在 2018年06月19日 22:46, lijiang 写道: > 在 2018年06月19日 11:16, Dave Young 写道: >> On 06/16/18 at 04:27pm, Lianbo Jiang wrote: >>> In kdump mode, we need to dump the old memory into vmcore file, >>> if SME is enabled in the first kernel, we must remap the old >>> memory in encrypted manner, which will be automatically decrypted >>> when we read from DRAM. It helps to parse the vmcore for some tools. >>> >>> Signed-off-by: Lianbo Jiang <liji...@redhat.com> >>> --- >>> Some changes: >>> 1. add a new file and modify Makefile. >>> 2. remove some code in sev_active(). >>> >>> arch/x86/kernel/Makefile | 1 + >>> arch/x86/kernel/crash_dump_encrypt.c | 53 >>> ++++++++++++++++++++++++++++++++++++ >>> fs/proc/vmcore.c | 20 ++++++++++---- >>> include/linux/crash_dump.h | 11 ++++++++ >>> 4 files changed, 79 insertions(+), 6 deletions(-) >>> create mode 100644 arch/x86/kernel/crash_dump_encrypt.c >>> >>> diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile >>> index 02d6f5c..afb5bad 100644 >>> --- a/arch/x86/kernel/Makefile >>> +++ b/arch/x86/kernel/Makefile >>> @@ -96,6 +96,7 @@ obj-$(CONFIG_KEXEC_CORE) += machine_kexec_$(BITS).o >>> obj-$(CONFIG_KEXEC_CORE) += relocate_kernel_$(BITS).o crash.o >>> obj-$(CONFIG_KEXEC_FILE) += kexec-bzimage64.o >>> obj-$(CONFIG_CRASH_DUMP) += crash_dump_$(BITS).o >>> +obj-$(CONFIG_AMD_MEM_ENCRYPT) += crash_dump_encrypt.o >>> obj-y += kprobes/ >>> obj-$(CONFIG_MODULES) += module.o >>> obj-$(CONFIG_DOUBLEFAULT) += doublefault.o >>> diff --git a/arch/x86/kernel/crash_dump_encrypt.c >>> b/arch/x86/kernel/crash_dump_encrypt.c >>> new file mode 100644 >>> index 0000000..e44ef33 >>> --- /dev/null >>> +++ b/arch/x86/kernel/crash_dump_encrypt.c >>> @@ -0,0 +1,53 @@ >>> +// SPDX-License-Identifier: GPL-2.0 >>> +/* >>> + * Memory preserving reboot related code. >>> + * >>> + * Created by: Lianbo Jiang (liji...@redhat.com) >>> + * Copyright (C) RedHat Corporation, 2018. All rights reserved >>> + */ >>> + >>> +#include <linux/errno.h> >>> +#include <linux/crash_dump.h> >>> +#include <linux/uaccess.h> >>> +#include <linux/io.h> >>> + >>> +/** >>> + * copy_oldmem_page_encrypted - copy one page from "oldmem encrypted" >>> + * @pfn: page frame number to be copied >>> + * @buf: target memory address for the copy; this can be in kernel address >>> + * space or user address space (see @userbuf) >>> + * @csize: number of bytes to copy >>> + * @offset: offset in bytes into the page (based on pfn) to begin the copy >>> + * @userbuf: if set, @buf is in user address space, use copy_to_user(), >>> + * otherwise @buf is in kernel address space, use memcpy(). >>> + * >>> + * Copy a page from "oldmem encrypted". For this page, there is no pte >>> + * mapped in the current kernel. We stitch up a pte, similar to >>> + * kmap_atomic. >>> + */ >>> + >>> +ssize_t copy_oldmem_page_encrypted(unsigned long pfn, char *buf, >>> + size_t csize, unsigned long offset, int userbuf) >>> +{ >>> + void *vaddr; >>> + >>> + if (!csize) >>> + return 0; >>> + >>> + vaddr = (__force void *)ioremap_encrypted(pfn << PAGE_SHIFT, >>> + PAGE_SIZE); >>> + if (!vaddr) >>> + return -ENOMEM; >>> + >>> + if (userbuf) { >>> + if (copy_to_user((void __user *)buf, vaddr + offset, csize)) { >>> + iounmap((void __iomem *)vaddr); >>> + return -EFAULT; >>> + } >>> + } else >>> + memcpy(buf, vaddr + offset, csize); >>> + >>> + set_iounmap_nonlazy(); >>> + iounmap((void __iomem *)vaddr); >>> + return csize; >>> +} >>> diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c >>> index a45f0af..5200266 100644 >>> --- a/fs/proc/vmcore.c >>> +++ b/fs/proc/vmcore.c >>> @@ -25,6 +25,8 @@ >>> #include <linux/uaccess.h> >>> #include <asm/io.h> >>> #include "internal.h" >>> +#include <linux/mem_encrypt.h> >>> +#include <asm/pgtable.h> >>> >>> /* List representing chunks of contiguous memory areas and their offsets in >>> * vmcore file. >>> @@ -86,7 +88,8 @@ static int pfn_is_ram(unsigned long pfn) >>> >>> /* Reads a page from the oldmem device from given offset. */ >>> static ssize_t read_from_oldmem(char *buf, size_t count, >>> - u64 *ppos, int userbuf) >>> + u64 *ppos, int userbuf, >>> + bool encrypted) >>> { >>> unsigned long pfn, offset; >>> size_t nr_bytes; >>> @@ -108,8 +111,11 @@ static ssize_t read_from_oldmem(char *buf, size_t >>> count, >>> if (pfn_is_ram(pfn) == 0) >>> memset(buf, 0, nr_bytes); >>> else { >>> - tmp = copy_oldmem_page(pfn, buf, nr_bytes, >>> - offset, userbuf); >>> + tmp = encrypted ? copy_oldmem_page_encrypted(pfn, >>> + buf, nr_bytes, offset, userbuf) >>> + : copy_oldmem_page(pfn, buf, nr_bytes, >>> + offset, userbuf); >>> + >>> if (tmp < 0) >>> return tmp; >>> } >>> @@ -143,7 +149,7 @@ void __weak elfcorehdr_free(unsigned long long addr) >>> */ >>> ssize_t __weak elfcorehdr_read(char *buf, size_t count, u64 *ppos) >>> { >>> - return read_from_oldmem(buf, count, ppos, 0); >>> + return read_from_oldmem(buf, count, ppos, 0, false); >> >> The elf header actually stays in kdump kernel reserved memory so it is >> not "oldmem", the original function is misleading and doing unnecessary >> things. But as for your patch maybe using it as is is good for the time >> being and add a code comment why the encrypted is "false". >> > Thank you, Dave. It is a good idea to add some comments for the code. > I rechecked the code, the elf header should be still the old memory in the > first kernel, > but why is the old memory unencrypted? Because it copies the elf header from > the memory > encrypted(user space) to the memory unencrypted(kernel space) when SME is > activated in the > first kernel, this operation just leads to decryption. > I just know your means, we allocated the memory unencrypted(kernel space) in reserved crash memory, from this point of view, it is not "oldmem". Thanks for your comments.
Thanks. Lianbo > Thanks. > Lianbo >> /* elfcorehdr stays in kdump kernel memory and it is not encrypted. */ >> return read_from_oldmem(buf, count, ppos, 0, false); >> >> >> I'm thinking to move the function to something like below, still not sure >> memremap works on every arches or not, still need more test >> >> diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c >> index cfb6674331fd..40c01cc42b38 100644 >> --- a/fs/proc/vmcore.c >> +++ b/fs/proc/vmcore.c >> @@ -136,6 +136,24 @@ static ssize_t read_from_oldmem(char *buf, size_t count, >> return read; >> } >> >> +static ssize_t read_from_mem(char *buf, size_t count, u64 *ppos) >> +{ >> + resource_size_t offset = (resource_size_t)*ppos; >> + char *kbuf; >> + >> + if (!count) >> + return 0; >> + >> + kbuf = memremap(offset, count, MEMREMAP_WB); >> + if (!kbuf) >> + return 0; >> + >> + memcpy(buf, kbuf, count); >> + memunmap(kbuf); >> + >> + return count; >> +} >> + >> /* >> * Architectures may override this function to allocate ELF header in 2nd >> kernel >> */ >> @@ -155,7 +173,7 @@ void __weak elfcorehdr_free(unsigned long long addr) >> */ >> ssize_t __weak elfcorehdr_read(char *buf, size_t count, u64 *ppos) >> { >> - return read_from_oldmem(buf, count, ppos, 0); >> + return read_from_mem(buf, count, ppos); >> } >> >> /* >> >> >>> } >>> >>> /* >>> @@ -151,7 +157,7 @@ ssize_t __weak elfcorehdr_read(char *buf, size_t count, >>> u64 *ppos) >>> */ >>> ssize_t __weak elfcorehdr_read_notes(char *buf, size_t count, u64 *ppos) >>> { >>> - return read_from_oldmem(buf, count, ppos, 0); >>> + return read_from_oldmem(buf, count, ppos, 0, sme_active()); >>> } >>> >>> /* >>> @@ -161,6 +167,7 @@ int __weak remap_oldmem_pfn_range(struct vm_area_struct >>> *vma, >>> unsigned long from, unsigned long pfn, >>> unsigned long size, pgprot_t prot) >>> { >>> + prot = pgprot_encrypted(prot); >>> return remap_pfn_range(vma, from, pfn, size, prot); >>> } >>> >>> @@ -235,7 +242,8 @@ static ssize_t __read_vmcore(char *buffer, size_t >>> buflen, loff_t *fpos, >>> m->offset + m->size - *fpos, >>> buflen); >>> start = m->paddr + *fpos - m->offset; >>> - tmp = read_from_oldmem(buffer, tsz, &start, userbuf); >>> + tmp = read_from_oldmem(buffer, tsz, &start, userbuf, >>> + sme_active()); >>> if (tmp < 0) >>> return tmp; >>> buflen -= tsz; >>> diff --git a/include/linux/crash_dump.h b/include/linux/crash_dump.h >>> index f7ac2aa..f3414ff 100644 >>> --- a/include/linux/crash_dump.h >>> +++ b/include/linux/crash_dump.h >>> @@ -25,6 +25,17 @@ extern int remap_oldmem_pfn_range(struct vm_area_struct >>> *vma, >>> >>> extern ssize_t copy_oldmem_page(unsigned long, char *, size_t, >>> unsigned long, int); >>> +#ifdef CONFIG_AMD_MEM_ENCRYPT >>> +extern ssize_t copy_oldmem_page_encrypted(unsigned long pfn, char *buf, >>> + size_t csize, unsigned long offset, >>> + int userbuf); >>> +#else >>> +static inline ssize_t copy_oldmem_page_encrypted(unsigned long pfn, char >>> *buf, >>> + size_t csize, unsigned long offset, >>> + int userbuf) { >> >> Personally I prefer below because it is too long: >> >> static inline >> ssize_t copy_oldmem_page_encrypted(unsigned long pfn, char *buf, size_t >> csize, >> unsigned long offset, int userbuf) >> { >> return 0; >> } >> >> >>> + return csize; >> >> As above it should be return 0; >> Great, Thank you, Dave. Lianbo >>> +} >>> +#endif >>> void vmcore_cleanup(void); >>> >>> /* Architecture code defines this if there are other possible ELF >>> -- >>> 2.9.5 >>> >>> >>> _______________________________________________ >>> 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