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.)
Thanks.
Itsuro Oda
=== 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@xxxxxxxxxxxxx>
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