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Message-ID: <20190402075939.GA6560@localhost.localdomain>
Date: Tue, 2 Apr 2019 15:59:39 +0800
From: Chao Fan <fanc.fnst@...fujitsu.com>
To: Pingfan Liu <kernelfans@...il.com>
CC: <x86@...nel.org>, Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
"H. Peter Anvin" <hpa@...or.com>, Baoquan He <bhe@...hat.com>,
Will Deacon <will.deacon@....com>,
Nicolas Pitre <nico@...aro.org>,
"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
Ard Biesheuvel <ard.biesheuvel@...aro.org>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCHv3] x86/boot/KASLR: skip the specified crashkernel region
On Tue, Apr 02, 2019 at 02:58:53PM +0800, Pingfan Liu wrote:
>On Tue, Apr 2, 2019 at 1:20 PM Chao Fan <fanc.fnst@...fujitsu.com> wrote:
>>
>> On Tue, Apr 02, 2019 at 12:10:46PM +0800, Pingfan Liu wrote:
>> >crashkernel=x@y or or =range1:size1[,range2:size2,...]@offset option may
>> or or?
>> >fail to reserve the required memory region if KASLR puts kernel into the
>> >region. To avoid this uncertainty, asking KASLR to skip the required
>> >region.
>> >
>> >Signed-off-by: Pingfan Liu <kernelfans@...il.com>
>> >Cc: Thomas Gleixner <tglx@...utronix.de>
>> >Cc: Ingo Molnar <mingo@...hat.com>
>> >Cc: Borislav Petkov <bp@...en8.de>
>> >Cc: "H. Peter Anvin" <hpa@...or.com>
>> >Cc: Baoquan He <bhe@...hat.com>
>> >Cc: Will Deacon <will.deacon@....com>
>> >Cc: Nicolas Pitre <nico@...aro.org>
>> >Cc: Pingfan Liu <kernelfans@...il.com>
>> >Cc: Chao Fan <fanc.fnst@...fujitsu.com>
>> >Cc: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
>> >Cc: Ard Biesheuvel <ard.biesheuvel@...aro.org>
>> >Cc: linux-kernel@...r.kernel.org
>> >---
>> [...]
>> >+
>> >+/* handle crashkernel=x@y or =range1:size1[,range2:size2,...]@offset options */
>>
>> Before review, I want to say more about the background.
>> It's very hard to review the code for someone who is not so familiar
>> with kdump, so could you please explain more ahout
>> the uasge of crashkernel=range1:size1[,range2:size2,...]@offset.
>> And also there are so many jobs who are parsing string. So I really
>> need your help to understand the PATCH.
>>
>> >+static void mem_avoid_specified_crashkernel_region(char *option)
>> >+{
>> >+ unsigned long long crash_size, crash_base = 0;
>> >+ char *first_colon, *first_space, *cur = option;
>> Is there a tab after char?
>> >+
>> >+ first_colon = strchr(option, ':');
>> >+ first_space = strchr(option, ' ');
>> >+ /* if contain ":" */
>> >+ if (first_colon && (!first_space || first_colon < first_space)) {
>> >+ int i;
>> >+ u64 total_sz = 0;
>> >+ struct boot_e820_entry *entry;
>> >+
>> >+ for (i = 0; i < boot_params->e820_entries; i++) {
>> >+ entry = &boot_params->e820_table[i];
>> >+ /* Skip non-RAM entries. */
>> >+ if (entry->type != E820_TYPE_RAM)
>> >+ continue;
>> >+ total_sz += entry->size;
>> I wonder whether it's needed to consider the memory ranges here.
>> I think it's OK to only record the regions should to be avoid.
>Maybe not catch you exactly. In the case of
>crashkernel=range1:size1[,range2:size2,...]@offset, the size of avoid
>region depends on the size of total system ram.
Got it, I midunderstand it.
Thanks,
Chao Fan
>> I remeber I ever talked with Baoquan about the similiar problems.
>> @Baoquan, I am not sure if I misunderstand something.
>>
>> Thanks,
>> Chao Fan
>> >+ }
>> >+ handle_crashkernel_mem(option, total_sz, &crash_size,
>> >+ &crash_base);
>> >+ } else {
>> >+ crash_size = memparse(option, &cur);
>> >+ if (option == cur)
>> >+ return;
>> >+ while (*cur && *cur != ' ' && *cur != '@')
>> >+ cur++;
>> >+ if (*cur == '@') {
>> >+ option = cur + 1;
>> >+ crash_base = memparse(option, &cur);
>> >+ }
>> >+ }
>> >+ if (crash_base) {
>> >+ mem_avoid[MEM_AVOID_CRASHKERNEL].start = crash_base;
>> >+ mem_avoid[MEM_AVOID_CRASHKERNEL].size = crash_size;
>> >+ } else {
>> >+ /*
>> >+ * Clearing mem_avoid if no offset is given. This is consistent
>> >+ * with kernel, which uses the last crashkernel= option.
>> >+ */
>> >+ mem_avoid[MEM_AVOID_CRASHKERNEL].start = 0;
>> >+ mem_avoid[MEM_AVOID_CRASHKERNEL].size = 0;
>> >+ }
>> >+}
>> >
>> > static void handle_mem_options(void)
>> > {
>> >@@ -248,7 +358,7 @@ static void handle_mem_options(void)
>> > u64 mem_size;
>> >
>> > if (!strstr(args, "memmap=") && !strstr(args, "mem=") &&
>> >- !strstr(args, "hugepages"))
>> >+ !strstr(args, "hugepages") && !strstr(args, "crashkernel="))
>> > return;
>> >
>> > tmp_cmdline = malloc(len + 1);
>> >@@ -284,6 +394,8 @@ static void handle_mem_options(void)
>> > goto out;
>> >
>> > mem_limit = mem_size;
>> >+ } else if (strstr(param, "crashkernel")) {
>> >+ mem_avoid_specified_crashkernel_region(val);
>> > }
>> > }
>> >
>> >@@ -412,7 +524,7 @@ 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 */
>> >+ /* Mark the regions we need to avoid */
>> > handle_mem_options();
>> >
>> > /* Enumerate the immovable memory regions */
>> >--
>> >2.7.4
>> >
>> >
>> >
>>
>>
>
>
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