[Crash-utility] [PATCH] crash: execution machine pagesize differs

[Cliff Wickman]

This patch allows a machine to read a dump when that dump was taken on
a machine with a larger page size.
 e.g. we had a dump of a 64k pagesize system, and ran crash on a
      machine with a 16k pagesize.

Diffed against crash-4.0-7.6

Signed-off-by: Cliff Wickman <cpw at sgi.com>

---
 diskdump.c |   25 +++++++++++++++++++------
 tools.c    |    2 ++
 2 files changed, 21 insertions(+), 6 deletions(-)

Index: crash-4.0-7.6.ia64/diskdump.c
===================================================================
--- crash-4.0-7.6.ia64.orig/diskdump.c
+++ crash-4.0-7.6.ia64/diskdump.c
@@ -107,7 +107,7 @@ static int read_dump_header(char *file)
 	struct disk_dump_sub_header *sub_header = NULL;
 	struct kdump_sub_header *sub_header_kdump = NULL;
 	int bitmap_len;
-	const int block_size = (int)sysconf(_SC_PAGESIZE);
+	int block_size = (int)sysconf(_SC_PAGESIZE);
 	off_t offset;
 	const off_t failed = (off_t)-1;
 	ulong pfn;
@@ -165,12 +165,25 @@ static int read_dump_header(char *file)
 	    machine_type_mismatch(file, "PPC64", NULL, 0))
 		goto err;
 
-	if (header->block_size != block_size) {
-		error(INFO, "%s: block size in the dump header does not match"
-	            " with system page size\n",
-			DISKDUMP_VALID() ? "diskdump" : "compressed kdump");
-		goto err;
+	/*
+	 * Up to here, the header was assumed to be one page in size.
+	 * We checked utsname and signature, which are up front in the
+	 * header. But all of the task array may not have been entirely
+	 * read if the executing machines's page size is smaller than that
+	 * of the dumped machine.
+	 * Re-read the entire header if its block_size is bigger than the
+	 * executing machine's page size.
+	 */
+	if (header->block_size > block_size) {
+		block_size = header->block_size;
+		free(header);
+		if ((header = malloc(block_size)) == NULL)
+			error(FATAL,
+	     "diskdump / compressed kdump: cannot malloc block_size buffer\n");
+		lseek(dd->dfd, 0, SEEK_SET);
+		read(dd->dfd, header, block_size);
 	}
+
 	dd->block_size  = block_size;
 	dd->block_shift = ffs(block_size) - 1;