[mips*/octeon] Add support for byte swapped initramfs to handle u-boot and kernel running with a different endianness.

debian/changelog

@@ -84,6 +84,8 @@ linux (4.5.4-1) UNRELEASED; urgency=medium
   * [mips*] Fix PR_SET_FPMODE issues with multi-threaded programs.
   * [i386] Stop recommending libc6-i686.
   * [arm,x86] Fix memory corruption in KVM with THP enabled.
+  * [mips*/octeon] Add support for byte swapped initramfs to handle u-boot and
+    kernel running with a different endianness.
 
   [ Roger Shimizu ]
   * netfilter: Enable NF_DUP_NETDEV / NFT_DUP_NETDEV / NFT_FWD_NETDEV

debian/patches/features/mips/MIPS-Octeon-detect-and-fix-byte-swapped-initramfs.patch

@@ -0,0 +1,83 @@
+From: Aurelien Jarno <aurelien@aurel32.net>
+Date: Wed, 11 May 2016 00:37:42 +0200
+Subject: MIPS: Octeon: detect and fix byte swapped initramfs
+Origin: https://patchwork.linux-mips.org/patch/13219/
+
+Octeon machines support running in little endian mode. U-Boot usually
+runs in big endian-mode. Therefore the initramfs is loaded in big endian
+mode, and the kernel later tries to access it in little endian mode.
+
+This patch fixes that by detecting byte swapped initramfs using either the
+CPIO header or the header from standard compression methods, and
+byte swaps it if needed. It first checks that the header doesn't match
+in the native endianness to avoid false detections. It uses the kernel
+decompress library so that we don't have to maintain the list of magics
+if some decompression methods are added to the kernel.
+
+Cc: Ralf Baechle <ralf@linux-mips.org>
+Acked-by: David Daney <david.daney@cavium.com>
+Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
+---
+ arch/mips/kernel/setup.c | 32 ++++++++++++++++++++++++++++++++
+ 1 file changed, 32 insertions(+)
+
+diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
+index 4f60734..8841d7982 100644
+--- a/arch/mips/kernel/setup.c
++++ b/arch/mips/kernel/setup.c
+@@ -26,6 +26,7 @@
+ #include <linux/sizes.h>
+ #include <linux/device.h>
+ #include <linux/dma-contiguous.h>
++#include <linux/decompress/generic.h>
+ 
+ #include <asm/addrspace.h>
+ #include <asm/bootinfo.h>
+@@ -250,6 +251,35 @@ disable:
+ 	return 0;
+ }
+ 
++/* In some conditions (e.g. big endian bootloader with a little endian
++   kernel), the initrd might appear byte swapped.  Try to detect this and
++   byte swap it if needed.  */
++static void __init maybe_bswap_initrd(void)
++{
++#if defined(CONFIG_CPU_CAVIUM_OCTEON)
++	u64 buf;
++
++	/* Check for CPIO signature */
++	if (!memcmp((void *)initrd_start, "070701", 6))
++		return;
++
++	/* Check for compressed initrd */
++	if (decompress_method((unsigned char *)initrd_start, 8, NULL))
++		return;
++
++	/* Try again with a byte swapped header */
++	buf = swab64p((u64 *)initrd_start);
++	if (!memcmp(&buf, "070701", 6) ||
++	    decompress_method((unsigned char *)(&buf), 8, NULL)) {
++		unsigned long i;
++
++		pr_info("Byteswapped initrd detected\n");
++		for (i = initrd_start; i < ALIGN(initrd_end, 8); i += 8)
++			swab64s((u64 *)i);
++	}
++#endif
++}
++
+ static void __init finalize_initrd(void)
+ {
+ 	unsigned long size = initrd_end - initrd_start;
+@@ -263,6 +293,8 @@ static void __init finalize_initrd(void)
+ 		goto disable;
+ 	}
+ 
++	maybe_bswap_initrd();
++
+ 	reserve_bootmem(__pa(initrd_start), size, BOOTMEM_DEFAULT);
+ 	initrd_below_start_ok = 1;
+ 
+-- 
+2.8.1
+

debian/patches/series

@@ -61,6 +61,7 @@ features/mips/MIPS-Loongson-3-Add-Loongson-LS3A-RS780E-1-way-machi.patch
 features/mips/MIPS-octeon-Add-support-for-the-UBNT-E200-board.patch
 features/mips/libata-support-AHCI-on-OCTEON-platform.patch
 features/mips/MIPS-Octeon-Add-Octeon-III-CN7xxx-interface-detection.patch
+features/mips/MIPS-Octeon-detect-and-fix-byte-swapped-initramfs.patch
 features/x86/x86-memtest-WARN-if-bad-RAM-found.patch
 features/x86/x86-make-x32-syscall-support-conditional.patch
 features/sparc/hwrng-n2-attach-on-t5-m5-t7-m7-sparc-cpus.patch