qemu

qemu_elf.c (4858B)

---

 /*
  * Copyright (c) 2018 Virtuozzo International GmbH
  *
  * This work is licensed under the terms of the GNU GPL, version 2 or later.
  *
  */
 
 #include "qemu/osdep.h"
 #include "err.h"
 #include "qemu_elf.h"
 
 #define QEMU_NOTE_NAME "QEMU"
 
 #ifndef ROUND_UP
 #define ROUND_UP(n, d) (((n) + (d) - 1) & -(0 ? (n) : (d)))
 #endif
 
 #ifndef DIV_ROUND_UP
 #define DIV_ROUND_UP(n, d) (((n) + (d) - 1) / (d))
 #endif
 
 #define ELF_NOTE_SIZE(hdr_size, name_size, desc_size)   \
     ((DIV_ROUND_UP((hdr_size), 4) +                     \
       DIV_ROUND_UP((name_size), 4) +                    \
       DIV_ROUND_UP((desc_size), 4)) * 4)
 
 int is_system(QEMUCPUState *s)
 {
     return s->gs.base >> 63;
 }
 
 static char *nhdr_get_name(Elf64_Nhdr *nhdr)
 {
     return (char *)nhdr + ROUND_UP(sizeof(*nhdr), 4);
 }
 
 static void *nhdr_get_desc(Elf64_Nhdr *nhdr)
 {
     return nhdr_get_name(nhdr) + ROUND_UP(nhdr->n_namesz, 4);
 }
 
 static Elf64_Nhdr *nhdr_get_next(Elf64_Nhdr *nhdr)
 {
     return (void *)((uint8_t *)nhdr + ELF_NOTE_SIZE(sizeof(*nhdr),
                 nhdr->n_namesz, nhdr->n_descsz));
 }
 
 Elf64_Phdr *elf64_getphdr(void *map)
 {
     Elf64_Ehdr *ehdr = map;
     Elf64_Phdr *phdr = (void *)((uint8_t *)map + ehdr->e_phoff);
 
     return phdr;
 }
 
 Elf64_Half elf_getphdrnum(void *map)
 {
     Elf64_Ehdr *ehdr = map;
 
     return ehdr->e_phnum;
 }
 
 static int init_states(QEMU_Elf *qe)
 {
     Elf64_Phdr *phdr = elf64_getphdr(qe->map);
     Elf64_Nhdr *start = (void *)((uint8_t *)qe->map + phdr[0].p_offset);
     Elf64_Nhdr *end = (void *)((uint8_t *)start + phdr[0].p_memsz);
     Elf64_Nhdr *nhdr;
     size_t cpu_nr = 0;
 
     if (phdr[0].p_type != PT_NOTE) {
         eprintf("Failed to find PT_NOTE\n");
         return 1;
     }
 
     qe->has_kernel_gs_base = 1;
 
     for (nhdr = start; nhdr < end; nhdr = nhdr_get_next(nhdr)) {
         if (!strcmp(nhdr_get_name(nhdr), QEMU_NOTE_NAME)) {
             QEMUCPUState *state = nhdr_get_desc(nhdr);
 
             if (state->size < sizeof(*state)) {
                 eprintf("CPU #%zu: QEMU CPU state size %u doesn't match\n",
                         cpu_nr, state->size);
                 /*
                  * We assume either every QEMU CPU state has KERNEL_GS_BASE or
                  * no one has.
                  */
                 qe->has_kernel_gs_base = 0;
             }
             cpu_nr++;
         }
     }
 
     printf("%zu CPU states has been found\n", cpu_nr);
 
     qe->state = malloc(sizeof(*qe->state) * cpu_nr);
     if (!qe->state) {
         return 1;
     }
 
     cpu_nr = 0;
 
     for (nhdr = start; nhdr < end; nhdr = nhdr_get_next(nhdr)) {
         if (!strcmp(nhdr_get_name(nhdr), QEMU_NOTE_NAME)) {
             qe->state[cpu_nr] = nhdr_get_desc(nhdr);
             cpu_nr++;
         }
     }
 
     qe->state_nr = cpu_nr;
 
     return 0;
 }
 
 static void exit_states(QEMU_Elf *qe)
 {
     free(qe->state);
 }
 
 static bool check_ehdr(QEMU_Elf *qe)
 {
     Elf64_Ehdr *ehdr = qe->map;
 
     if (sizeof(Elf64_Ehdr) > qe->size) {
         eprintf("Invalid input dump file size\n");
         return false;
     }
 
     if (memcmp(ehdr->e_ident, ELFMAG, SELFMAG)) {
         eprintf("Invalid ELF signature, input file is not ELF\n");
         return false;
     }
 
     if (ehdr->e_ident[EI_CLASS] != ELFCLASS64 ||
             ehdr->e_ident[EI_DATA] != ELFDATA2LSB) {
         eprintf("Invalid ELF class or byte order, must be 64-bit LE\n");
         return false;
     }
 
     if (ehdr->e_ident[EI_VERSION] != EV_CURRENT) {
         eprintf("Invalid ELF version\n");
         return false;
     }
 
     if (ehdr->e_machine != EM_X86_64) {
         eprintf("Invalid input dump architecture, only x86_64 is supported\n");
         return false;
     }
 
     if (ehdr->e_type != ET_CORE) {
         eprintf("Invalid ELF type, must be core file\n");
         return false;
     }
 
     /*
      * ELF dump file must contain one PT_NOTE and at least one PT_LOAD to
      * restore physical address space.
      */
     if (ehdr->e_phnum < 2) {
         eprintf("Invalid number of ELF program headers\n");
         return false;
     }
 
     return true;
 }
 
 int QEMU_Elf_init(QEMU_Elf *qe, const char *filename)
 {
     GError *gerr = NULL;
     int err = 0;
 
     qe->gmf = g_mapped_file_new(filename, TRUE, &gerr);
     if (gerr) {
         eprintf("Failed to map ELF dump file \'%s\'\n", filename);
         g_error_free(gerr);
         return 1;
     }
 
     qe->map = g_mapped_file_get_contents(qe->gmf);
     qe->size = g_mapped_file_get_length(qe->gmf);
 
     if (!check_ehdr(qe)) {
         eprintf("Input file has the wrong format\n");
         err = 1;
         goto out_unmap;
     }
 
     if (init_states(qe)) {
         eprintf("Failed to extract QEMU CPU states\n");
         err = 1;
         goto out_unmap;
     }
 
     return 0;
 
 out_unmap:
     g_mapped_file_unref(qe->gmf);
 
     return err;
 }
 
 void QEMU_Elf_exit(QEMU_Elf *qe)
 {
     exit_states(qe);
     g_mapped_file_unref(qe->gmf);
 }