[Crash-utility] Re: handle x86_64 xen code/data relocation

Hi all, Recent version of xen (ex. RHEL5.2, 3.2.0) on the x86_64 moves the physical(machine) address of xen code/data area after the system started up. The start address of this is stored in 'xen_phys_start'. Thus to get a machine address of a xen text symbol from its virtual address, calculate "va - __XEN_VIRT_START + xen_phys_start". crash and makedumpfile command need the value of xen_phys_start. They know the virtual address of 'xen_phys_start' symbol but no way to extract the value of xen_phys_start. I think adding the xen_phys_start value to the CRASHINFO ElfNote section at first. (Plan A: patch for xen hypervisor code attaced) It is smallest modification necessary over all. On the other hand there is a opinion that it is better to upgrade a user-package than a hypervisor or kernel package. The xen_phys_start value can be got from /proc/iomem. ------------------------------------------------------- # cat /proc/iomem ... 7e600000-7f5fffff : Hypervisor code and data *** this line ... ------------------------------------------------------- So the kexec-tools can handle it theoretically. The Plan B is that kexec-tools adds another ElfNote section which holds the xen_phys_start value. The attached patch works well though I am concern about it is a bit tricky. Which plan is better ? Or more good implementation ? Please comment. (note that crash and makedumpfile modification is same degree for both plan.)

=== Plan A (modify the xen hypervisor. It is for RHEL5.2 but almost same for other version) === --- include/xen/elfcore.h.org 2008-04-17 14:11:41.000000000 +0900 +++ include/xen/elfcore.h 2008-04-17 14:11:57.000000000 +0900 @@ -66,6 +66,7 @@ unsigned long xen_compile_time; unsigned long tainted; #ifdef CONFIG_X86 + unsigned long xen_phys_start; unsigned long dom0_pfn_to_mfn_frame_list_list; #endif } crash_xen_info_t; --- arch/x86/crash.c.org 2008-04-17 14:12:51.000000000 +0900 +++ arch/x86/crash.c 2008-04-17 14:13:13.000000000 +0900 @@ -102,6 +102,7 @@ hvm_disable(); info = kexec_crash_save_info(); + info->xen_phys_start = xen_phys_start; info->dom0_pfn_to_mfn_frame_list_list = arch_get_pfn_to_mfn_frame_list_list(dom0); } ================================================================ === Plan B (modify the kexec-tools. proof of concept version) === diff -ru kexec-tools-testing-20080324.org/kexec/arch/x86_64/crashdump-x86_64.c kexec-tools-testing-20080324/kexec/arch/x86_64/crashdump-x86_64.c --- kexec-tools-testing-20080324.org/kexec/arch/x86_64/crashdump-x86_64.c 2008-03-21 13:16:28.000000000 +0900 +++ kexec-tools-testing-20080324/kexec/arch/x86_64/crashdump-x86_64.c 2008-04-22 15:15:08.000000000 +0900 @@ -73,6 +73,25 @@ return -1; } +static int get_hypervisor_paddr(struct kexec_info *info) +{ + uint64_t start; + + if (!xen_present()) + return 0; + + if (parse_iomem_single("Hypervisor code and data\n", &start, NULL) == 0) { + info->hypervisor_paddr_start = start; +#ifdef DEBUG + printf("kernel load physical addr start = 0x%016Lx\n", start); +#endif + return 0; + } + + fprintf(stderr, "Cannot determine hypervisor physical load addr\n"); + return -1; +} + /* Retrieve info regarding virtual address kernel has been compiled for and * size of the kernel from /proc/kcore. Current /proc/kcore parsing from * from kexec-tools fails because of malformed elf notes. A kernel patch has @@ -581,6 +600,9 @@ if (get_kernel_paddr(info)) return -1; + if (get_hypervisor_paddr(info)) + return -1; + if (get_kernel_vaddr_and_size(info)) return -1; @@ -620,6 +642,9 @@ */ elfcorehdr = add_buffer(info, tmp, sz, 16*1024, align, min_base, max_addr, -1); + if (info->hypervisor_paddr_start && xen_present()) { + *(info->hypervisor_paddr_loc) += elfcorehdr; + } if (delete_memmap(memmap_p, elfcorehdr, sz) < 0) return -1; cmdline_add_memmap(mod_cmdline, memmap_p); diff -ru kexec-tools-testing-20080324.org/kexec/crashdump.c kexec-tools-testing-20080324/kexec/crashdump.c --- kexec-tools-testing-20080324.org/kexec/crashdump.c 2008-03-21 13:16:28.000000000 +0900 +++ kexec-tools-testing-20080324/kexec/crashdump.c 2008-04-22 15:33:47.000000000 +0900 @@ -36,8 +36,10 @@ #define FUNC crash_create_elf64_headers #define EHDR Elf64_Ehdr #define PHDR Elf64_Phdr +#define NHDR Elf64_Nhdr #include "crashdump-elf.c" #undef ELF_WIDTH +#undef NHDR #undef PHDR #undef EHDR #undef FUNC @@ -46,8 +48,10 @@ #define FUNC crash_create_elf32_headers #define EHDR Elf32_Ehdr #define PHDR Elf32_Phdr +#define NHDR Elf32_Nhdr #include "crashdump-elf.c" #undef ELF_WIDTH +#undef NHDR #undef PHDR #undef EHDR #undef FUNC diff -ru kexec-tools-testing-20080324.org/kexec/crashdump-elf.c kexec-tools-testing-20080324/kexec/crashdump-elf.c --- kexec-tools-testing-20080324.org/kexec/crashdump-elf.c 2008-01-11 12:13:48.000000000 +0900 +++ kexec-tools-testing-20080324/kexec/crashdump-elf.c 2008-04-22 15:35:16.000000000 +0900 @@ -1,6 +1,6 @@ -#if !defined(FUNC) || !defined(EHDR) || !defined(PHDR) -#error FUNC, EHDR and PHDR must be defined +#if !defined(FUNC) || !defined(EHDR) || !defined(PHDR) || !defined(NHDR) +#error FUNC, EHDR, PHDR and NHDR must be defined #endif #if (ELF_WIDTH == 64) @@ -37,6 +37,7 @@ uint64_t vmcoreinfo_addr, vmcoreinfo_len; int has_vmcoreinfo = 0; int (*get_note_info)(int cpu, uint64_t *addr, uint64_t *len); + int has_hypervisor_paddr_start = 0; if (xen_present()) nr_cpus = xen_get_nr_phys_cpus(); @@ -78,6 +79,11 @@ sz += sizeof(PHDR); } + if (info->hypervisor_paddr_start && xen_present()) { + sz += sizeof(PHDR) + sizeof(NHDR) + 4 + sizeof(unsigned long); + has_hypervisor_paddr_start = 1; + } + /* * Make sure the ELF core header is aligned to at least 1024. * We do this because the secondary kernel gets the ELF core @@ -168,6 +174,22 @@ dbgprintf_phdr("vmcoreinfo header", phdr); } + if (has_hypervisor_paddr_start) { + phdr = (PHDR *) bufp; + bufp += sizeof(PHDR); + phdr->p_type = PT_NOTE; + phdr->p_flags = 0; + phdr->p_offset = phdr->p_paddr = 0; + phdr->p_vaddr = 0; + phdr->p_filesz = phdr->p_memsz = sizeof(NHDR) + 4 + sizeof(unsigned long); + phdr->p_align = 0; + + (elf->e_phnum)++; + dbgprintf_phdr("hypervisor phys addr header", phdr); + + info->hypervisor_paddr_loc = (unsigned long *)&phdr->p_offset; + } + /* Setup an PT_LOAD type program header for the region where * Kernel is mapped if info->kern_size is non-zero. */ @@ -225,6 +247,24 @@ (elf->e_phnum)++; dbgprintf_phdr("Elf header", phdr); } + + if (has_hypervisor_paddr_start) { + NHDR *nhdr; + unsigned int offset = (void *)bufp - *buf; + + nhdr = (NHDR *) bufp; + bufp += sizeof(NHDR); + nhdr->n_namesz = 4; + nhdr->n_descsz = sizeof(unsigned long); + nhdr->n_type = 0x1000003; + memcpy(bufp, "Xen", 4); + bufp += 4; + *((unsigned long *)bufp) = info->hypervisor_paddr_start; + bufp += sizeof(unsigned long); + + *(info->hypervisor_paddr_loc) = offset; + } + return 0; } diff -ru kexec-tools-testing-20080324.org/kexec/kexec.h kexec-tools-testing-20080324/kexec/kexec.h --- kexec-tools-testing-20080324.org/kexec/kexec.h 2008-03-21 13:16:28.000000000 +0900 +++ kexec-tools-testing-20080324/kexec/kexec.h 2008-04-22 15:08:57.000000000 +0900 @@ -123,6 +123,8 @@ unsigned long kern_vaddr_start; unsigned long kern_paddr_start; unsigned long kern_size; + unsigned long hypervisor_paddr_start; + unsigned long *hypervisor_paddr_loc; }; void usage(void); ====================================================================================== -- Itsuro ODA <oda(a)valinux.co.jp&gt; _______________________________________________ kexec mailing list kexec(a)lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec