@ static int __change_page_attr_set_clr(struct cpa_data *cpa)
* preservation check.
*/
cpa->numpages = numpages;
ret = change_page_attr_addr(cpa);

ret = __change_page_attr(cpa, checkalias);
if (ret)
return ret;

if (checkalias) {
ret = cpa_process_alias(cpa);
if (ret)
return ret;
}

/*
* Adjust the number of pages with the result of the
* CPA operation. Either a large page has been
Expand Down Expand Up @@ -703,7 +695,7 @@ static int change_page_attr_set_clr(unsigned long addr, int numpages,
cpa.mask_clr = mask_clr;
cpa.flushtlb = 0;

ret = __change_page_attr_set_clr(&cpa);
ret = __change_page_attr_set_clr(&cpa, 1);

/*
* Check whether we really changed something:
Expand Down Expand Up @@ -841,7 +833,7 @@ static int __set_pages_p(struct page *page, int numpages)
.mask_set = __pgprot(_PAGE_PRESENT | _PAGE_RW),
.mask_clr = __pgprot(0)};

return __change_page_attr_set_clr(&cpa);
return __change_page_attr_set_clr(&cpa, 1);
}

static int __set_pages_np(struct page *page, int numpages)
Expand All @@ -851,7 +843,7 @@ static int __set_pages_np(struct page *page, int numpages)
.mask_set = __pgprot(0),
.mask_clr = __pgprot(_PAGE_PRESENT | _PAGE_RW)};

return __change_page_attr_set_clr(&cpa);
return __change_page_attr_set_clr(&cpa, 1);
}

void kernel_map_pages(struct page *page, int numpages, int enable)
Expand Down

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