[patch V2 03/10] x86/mm/cpa: Allow range check for static protections

Thomas Gleixner
2018-09-14T13:21:07Z

[-- Attachment #1: x86-mm-cpa--Allow-range-check-for-static-protections.patch --]
[-- Type: text/plain, Size: 6307 bytes --]

Checking static protections only page by page is slow especially for huge
pages. To allow quick checks over a complete range, add the ability to do
that.

Make the checks inclusive so the ranges can be directly used for debug output
later.

No functional change.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
arch/x86/mm/pageattr.c | 69 +++++++++++++++++++++++++++++++------------------
1 file changed, 44 insertions(+), 25 deletions(-)

--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -286,22 +286,29 @@ static void cpa_flush_array(unsigned lon
}
}

+static bool overlaps(unsigned long r1_start, unsigned long r1_end,
+ unsigned long r2_start, unsigned long r2_end)
+{
+ return (r1_start <= r2_end && r1_end >= r2_start) ||
+ (r2_start <= r1_end && r2_end >= r1_start);
+}
+
#ifdef CONFIG_PCI_BIOS
/*
* The BIOS area between 640k and 1Mb needs to be executable for PCI BIOS
* based config access (CONFIG_PCI_GOBIOS) support.
*/
#define BIOS_PFN PFN_DOWN(BIOS_BEGIN)
-#define BIOS_PFN_END PFN_DOWN(BIOS_END)
+#define BIOS_PFN_END PFN_DOWN(BIOS_END - 1)

-static pgprotval_t protect_pci_bios(unsigned long pfn)
+static pgprotval_t protect_pci_bios(unsigned long spfn, unsigned long epfn)
{
- if (pcibios_enabled && within(pfn, BIOS_PFN, BIOS_PFN_END))
+ if (pcibios_enabled && overlaps(spfn, epfn, BIOS_PFN, BIOS_PFN_END))
return _PAGE_NX;
return 0;
}
#else
-static pgprotval_t protect_pci_bios(unsigned long pfn)
+static pgprotval_t protect_pci_bios(unsigned long spfn, unsigned long epfn)
{
return 0;
}
@@ -312,12 +319,17 @@ static pgprotval_t protect_pci_bios(unsi
* aliases. This also includes __ro_after_init, so do not enforce until
* kernel_set_to_readonly is true.
*/
-static pgprotval_t protect_rodata(unsigned long pfn)
+static pgprotval_t protect_rodata(unsigned long spfn, unsigned long epfn)
{
- unsigned long start_pfn = __pa_symbol(__start_rodata) >> PAGE_SHIFT;
- unsigned long end_pfn = __pa_symbol(__end_rodata) >> PAGE_SHIFT;
+ unsigned long epfn_ro, spfn_ro = PFN_DOWN(__pa_symbol(__start_rodata));
+
+ /*
+ * Note: __end_rodata is at page aligned and not inclusive, so
+ * subtract 1 to get the last enforced PFN in the rodata area.
+ */
+ epfn_ro = PFN_DOWN(__pa_symbol(__end_rodata)) - 1;

- if (kernel_set_to_readonly && within(pfn, start_pfn, end_pfn))
+ if (kernel_set_to_readonly && overlaps(spfn, epfn, spfn_ro, epfn_ro))
return _PAGE_RW;
return 0;
}
@@ -327,9 +339,12 @@ static pgprotval_t protect_rodata(unsign
* not cover __inittext since that is gone after boot. On 64bit we do not
* enforce !NX on the low mapping
*/
-static pgprotval_t protect_kernel_text(unsigned long address)
+static pgprotval_t protect_kernel_text(unsigned long start, unsigned long end)
{
- if (within(address, (unsigned long)_text, (unsigned long)_etext))
+ unsigned long t_end = (unsigned long)_etext - 1;
+ unsigned long t_start = (unsigned long)_text;
+
+ if (overlaps(start, end, t_start, t_end))
return _PAGE_NX;
return 0;
}
@@ -344,13 +359,14 @@ static pgprotval_t protect_kernel_text(u
* This will preserve the large page mappings for kernel text/data at no
* extra cost.
*/
-static pgprotval_t protect_kernel_text_ro(unsigned long address)
+static pgprotval_t protect_kernel_text_ro(unsigned long start,
+ unsigned long end)
{
- unsigned long end = (unsigned long)__end_rodata_hpage_align;
- unsigned long start = (unsigned long)_text;
+ unsigned long t_end = (unsigned long)__end_rodata_hpage_align - 1;
+ unsigned long t_start = (unsigned long)_text;
unsigned int level;

- if (!kernel_set_to_readonly || !within(address, start, end))
+ if (!kernel_set_to_readonly || !overlaps(start, end, t_start, t_end))
return 0;
/*
* Don't enforce the !RW mapping for the kernel text mapping, if
@@ -364,12 +380,13 @@ static pgprotval_t protect_kernel_text_r
* so the protections for kernel text and identity mappings have to
* be the same.
*/
- if (lookup_address(address, &level) && (level != PG_LEVEL_4K))
+ if (lookup_address(start, &level) && (level != PG_LEVEL_4K))
return _PAGE_RW;
return 0;
}
#else
-static pgprotval_t protect_kernel_text_ro(unsigned long address)
+static pgprotval_t protect_kernel_text_ro(unsigned long start,
+ unsigned long end)
{
return 0;
}
@@ -381,18 +398,20 @@ static pgprotval_t protect_kernel_text_r
* 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,
- unsigned long pfn)
+static inline pgprot_t static_protections(pgprot_t prot, unsigned long start,
+ unsigned long pfn, unsigned long npg)
{
pgprotval_t forbidden;
+ unsigned long end;

/* Operate on the virtual address */
- forbidden = protect_kernel_text(address);
- forbidden |= protect_kernel_text_ro(address);
+ end = start + npg * PAGE_SIZE - 1;
+ forbidden = protect_kernel_text(start, end);
+ forbidden |= protect_kernel_text_ro(start, end);

/* Check the PFN directly */
- forbidden |= protect_pci_bios(pfn);
- forbidden |= protect_rodata(pfn);
+ forbidden |= protect_pci_bios(pfn, pfn + npg - 1);
+ forbidden |= protect_rodata(pfn, pfn + npg - 1);

return __pgprot(pgprot_val(prot) & ~forbidden);
}
@@ -664,10 +683,10 @@ static int __should_split_large_page(pte
* in it results in a different pgprot than the first one of the
* requested range. If yes, then the page needs to be split.
*/
- new_prot = static_protections(req_prot, address, pfn);
+ new_prot = static_protections(req_prot, address, pfn, 1);
pfn = old_pfn;
for (i = 0, addr = lpaddr; i < numpages; i++, addr += PAGE_SIZE, pfn++) {
- pgprot_t chk_prot = static_protections(req_prot, addr, pfn);
+ pgprot_t chk_prot = static_protections(req_prot, addr, pfn, 1);

if (pgprot_val(chk_prot) != pgprot_val(new_prot))
return 1;
@@ -1277,7 +1296,7 @@ static int __change_page_attr(struct cpa
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, pfn);
+ new_prot = static_protections(new_prot, address, pfn, 1);

new_prot = pgprot_clear_protnone_bits(new_prot);