[Qemu-devel] [PATCH v5 10/11] hw/arm: pass pristine kernel image to guest firmware over fw_cfg

[Laszlo Ersek]

Introduce the new boolean field "arm_boot_info.firmware_loaded". When this
field is set, it means that the portion of guest DRAM that the VCPU
normally starts to execute, or the pflash chip that the VCPU normally
starts to execute, has been populated by board-specific code with
full-fledged guest firmware code, before the board calls
arm_load_kernel().

Simultaneously, "arm_boot_info.firmware_loaded" guarantees that the board
code has set up the global firmware config instance, for arm_load_kernel()
to find with fw_cfg_find().

Guest kernel (-kernel) and guest firmware (-bios, -pflash) has always been
possible to specify independently on the command line. The following cases
should be considered:

nr  -bios    -pflash  -kernel  description
             unit#0
--  -------  -------  -------  -------------------------------------------
1   present  present  absent   Board code rejects this case, -bios and
    present  present  present  -pflash unit#0 are exclusive. Left intact
                               by this patch.

2   absent   absent   present  Traditional kernel loading, with qemu's
                               minimal board firmware. Left intact by this
                               patch.

3   absent   present  absent   Preexistent case for booting guest firmware
    present  absent   absent   loaded with -bios or -pflash. Left intact
                               by this patch.

4   absent   absent   absent   Preexistent case for not loading any
                               firmware or kernel up-front. Left intact by
                               this patch.

5   present  absent   present  New case introduced by this patch: kernel
    absent   present  present  image is passed to externally loaded
                               firmware in unmodified form, using fw_cfg.

An easy way to see that this patch doesn't interfere with existing cases
is to realize that "info->firmware_loaded" is constant zero at this point.
Which makes the "outer" condition unchanged, and the "inner" condition
(with the fw_cfg-related code) dead.

Signed-off-by: Laszlo Ersek <address@hidden>
---

Notes:
    v5:
    - load_image_to_fw_cfg(): fall back to plaintext loading if gunzipping
      fails [Alex]
    - not a trivial change, dropping Peter's R-b
    
    v4:
    - drop space "between function name and open parenthesis '('" [Peter]
    
    v3:
    - unchanged

 include/hw/arm/arm.h |  5 +++
 hw/arm/boot.c        | 88 +++++++++++++++++++++++++++++++++++++++++++++++++---
 2 files changed, 88 insertions(+), 5 deletions(-)

diff --git a/include/hw/arm/arm.h b/include/hw/arm/arm.h
index cefc9e6..dd69d66 100644
--- a/include/hw/arm/arm.h
+++ b/include/hw/arm/arm.h
@@ -65,8 +65,13 @@ struct arm_boot_info {
     int is_linux;
     hwaddr initrd_start;
     hwaddr initrd_size;
     hwaddr entry;
+
+    /* Boot firmware has been loaded, typically at address 0, with -bios or
+     * -pflash. It also implies that fw_cfg_find() will succeed.
+     */
+    bool firmware_loaded;
 };
 void arm_load_kernel(ARMCPU *cpu, struct arm_boot_info *info);
 
 /* Multiplication factor to convert from system clock ticks to qemu timer
diff --git a/hw/arm/boot.c b/hw/arm/boot.c
index e6a3c5b..17bdaee 100644
--- a/hw/arm/boot.c
+++ b/hw/arm/boot.c
@@ -477,8 +477,57 @@ static void do_cpu_reset(void *opaque)
         }
     }
 }
 
+/**
+ * load_image_to_fw_cfg() - Load an image file into an fw_cfg entry identified
+ *                          by key.
+ * @fw_cfg:         The firmware config instance to store the data in.
+ * @size_key:       The firmware config key to store the size of the loaded
+ *                  data under, with fw_cfg_add_i32().
+ * @data_key:       The firmware config key to store the loaded data under,
+ *                  with fw_cfg_add_bytes().
+ * @image_name:     The name of the image file to load. If it is NULL, the
+ *                  function returns without doing anything.
+ * @try_decompress: Whether the image should be decompressed (gunzipped) before
+ *                  adding it to fw_cfg. If decompression fails, the image is
+ *                  loaded as-is.
+ *
+ * In case of failure, the function prints an error message to stderr and the
+ * process exits with status 1.
+ */
+static void load_image_to_fw_cfg(FWCfgState *fw_cfg, uint16_t size_key,
+                                 uint16_t data_key, const char *image_name,
+                                 bool try_decompress)
+{
+    size_t size = -1;
+    uint8_t *data;
+
+    if (image_name == NULL) {
+        return;
+    }
+
+    if (try_decompress) {
+        size = load_image_gzipped_buffer(image_name,
+                                         LOAD_IMAGE_MAX_GUNZIP_BYTES, &data);
+    }
+
+    if (size == (size_t)-1) {
+        gchar *contents;
+        gsize length;
+
+        if (!g_file_get_contents(image_name, &contents, &length, NULL)) {
+            fprintf(stderr, "failed to load \"%s\"\n", image_name);
+            exit(1);
+        }
+        size = length;
+        data = (uint8_t *)contents;
+    }
+
+    fw_cfg_add_i32(fw_cfg, size_key, size);
+    fw_cfg_add_bytes(fw_cfg, data_key, data, size);
+}
+
 void arm_load_kernel(ARMCPU *cpu, struct arm_boot_info *info)
 {
     CPUState *cs;
     int kernel_size;
@@ -499,21 +548,50 @@ void arm_load_kernel(ARMCPU *cpu, struct arm_boot_info 
*info)
         qemu_register_reset(do_cpu_reset, ARM_CPU(cs));
     }
 
     /* Load the kernel.  */
-    if (!info->kernel_filename) {
+    if (!info->kernel_filename || info->firmware_loaded) {
 
         if (have_dtb(info)) {
-            /* If we have a device tree blob, but no kernel to supply it to,
-             * copy it to the base of RAM for a bootloader to pick up.
+            /* If we have a device tree blob, but no kernel to supply it to (or
+             * the kernel is supposed to be loaded by the bootloader), copy the
+             * DTB to the base of RAM for the bootloader to pick up.
              */
             if (load_dtb(info->loader_start, info, 0) < 0) {
                 exit(1);
             }
         }
 
-        /* If no kernel specified, do nothing; we will start from address 0
-         * (typically a boot ROM image) in the same way as hardware.
+        if (info->kernel_filename) {
+            FWCfgState *fw_cfg;
+            bool try_decompressing_kernel;
+
+            fw_cfg = fw_cfg_find();
+            try_decompressing_kernel = arm_feature(&cpu->env,
+                                                   ARM_FEATURE_AARCH64);
+
+            /* Expose the kernel, the command line, and the initrd in fw_cfg.
+             * We don't process them here at all, it's all left to the
+             * firmware.
+             */
+            load_image_to_fw_cfg(fw_cfg,
+                                 FW_CFG_KERNEL_SIZE, FW_CFG_KERNEL_DATA,
+                                 info->kernel_filename,
+                                 try_decompressing_kernel);
+            load_image_to_fw_cfg(fw_cfg,
+                                 FW_CFG_INITRD_SIZE, FW_CFG_INITRD_DATA,
+                                 info->initrd_filename, false);
+
+            if (info->kernel_cmdline) {
+                fw_cfg_add_i32(fw_cfg, FW_CFG_CMDLINE_SIZE,
+                               strlen(info->kernel_cmdline) + 1);
+                fw_cfg_add_string(fw_cfg, FW_CFG_CMDLINE_DATA,
+                                  info->kernel_cmdline);
+            }
+        }
+
+        /* We will start from address 0 (typically a boot ROM image) in the
+         * same way as hardware.
          */
         return;
     }
 
-- 
1.8.3.1