Re: [PATCH v4] m68k: write bootinfo as rom section and re-randomize on reboot

Laurent Vivier Fri, 21 Oct 2022 15:35:27 -0700

Le 17/10/2022 à 22:29, Jason A. Donenfeld a écrit :

Rather than poking directly into RAM, add the bootinfo block as a proper
ROM, so that it's restored when rebooting the system. This way, if the
guest corrupts any of the bootinfo items, but then tries to reboot,
it'll still be restored back to normal as expected.


Then, since the RNG seed needs to be fresh on each boot, regenerate the
RNG seed in the ROM when reseting the CPU.

Cc: Geert Uytterhoeven <ge...@linux-m68k.org>
Cc: Laurent Vivier <laur...@vivier.eu>
Signed-off-by: Jason A. Donenfeld <ja...@zx2c4.com>
---
  hw/m68k/bootinfo.h | 48 +++++++++++++++----------------
  hw/m68k/q800.c     | 71 +++++++++++++++++++++++++++++++++-------------
  hw/m68k/virt.c     | 51 +++++++++++++++++++++++----------
  3 files changed, 111 insertions(+), 59 deletions(-)


Notes:
- don't send your patch as a reply to a previous version
- add an history:

v4: replace  (void *)(((unsigned long)base + 3) & ~3) by
             (void *)(((uintptr_t)base + 3) & ~3);

Reviewed-by: Laurent Vivier <laur...@vivier.eu>

Thanks,
Laurent

diff --git a/hw/m68k/bootinfo.h b/hw/m68k/bootinfo.h
index 897162b818..67e6b66b7d 100644
--- a/hw/m68k/bootinfo.h
+++ b/hw/m68k/bootinfo.h
@@ -12,66 +12,66 @@
  #ifndef HW_M68K_BOOTINFO_H
  #define HW_M68K_BOOTINFO_H

-#define BOOTINFO0(as, base, id) \

+#define BOOTINFO0(base, id) \
      do { \
-        stw_phys(as, base, id); \
+        stw_p(base, id); \
          base += 2; \
-        stw_phys(as, base, sizeof(struct bi_record)); \
+        stw_p(base, sizeof(struct bi_record)); \
          base += 2; \
      } while (0)

-#define BOOTINFO1(as, base, id, value) \

+#define BOOTINFO1(base, id, value) \
      do { \
-        stw_phys(as, base, id); \
+        stw_p(base, id); \
          base += 2; \
-        stw_phys(as, base, sizeof(struct bi_record) + 4); \
+        stw_p(base, sizeof(struct bi_record) + 4); \
          base += 2; \
-        stl_phys(as, base, value); \
+        stl_p(base, value); \
          base += 4; \
      } while (0)

-#define BOOTINFO2(as, base, id, value1, value2) \

+#define BOOTINFO2(base, id, value1, value2) \
      do { \
-        stw_phys(as, base, id); \
+        stw_p(base, id); \
          base += 2; \
-        stw_phys(as, base, sizeof(struct bi_record) + 8); \
+        stw_p(base, sizeof(struct bi_record) + 8); \
          base += 2; \
-        stl_phys(as, base, value1); \
+        stl_p(base, value1); \
          base += 4; \
-        stl_phys(as, base, value2); \
+        stl_p(base, value2); \
          base += 4; \
      } while (0)

-#define BOOTINFOSTR(as, base, id, string) \

+#define BOOTINFOSTR(base, id, string) \
      do { \
          int i; \
-        stw_phys(as, base, id); \
+        stw_p(base, id); \
          base += 2; \
-        stw_phys(as, base, \
+        stw_p(base, \
                   (sizeof(struct bi_record) + strlen(string) + \
                    1 /* null termination */ + 3 /* padding */) & ~3); \
          base += 2; \
          for (i = 0; string[i]; i++) { \
-            stb_phys(as, base++, string[i]); \
+            stb_p(base++, string[i]); \
          } \
-        stb_phys(as, base++, 0); \
-        base = (base + 3) & ~3; \
+        stb_p(base++, 0); \
+        base = (void *)(((uintptr_t)base + 3) & ~3); \
      } while (0)

-#define BOOTINFODATA(as, base, id, data, len) \

+#define BOOTINFODATA(base, id, data, len) \
      do { \
          int i; \
-        stw_phys(as, base, id); \
+        stw_p(base, id); \
          base += 2; \
-        stw_phys(as, base, \
+        stw_p(base, \
                   (sizeof(struct bi_record) + len + \
                    2 /* length field */ + 3 /* padding */) & ~3); \
          base += 2; \
-        stw_phys(as, base, len); \
+        stw_p(base, len); \
          base += 2; \
          for (i = 0; i < len; ++i) { \
-            stb_phys(as, base++, data[i]); \
+            stb_p(base++, data[i]); \
          } \
-        base = (base + 3) & ~3; \
+        base = (void *)(((uintptr_t)base + 3) & ~3); \
      } while (0)
  #endif
diff --git a/hw/m68k/q800.c b/hw/m68k/q800.c
index a4590c2cb0..e09e244ddc 100644
--- a/hw/m68k/q800.c
+++ b/hw/m68k/q800.c
@@ -321,11 +321,22 @@ static const TypeInfo glue_info = {
      },
  };

+typedef struct {

+    M68kCPU *cpu;
+    struct bi_record *rng_seed;
+} ResetInfo;
+
  static void main_cpu_reset(void *opaque)
  {
-    M68kCPU *cpu = opaque;
+    ResetInfo *reset_info = opaque;
+    M68kCPU *cpu = reset_info->cpu;
      CPUState *cs = CPU(cpu);

+ if (reset_info->rng_seed) {

+        qemu_guest_getrandom_nofail((void *)reset_info->rng_seed->data + 2,
+            be16_to_cpu(*(uint16_t *)reset_info->rng_seed->data));
+    }
+
      cpu_reset(cs);
      cpu->env.aregs[7] = ldl_phys(cs->as, 0);
      cpu->env.pc = ldl_phys(cs->as, 4);
@@ -386,6 +397,7 @@ static void q800_init(MachineState *machine)
      NubusBus *nubus;
      DeviceState *glue;
      DriveInfo *dinfo;
+    ResetInfo *reset_info;
      uint8_t rng_seed[32];

linux_boot = (kernel_filename != NULL);

@@ -396,9 +408,12 @@ static void q800_init(MachineState *machine)
          exit(1);
      }

+ reset_info = g_new0(ResetInfo, 1);

+
      /* init CPUs */
      cpu = M68K_CPU(cpu_create(machine->cpu_type));
-    qemu_register_reset(main_cpu_reset, cpu);
+    reset_info->cpu = cpu;
+    qemu_register_reset(main_cpu_reset, reset_info);

/* RAM */

      memory_region_add_subregion(get_system_memory(), 0, machine->ram);
@@ -598,6 +613,14 @@ static void q800_init(MachineState *machine)
      cs = CPU(cpu);
      if (linux_boot) {
          uint64_t high;
+        void *param_blob, *param_ptr, *param_rng_seed;
+
+        if (kernel_cmdline) {
+            param_blob = g_malloc(strlen(kernel_cmdline) + 1024);
+        } else {
+            param_blob = g_malloc(1024);
+        }
+
          kernel_size = load_elf(kernel_filename, NULL, NULL, NULL,
                                 &elf_entry, NULL, &high, NULL, 1,
                                 EM_68K, 0, 0);
@@ -607,23 +630,24 @@ static void q800_init(MachineState *machine)
          }
          stl_phys(cs->as, 4, elf_entry); /* reset initial PC */
          parameters_base = (high + 1) & ~1;
-
-        BOOTINFO1(cs->as, parameters_base, BI_MACHTYPE, MACH_MAC);
-        BOOTINFO1(cs->as, parameters_base, BI_FPUTYPE, FPU_68040);
-        BOOTINFO1(cs->as, parameters_base, BI_MMUTYPE, MMU_68040);
-        BOOTINFO1(cs->as, parameters_base, BI_CPUTYPE, CPU_68040);
-        BOOTINFO1(cs->as, parameters_base, BI_MAC_CPUID, CPUB_68040);
-        BOOTINFO1(cs->as, parameters_base, BI_MAC_MODEL, MAC_MODEL_Q800);
-        BOOTINFO1(cs->as, parameters_base,
+        param_ptr = param_blob;
+
+        BOOTINFO1(param_ptr, BI_MACHTYPE, MACH_MAC);
+        BOOTINFO1(param_ptr, BI_FPUTYPE, FPU_68040);
+        BOOTINFO1(param_ptr, BI_MMUTYPE, MMU_68040);
+        BOOTINFO1(param_ptr, BI_CPUTYPE, CPU_68040);
+        BOOTINFO1(param_ptr, BI_MAC_CPUID, CPUB_68040);
+        BOOTINFO1(param_ptr, BI_MAC_MODEL, MAC_MODEL_Q800);
+        BOOTINFO1(param_ptr,
                    BI_MAC_MEMSIZE, ram_size >> 20); /* in MB */
-        BOOTINFO2(cs->as, parameters_base, BI_MEMCHUNK, 0, ram_size);
-        BOOTINFO1(cs->as, parameters_base, BI_MAC_VADDR,
+        BOOTINFO2(param_ptr, BI_MEMCHUNK, 0, ram_size);
+        BOOTINFO1(param_ptr, BI_MAC_VADDR,
                    VIDEO_BASE + macfb_mode->offset);
-        BOOTINFO1(cs->as, parameters_base, BI_MAC_VDEPTH, graphic_depth);
-        BOOTINFO1(cs->as, parameters_base, BI_MAC_VDIM,
+        BOOTINFO1(param_ptr, BI_MAC_VDEPTH, graphic_depth);
+        BOOTINFO1(param_ptr, BI_MAC_VDIM,
                    (graphic_height << 16) | graphic_width);
-        BOOTINFO1(cs->as, parameters_base, BI_MAC_VROW, macfb_mode->stride);
-        BOOTINFO1(cs->as, parameters_base, BI_MAC_SCCBASE, SCC_BASE);
+        BOOTINFO1(param_ptr, BI_MAC_VROW, macfb_mode->stride);
+        BOOTINFO1(param_ptr, BI_MAC_SCCBASE, SCC_BASE);

rom = g_malloc(sizeof(*rom));

          memory_region_init_ram_ptr(rom, NULL, "m68k_fake_mac.rom",
@@ -632,13 +656,14 @@ static void q800_init(MachineState *machine)
          memory_region_add_subregion(get_system_memory(), MACROM_ADDR, rom);

if (kernel_cmdline) {

-            BOOTINFOSTR(cs->as, parameters_base, BI_COMMAND_LINE,
+            BOOTINFOSTR(param_ptr, BI_COMMAND_LINE,
                          kernel_cmdline);
          }

/* Pass seed to RNG. */

+        param_rng_seed = param_ptr;
          qemu_guest_getrandom_nofail(rng_seed, sizeof(rng_seed));
-        BOOTINFODATA(cs->as, parameters_base, BI_RNG_SEED,
+        BOOTINFODATA(param_ptr, BI_RNG_SEED,
                       rng_seed, sizeof(rng_seed));

/* load initrd */

@@ -653,13 +678,19 @@ static void q800_init(MachineState *machine)
              initrd_base = (ram_size - initrd_size) & TARGET_PAGE_MASK;
              load_image_targphys(initrd_filename, initrd_base,
                                  ram_size - initrd_base);
-            BOOTINFO2(cs->as, parameters_base, BI_RAMDISK, initrd_base,
+            BOOTINFO2(param_ptr, BI_RAMDISK, initrd_base,
                        initrd_size);
          } else {
              initrd_base = 0;
              initrd_size = 0;
          }
-        BOOTINFO0(cs->as, parameters_base, BI_LAST);
+        BOOTINFO0(param_ptr, BI_LAST);
+        rom_add_blob_fixed_as("bootinfo", param_blob, param_ptr - param_blob,
+                              parameters_base, cs->as);
+        reset_info->rng_seed = rom_ptr_for_as(cs->as, parameters_base,
+                                              param_ptr - param_blob) +
+                               (param_rng_seed - param_blob);
+        g_free(param_blob);
      } else {
          uint8_t *ptr;
          /* allocate and load BIOS */
diff --git a/hw/m68k/virt.c b/hw/m68k/virt.c
index f7b903ea1b..89c4108eb5 100644
--- a/hw/m68k/virt.c
+++ b/hw/m68k/virt.c
@@ -89,6 +89,7 @@ typedef struct {
      M68kCPU *cpu;
      hwaddr initial_pc;
      hwaddr initial_stack;
+    struct bi_record *rng_seed;
  } ResetInfo;

static void main_cpu_reset(void *opaque)

@@ -97,6 +98,11 @@ static void main_cpu_reset(void *opaque)
      M68kCPU *cpu = reset_info->cpu;
      CPUState *cs = CPU(cpu);

+ if (reset_info->rng_seed) {

+        qemu_guest_getrandom_nofail((void *)reset_info->rng_seed->data + 2,
+            be16_to_cpu(*(uint16_t *)reset_info->rng_seed->data));
+    }
+
      cpu_reset(cs);
      cpu->env.aregs[7] = reset_info->initial_stack;
      cpu->env.pc = reset_info->initial_pc;
@@ -212,6 +218,13 @@ static void virt_init(MachineState *machine)
      if (kernel_filename) {
          CPUState *cs = CPU(cpu);
          uint64_t high;
+        void *param_blob, *param_ptr, *param_rng_seed;
+
+        if (kernel_cmdline) {
+            param_blob = g_malloc(strlen(kernel_cmdline) + 1024);
+        } else {
+            param_blob = g_malloc(1024);
+        }

kernel_size = load_elf(kernel_filename, NULL, NULL, NULL,

                                 &elf_entry, NULL, &high, NULL, 1,
@@ -222,35 +235,37 @@ static void virt_init(MachineState *machine)
          }
          reset_info->initial_pc = elf_entry;
          parameters_base = (high + 1) & ~1;
+        param_ptr = param_blob;

- BOOTINFO1(cs->as, parameters_base, BI_MACHTYPE, MACH_VIRT);

-        BOOTINFO1(cs->as, parameters_base, BI_FPUTYPE, FPU_68040);
-        BOOTINFO1(cs->as, parameters_base, BI_MMUTYPE, MMU_68040);
-        BOOTINFO1(cs->as, parameters_base, BI_CPUTYPE, CPU_68040);
-        BOOTINFO2(cs->as, parameters_base, BI_MEMCHUNK, 0, ram_size);
+        BOOTINFO1(param_ptr, BI_MACHTYPE, MACH_VIRT);
+        BOOTINFO1(param_ptr, BI_FPUTYPE, FPU_68040);
+        BOOTINFO1(param_ptr, BI_MMUTYPE, MMU_68040);
+        BOOTINFO1(param_ptr, BI_CPUTYPE, CPU_68040);
+        BOOTINFO2(param_ptr, BI_MEMCHUNK, 0, ram_size);

- BOOTINFO1(cs->as, parameters_base, BI_VIRT_QEMU_VERSION,

+        BOOTINFO1(param_ptr, BI_VIRT_QEMU_VERSION,
                    ((QEMU_VERSION_MAJOR << 24) | (QEMU_VERSION_MINOR << 16) |
                     (QEMU_VERSION_MICRO << 8)));
-        BOOTINFO2(cs->as, parameters_base, BI_VIRT_GF_PIC_BASE,
+        BOOTINFO2(param_ptr, BI_VIRT_GF_PIC_BASE,
                    VIRT_GF_PIC_MMIO_BASE, VIRT_GF_PIC_IRQ_BASE);
-        BOOTINFO2(cs->as, parameters_base, BI_VIRT_GF_RTC_BASE,
+        BOOTINFO2(param_ptr, BI_VIRT_GF_RTC_BASE,
                    VIRT_GF_RTC_MMIO_BASE, VIRT_GF_RTC_IRQ_BASE);
-        BOOTINFO2(cs->as, parameters_base, BI_VIRT_GF_TTY_BASE,
+        BOOTINFO2(param_ptr, BI_VIRT_GF_TTY_BASE,
                    VIRT_GF_TTY_MMIO_BASE, VIRT_GF_TTY_IRQ_BASE);
-        BOOTINFO2(cs->as, parameters_base, BI_VIRT_CTRL_BASE,
+        BOOTINFO2(param_ptr, BI_VIRT_CTRL_BASE,
                    VIRT_CTRL_MMIO_BASE, VIRT_CTRL_IRQ_BASE);
-        BOOTINFO2(cs->as, parameters_base, BI_VIRT_VIRTIO_BASE,
+        BOOTINFO2(param_ptr, BI_VIRT_VIRTIO_BASE,
                    VIRT_VIRTIO_MMIO_BASE, VIRT_VIRTIO_IRQ_BASE);

if (kernel_cmdline) {

-            BOOTINFOSTR(cs->as, parameters_base, BI_COMMAND_LINE,
+            BOOTINFOSTR(param_ptr, BI_COMMAND_LINE,
                          kernel_cmdline);
          }

/* Pass seed to RNG. */

+        param_rng_seed = param_ptr;
          qemu_guest_getrandom_nofail(rng_seed, sizeof(rng_seed));
-        BOOTINFODATA(cs->as, parameters_base, BI_RNG_SEED,
+        BOOTINFODATA(param_ptr, BI_RNG_SEED,
                       rng_seed, sizeof(rng_seed));

/* load initrd */

@@ -265,13 +280,19 @@ static void virt_init(MachineState *machine)
              initrd_base = (ram_size - initrd_size) & TARGET_PAGE_MASK;
              load_image_targphys(initrd_filename, initrd_base,
                                  ram_size - initrd_base);
-            BOOTINFO2(cs->as, parameters_base, BI_RAMDISK, initrd_base,
+            BOOTINFO2(param_ptr, BI_RAMDISK, initrd_base,
                        initrd_size);
          } else {
              initrd_base = 0;
              initrd_size = 0;
          }
-        BOOTINFO0(cs->as, parameters_base, BI_LAST);
+        BOOTINFO0(param_ptr, BI_LAST);
+        rom_add_blob_fixed_as("bootinfo", param_blob, param_ptr - param_blob,
+                              parameters_base, cs->as);
+        reset_info->rng_seed = rom_ptr_for_as(cs->as, parameters_base,
+                                              param_ptr - param_blob) +
+                               (param_rng_seed - param_blob);
+        g_free(param_blob);
      }
  }

Re: [PATCH v4] m68k: write bootinfo as rom section and re-randomize on reboot

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