x86, boot: determine compressed code offset at compile time

Determine the compressed code offset (from the kernel runtime address)
at compile time.  This allows some minor optimizations in
arch/x86/boot/compressed/head_*.S, but more importantly it makes this
value available to the build process, which will enable a future patch
to export the necessary linear memory footprint into the bzImage
header.

[ Impact: cleanup, future patch enabling ]

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

1 files changed, 97 insertions, 0 deletions

diff --git a/arch/x86/boot/compressed/mkpiggy.c b/arch/x86/boot/compressed/mkpiggy.c
new file mode 100644
index 000000000000..bcbd36c41432
--- /dev/null
+++ b/arch/x86/boot/compressed/mkpiggy.c
@@ -0,0 +1,97 @@
+/* ----------------------------------------------------------------------- *
+ *
+ *  Copyright (C) 2009 Intel Corporation. All rights reserved.
+ *
+ *  This program is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU General Public License version
+ *  2 as published by the Free Software Foundation.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ *  02110-1301, USA.
+ *
+ *  H. Peter Anvin <hpa@linux.intel.com>
+ *
+ * ----------------------------------------------------------------------- */
+
+/*
+ * Compute the desired load offset from a compressed program; outputs
+ * a small assembly wrapper with the appropriate symbols defined.
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <inttypes.h>
+
+static uint32_t getle32(const void *p)
+{
+	const uint8_t *cp = p;
+
+	return (uint32_t)cp[0] + ((uint32_t)cp[1] << 8) +
+		((uint32_t)cp[2] << 16) + ((uint32_t)cp[3] << 24);
+}
+
+int main(int argc, char *argv[])
+{
+	uint32_t olen;
+	long ilen;
+	unsigned long offs;
+	FILE *f;
+
+	if (argc < 2) {
+		fprintf(stderr, "Usage: %s compressed_file\n", argv[0]);
+		return 1;
+	}
+
+	/* Get the information for the compressed kernel image first */
+
+	f = fopen(argv[1], "r");
+	if (!f) {
+		perror(argv[1]);
+		return 1;
+	}
+
+
+	if (fseek(f, -4L, SEEK_END)) {
+		perror(argv[1]);
+	}
+	fread(&olen, sizeof olen, 1, f);
+	ilen = ftell(f);
+	olen = getle32(&olen);
+	fclose(f);
+
+	/*
+	 * Now we have the input (compressed) and output (uncompressed)
+	 * sizes, compute the necessary decompression offset...
+	 */
+
+	offs = (olen > ilen) ? olen - ilen : 0;
+	offs += olen >> 12;	/* Add 8 bytes for each 32K block */
+	offs += 32*1024 + 18;	/* Add 32K + 18 bytes slack */
+	offs = (offs+4095) & ~4095; /* Round to a 4K boundary */
+
+	printf(".section \".rodata.compressed\",\"a\",@progbits\n");
+	printf(".globl z_input_len\n");
+	printf("z_input_len = %lu\n", ilen);
+	printf(".globl z_output_len\n");
+	printf("z_output_len = %lu\n", (unsigned long)olen);
+	printf(".globl z_extract_offset\n");
+	printf("z_extract_offset = 0x%lx\n", offs);
+	/* z_extract_offset_negative allows simplification of head_32.S */
+	printf(".globl z_extract_offset_negative\n");
+	printf("z_extract_offset_negative = -0x%lx\n", offs);
+
+	printf(".globl input_data, input_data_end\n");
+	printf("input_data:\n");
+	printf(".incbin \"%s\"\n", argv[1]);
+	printf("input_data_end:\n");
+
+	return 0;
+}