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Date: Tue, 16 May 2017 09:43:45 +0800
From: Dou Liyang <douly.fnst@...fujitsu.com>
To: Baoquan He <bhe@...hat.com>
CC: <tglx@...utronix.de>, <keescook@...omium.org>, <mingo@...nel.org>,
<m.mizuma@...fujitsu.com>, <linux-kernel@...r.kernel.org>,
<dyoung@...hat.com>, <dan.j.williams@...el.com>, <hpa@...or.com>,
<x86@...nel.org>
Subject: Re: [PATCH v5 2/3] KASLR: Handle memory limit specified by memmap and
mem option
At 05/16/2017 09:12 AM, Baoquan He wrote:
> On 05/16/17 at 08:56am, Dou Liyang wrote:
>> Hi Baoquan,
>>
>> At 05/13/2017 01:46 PM, Baoquan He wrote:
>>> 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. Do it now.
>>>
>>> Signed-off-by: Baoquan He <bhe@...hat.com>
>>> Tested-by: Masayoshi Mizuma <m.mizuma@...fujitsu.com>
>>> ---
>>> arch/x86/boot/compressed/kaslr.c | 68 +++++++++++++++++++++++++++++-----------
>>> 1 file changed, 50 insertions(+), 18 deletions(-)
>>>
>>> diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
>>> index 106e13b..e0eba12 100644
>>> --- a/arch/x86/boot/compressed/kaslr.c
>>> +++ b/arch/x86/boot/compressed/kaslr.c
>>> @@ -88,6 +88,10 @@ struct mem_vector {
>>> static bool memmap_too_large;
>>>
>>>
>>> +/* 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,
>>> @@ -138,16 +142,23 @@ 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;
>>> + /* Fall through */
>>> + 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;
>>> @@ -173,9 +184,14 @@ 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;
>>
>> Baoquan,
>>
>> I am not sure about setting the value of mem_limit to mem_size directly.
>>
>> If the command line has both the "memmap" and "mem", such as
>> ... mem=2G memmap=4G ...
>>
>> ...in that code, the mem_limit may be 4G not 2G.
>
> No, could you tell why you want to add both "memmap=nnKMG" and "mem=" at
> the same time? As you sid, what if I add "mem=4G mem=2G mem=1G"?
Just for testing :)
Ok, thanks, I see. We should be responsible for our command line. don't
need to consider with these situations in kernel.
Thanks,
Liyang.
>
>>
>> In my opinion, How about following:
>>
>> mem_limit = mem_limit > mem_size ? mem_size : mem_limit;
>>
>>> +
>>> continue;
>>> + }
>>>
>>> mem_avoid[MEM_AVOID_MEMMAP_BEGIN + i].start = start;
>>> mem_avoid[MEM_AVOID_MEMMAP_BEGIN + i].size = size;
>>> @@ -187,19 +203,15 @@ static void mem_avoid_memmap(char *str)
>>> memmap_too_large = true;
>>> }
>>>
>>> -
>>> -/*
>>> - * handle_mem_memmap will also cover 'mem=' issue in next patch. Will remove
>>> - * this note later.
>>> - */
>>> static int handle_mem_memmap(void)
>>> {
>>> char *args = (char *)get_cmd_line_ptr();
>>> size_t len = strlen((char *)args);
>>> char *tmp_cmdline;
>>> char *param, *val;
>>> + u64 mem_size;
>>>
>>> - if (!strstr(args, "memmap="))
>>> + if (!strstr(args, "memmap=") && !strstr(args, "mem="))
>>> return 0;
>>>
>>> tmp_cmdline = malloc(len + 1);
>>> @@ -222,8 +234,20 @@ 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;
>>
>> The same as above.
>>
>> Thanks,
>> Liyang.
>>
>>> + }
>>> }
>>>
>>> free(tmp_cmdline);
>>> @@ -460,7 +484,8 @@ 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)
>>> @@ -474,8 +499,15 @@ 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) {
>>> @@ -489,7 +521,7 @@ 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. */
>>>
>>
>>
>
>
>
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