On Thu, Jul 9, 2020 at 6:30 PM HATAYAMA Daisuke <d.hatayama@xxxxxxxxxxx> wrote: > > We faced recently a memory dump collected by sadump where unused part > of register values are non-zero. For the crash dump, calculating > kaslr_offset fails because it is based on the assumption that unused > part of register values in the sadump format are always zero cleared. > > The problem is that used and unused part of register values are > rigorously indistinguishable in the sadump format. Although there is > kernel data structure that represents a map between logical cpu > numbers and lapic ids, they cannot be used in order to calculate > kaslr_offset. > > To fix this, we have no choice but use a trial-and-error approach: try > to use each entry of register values in order until we find a good > pair of cr3 and idtr by which we can refer to linux_banner symbol as > expected. > > Signed-off-by: HATAYAMA Daisuke <d.hatayama@xxxxxxxxxxx> I've replaced some indent spaces with tabs and merged: https://github.com/makedumpfile/makedumpfile/commit/3c0cf7a93cff83f1e711e241eb47fcb096a451c5 Thanks, Kazu > --- > sadump_info.c | 140 ++++++++++++++++++++++++++++++++++++++++------------------ > 1 file changed, 97 insertions(+), 43 deletions(-) > > diff --git a/sadump_info.c b/sadump_info.c > index 46867ce..aa9a048 100644 > --- a/sadump_info.c > +++ b/sadump_info.c > @@ -101,6 +101,7 @@ static int lookup_diskset(unsigned long long whole_offset, int *diskid, > unsigned long long *disk_offset); > static int max_mask_cpu(void); > static int cpu_online_mask_init(void); > +static int linux_banner_sanity_check(ulong cr3); > static int per_cpu_init(void); > static int get_data_from_elf_note_desc(const char *note_buf, uint32_t n_descsz, > char *name, uint32_t n_type, char **data); > @@ -1293,6 +1294,30 @@ finish: > return ret; > } > > +static int linux_banner_sanity_check(ulong cr3) > +{ > + unsigned long linux_banner_paddr; > + char buf[sizeof("Linux version")]; > + > + linux_banner_paddr = vtop4_x86_64_pagetable(SYMBOL(linux_banner), cr3); > + if (linux_banner_paddr == NOT_PADDR) { > + DEBUG_MSG("sadump: linux_banner address translation failed\n"); > + return FALSE; > + } > + > + if (!readmem(PADDR, linux_banner_paddr, &buf, sizeof(buf))) { > + DEBUG_MSG("sadump: reading linux_banner failed\n"); > + return FALSE; > + } > + > + if (!STRNEQ(buf, "Linux version")) { > + DEBUG_MSG("sadump: linux_banner sanity check failed\n"); > + return FALSE; > + } > + > + return TRUE; > +} > + > /* > * Calculate kaslr_offset and phys_base > * > @@ -1370,59 +1395,86 @@ 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; > + struct sadump_smram_cpu_state smram; > int apicid; > unsigned long divide_error_vmcore, divide_error_vmlinux; > unsigned long kaslr_offset, phys_base; > unsigned long kaslr_offset_kdump, phys_base_kdump; > + int sanity_check_passed = FALSE; > > - 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"); > + > + DEBUG_MSG("sadump: apicid: %d\n", apicid); > + > + if (!get_smram_cpu_state(apicid, &smram)) { > + ERRMSG("get_smram_cpu_state error\n"); > + return FALSE; > + } > + > + idtr = ((uint64_t)smram.IdtUpper)<<32|(uint64_t)smram.IdtLower; > + > + if (!smram.Cr3 || !idtr) { > + DEBUG_MSG("sadump: cr3: %lx idt: %lx, skipped\n", > + smram.Cr3, > + idtr); > + continue; > + } > + > + if ((SYMBOL(pti_init) != NOT_FOUND_SYMBOL) || > + (SYMBOL(kaiser_init) != NOT_FOUND_SYMBOL)) > + cr3 = smram.Cr3 & ~(CR3_PCID_MASK|PTI_USER_PGTABLE_MASK); > + else > + cr3 = smram.Cr3 & ~CR3_PCID_MASK; > + > + /* Convert virtual address of IDT table to physical address */ > + idtr_paddr = vtop4_x86_64_pagetable(idtr, cr3); > + if (idtr_paddr == NOT_PADDR) { > + DEBUG_MSG("sadump: converting IDT physical address " > + "failed.\n"); > + continue; > + } > + > + /* 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=%" PRIx64 "\n", idtr); > + DEBUG_MSG("sadump: cr3=%" PRIx64 "\n", cr3); > + DEBUG_MSG("sadump: idtr(phys)=%" PRIx64 "\n", idtr_paddr); > + 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()) { > + ERRMSG("Reading symbol table failed\n"); > return FALSE; > } > > - if (memcmp(&smram, &zero, sizeof(smram)) != 0) > + /* Sanity check */ > + if (linux_banner_sanity_check(cr3)) { > + sanity_check_passed = TRUE; > 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; > - if ((SYMBOL(pti_init) != NOT_FOUND_SYMBOL) || > - (SYMBOL(kaiser_init) != NOT_FOUND_SYMBOL)) > - cr3 = smram.Cr3 & ~(CR3_PCID_MASK|PTI_USER_PGTABLE_MASK); > - else > - cr3 = smram.Cr3 & ~CR3_PCID_MASK; > - > - /* 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=%" PRIx64 "\n", idtr); > - DEBUG_MSG("sadump: cr3=%" PRIx64 "\n", cr3); > - DEBUG_MSG("sadump: idtr(phys)=%" PRIx64 "\n", idtr_paddr); > - DEBUG_MSG("sadump: devide_error(vmlinux)=%lx\n", > - divide_error_vmlinux); > - DEBUG_MSG("sadump: devide_error(vmcore)=%lx\n", > - divide_error_vmcore); > + info->kaslr_offset = 0; > + info->phys_base = 0; > + } > > - /* Reload symbol */ > - if (!get_symbol_info()) > - return FALSE; > + if (!sanity_check_passed) { > + ERRMSG("failed to calculate kaslr_offset and phys_base; " > + "default to 0\n"); > + info->kaslr_offset = 0; > + info->phys_base = 0; > + return TRUE; > + } > > /* > * Check if current kaslr_offset/phys_base is for 1st kernel or 2nd > @@ -1430,13 +1482,15 @@ calc_kaslr_offset(void) > * from vmcoreinfo > */ > if (get_kaslr_offset_from_vmcoreinfo(cr3, &kaslr_offset_kdump, > - &phys_base_kdump)) { > + &phys_base_kdump)) { > info->kaslr_offset = kaslr_offset_kdump; > info->phys_base = phys_base_kdump; > > /* Reload symbol */ > - if (!get_symbol_info()) > + if (!get_symbol_info()) { > + ERRMSG("Reading symbol table failed\n"); > return FALSE; > + } > } > > DEBUG_MSG("sadump: kaslr_offset=%lx\n", info->kaslr_offset); > -- > 1.8.3.1 > > > _______________________________________________ > kexec mailing list > kexec@xxxxxxxxxxxxxxxxxxx > http://lists.infradead.org/mailman/listinfo/kexec _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
