Messages in this thread | | | Date | Wed, 6 Dec 2017 09:13:38 +0800 | From | Chao Fan <> | Subject | Re: [PATCH v3 1/4] kaslr: add immovable_mem=nn[KMG]@ss[KMG] to specify extracting memory |
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On Tue, Dec 05, 2017 at 11:42:42AM -0800, Kees Cook wrote: >On Tue, Dec 5, 2017 at 12:51 AM, Chao Fan <fanc.fnst@cn.fujitsu.com> wrote: >> In current code, kaslr may choose the memory region in movable >> nodes to extract kernel, which will make the nodes can't be hot-removed. >> To solve it, we can specify the memory region in immovable node. >> Create immovable_mem to store the regions in immovable_mem, where should >> be chosen by kaslr. >> >> Multiple regions can be specified, comma delimited. >> Considering the usage of memory, only support for 4 regions. >> 4 regions contains 2 nodes at least, enough for kernel to extract. >> >> Also change the "handle_mem_memmap" to "handle_mem_filter", since >> it will not only handle memmap parameter now. >
Hi Kees,
Thanks for your reply.
>I would put all immovable region functions and variables behind >#ifdefs. e.g. parse_immovable_mem() is unused without
Yes, you are right.
>CONFIG_MEMORY_HOTPLUG. I also wonder if it might be possible to reuse >some of the parsing code and just pass in which array you're updating
I will try to change it in the next version.
Thanks, Chao Fan
>(i.e. memmap array vs immovable array). >
>-Kees > >> >> Signed-off-by: Chao Fan <fanc.fnst@cn.fujitsu.com> >> --- >> arch/x86/boot/compressed/kaslr.c | 80 ++++++++++++++++++++++++++++++++++++++-- >> 1 file changed, 77 insertions(+), 3 deletions(-) >> >> diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c >> index a63fbc25ce84..0bbbaf5f6370 100644 >> --- a/arch/x86/boot/compressed/kaslr.c >> +++ b/arch/x86/boot/compressed/kaslr.c >> @@ -108,6 +108,15 @@ enum mem_avoid_index { >> >> static struct mem_vector mem_avoid[MEM_AVOID_MAX]; >> >> +/* Only supporting at most 4 immovable memory regions with kaslr */ >> +#define MAX_IMMOVABLE_MEM 4 >> + >> +/* Store the memory regions in immovable node */ >> +static struct mem_vector immovable_mem[MAX_IMMOVABLE_MEM]; >> + >> +/* The immovable regions user specify, not more than 4 */ >> +static int num_immovable_region; >> + >> static bool mem_overlaps(struct mem_vector *one, struct mem_vector *two) >> { >> /* Item one is entirely before item two. */ >> @@ -168,6 +177,38 @@ parse_memmap(char *p, unsigned long long *start, unsigned long long *size) >> return -EINVAL; >> } >> >> +static int parse_immovable_mem(char *p, >> + unsigned long long *start, >> + unsigned long long *size) >> +{ >> + char *oldp; >> + >> + if (!p) >> + return -EINVAL; >> + >> + oldp = p; >> + *size = memparse(p, &p); >> + if (p == oldp) >> + return -EINVAL; >> + >> + /* We support nn[KMG]@ss[KMG] and nn[KMG]. */ >> + switch (*p) { >> + case '@': >> + *start = memparse(p + 1, &p); >> + return 0; >> + default: >> + /* >> + * If w/o offset, only size specified, immovable_mem=nn[KMG] >> + * has the same behaviour as immovable_mem=nn[KMG]@0. It means >> + * the region starts from 0. >> + */ >> + *start = 0; >> + return 0; >> + } >> + >> + return -EINVAL; >> +} >> + >> static void mem_avoid_memmap(char *str) >> { >> static int i; >> @@ -207,7 +248,37 @@ static void mem_avoid_memmap(char *str) >> memmap_too_large = true; >> } >> >> -static int handle_mem_memmap(void) >> +#ifdef CONFIG_MEMORY_HOTPLUG >> +static void parse_immovable_mem_regions(char *str) >> +{ >> + static int i; >> + >> + while (str && (i < MAX_IMMOVABLE_MEM)) { >> + int rc; >> + unsigned long long start, size; >> + char *k = strchr(str, ','); >> + >> + if (k) >> + *k++ = 0; >> + >> + rc = parse_immovable_mem(str, &start, &size); >> + if (rc < 0) >> + break; >> + str = k; >> + >> + immovable_mem[i].start = start; >> + immovable_mem[i].size = size; >> + i++; >> + } >> + num_immovable_region = i; >> +} >> +#else >> +static inline void parse_immovable_mem_regions(char *str) >> +{ >> +} >> +#endif >> + >> +static int handle_mem_filter(void) >> { >> char *args = (char *)get_cmd_line_ptr(); >> size_t len = strlen((char *)args); >> @@ -215,7 +286,8 @@ static int handle_mem_memmap(void) >> char *param, *val; >> u64 mem_size; >> >> - if (!strstr(args, "memmap=") && !strstr(args, "mem=")) >> + if (!strstr(args, "memmap=") && !strstr(args, "mem=") && >> + !strstr(args, "immovable_mem=")) >> return 0; >> >> tmp_cmdline = malloc(len + 1); >> @@ -240,6 +312,8 @@ static int handle_mem_memmap(void) >> >> if (!strcmp(param, "memmap")) { >> mem_avoid_memmap(val); >> + } else if (!strcmp(param, "immovable_mem")) { >> + parse_immovable_mem_regions(val); >> } else if (!strcmp(param, "mem")) { >> char *p = val; >> >> @@ -379,7 +453,7 @@ static void mem_avoid_init(unsigned long input, unsigned long input_size, >> /* We don't need to set a mapping for setup_data. */ >> >> /* Mark the memmap regions we need to avoid */ >> - handle_mem_memmap(); >> + handle_mem_filter(); >> >> #ifdef CONFIG_X86_VERBOSE_BOOTUP >> /* Make sure video RAM can be used. */ >> -- >> 2.14.3 >> >> >> > > > >-- >Kees Cook >Pixel Security > >
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