liminix

commit c5c5f1687a14a44b59483727d7332c3c29a198fe
parent 80793aa694ec812acdb1c69ee89c2951bb0f0bd4
Author: Daniel Barlow <dan@telent.net>
Date:   Thu,  2 Nov 2023 13:43:24 +0000

patch qemu to load uncompressed ARM kernels at correct offset

Diffstat:
M
overlay.nix
 | 
7
+++++++
A
pkgs/qemu/arm-image-friendly-load-addr.patch
 | 
31
+++++++++++++++++++++++++++++++

2 files changed, 38 insertions(+), 0 deletions(-)
diff --git a/overlay.nix b/overlay.nix
@@ -183,5 +183,12 @@ extraPkgs // {
           "\nsed -i.bak 's/linux.*-mips/linux-mops/' Configure\n");
   });
 
+  qemu = prev.qemu.overrideAttrs (o: {
+    patches = o.patches ++ [
+      ./pkgs/qemu/arm-image-friendly-load-addr.patch
+
+    ];
+  });
+
   pppBuild = prev.ppp;
 }
diff --git a/pkgs/qemu/arm-image-friendly-load-addr.patch b/pkgs/qemu/arm-image-friendly-load-addr.patch
@@ -0,0 +1,31 @@
+Loading kernel at offset 0x10000 works only for zImage, but not for Image,
+because the kernel expect the start of decompressed kernel (.head.text) to be
+at an address that's a distance that's 16MB aligned from  PAGE_OFFSET +
+TEXT_OFFSET (see vmlinux.lds.S). This check is enfornced in __fixup_pv_table in
+arch/arm/kernel/head.S TEXT_OFFSET is 0x00008000, so a 16MB alignment needs to
+have a "0x8000" in the lower 16 bits so that they cancel out. Currently the
+offset Qemu loads it at is 0x10000.
+
+With zImage, this need is met because zImage loads the uncompressed Image
+correctly, however when loading an Image and executing directly Qemu is
+required it to load it at the correct location. Doing so, doesn't break Qemu's
+zImage loading. With this patch, both zImage and Image work correctly.
+
+Original patch from https://patchwork.kernel.org/project/linux-arm-kernel/patch/1395718484-20424-1-git-send-email-joelf@ti.com/ was
+Signed-off-by: Joel Fernandes <joelf@ti.com>
+
+(Edited by Daniel Barlow to apply cleanly to more recent QEMU)
+
+diff --git a/hw/arm/boot.c b/hw/arm/boot.c
+index ada2717f76..18bcdd45d2 100644
+--- a/hw/arm/boot.c
++++ b/hw/arm/boot.c
+@@ -32,7 +32,7 @@
+  */
+ #define KERNEL_ARGS_ADDR   0x100
+ #define KERNEL_NOLOAD_ADDR 0x02000000
+-#define KERNEL_LOAD_ADDR   0x00010000
++#define KERNEL_LOAD_ADDR   0x00008000
+ #define KERNEL64_LOAD_ADDR 0x00080000
+ 
+ #define ARM64_TEXT_OFFSET_OFFSET    8