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

Hi, Yes. There is no problem for us to analyze a dump. I think the makedumpfile utility can have a workaround too. I like the Plan A too. So I will send a patch of Plan A to the xen-devel mailing list. Thanks. Itsuro Oda On Tue, 20 May 2008 08:49:19 -0400 Dave Anderson <anderson(a)redhat.com&gt; wrote: > Simon Horman wrote: > > On Tue, Apr 22, 2008 at 05:32:03PM +0900, Itsuro ODA wrote: > >> 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.) > > > > Hi Oda-san, > > > > I think that in terms of simplicity plan A is a clear > > winner. That is assuming tha the changes to crash > > and makedumpfile are more or less the same for both > > plan A and plan B. > > > > However, if there is a reason that it makes sense to include > > the change in kexec-tools and make a fresh release, I'm happy to do so. > > I was the one who suggested a user-space alternative, but reconsidering it, > I also agree that plan A is preferable, primarily for simplicity's sake in > both kexec-tools (no changes) and in the crash utility (a couple lines that > have already been added in the latest version). > > > Dave > > > > >> === 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 > > > -- Itsuro ODA <oda(a)valinux.co.jp&gt;