handle x86_64 xen code/data relocation
Simon Horman
horms at verge.net.au
Mon May 19 23:58:39 EDT 2008
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.
> === 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 at valinux.co.jp>
>
>
> _______________________________________________
> kexec mailing list
> kexec at lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/kexec
--
$BJuRX(B $B@>Lg(B ($B%[%&%^%s!&%5%$%b%s(B) | Simon Horman (Horms)
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