Messages in this thread Patch in this message | | | From | Baoquan He <> | Subject | [PATCH v3 2/3] KASLR: Handle memory limit specified by memmap and mem option | Date | Wed, 26 Apr 2017 18:16:11 +0800 |
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Option mem= will limit the max address a system can use and any memory region above the limit will be removed.
Furthermore, memmap=nn[KMG] which has no offset specified has the same behaviour as mem=.
KASLR needs to consider this when choosing the random position for decompressing the kernel.
This patch implements that.
Signed-off-by: Baoquan He <bhe@redhat.com> Acked-by: Kees Cook <keescook@chromium.org> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: x86@kernel.org Cc: Kees Cook <keescook@chromium.org> Cc: Yinghai Lu <yinghai@kernel.org> Cc: Borislav Petkov <bp@suse.de> --- arch/x86/boot/compressed/kaslr.c | 60 ++++++++++++++++++++++++++++++++-------- 1 file changed, 48 insertions(+), 12 deletions(-)
diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c index 53a06ec..e5eb0c3 100644 --- a/arch/x86/boot/compressed/kaslr.c +++ b/arch/x86/boot/compressed/kaslr.c @@ -78,6 +78,10 @@ static bool memmap_too_large; extern unsigned long get_cmd_line_ptr(void); +/* Store memory limit specified by "mem=nn[KMG]" or "memmap=nn[KMG]" */ +unsigned long long mem_limit = ULLONG_MAX; + + enum mem_avoid_index { MEM_AVOID_ZO_RANGE = 0, MEM_AVOID_INITRD, @@ -128,16 +132,22 @@ parse_memmap(char *p, unsigned long long *start, unsigned long long *size) return -EINVAL; switch (*p) { - case '@': - /* Skip this region, usable */ - *start = 0; - *size = 0; - return 0; case '#': case '$': case '!': *start = memparse(p + 1, &p); return 0; + case '@': + /* memmap=nn@ss specifies usable region, should be skipped */ + *size = 0; + default: + /* + * If w/o offset, only size specified, memmap=nn[KMG] has the + * same behaviour as mem=nn[KMG]. It limits the max address + * system can use. Region above the limit should be avoided. + */ + *start = 0; + return 0; } return -EINVAL; @@ -163,9 +173,14 @@ static void mem_avoid_memmap(char *str) if (rc < 0) break; str = k; - /* A usable region that should not be skipped */ - if (size == 0) + + if (start == 0) { + /* Store the specified memory limit if size > 0 */ + if (size > 0) + mem_limit = size; + continue; + } mem_avoid[MEM_AVOID_MEMMAP_BEGIN + i].start = start; mem_avoid[MEM_AVOID_MEMMAP_BEGIN + i].size = size; @@ -189,6 +204,7 @@ static int handle_mem_memmap(void) size_t len = strlen((char *)args); char *tmp_cmdline; char *param, *val; + u64 mem_size; tmp_cmdline = malloc(COMMAND_LINE_SIZE); if (!tmp_cmdline ) @@ -211,8 +227,20 @@ static int handle_mem_memmap(void) return -1; } - if (!strcmp(param, "memmap")) + if (!strcmp(param, "memmap")) { mem_avoid_memmap(val); + } else if (!strcmp(param, "mem")) { + char *p = val; + + if (!strcmp(p, "nopentium")) + continue; + mem_size = memparse(p, &p); + if (mem_size == 0) { + free(tmp_cmdline); + return -EINVAL; + } + mem_limit = mem_size; + } } free(tmp_cmdline); @@ -449,7 +477,8 @@ static void process_e820_entry(struct boot_e820_entry *entry, { struct mem_vector region, overlap; struct slot_area slot_area; - unsigned long start_orig; + unsigned long start_orig, end; + struct boot_e820_entry cur_entry; /* Skip non-RAM entries. */ if (entry->type != E820_TYPE_RAM) @@ -463,8 +492,15 @@ static void process_e820_entry(struct boot_e820_entry *entry, if (entry->addr + entry->size < minimum) return; - region.start = entry->addr; - region.size = entry->size; + /* Ignore entries above memory limit */ + end = min(entry->size + entry->addr, mem_limit); + if (entry->addr >= end) + return; + cur_entry.addr = entry->addr; + cur_entry.size = end - entry->addr; + + region.start = cur_entry.addr; + region.size = cur_entry.size; /* Give up if slot area array is full. */ while (slot_area_index < MAX_SLOT_AREA) { @@ -478,7 +514,7 @@ static void process_e820_entry(struct boot_e820_entry *entry, region.start = ALIGN(region.start, CONFIG_PHYSICAL_ALIGN); /* Did we raise the address above this e820 region? */ - if (region.start > entry->addr + entry->size) + if (region.start > cur_entry.addr + cur_entry.size) return; /* Reduce size by any delta from the original address. */ -- 2.5.5
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