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Date: Wed, 6 Dec 2017 09:13:38 +0800
From: Chao Fan <fanc.fnst@...fujitsu.com>
To: Kees Cook <keescook@...omium.org>
CC: LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
"H. Peter Anvin" <hpa@...or.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Baoquan He <bhe@...hat.com>,
<yasu.isimatu@...il.com>, <indou.takao@...fujitsu.com>,
<caoj.fnst@...fujitsu.com>, Dou Liyang <douly.fnst@...fujitsu.com>
Subject: Re: [PATCH v3 1/4] kaslr: add immovable_mem=nn[KMG]@ss[KMG] to
specify extracting memory
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@...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@...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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