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-rw-r--r--hw/arm/boot.c18
1 files changed, 18 insertions, 0 deletions
diff --git a/hw/arm/boot.c b/hw/arm/boot.c
index 20c71d7d96..586baa9b64 100644
--- a/hw/arm/boot.c
+++ b/hw/arm/boot.c
@@ -24,6 +24,7 @@
 #include "qemu/config-file.h"
 #include "qemu/option.h"
 #include "exec/address-spaces.h"
+#include "qemu/units.h"
 
 /* Kernel boot protocol is specified in the kernel docs
  * Documentation/arm/Booting and Documentation/arm64/booting.txt
@@ -36,6 +37,8 @@
 #define ARM64_TEXT_OFFSET_OFFSET    8
 #define ARM64_MAGIC_OFFSET          56
 
+#define BOOTLOADER_MAX_SIZE         (4 * KiB)
+
 AddressSpace *arm_boot_address_space(ARMCPU *cpu,
                                      const struct arm_boot_info *info)
 {
@@ -184,6 +187,8 @@ static void write_bootloader(const char *name, hwaddr addr,
         code[i] = tswap32(insn);
     }
 
+    assert((len * sizeof(uint32_t)) < BOOTLOADER_MAX_SIZE);
+
     rom_add_blob_fixed_as(name, code, len * sizeof(uint32_t), addr, as);
 
     g_free(code);
@@ -919,6 +924,19 @@ static uint64_t load_aarch64_image(const char *filename, hwaddr mem_base,
         memcpy(&hdrvals, buffer + ARM64_TEXT_OFFSET_OFFSET, sizeof(hdrvals));
         if (hdrvals[1] != 0) {
             kernel_load_offset = le64_to_cpu(hdrvals[0]);
+
+            /*
+             * We write our startup "bootloader" at the very bottom of RAM,
+             * so that bit can't be used for the image. Luckily the Image
+             * format specification is that the image requests only an offset
+             * from a 2MB boundary, not an absolute load address. So if the
+             * image requests an offset that might mean it overlaps with the
+             * bootloader, we can just load it starting at 2MB+offset rather
+             * than 0MB + offset.
+             */
+            if (kernel_load_offset < BOOTLOADER_MAX_SIZE) {
+                kernel_load_offset += 2 * MiB;
+            }
         }
     }