diff options
| -rw-r--r-- | arch/x86/mm/init.c | 41 | ||||
| -rw-r--r-- | drivers/char/mem.c | 82 |
2 files changed, 82 insertions, 41 deletions
diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c index 222f5b756137..dba71b25a546 100644 --- a/arch/x86/mm/init.c +++ b/arch/x86/mm/init.c @@ -318,21 +318,40 @@ unsigned long __init_refok init_memory_mapping(unsigned long start, * 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) diff --git a/drivers/char/mem.c b/drivers/char/mem.c index 145179033716..b1ac8d419a73 100644 --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -58,6 +58,10 @@ static inline int valid_mmap_phys_addr_range(unsigned long pfn, size_t size) #endif #ifdef CONFIG_STRICT_DEVMEM +static inline int page_is_allowed(unsigned long pfn) +{ + return devmem_is_allowed(pfn); +} static inline int range_is_allowed(unsigned long pfn, unsigned long size) { u64 from = ((u64)pfn) << PAGE_SHIFT; @@ -77,6 +81,10 @@ static inline int range_is_allowed(unsigned long pfn, unsigned long size) return 1; } #else +static inline int page_is_allowed(unsigned long pfn) +{ + return 1; +} static inline int range_is_allowed(unsigned long pfn, unsigned long size) { return 1; @@ -118,23 +126,31 @@ static ssize_t read_mem(struct file *file, char __user *buf, while (count > 0) { unsigned long remaining; + int allowed; sz = size_inside_page(p, count); - if (!range_is_allowed(p >> PAGE_SHIFT, count)) + allowed = page_is_allowed(p >> PAGE_SHIFT); + if (!allowed) return -EPERM; + if (allowed == 2) { + /* Show zeros for restricted memory. */ + remaining = clear_user(buf, sz); + } else { + /* + * On ia64 if a page has been mapped somewhere as + * uncached, then it must also be accessed uncached + * by the kernel or data corruption may occur. + */ + ptr = xlate_dev_mem_ptr(p); + if (!ptr) + return -EFAULT; - /* - * On ia64 if a page has been mapped somewhere as uncached, then - * it must also be accessed uncached by the kernel or data - * corruption may occur. - */ - ptr = xlate_dev_mem_ptr(p); - if (!ptr) - return -EFAULT; + remaining = copy_to_user(buf, ptr, sz); + + unxlate_dev_mem_ptr(p, ptr); + } - remaining = copy_to_user(buf, ptr, sz); - unxlate_dev_mem_ptr(p, ptr); if (remaining) return -EFAULT; @@ -174,30 +190,36 @@ static ssize_t write_mem(struct file *file, const char __user *buf, #endif while (count > 0) { + int allowed; + sz = size_inside_page(p, count); - if (!range_is_allowed(p >> PAGE_SHIFT, sz)) + allowed = page_is_allowed(p >> PAGE_SHIFT); + if (!allowed) return -EPERM; - /* - * On ia64 if a page has been mapped somewhere as uncached, then - * it must also be accessed uncached by the kernel or data - * corruption may occur. - */ - ptr = xlate_dev_mem_ptr(p); - if (!ptr) { - if (written) - break; - return -EFAULT; - } + /* Skip actual writing when a page is marked as restricted. */ + if (allowed == 1) { + /* + * On ia64 if a page has been mapped somewhere as + * uncached, then it must also be accessed uncached + * by the kernel or data corruption may occur. + */ + ptr = xlate_dev_mem_ptr(p); + if (!ptr) { + if (written) + break; + return -EFAULT; + } - copied = copy_from_user(ptr, buf, sz); - unxlate_dev_mem_ptr(p, ptr); - if (copied) { - written += sz - copied; - if (written) - break; - return -EFAULT; + copied = copy_from_user(ptr, buf, sz); + unxlate_dev_mem_ptr(p, ptr); + if (copied) { + written += sz - copied; + if (written) + break; + return -EFAULT; + } } buf += sz; |