[Qemu-devel] [PATCH v3 0/4] ARM: load_dtb() changes for -bios and ELF images

[Qemu-devel] [PATCH v3 0/4] ARM: load_dtb() changes for -bios and ELF images

[Ard Biesheuvel]

I split off these patches from the series I sent last week. Peter's NOR flash
patch has been merged in the mean time, and the CPU reset patch needs to be
discussed more widely before we can move forward with it.

So what remains are changes in the DTB handling in hw/arm/boot.c, to load a
DTB even when using -bios or using -kernel but with an ELF image.

Changes since v2:
- handle ELF images below base of RAM
- improve comments
- add R-b to #2

Changes since v1:
- updated load_dtb() to take an address limit and return the dtb size, or 0
  if it didn't fit
- don't fail in the ELF case only because the DTB clashes with the ELF segments,
  in that case, just proceed without it
- reshuffled order, added R-b to #1

Ard Biesheuvel (4):
  hw/arm/boot: load DTB as a ROM image
  hw/arm/boot: pass an address limit to and return size from load_dtb()
  hw/arm/boot: load device tree to base of DRAM if no -kernel option was
    passed
  hw/arm/boot: enable DTB support when booting ELF images

 hw/arm/boot.c | 71 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 65 insertions(+), 6 deletions(-)

-- 
1.8.3.2

[Qemu-devel] [PATCH v3 1/4] hw/arm/boot: load DTB as a ROM image

[Ard Biesheuvel]

In order to make the device tree blob (DTB) available in memory not only at
first boot, but also after system reset, use rom_blob_add_fixed() to install
it into memory.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 hw/arm/boot.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/hw/arm/boot.c b/hw/arm/boot.c
index e32f2f415885..50eca931e1a4 100644
--- a/hw/arm/boot.c
+++ b/hw/arm/boot.c
@@ -396,7 +396,10 @@ static int load_dtb(hwaddr addr, const struct arm_boot_info *binfo)
 
     qemu_fdt_dumpdtb(fdt, size);
 
-    cpu_physical_memory_write(addr, fdt, size);
+    /* Put the DTB into the memory map as a ROM image: this will ensure
+     * the DTB is copied again upon reset, even if addr points into RAM.
+     */
+    rom_add_blob_fixed("dtb", fdt, size, addr);
 
     g_free(fdt);
 
-- 
1.8.3.2

[Qemu-devel] [PATCH v3 2/4] hw/arm/boot: pass an address limit to and return size from load_dtb()

[Ard Biesheuvel]

Add an address limit input parameter to load_dtb() so that we can
tell load_dtb() how much memory the dtb is allowed to consume. If
the dtb doesn't fit, return 0, otherwise return the actual size of
the loaded dtb.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 hw/arm/boot.c | 34 +++++++++++++++++++++++++++++++---
 1 file changed, 31 insertions(+), 3 deletions(-)

diff --git a/hw/arm/boot.c b/hw/arm/boot.c
index 50eca931e1a4..2083aeb95d80 100644
--- a/hw/arm/boot.c
+++ b/hw/arm/boot.c
@@ -312,7 +312,26 @@ static void set_kernel_args_old(const struct arm_boot_info *info)
     }
 }
 
-static int load_dtb(hwaddr addr, const struct arm_boot_info *binfo)
+/**
+ * load_dtb() - load a device tree binary image into memory
+ * @addr:       the address to load the image at
+ * @binfo:      struct describing the boot environment
+ * @addr_limit: upper limit of the available memory area at @addr
+ *
+ * Load a device tree supplied by the machine or by the user  with the
+ * '-dtb' command line option, and put it at offset @addr in target
+ * memory.
+ *
+ * If @addr_limit contains a meaningful value (i.e., it is strictly greater
+ * than @addr), the device tree is only loaded if its size does not exceed
+ * the limit.
+ *
+ * Returns: the size of the device tree image on success,
+ *          0 if the image size exceeds the limit,
+ *          -1 on errors.
+ */
+static int load_dtb(hwaddr addr, const struct arm_boot_info *binfo,
+                    hwaddr addr_limit)
 {
     void *fdt = NULL;
     int size, rc;
@@ -341,6 +360,15 @@ static int load_dtb(hwaddr addr, const struct arm_boot_info *binfo)
         }
     }
 
+    if (addr_limit > addr && size > (addr_limit - addr)) {
+        /* Installing the device tree blob at addr would exceed addr_limit.
+         * Whether this constitutes failure is up to the caller to decide,
+         * so just return 0 as size, i.e., no error.
+         */
+        g_free(fdt);
+        return 0;
+    }
+
     acells = qemu_fdt_getprop_cell(fdt, "/", "#address-cells");
     scells = qemu_fdt_getprop_cell(fdt, "/", "#size-cells");
     if (acells == 0 || scells == 0) {
@@ -403,7 +431,7 @@ static int load_dtb(hwaddr addr, const struct arm_boot_info *binfo)
 
     g_free(fdt);
 
-    return 0;
+    return size;
 
 fail:
     g_free(fdt);
@@ -572,7 +600,7 @@ void arm_load_kernel(ARMCPU *cpu, struct arm_boot_info *info)
              */
             hwaddr dtb_start = QEMU_ALIGN_UP(info->initrd_start + initrd_size,
                                              4096);
-            if (load_dtb(dtb_start, info)) {
+            if (load_dtb(dtb_start, info, 0) < 0) {
                 exit(1);
             }
             fixupcontext[FIXUP_ARGPTR] = dtb_start;
-- 
1.8.3.2

[Qemu-devel] [PATCH v3 3/4] hw/arm/boot: load device tree to base of DRAM if no -kernel option was passed

[Ard Biesheuvel]

If we are running the 'virt' machine, we may have a device tree blob but no
kernel to supply it to if no -kernel option was passed. In that case, copy it
to the base of RAM where it can be picked up by a bootloader.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 hw/arm/boot.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/hw/arm/boot.c b/hw/arm/boot.c
index 2083aeb95d80..1bed02db6fdd 100644
--- a/hw/arm/boot.c
+++ b/hw/arm/boot.c
@@ -490,6 +490,16 @@ void arm_load_kernel(ARMCPU *cpu, struct arm_boot_info *info)
 
     /* Load the kernel.  */
     if (!info->kernel_filename) {
+
+        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 (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.
          */
-- 
1.8.3.2

[Qemu-devel] [PATCH v3 4/4] hw/arm/boot: enable DTB support when booting ELF images

[Ard Biesheuvel]

Add support for loading DTB images when booting ELF images using
-kernel. If there are no conflicts with the placement of the ELF
segments, the DTB image is loaded at the base of RAM.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 hw/arm/boot.c | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/hw/arm/boot.c b/hw/arm/boot.c
index 1bed02db6fdd..c8dc34f0865b 100644
--- a/hw/arm/boot.c
+++ b/hw/arm/boot.c
@@ -482,7 +482,7 @@ void arm_load_kernel(ARMCPU *cpu, struct arm_boot_info *info)
     int kernel_size;
     int initrd_size;
     int is_linux = 0;
-    uint64_t elf_entry;
+    uint64_t elf_entry, elf_low_addr, elf_high_addr;
     int elf_machine;
     hwaddr entry, kernel_load_offset;
     int big_endian;
@@ -549,7 +549,25 @@ 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);
+                           &elf_low_addr, &elf_high_addr, big_endian,
+                           elf_machine, 1);
+    if (kernel_size > 0 && have_dtb(info)) {
+        /* If there is still some room left at the base of RAM, try and put
+         * the DTB there like we do for images loaded with -bios or -pflash.
+         */
+        if (elf_low_addr > info->loader_start
+            || elf_high_addr < info->loader_start) {
+            /* Pass elf_low_addr as address limit to load_dtb if it may be
+             * pointing into RAM, otherwise pass '0' (no limit)
+             */
+            if (elf_low_addr < info->loader_start) {
+                elf_low_addr = 0;
+            }
+            if (load_dtb(info->loader_start, info, elf_low_addr) < 0) {
+                exit(1);
+            }
+        }
+    }
     entry = elf_entry;
     if (kernel_size < 0) {
         kernel_size = load_uimage(info->kernel_filename, &entry, NULL,
-- 
1.8.3.2