From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2997907AbdDZKRy (ORCPT ); Wed, 26 Apr 2017 06:17:54 -0400 Received: from mx1.redhat.com ([209.132.183.28]:35534 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2997614AbdDZKRi (ORCPT ); Wed, 26 Apr 2017 06:17:38 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 5FA4DC0567A2 Authentication-Results: ext-mx08.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx08.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=xpang@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com 5FA4DC0567A2 Reply-To: xlpang@redhat.com Subject: Re: [PATCH v4 1/3] kexec: Move vmcoreinfo out of the kernel's .bss section References: <1492688374-27903-1-git-send-email-xlpang@redhat.com> <20170426071916.GD5381@dhcp-128-65.nay.redhat.com> <59006DAB.8030908@redhat.com> To: Dave Young , Xunlei Pang Cc: Juergen Gross , linux-s390@vger.kernel.org, linux-ia64@vger.kernel.org, Baoquan He , kexec@lists.infradead.org, Petr Tesarik , linux-kernel@vger.kernel.org, Eric Biederman , Hari Bathini , akpm@linux-foundation.org, Michael Holzheu From: Xunlei Pang Message-ID: <59007405.6070107@redhat.com> Date: Wed, 26 Apr 2017 18:18:45 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 MIME-Version: 1.0 In-Reply-To: <59006DAB.8030908@redhat.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Wed, 26 Apr 2017 10:17:38 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 >>> Cc: Michael Holzheu >>> Cc: Juergen Gross >>> Signed-off-by: Xunlei Pang >>> --- >>> 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 >>> >>> /* 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@lists.infradead.org >>> http://lists.infradead.org/mailman/listinfo/kexec >> Thanks >> Dave >> >> _______________________________________________ >> kexec mailing list >> kexec@lists.infradead.org >> http://lists.infradead.org/mailman/listinfo/kexec