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SubjectRe: [PATCH v4 1/3] kexec: Move vmcoreinfo out of the kernel's .bss section
Am Thu, 20 Apr 2017 19:39:32 +0800
schrieb Xunlei Pang <xlpang@redhat.com>:

> 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@xmission.com>
> Cc: Michael Holzheu <holzheu@linux.vnet.ibm.com>
> Cc: Juergen Gross <jgross@suse.com>
> Signed-off-by: Xunlei Pang <xlpang@redhat.com>

Now s390 seems to work with the patches. I tested kdump and
zfcpdump.

Tested-by: Michael Holzheu <holzheu@linux.vnet.ibm.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 */
> + 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);
>

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