[PATCH 3/3] makedumpfile: sadump: Fix a KASLR problem of sadump
Hatayama, Daisuke
d.hatayama at jp.fujitsu.com
Fri Oct 13 05:05:52 PDT 2017
> -----Original Message-----
> From: Takao Indoh [mailto:indou.takao at jp.fujitsu.com]
> Sent: Tuesday, October 10, 2017 6:27 PM
> To: ats-kumagai at wm.jp.nec.com; Hatayama, Daisuke
> <d.hatayama at jp.fujitsu.com>
> Cc: kexec at lists.infradead.org
> Subject: [PATCH 3/3] makedumpfile: sadump: Fix a KASLR problem of sadump
>
> This patch fix a problem that makedumpfile cannot handle a dumpfile
> which is captured by sadump in KASLR enabled kernel.
>
> When KASLR feature is enabled, a kernel is placed on the memory randomly
> and therefore makedumpfile cannot handle a dumpfile captured by sadump
> because addresses of kernel symbols in System.map or vmlinux are
> different from actual addresses.
>
> To solve this problem, we need to calculate kaslr offset(the difference
> between original symbol address and actual address) and phys_base, and
> adjust symbol table of makedumpfile. In the case of dumpfile of kdump,
> these information is included in the header, but dumpfile of sadump does
> not have such a information.
>
> This patch calculate kaslr offset and phys_base to solve this problem.
> Please see the comment in the calc_kaslr_offset() for the detail idea.
> The basic idea is getting register (IDTR and CR3) from dump header, and
> calculate kaslr_offset/phys_base using them.
>
> Signed-off-by: Takao Indoh <indou.takao at jp.fujitsu.com>
> ---
> makedumpfile.c | 13 ++
> makedumpfile.h | 5 +-
> sadump_info.c | 417
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
> 3 files changed, 432 insertions(+), 3 deletions(-)
>
> diff --git a/makedumpfile.c b/makedumpfile.c
> index 5f2ca7d..a246cbb 100644
> --- a/makedumpfile.c
> +++ b/makedumpfile.c
> @@ -1554,6 +1554,10 @@ get_symbol_info(void)
> SYMBOL_INIT(demote_segment_4k, "demote_segment_4k");
> SYMBOL_INIT(cur_cpu_spec, "cur_cpu_spec");
>
> + SYMBOL_INIT(divide_error, "divide_error");
> + SYMBOL_INIT(idt_table, "idt_table");
> + SYMBOL_INIT(saved_command_line, "saved_command_line");
> +
> return TRUE;
> }
>
> @@ -2249,6 +2253,15 @@ write_vmcoreinfo_data(void)
> WRITE_NUMBER_UNSIGNED("kimage_voffset", kimage_voffset);
> #endif
>
> + if (info->flag_sadump) {
> + if (info->phys_base)
> + fprintf(info->file_vmcoreinfo, "%s%lu\n",
> STR_NUMBER("phys_base"),
> + info->phys_base);
> + if (info->kaslr_offset)
> + fprintf(info->file_vmcoreinfo, "%s%lx\n",
> STR_KERNELOFFSET,
> + info->kaslr_offset);
> + }
> +
Is the sadump condition necessary?
I think these information is always useful.
> /*
> * write the source file of 1st kernel
> */
> diff --git a/makedumpfile.h b/makedumpfile.h
> index f48dc0b..6566241 100644
> --- a/makedumpfile.h
> +++ b/makedumpfile.h
> @@ -1599,6 +1599,9 @@ struct symbol_table {
> unsigned long long cpu_online_mask;
> unsigned long long __cpu_online_mask;
> unsigned long long kexec_crash_image;
> + unsigned long long divide_error;
> + unsigned long long idt_table;
> + unsigned long long saved_command_line;
>
> /*
> * symbols on ppc64 arch
> @@ -1960,7 +1963,7 @@ int iomem_for_each_line(char *match, int
> (*callback)(void *data, int nr,
> unsigned long
> length),
> void *data);
> int is_bigendian(void);
> -
> +int get_symbol_info(void);
>
> /*
> * for Xen extraction
> diff --git a/sadump_info.c b/sadump_info.c
> index 7dd22e7..dafa9e7 100644
> --- a/sadump_info.c
> +++ b/sadump_info.c
> @@ -1035,6 +1035,412 @@ sadump_get_max_mapnr(void)
>
> #ifdef __x86_64__
>
> +/*
> + * Get address of vector0 interrupt handler (Devide Error) form Interrupt
> + * Descriptor Table.
> + */
> +static unsigned long
> +get_vec0_addr(ulong idtr)
> +{
> + ulong buf[16];
> + ulong *ip, i1, i2, addr;
> +
> + readmem(PADDR, idtr, buf, sizeof(buf));
> +
> + ip = (ulong *)buf;
> +
> + i1 = *ip;
> + i2 = *(ip+1);
> +
> + i2 <<= 32;
> + addr = i2 & 0xffffffff00000000;
> + addr |= (i1 & 0xffff);
> + i1 >>= 32;
> + addr |= (i1 & 0xffff0000);
> +
> + return addr;
> +}
As the comment I did in the review of crash utility side, I prefer a
style using structure like below for readability.
Also, readmem() in makedumpfile doesn't support long jump at fault, so
we need error handling around readmem(). ULONGMAX as error status?
static unsigend long
get_vec0_addr(ulong idtr)
{
struct gate_struct64 {
uint16_t offset_low;
uint16_t segment;
uint32_t ist : 3, zero0 : 5, type : 5, dpl : 2, p : 1;
uint16_t offset_middle;
uint32_t offset_high;
uint32_t zero1;
} __attribute__((packed)) gate;
if (!readmem(PADDR, idtr, &gate, sizeof(gate)))
return ULONGMAX;
return ((ulong)gate.offset_high << 32)
+ ((ulong)gate.offset_middle << 16)
+ gate.offset_low;
}
> +
> +/*
> + * Parse a string of [size[KMG]@]offset[KMG]
> + * Import from Linux kernel(lib/cmdline.c)
> + */
> +static ulong memparse(char *ptr, char **retptr)
> +{
> + char *endptr;
> +
> + unsigned long long ret = strtoull(ptr, &endptr, 0);
> +
> + switch (*endptr) {
> + case 'E':
> + case 'e':
> + ret <<= 10;
> + case 'P':
> + case 'p':
> + ret <<= 10;
> + case 'T':
> + case 't':
> + ret <<= 10;
> + case 'G':
> + case 'g':
> + ret <<= 10;
> + case 'M':
> + case 'm':
> + ret <<= 10;
> + case 'K':
> + case 'k':
> + ret <<= 10;
> + endptr++;
> + default:
> + break;
> + }
> +
> + if (retptr)
> + *retptr = endptr;
> +
> + return ret;
> +}
> +
> +/*
> + * Find "elfcorehdr=" in the boot parameter of kernel and return the address
> + * of elfcorehdr.
> + */
> +static ulong
> +get_elfcorehdr(ulong cr3)
> +{
> + char cmdline[BUFSIZE], *ptr;
> + ulong cmdline_vaddr;
> + ulong cmdline_paddr;
> + ulong buf_vaddr, buf_paddr;
> + char elfcorehdr_val[16], *end;
> + ulong elfcorehdr_addr = 0, elfcorehdr_size = 0;
> +
> + if (SYMBOL(saved_command_line) == NOT_FOUND_SYMBOL) {
> + ERRMSG("Can't get the symbol of saved_command_line.\n");
> + return 0;
> + }
> + cmdline_vaddr = SYMBOL(saved_command_line);
> + if ((cmdline_paddr = vtop4_x86_64_pagetable(cmdline_vaddr, cr3)) ==
> NOT_PADDR)
> + return 0;
> +
> + DEBUG_MSG("sadump: cmdline vaddr: %lx\n", cmdline_vaddr);
> + DEBUG_MSG("sadump: cmdline paddr: %lx\n", cmdline_paddr);
> +
> + if (!readmem(PADDR, cmdline_paddr, &buf_vaddr, sizeof(ulong)))
> + return 0;
> +
> + if ((buf_paddr = vtop4_x86_64_pagetable(buf_vaddr, cr3)) ==
> NOT_PADDR)
> + return 0;
> +
> + DEBUG_MSG("sadump: cmdline buf vaddr: %lx\n", buf_vaddr);
> + DEBUG_MSG("sadump: cmdline buf paddr: %lx\n", buf_paddr);
> +
> + memset(cmdline, 0, BUFSIZE);
> + if (!readmem(PADDR, buf_paddr, cmdline, BUFSIZE))
> + return 0;
> +
> + ptr = strstr(cmdline, "elfcorehdr=");
> + if (!ptr)
> + return 0;
> +
> + ptr += strlen("elfcorehdr=");
> + memset(elfcorehdr_val, 0, sizeof(elfcorehdr_val));
> + sscanf(ptr, "%s", elfcorehdr_val);
> +
> + DEBUG_MSG("sadump: 2nd kernel detected.\n");
> + DEBUG_MSG("sadump: elfcorehdr=%s\n", elfcorehdr_val);
> +
> + /* elfcorehdr=[size[KMG]@]offset[KMG] */
> + elfcorehdr_addr = memparse(elfcorehdr_val, &end);
Is it possible to remove elfcorehdr_val by:
elfcorehdr_addr = memparse(ptr, &end);
> + if (*end == '@') {
> + elfcorehdr_size = elfcorehdr_addr;
> + elfcorehdr_addr = memparse(end + 1, &end);
> + }
> +
> + DEBUG_MSG("sadump: elfcorehdr_addr: %lx\n", elfcorehdr_addr);
> + DEBUG_MSG("sadump: elfcorehdr_size: %lx\n", elfcorehdr_size);
> +
> + return elfcorehdr_addr;
> +}
> +
> +/*
> + * Get vmcoreinfo from elfcorehdr.
> + * Some codes are imported from Linux kernel(fs/proc/vmcore.c)
> + */
> +#define DIV_ROUND_UP(n,d) (((n) + (d) - 1) / (d))
Please use divideup() macro defined in common.h instead.
> +static int
> +get_vmcoreinfo_in_kdump_kernel(ulong elfcorehdr, ulong *addr, int *len)
> +{
> + unsigned char e_ident[EI_NIDENT];
> + Elf64_Ehdr ehdr;
> + Elf64_Phdr phdr;
> + Elf64_Nhdr nhdr;
> + ulong ptr;
> + ulong nhdr_offset = 0;
> + int i;
> +
> + if (!readmem(PADDR, elfcorehdr, e_ident, EI_NIDENT))
> + return FALSE;
> +
> + if (e_ident[EI_CLASS] != ELFCLASS64) {
> + ERRMSG("Only ELFCLASS64 is supportd\n");
> + return FALSE;
> + }
> +
> + if (!readmem(PADDR, elfcorehdr, &ehdr, sizeof(ehdr)))
> + return FALSE;
> +
> + /* Sanity Check */
> + if (memcmp(ehdr.e_ident, ELFMAG, SELFMAG) != 0 ||
> + (ehdr.e_type != ET_CORE) ||
> + ehdr.e_ident[EI_CLASS] != ELFCLASS64 ||
> + ehdr.e_ident[EI_VERSION] != EV_CURRENT ||
> + ehdr.e_version != EV_CURRENT ||
> + ehdr.e_ehsize != sizeof(Elf64_Ehdr) ||
> + ehdr.e_phentsize != sizeof(Elf64_Phdr) ||
> + ehdr.e_phnum == 0) {
> + ERRMSG("Invalid elf header\n");
> + return FALSE;
> + }
> +
> + ptr = elfcorehdr + sizeof(ehdr);
ptr = elfcorehdr + ehdr.e_phoff; is better.
> + for (i = 0; i < ehdr.e_phnum; i++) {
> + ulong offset;
> + char name[16];
> +
> + if (!readmem(PADDR, ptr, &phdr, sizeof(phdr)))
> + return FALSE;
> +
> + ptr += sizeof(phdr);
> + if (phdr.p_type != PT_NOTE)
> + continue;
> +
> + offset = phdr.p_offset;
> + if (!readmem(PADDR, offset, &nhdr, sizeof(nhdr)))
> + return FALSE;
> +
> + offset += DIV_ROUND_UP(sizeof(Elf64_Nhdr),
> sizeof(Elf64_Word))*
> + sizeof(Elf64_Word);
> + memset(name, 0, sizeof(name));
> + if (!readmem(PADDR, offset, name, sizeof(name)))
> + return FALSE;
> +
> + if(!strcmp(name, "VMCOREINFO")) {
> + nhdr_offset = offset;
> + break;
> + }
> + }
> +
> + if (!nhdr_offset)
> + return FALSE;
> +
> + *addr = nhdr_offset +
> + DIV_ROUND_UP(nhdr.n_namesz, sizeof(Elf64_Word))*
> + sizeof(Elf64_Word);
> + *len = nhdr.n_descsz;
> +
> + DEBUG_MSG("sadump: vmcoreinfo addr: %lx\n", *addr);
> + DEBUG_MSG("sadump: vmcoreinfo len: %d\n", *len);
> +
> + return TRUE;
> +}
> +
> +/*
> + * Check if current kaslr_offset/phys_base is for 1st kernel or 2nd kernel.
> + * If we are in 2nd kernel, get kaslr_offset/phys_base from vmcoreinfo.
> + *
> + * 1. Get command line and try to retrieve "elfcorehdr=" boot parameter
> + * 2. If "elfcorehdr=" is not found in command line, we are in 1st kernel.
> + * There is nothing to do.
> + * 3. If "elfcorehdr=" is found, we are in 2nd kernel. Find vmcoreinfo
> + * using "elfcorehdr=" and retrieve kaslr_offset/phys_base from
> vmcoreinfo.
> + */
> +int
> +get_kaslr_offset_from_vmcoreinfo(ulong cr3, ulong *kaslr_offset,
> + ulong *phys_base)
> +{
> + ulong elfcorehdr_addr = 0;
> + ulong vmcoreinfo_addr;
> + int vmcoreinfo_len;
> + char *buf, *pos, *endptr;
> + int ret = FALSE;
> +
> + elfcorehdr_addr = get_elfcorehdr(cr3);
> + if (!elfcorehdr_addr)
> + return FALSE;
> +
> + if (!get_vmcoreinfo_in_kdump_kernel(elfcorehdr_addr,
> &vmcoreinfo_addr,
> + &vmcoreinfo_len))
> + return FALSE;
> +
> + DEBUG_MSG("sadump: Find vmcoreinfo in kdump memory\n");
> +
> + buf = malloc(vmcoreinfo_len);
Zero check for vmcoreinfo_len and NULL check for buf are needed
respectively.
> + if (!readmem(PADDR, vmcoreinfo_addr, buf, vmcoreinfo_len))
> + goto finish;
> +
> + pos = strstr(buf, STR_NUMBER("phys_base"));
> + if (!pos)
> + goto finish;
> + *phys_base = strtoull(pos + strlen(STR_NUMBER("phys_base")),
> &endptr, 0);
> +
> + pos = strstr(buf, STR_KERNELOFFSET);
> + if (!pos)
> + goto finish;
> + *kaslr_offset = strtoull(pos + strlen(STR_KERNELOFFSET), &endptr,
> 16);
I think endptr can be removed.
> + ret = TRUE;
> +
> +finish:
> + free(buf);
> + return ret;
> +}
> +
> +/*
> + * Calculate kaslr_offset and phys_base
> + *
> + * kaslr_offset:
> + * The difference between original address in vmlinux and actual address
> + * placed randomly by kaslr feature. To be more accurate,
> + * kaslr_offset = actual address - original address
> + *
> + * phys_base:
> + * Physical address where the kerenel is placed. In other words, it's a
> + * physical address of __START_KERNEL_map. This is also decided randomly
> by
> + * kaslr.
> + *
> + * kaslr offset and phys_base are calculated as follows:
> + *
> + * kaslr_offset:
> + * 1) Get IDTR and CR3 value from the dump header.
> + * 2) Get a virtual address of IDT from IDTR value
> + * --- (A)
> + * 3) Translate (A) to physical address using CR3, which points a top of
> + * page table.
> + * --- (B)
> + * 4) Get an address of vector0 (Devide Error) interrupt handler from
> + * IDT, which are pointed by (B).
> + * --- (C)
> + * 5) Get an address of symbol "divide_error" form vmlinux
> + * --- (D)
> + *
> + * Now we have two addresses:
> + * (C)-> Actual address of "divide_error"
> + * (D)-> Original address of "divide_error" in the vmlinux
> + *
> + * kaslr_offset can be calculated by the difference between these two
> + * value.
> + *
> + * phys_base;
> + * 1) Get IDT virtual address from vmlinux
> + * --- (E)
> + *
> + * So phys_base can be calculated using relationship of directly mapped
> + * address.
> + *
> + * phys_base =
> + * Physical address(B) -
> + * (Virtual address(E) + kaslr_offset - __START_KERNEL_map)
> + *
> + * Note that the address (A) cannot be used instead of (E) because (A) is
> + * not direct map address, it's a fixed map address.
> + *
> + * This solution works in most every case, but does not work in the
> + * following case.
> + *
> + * 1) If the dump is captured on early stage of kernel boot, IDTR points
> + * early IDT table(early_idts) instead of normal IDT(idt_table).
> + * 2) If the dump is captured whle kdump is working, IDTR points
> + * IDT table of 2nd kernel, not 1st kernel.
> + *
> + * Current implementation does not support the case 1), need
> + * enhancement in the future. For the case 2), get kaslr_offset and
> + * phys_base as follows.
> + *
> + * 1) Get kaslr_offset and phys_base using the above solution.
> + * 2) Get kernel boot parameter from "saved_command_line"
> + * 3) If "elfcorehdr=" is not included in boot parameter, we are in the
> + * first kernel, nothing to do any more.
> + * 4) If "elfcorehdr=" is included in boot parameter, we are in the 2nd
> + * kernel. Retrieve vmcoreinfo from address of "elfcorehdr=" and
> + * get kaslr_offset and phys_base from vmcoreinfo.
> + */
> +int
> +calc_kaslr_offset(void)
> +{
> + struct sadump_header *sh = si->sh_memory;
> + uint64_t idtr = 0, cr3 = 0, idtr_paddr;
> + struct sadump_smram_cpu_state smram, zero;
> + int apicid;
> + unsigned long divide_error_vmcore, divide_error_vmlinux;
> +
> + unsigned long kaslr_offset_kdump, phys_base_kdump;
> + unsigned long kaslr_offset, phys_base;
> +
> + memset(&zero, 0, sizeof(zero));
> + for (apicid = 0; apicid < sh->nr_cpus; ++apicid) {
> + if (!get_smram_cpu_state(apicid, &smram)) {
> + ERRMSG("get_smram_cpu_state error\n");
> + return FALSE;
> + }
> +
> + if (memcmp(&smram, &zero, sizeof(smram)) != 0)
> + break;
> + }
> + if (apicid >= sh->nr_cpus) {
> + ERRMSG("Can't get smram state\n");
> + return FALSE;
> + }
> +
> + idtr = ((uint64_t)smram.IdtUpper)<<32 | (uint64_t)smram.IdtLower;
> + cr3 = smram.Cr3;
> +
> + /* Convert virtual address of IDT table to physical address */
> + if ((idtr_paddr = vtop4_x86_64_pagetable(idtr, cr3)) == NOT_PADDR)
> + return FALSE;
> +
> + /* Now we can calculate kaslr_offset and phys_base */
> + divide_error_vmlinux = SYMBOL(divide_error);
> + divide_error_vmcore = get_vec0_addr(idtr_paddr);
> + kaslr_offset = divide_error_vmcore - divide_error_vmlinux;
> + phys_base = idtr_paddr -
> + (SYMBOL(idt_table) + kaslr_offset - __START_KERNEL_map);
> +
> + info->kaslr_offset = kaslr_offset;
> + info->phys_base = phys_base;
> +
> + DEBUG_MSG("sadump: idtr=%lx\n", idtr);
> + DEBUG_MSG("sadump: cr3=%lx\n", cr3);
> + DEBUG_MSG("sadump: idtr(phys)=%lx\n", idtr_paddr);
Use PRIx64 defined in inttypes.h for uint64_t just as:
DEBUG_MSG("sadump: idtr=" PRIx64 "\n", idtr);
> + DEBUG_MSG("sadump: devide_error(vmlinux)=%lx\n",
> + divide_error_vmlinux);
> + DEBUG_MSG("sadump: devide_error(vmcore)=%lx\n",
> + divide_error_vmcore);
> +
> + /* Reload symbol */
> + if (!get_symbol_info())
> + return FALSE;
> +
> + /*
> + * Check if current kaslr_offset/phys_base is for 1st kernel or 2nd
> + * kernel. If we are in 2nd kernel, get kaslr_offset/phys_base
> + * from vmcoreinfo
> + */
> + if (get_kaslr_offset_from_vmcoreinfo(cr3, &kaslr_offset_kdump,
> + &phys_base_kdump)) {
> + info->kaslr_offset = kaslr_offset_kdump;
> + info->phys_base = phys_base_kdump;
> +
> + /* Reload symbol */
> + if (!get_symbol_info())
> + return FALSE;
> + }
> +
> + DEBUG_MSG("sadump: kaslr_offset=%lx\n", info->kaslr_offset);
> + DEBUG_MSG("sadump: phys_base=%lx\n", info->phys_base);
> +
> + return TRUE;
> +}
> +
> int
> sadump_virt_phys_base(void)
> {
> @@ -1065,6 +1471,9 @@ sadump_virt_phys_base(void)
> }
>
> failed:
> + if (calc_kaslr_offset())
> + return TRUE;
> +
> info->phys_base = 0;
>
> DEBUG_MSG("sadump: failed to calculate phys_base; default to 0\n");
> @@ -1518,10 +1927,14 @@ cpu_to_apicid(int cpu, int *apicid)
> if (!readmem(VADDR, SYMBOL(x86_bios_cpu_apicid_early_ptr),
> &early_ptr, sizeof(early_ptr)))
> return FALSE;
> -
> + /*
> + * Note: SYMBOL(name) value is adjusted by
> info->kaslr_offset,
> + * but per_cpu symbol does not need to be adjusted becasue
> it
> + * is not affectd by kaslr.
> + */
> apicid_addr = early_ptr
> ?
> SYMBOL(x86_bios_cpu_apicid_early_map)+cpu*sizeof(uint16_t)
> - : per_cpu_ptr(SYMBOL(x86_bios_cpu_apicid), cpu);
> + : per_cpu_ptr(SYMBOL(x86_bios_cpu_apicid) -
> info->kaslr_offset, cpu);
>
> if (!readmem(VADDR, apicid_addr, &apicid_u16,
> sizeof(uint16_t)))
> return FALSE;
> --
> 2.9.5
More information about the kexec
mailing list