[PATCH v4 1/3] kexec: Move vmcoreinfo out of the kernel's .bss section
Xunlei Pang
xpang at redhat.com
Wed Apr 26 03:18:45 PDT 2017
On 04/26/2017 at 05:51 PM, Xunlei Pang wrote:
> On 04/26/2017 at 03:19 PM, Dave Young wrote:
>> Add ia64i list, and s390 list although Michael has tested it
>>
>> On 04/20/17 at 07:39pm, Xunlei Pang wrote:
>>> As Eric said,
>>> "what we need to do is move the variable vmcoreinfo_note out
>>> of the kernel's .bss section. And modify the code to regenerate
>>> and keep this information in something like the control page.
>>>
>>> Definitely something like this needs a page all to itself, and ideally
>>> far away from any other kernel data structures. I clearly was not
>>> watching closely the data someone decided to keep this silly thing
>>> in the kernel's .bss section."
>>>
>>> This patch allocates extra pages for these vmcoreinfo_XXX variables,
>>> one advantage is that it enhances some safety of vmcoreinfo, because
>>> vmcoreinfo now is kept far away from other kernel data structures.
>>>
>>> Suggested-by: Eric Biederman <ebiederm at xmission.com>
>>> Cc: Michael Holzheu <holzheu at linux.vnet.ibm.com>
>>> Cc: Juergen Gross <jgross at suse.com>
>>> Signed-off-by: Xunlei Pang <xlpang at redhat.com>
>>> ---
>>> v3->v4:
>>> -Rebased on the latest linux-next
>>> -Handle S390 vmcoreinfo_note properly
>>> -Handle the newly-added xen/mmu_pv.c
>>>
>>> arch/ia64/kernel/machine_kexec.c | 5 -----
>>> arch/s390/kernel/machine_kexec.c | 1 +
>>> arch/s390/kernel/setup.c | 6 ------
>>> arch/x86/kernel/crash.c | 2 +-
>>> arch/x86/xen/mmu_pv.c | 4 ++--
>>> include/linux/crash_core.h | 2 +-
>>> kernel/crash_core.c | 27 +++++++++++++++++++++++----
>>> kernel/ksysfs.c | 2 +-
>>> 8 files changed, 29 insertions(+), 20 deletions(-)
>>>
>>> diff --git a/arch/ia64/kernel/machine_kexec.c b/arch/ia64/kernel/machine_kexec.c
>>> index 599507b..c14815d 100644
>>> --- a/arch/ia64/kernel/machine_kexec.c
>>> +++ b/arch/ia64/kernel/machine_kexec.c
>>> @@ -163,8 +163,3 @@ void arch_crash_save_vmcoreinfo(void)
>>> #endif
>>> }
>>>
>>> -phys_addr_t paddr_vmcoreinfo_note(void)
>>> -{
>>> - return ia64_tpa((unsigned long)(char *)&vmcoreinfo_note);
>>> -}
>>> -
>>> diff --git a/arch/s390/kernel/machine_kexec.c b/arch/s390/kernel/machine_kexec.c
>>> index 49a6bd4..3d0b14a 100644
>>> --- a/arch/s390/kernel/machine_kexec.c
>>> +++ b/arch/s390/kernel/machine_kexec.c
>>> @@ -246,6 +246,7 @@ void arch_crash_save_vmcoreinfo(void)
>>> VMCOREINFO_SYMBOL(lowcore_ptr);
>>> VMCOREINFO_SYMBOL(high_memory);
>>> VMCOREINFO_LENGTH(lowcore_ptr, NR_CPUS);
>>> + mem_assign_absolute(S390_lowcore.vmcore_info, paddr_vmcoreinfo_note());
>>> }
>>>
>>> void machine_shutdown(void)
>>> diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c
>>> index 3ae756c..3d1d808 100644
>>> --- a/arch/s390/kernel/setup.c
>>> +++ b/arch/s390/kernel/setup.c
>>> @@ -496,11 +496,6 @@ static void __init setup_memory_end(void)
>>> pr_notice("The maximum memory size is %luMB\n", memory_end >> 20);
>>> }
>>>
>>> -static void __init setup_vmcoreinfo(void)
>>> -{
>>> - mem_assign_absolute(S390_lowcore.vmcore_info, paddr_vmcoreinfo_note());
>>> -}
>>> -
>>> #ifdef CONFIG_CRASH_DUMP
>>>
>>> /*
>>> @@ -939,7 +934,6 @@ void __init setup_arch(char **cmdline_p)
>>> #endif
>>>
>>> setup_resources();
>>> - setup_vmcoreinfo();
>>> setup_lowcore();
>>> smp_fill_possible_mask();
>>> cpu_detect_mhz_feature();
>>> diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
>>> index 22217ec..44404e2 100644
>>> --- a/arch/x86/kernel/crash.c
>>> +++ b/arch/x86/kernel/crash.c
>>> @@ -457,7 +457,7 @@ static int prepare_elf64_headers(struct crash_elf_data *ced,
>>> bufp += sizeof(Elf64_Phdr);
>>> phdr->p_type = PT_NOTE;
>>> phdr->p_offset = phdr->p_paddr = paddr_vmcoreinfo_note();
>>> - phdr->p_filesz = phdr->p_memsz = sizeof(vmcoreinfo_note);
>>> + phdr->p_filesz = phdr->p_memsz = VMCOREINFO_NOTE_SIZE;
>>> (ehdr->e_phnum)++;
>>>
>>> #ifdef CONFIG_X86_64
>>> diff --git a/arch/x86/xen/mmu_pv.c b/arch/x86/xen/mmu_pv.c
>>> index 9d9ae66..35543fa 100644
>>> --- a/arch/x86/xen/mmu_pv.c
>>> +++ b/arch/x86/xen/mmu_pv.c
>>> @@ -2723,8 +2723,8 @@ void xen_destroy_contiguous_region(phys_addr_t pstart, unsigned int order)
>>> phys_addr_t paddr_vmcoreinfo_note(void)
>>> {
>>> if (xen_pv_domain())
>>> - return virt_to_machine(&vmcoreinfo_note).maddr;
>>> + return virt_to_machine(vmcoreinfo_note).maddr;
>>> else
>>> - return __pa_symbol(&vmcoreinfo_note);
>>> + return __pa(vmcoreinfo_note);
>>> }
>>> #endif /* CONFIG_KEXEC_CORE */
>>> diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h
>>> index eb71a70..ba283a2 100644
>>> --- a/include/linux/crash_core.h
>>> +++ b/include/linux/crash_core.h
>>> @@ -53,7 +53,7 @@
>>> #define VMCOREINFO_PHYS_BASE(value) \
>>> vmcoreinfo_append_str("PHYS_BASE=%lx\n", (unsigned long)value)
>>>
>>> -extern u32 vmcoreinfo_note[VMCOREINFO_NOTE_SIZE/4];
>>> +extern u32 *vmcoreinfo_note;
>>> extern size_t vmcoreinfo_size;
>>> extern size_t vmcoreinfo_max_size;
>>>
>>> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
>>> index fcbd568..0321f04 100644
>>> --- a/kernel/crash_core.c
>>> +++ b/kernel/crash_core.c
>>> @@ -14,10 +14,10 @@
>>> #include <asm/sections.h>
>>>
>>> /* vmcoreinfo stuff */
>>> -static unsigned char vmcoreinfo_data[VMCOREINFO_BYTES];
>>> -u32 vmcoreinfo_note[VMCOREINFO_NOTE_SIZE/4];
>>> +static unsigned char *vmcoreinfo_data;
>>> size_t vmcoreinfo_size;
>>> -size_t vmcoreinfo_max_size = sizeof(vmcoreinfo_data);
>>> +size_t vmcoreinfo_max_size = VMCOREINFO_BYTES;
>>> +u32 *vmcoreinfo_note;
>>>
>>> /*
>>> * parsing the "crashkernel" commandline
>>> @@ -326,6 +326,9 @@ static void update_vmcoreinfo_note(void)
>>>
>>> void crash_save_vmcoreinfo(void)
>>> {
>>> + if (!vmcoreinfo_note)
>>> + return;
>>> +
>>> vmcoreinfo_append_str("CRASHTIME=%ld\n", get_seconds());
>>> update_vmcoreinfo_note();
>>> }
>>> @@ -356,11 +359,27 @@ void __weak arch_crash_save_vmcoreinfo(void)
>>>
>>> phys_addr_t __weak paddr_vmcoreinfo_note(void)
>>> {
>>> - return __pa_symbol((unsigned long)(char *)&vmcoreinfo_note);
>>> + return __pa(vmcoreinfo_note);
>>> }
>>>
>>> static int __init crash_save_vmcoreinfo_init(void)
>>> {
>>> + /* One page should be enough for VMCOREINFO_BYTES under all archs */
>> Can we add a comment in the VMCOREINFO_BYTES header file about the one
>> page assumption?
>>
>> Or just define the VMCOREINFO_BYTES as PAGE_SIZE instead of 4096
> Yes, I considered this before, but VMCOREINFO_BYTES is also used by VMCOREINFO_NOTE_SIZE
> definition which is exported to sysfs, also some platform has larger page size(64KB), so
> I didn't touch this 4096 value.
>
> I think I should use kmalloc() to allocate both of them, then move this comment to Patch3
> kimage_crash_copy_vmcoreinfo().
But on the other hand, using a separate page for them seems safer compared with
using frequently-used slab, what's your opinion?
Regards,
Xunlei
>
> Regards,
> Xunlei
>
>>
>>> + vmcoreinfo_data = (unsigned char *)get_zeroed_page(GFP_KERNEL);
>>> + if (!vmcoreinfo_data) {
>>> + pr_warn("Memory allocation for vmcoreinfo_data failed\n");
>>> + return -ENOMEM;
>>> + }
>>> +
>>> + vmcoreinfo_note = alloc_pages_exact(VMCOREINFO_NOTE_SIZE,
>>> + GFP_KERNEL | __GFP_ZERO);
>>> + if (!vmcoreinfo_note) {
>>> + free_page((unsigned long)vmcoreinfo_data);
>>> + vmcoreinfo_data = NULL;
>>> + pr_warn("Memory allocation for vmcoreinfo_note failed\n");
>>> + return -ENOMEM;
>>> + }
>>> +
>>> VMCOREINFO_OSRELEASE(init_uts_ns.name.release);
>>> VMCOREINFO_PAGESIZE(PAGE_SIZE);
>>>
>>> diff --git a/kernel/ksysfs.c b/kernel/ksysfs.c
>>> index 23cd706..c40a4e5 100644
>>> --- a/kernel/ksysfs.c
>>> +++ b/kernel/ksysfs.c
>>> @@ -134,7 +134,7 @@ static ssize_t vmcoreinfo_show(struct kobject *kobj,
>>> {
>>> phys_addr_t vmcore_base = paddr_vmcoreinfo_note();
>>> return sprintf(buf, "%pa %x\n", &vmcore_base,
>>> - (unsigned int)sizeof(vmcoreinfo_note));
>>> + (unsigned int)VMCOREINFO_NOTE_SIZE);
>>> }
>>> KERNEL_ATTR_RO(vmcoreinfo);
>>>
>>> --
>>> 1.8.3.1
>>>
>>>
>>> _______________________________________________
>>> kexec mailing list
>>> kexec at lists.infradead.org
>>> http://lists.infradead.org/mailman/listinfo/kexec
>> Thanks
>> Dave
>>
>> _______________________________________________
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