Attachment 151669 Details for Bug 234069 – fail mmaps that span incompatible attributes

[patch] fail mmaps that span incompatible attributes

ia64-mmap-validation (text/plain), 2.59 KB, created by Bjorn Helgaas on 2007-04-04 15:30:13 UTC

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Creator: Bjorn Helgaas

Created: 2007-04-04 15:30:13 UTC

Size: 2.59 KB

patch

obsolete

>ia64: fail mmaps that span areas with incompatible attributes
>
>Example memory map (from HP sx1000 with VGA enabled):
>    0x00000 - 0x9FFFF supports only WB (cacheable) access
>    0xA0000 - 0xBFFFF supports only UC (uncacheable) access
>    0xC0000 - 0xFFFFF supports only WB (cacheable) access
>
>Some versions of X map the entire 0x00000-0xFFFFF area at once.  With the
>example above, this mmap must fail because there's no memory attribute that's
>safe for the entire area.
>
>Prior to this patch, we performed the mmap with a UC mapping.  When X
>accessed the WB memory at 0xC0000, it caused an MCA.  The crash can happen
>when mapping 0xC0000 from either /dev/mem or a /sys/.../legacy_mem file.
>
>Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
>
>Index: linux-2.6.18.ia64/arch/ia64/kernel/efi.c
>===================================================================
>--- linux-2.6.18.ia64.orig/arch/ia64/kernel/efi.c	2007-03-23 05:18:28.000000000 -0600
>+++ linux-2.6.18.ia64/arch/ia64/kernel/efi.c	2007-03-23 06:32:28.000000000 -0600
>@@ -660,6 +660,29 @@
> 	return NULL;
> }
> 
>+static int
>+efi_memmap_intersects (unsigned long phys_addr, unsigned long size)
>+{
>+	void *efi_map_start, *efi_map_end, *p;
>+	efi_memory_desc_t *md;
>+	u64 efi_desc_size;
>+	unsigned long end;
>+
>+	efi_map_start = __va(ia64_boot_param->efi_memmap);
>+	efi_map_end   = efi_map_start + ia64_boot_param->efi_memmap_size;
>+	efi_desc_size = ia64_boot_param->efi_memdesc_size;
>+
>+	end = phys_addr + size;
>+
>+	for (p = efi_map_start; p < efi_map_end; p += efi_desc_size) {
>+		md = p;
>+
>+		if (md->phys_addr < end && efi_md_end(md) > phys_addr)
>+			return 1;
>+	}
>+	return 0;
>+}
>+
> u32
> efi_mem_type (unsigned long phys_addr)
> {
>@@ -766,11 +789,28 @@
> int
> valid_mmap_phys_addr_range (unsigned long pfn, unsigned long size)
> {
>+	unsigned long phys_addr = pfn << PAGE_SHIFT;
>+	u64 attr;
>+
>+	attr = efi_mem_attribute(phys_addr, size);
>+
> 	/*
>-	 * MMIO regions are often missing from the EFI memory map.
>-	 * We must allow mmap of them for programs like X, so we
>-	 * currently can't do any useful validation.
>+	 * /dev/mem mmap uses normal user pages, so we don't need the entire
>+	 * granule, but the entire region we're mapping must support the same
>+	 * attribute.
> 	 */
>+	if (attr & EFI_MEMORY_WB || attr & EFI_MEMORY_UC)
>+		return 1;
>+
>+	/*
>+	 * Intel firmware doesn't tell us about all the MMIO regions, so
>+	 * in general we have to allow mmap requests.  But if EFI *does*
>+	 * tell us about anything inside this region, we should deny it.
>+	 * The user can always map a smaller region to avoid the overlap.
>+	 */
>+	if (efi_memmap_intersects(phys_addr, size))
>+		return 0;
>+
> 	return 1;
> }
>

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Attachments on bug 234069: 151665 | 151666 | 151667 | 151668 | 151669