makedumpfile '--mem-usage' use-case is currently broken on x86_64 with latest kernels (see a sample log below with 4.19 kernel): [root@hp-dl380pgen8-02-vm-15 ~]# makedumpfile -f --mem-usage /proc/kcore The kernel version is not supported. The makedumpfile operation may be incomplete. <snip..> set_kcore_vmcoreinfo: Can't get the offset of VMCOREINFO(/proc/kcore). Success makedumpfile Failed. It seems that the issue is seen because KCORE_REMAP which was added to recent kernels and appears as a PT_LOAD in '/proc/kcore'. I have recently proposed a kernel patch which allows appending 'page_offset_base' for x86_64 platforms to vmcoreinfo, so that user-space tools can use the same as a standard interface to determine the start of direct mapping of all physical memory (see [0]). This in in-line with the philosophy being proposed by kernel maintainers where one can use the vmcoreinfo note in user-land (from '/proc/kcore') to retrieve machine specific symbols or strings being appended to the vmcoreinfo even for live-debugging of the primary kernel as a standard interface exposed by kernel for sharing machine specific details with the user-land. With this fix, the '--mem-usage' use case works fine on the x86_64 machines even with newer kernels: [root@ibm-x3650m4-01-vm-16 makedumpfile]# makedumpfile -f --mem-usage /proc/kcore -D The kernel version is not supported. The makedumpfile operation may be incomplete. <..snip..> Linux kdump VMCOREINFO PT_NOTE found in /proc/kcore page_size : 4096 info->page_offset : ffff880000000000 <..snip..>The kernel doesn't support mmap(),read() will be used instead. TYPE PAGES EXCLUDABLE DESCRIPTION ---------------------------------------------------------------------- ZERO 20846 yes Pages filled with zero NON_PRI_CACHE 57371 yes Cache pages without private flag PRI_CACHE 1 yes Cache pages with private flag USER 13841 yes User process pages FREE 777956 yes Free pages KERN_DATA 55625 no Dumpable kernel data page size: 4096 Total pages on system: 925640 Total size on system: 3791421440 Byte [0]. https://lkml.org/lkml/2018/10/27/86 I will send a follow-up patch to read 'kaslr_offset' for x86_64 cases from vmcoreinfo inside '/proc/kcore' after this patchset is applied. Cc: Baoquan He <bhe@xxxxxxxxxx> Cc: Kazuhito Hagio <k-hagio@xxxxxxxxxxxxx> Signed-off-by: Bhupesh Sharma <bhsharma@xxxxxxxxxx> --- arch/x86_64.c | 17 +++++++++++++++++ makedumpfile.c | 2 ++ makedumpfile.h | 1 + 3 files changed, 20 insertions(+) diff --git a/arch/x86_64.c b/arch/x86_64.c index 2b3c0bb356a1..a5fbdf26b8e7 100644 --- a/arch/x86_64.c +++ b/arch/x86_64.c @@ -98,6 +98,22 @@ get_page_offset_x86_64(void) return TRUE; } + /* Calculate 'info->page_offset'. */ + + /* Since kernel version 4.19, '/proc/kcore' contains a new + * PT_NOTE which carries the VMCOREINFO information. + * + * If the same is available, use it as it already contains the + * value of 'page_offset_base' on the machine. + */ + if (info->flag_kcore_contains_vmcoreinfo && + (NUMBER(page_offset_base) != NOT_FOUND_NUMBER)) { + page_offset_base = NUMBER(page_offset_base); + info->page_offset = page_offset_base; + DEBUG_MSG("info->page_offset : %lx\n", info->page_offset); + return TRUE; + } + if (get_num_pt_loads()) { for (i = 0; get_pt_load(i, &phys_start, NULL, &virt_start, NULL); @@ -106,6 +122,7 @@ get_page_offset_x86_64(void) && virt_start < __START_KERNEL_map && phys_start != NOT_PADDR) { info->page_offset = virt_start - phys_start; + DEBUG_MSG("info->page_offset : %lx\n", info->page_offset); return TRUE; } } diff --git a/makedumpfile.c b/makedumpfile.c index a1b8d8ff5a84..668e3ec3956c 100644 --- a/makedumpfile.c +++ b/makedumpfile.c @@ -2319,6 +2319,7 @@ write_vmcoreinfo_data(void) WRITE_NUMBER("PAGE_BUDDY_MAPCOUNT_VALUE", PAGE_BUDDY_MAPCOUNT_VALUE); WRITE_NUMBER("phys_base", phys_base); + WRITE_NUMBER("page_offset_base", page_offset_base); WRITE_NUMBER("HUGETLB_PAGE_DTOR", HUGETLB_PAGE_DTOR); #ifdef __aarch64__ @@ -2719,6 +2720,7 @@ read_vmcoreinfo(void) READ_NUMBER("PAGE_BUDDY_MAPCOUNT_VALUE", PAGE_BUDDY_MAPCOUNT_VALUE); READ_NUMBER("phys_base", phys_base); + READ_NUMBER("page_offset_base", page_offset_base); #ifdef __aarch64__ READ_NUMBER("VA_BITS", VA_BITS); READ_NUMBER_UNSIGNED("PHYS_OFFSET", PHYS_OFFSET); diff --git a/makedumpfile.h b/makedumpfile.h index 77f7ec8e3867..09e14f0ef86c 100644 --- a/makedumpfile.h +++ b/makedumpfile.h @@ -1920,6 +1920,7 @@ struct number_table { long MAX_PHYSMEM_BITS; long HUGETLB_PAGE_DTOR; long phys_base; + unsigned long page_offset_base; #ifdef __aarch64__ long VA_BITS; unsigned long PHYS_OFFSET; -- 2.7.4 _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
