[Qemu-devel] [PATCH] hw/arm/boot: get AArch64 kernel Image load offset from Image file

[Rob Herring]

From: Rob Herring <address@hidden>

The AArch64 kermel Image format defines the load offset in its header.
Retrieve the offset from the file instead of hardcoding it to 0x80000.

Use of the hardcoded value will break when text_offset randomization is
added to the kernel.

Signed-off-by: Rob Herring <address@hidden>
---
 hw/arm/boot.c | 32 ++++++++++++++++++++++++++++++--
 1 file changed, 30 insertions(+), 2 deletions(-)

diff --git a/hw/arm/boot.c b/hw/arm/boot.c
index 3d1f4a2..4adce9e 100644
--- a/hw/arm/boot.c
+++ b/hw/arm/boot.c
@@ -24,7 +24,14 @@
  */
 #define KERNEL_ARGS_ADDR 0x100
 #define KERNEL_LOAD_ADDR 0x00010000
-#define KERNEL64_LOAD_ADDR 0x00080000
+
+typedef struct {
+    uint32_t code[2];
+    uint64_t text_offset;
+    uint64_t res[5];
+    uint32_t magic;
+    uint32_t res5;
+} aarch64_image_header_t;
 
 typedef enum {
     FIXUP_NONE = 0,   /* do nothing */
@@ -441,6 +448,26 @@ static void do_cpu_reset(void *opaque)
     }
 }
 
+static hwaddr aarch64_get_image_offset(const char *filename)
+{
+    int fd, size;
+    aarch64_image_header_t hdr;
+
+    fd = open(filename, O_RDONLY | O_BINARY);
+    if (fd < 0) {
+        return 0;
+    }
+
+    size = read(fd, &hdr, sizeof(hdr));
+    close(fd);
+
+    if (size < sizeof(aarch64_image_header_t) ||
+        le32_to_cpu(hdr.magic) != 0x644d5241) {
+        return 0;
+    }
+    return le32_to_cpu(hdr.text_offset);
+}
+
 void arm_load_kernel(ARMCPU *cpu, struct arm_boot_info *info)
 {
     CPUState *cs = CPU(cpu);
@@ -463,7 +490,7 @@ void arm_load_kernel(ARMCPU *cpu, struct arm_boot_info 
*info)
 
     if (arm_feature(&cpu->env, ARM_FEATURE_AARCH64)) {
         primary_loader = bootloader_aarch64;
-        kernel_load_offset = KERNEL64_LOAD_ADDR;
+        kernel_load_offset = aarch64_get_image_offset(info->kernel_filename);
         elf_machine = EM_AARCH64;
     } else {
         primary_loader = bootloader;
@@ -505,6 +532,7 @@ void arm_load_kernel(ARMCPU *cpu, struct arm_boot_info 
*info)
     /* Assume that raw images are linux kernels, and ELF images are not.  */
     kernel_size = load_elf(info->kernel_filename, NULL, NULL, &elf_entry,
                            NULL, NULL, big_endian, elf_machine, 1);
+
     entry = elf_entry;
     if (kernel_size < 0) {
         kernel_size = load_uimage(info->kernel_filename, &entry, NULL,
-- 
1.9.1