powerpc/fadump: Fix endianess issues in firmware assisted dump handling

Firmware-assisted dump (fadump) kernel code is not endian safe. The
below patch fixes this issue. Tested this patch with upstream kernel.
Below output shows crash tool successfully opening LE fadump vmcore.

    # crash vmlinux vmcore
    GNU gdb (GDB) 7.6
    This GDB was configured as "powerpc64le-unknown-linux-gnu"...

          KERNEL: vmlinux
        DUMPFILE: vmcore
    	CPUS: 16
    	DATE: Wed Dec 31 19:00:00 1969
          UPTIME: 00:03:28
    LOAD AVERAGE: 0.46, 0.86, 0.41
           TASKS: 268
        NODENAME: linux-dhr2
         RELEASE: 3.17.0-rc5-7-default
         VERSION: #6 SMP Tue Sep 30 01:06:34 EDT 2014
         MACHINE: ppc64le  (4116 Mhz)
          MEMORY: 40 GB
           PANIC: "Oops: Kernel access of bad area, sig: 11 [#1]" (check log for details)
    	 PID: 6223
         COMMAND: "bash"
    	TASK: c0000009661b2500  [THREAD_INFO: c000000967ac0000]
    	 CPU: 2
           STATE: TASK_RUNNING (PANIC)
Signed-off-by: Hari Bathini <hbathini@linux.vnet.ibm.com>
[mpe: Make the comment in pSeries_lpar_hptab_clear() clearer]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/fadump.h

@@ -70,39 +70,39 @@
 #define CPU_UNKNOWN		(~((u32)0))
 
 /* Utility macros */
-#define SKIP_TO_NEXT_CPU(reg_entry)			\
-({							\
-	while (reg_entry->reg_id != REG_ID("CPUEND"))	\
-		reg_entry++;				\
-	reg_entry++;					\
+#define SKIP_TO_NEXT_CPU(reg_entry)					\
+({									\
+	while (be64_to_cpu(reg_entry->reg_id) != REG_ID("CPUEND"))	\
+		reg_entry++;						\
+	reg_entry++;							\
 })
 
 /* Kernel Dump section info */
 struct fadump_section {
-	u32	request_flag;
-	u16	source_data_type;
-	u16	error_flags;
-	u64	source_address;
-	u64	source_len;
-	u64	bytes_dumped;
-	u64	destination_address;
+	__be32	request_flag;
+	__be16	source_data_type;
+	__be16	error_flags;
+	__be64	source_address;
+	__be64	source_len;
+	__be64	bytes_dumped;
+	__be64	destination_address;
 };
 
 /* ibm,configure-kernel-dump header. */
 struct fadump_section_header {
-	u32	dump_format_version;
-	u16	dump_num_sections;
-	u16	dump_status_flag;
-	u32	offset_first_dump_section;
+	__be32	dump_format_version;
+	__be16	dump_num_sections;
+	__be16	dump_status_flag;
+	__be32	offset_first_dump_section;
 
 	/* Fields for disk dump option. */
-	u32	dd_block_size;
-	u64	dd_block_offset;
-	u64	dd_num_blocks;
-	u32	dd_offset_disk_path;
+	__be32	dd_block_size;
+	__be64	dd_block_offset;
+	__be64	dd_num_blocks;
+	__be32	dd_offset_disk_path;
 
 	/* Maximum time allowed to prevent an automatic dump-reboot. */
-	u32	max_time_auto;
+	__be32	max_time_auto;
 };
 
 /*
@@ -174,15 +174,15 @@ static inline u64 str_to_u64(const char *str)
 
 /* Register save area header. */
 struct fadump_reg_save_area_header {
-	u64		magic_number;
-	u32		version;
-	u32		num_cpu_offset;
+	__be64		magic_number;
+	__be32		version;
+	__be32		num_cpu_offset;
 };
 
 /* Register entry. */
 struct fadump_reg_entry {
-	u64		reg_id;
-	u64		reg_value;
+	__be64		reg_id;
+	__be64		reg_value;
 };
 
 /* fadump crash info structure */

arch/powerpc/platforms/pseries/lpar.c

@@ -43,6 +43,7 @@
 #include <asm/trace.h>
 #include <asm/firmware.h>
 #include <asm/plpar_wrappers.h>
+#include <asm/fadump.h>
 
 #include "pseries.h"
 
@@ -247,8 +248,17 @@ static void pSeries_lpar_hptab_clear(void)
 	}
 
 #ifdef __LITTLE_ENDIAN__
-	/* Reset exceptions to big endian */
-	if (firmware_has_feature(FW_FEATURE_SET_MODE)) {
+	/*
+	 * Reset exceptions to big endian.
+	 *
+	 * FIXME this is a hack for kexec, we need to reset the exception
+	 * endian before starting the new kernel and this is a convenient place
+	 * to do it.
+	 *
+	 * This is also called on boot when a fadump happens. In that case we
+	 * must not change the exception endian mode.
+	 */
+	if (firmware_has_feature(FW_FEATURE_SET_MODE) && !is_fadump_active()) {
 		long rc;
 
 		rc = pseries_big_endian_exceptions();