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author | Stefan Agner <stefan.agner@toradex.com> | 2017-12-13 21:31:49 +0100 |
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committer | Marcel Ziswiler <marcel.ziswiler@toradex.com> | 2017-12-21 15:14:59 +0100 |
commit | 688f897ddd96968cf59a2d67afe2a394a0bf8ab3 (patch) | |
tree | e303dd2f94a5c670a318008c891674e116558e6b /arch/x86/mm/init.c | |
parent | a898b45a9c18bd9d723f82576a5b32a102808a09 (diff) | |
parent | fb2d2dee504a963efdcb76517b5cdf25444cf535 (diff) |
Merge remote-tracking branch 'linux-fslc/4.9-1.0.x-imx' into toradex_4.9-1.0.x-imx-next
Diffstat (limited to 'arch/x86/mm/init.c')
-rw-r--r-- | arch/x86/mm/init.c | 41 |
1 files changed, 30 insertions, 11 deletions
diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c index 22af912d66d2..889e7619a091 100644 --- a/arch/x86/mm/init.c +++ b/arch/x86/mm/init.c @@ -643,21 +643,40 @@ void __init init_mem_mapping(void) * devmem_is_allowed() checks to see if /dev/mem access to a certain address * is valid. The argument is a physical page number. * - * - * On x86, access has to be given to the first megabyte of ram because that area - * contains BIOS code and data regions used by X and dosemu and similar apps. - * Access has to be given to non-kernel-ram areas as well, these contain the PCI - * mmio resources as well as potential bios/acpi data regions. + * On x86, access has to be given to the first megabyte of RAM because that + * area traditionally contains BIOS code and data regions used by X, dosemu, + * and similar apps. Since they map the entire memory range, the whole range + * must be allowed (for mapping), but any areas that would otherwise be + * disallowed are flagged as being "zero filled" instead of rejected. + * Access has to be given to non-kernel-ram areas as well, these contain the + * PCI mmio resources as well as potential bios/acpi data regions. */ int devmem_is_allowed(unsigned long pagenr) { - if (pagenr < 256) - return 1; - if (iomem_is_exclusive(pagenr << PAGE_SHIFT)) + if (page_is_ram(pagenr)) { + /* + * For disallowed memory regions in the low 1MB range, + * request that the page be shown as all zeros. + */ + if (pagenr < 256) + return 2; + + return 0; + } + + /* + * This must follow RAM test, since System RAM is considered a + * restricted resource under CONFIG_STRICT_IOMEM. + */ + if (iomem_is_exclusive(pagenr << PAGE_SHIFT)) { + /* Low 1MB bypasses iomem restrictions. */ + if (pagenr < 256) + return 1; + return 0; - if (!page_is_ram(pagenr)) - return 1; - return 0; + } + + return 1; } void free_init_pages(char *what, unsigned long begin, unsigned long end) |