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>

arch/x86/boot/compressed/Makefile

@@ -19,6 +19,8 @@ KBUILD_AFLAGS  := $(KBUILD_CFLAGS) -D__ASSEMBLY__
 LDFLAGS := -m elf_$(UTS_MACHINE)
 LDFLAGS_vmlinux := -T
 
+hostprogs-y	:= mkpiggy
+
 $(obj)/vmlinux: $(obj)/vmlinux.lds $(obj)/head_$(BITS).o $(obj)/misc.o $(obj)/piggy.o FORCE
 	$(call if_changed,ld)
 	@:
@@ -50,6 +52,9 @@ suffix-$(CONFIG_KERNEL_GZIP)	:= gz
 suffix-$(CONFIG_KERNEL_BZIP2)	:= bz2
 suffix-$(CONFIG_KERNEL_LZMA)	:= lzma
 
-LDFLAGS_piggy.o := -r --format binary --oformat $(CONFIG_OUTPUT_FORMAT) -T
-$(obj)/piggy.o: $(obj)/vmlinux.scr $(obj)/vmlinux.bin.$(suffix-y) FORCE
-	$(call if_changed,ld)
+quiet_cmd_mkpiggy = MKPIGGY $@
+      cmd_mkpiggy = $(obj)/mkpiggy $< > $@ || ( rm -f $@ ; false )
+
+targets += piggy.S
+$(obj)/piggy.S: $(obj)/vmlinux.bin.$(suffix-y) $(obj)/mkpiggy FORCE
+	$(call if_changed,mkpiggy)

arch/x86/boot/compressed/head_32.S

@@ -75,18 +75,8 @@ ENTRY(startup_32)
 	movl	$LOAD_PHYSICAL_ADDR, %ebx
 #endif
 
-	/* Replace the compressed data size with the uncompressed size */
-	subl	input_len(%ebp), %ebx
-	movl	output_len(%ebp), %eax
-	addl	%eax, %ebx
-	/* Add 8 bytes for every 32K input block */
-	shrl	$12, %eax
-	addl	%eax, %ebx
-	/* Add 32K + 18 bytes of extra slack */
-	addl	$(32768 + 18), %ebx
-	/* Align on a 4K boundary */
-	addl	$4095, %ebx
-	andl	$~4095, %ebx
+	/* Target address to relocate to for decompression */
+	addl	$z_extract_offset, %ebx
 
 	/* Set up the stack */
 	leal	boot_stack_end(%ebx), %esp
@@ -142,12 +132,10 @@ relocated:
 /*
  * Do the decompression, and jump to the new kernel..
  */
-	movl	output_len(%ebx), %eax
-	pushl	%eax
+	leal	z_extract_offset_negative(%ebx), %ebp
 				/* push arguments for decompress_kernel: */
 	pushl	%ebp		/* output address */
-	movl	input_len(%ebx), %eax
-	pushl	%eax		/* input_len */
+	pushl	$z_input_len	/* input_len */
 	leal	input_data(%ebx), %eax
 	pushl	%eax		/* input_data */
 	leal	boot_heap(%ebx), %eax
@@ -155,14 +143,12 @@ relocated:
 	pushl	%esi		/* real mode pointer */
 	call	decompress_kernel
 	addl	$20, %esp
-	popl	%ecx
 
 #if CONFIG_RELOCATABLE
 /*
  * Find the address of the relocations.
  */
-	movl	%ebp, %edi
-	addl	%ecx, %edi
+	leal	z_output_len(%ebp), %edi
 
 /*
  * Calculate the delta between where vmlinux was compiled to run

arch/x86/boot/compressed/head_64.S

@@ -90,16 +90,8 @@ ENTRY(startup_32)
 	movl	$CONFIG_PHYSICAL_START, %ebx
 #endif
 
-	/* Replace the compressed data size with the uncompressed size */
-	subl	input_len(%ebp), %ebx
-	movl	output_len(%ebp), %eax
-	addl	%eax, %ebx
-	/* Add 8 bytes for every 32K input block */
-	shrl	$12, %eax
-	addl	%eax, %ebx
-	/* Add 32K + 18 bytes of extra slack and align on a 4K boundary */
-	addl	$(32768 + 18 + 4095), %ebx
-	andl	$~4095, %ebx
+	/* Target address to relocate to for decompression */
+	addl	$z_extract_offset, %ebx
 
 /*
  * Prepare for entering 64 bit mode
@@ -224,6 +216,9 @@ ENTRY(startup_64)
 	 * If it is a relocatable kernel then decompress and run the kernel
 	 * from load address aligned to 2MB addr, otherwise decompress and
 	 * run the kernel from CONFIG_PHYSICAL_START
+	 *
+	 * We cannot rely on the calculation done in 32-bit mode, since we
+	 * may have been invoked via the 64-bit entry point.
 	 */
 
 	/* Start with the delta to where the kernel will run at. */
@@ -237,17 +232,8 @@ ENTRY(startup_64)
 	movq	%rbp, %rbx
 #endif
 
-	/* Replace the compressed data size with the uncompressed size */
-	movl	input_len(%rip), %eax
-	subq	%rax, %rbx
-	movl	output_len(%rip), %eax
-	addq	%rax, %rbx
-	/* Add 8 bytes for every 32K input block */
-	shrq	$12, %rax
-	addq	%rax, %rbx
-	/* Add 32K + 18 bytes of extra slack and align on a 4K boundary */
-	addq	$(32768 + 18 + 4095), %rbx
-	andq	$~4095, %rbx
+	/* Target address to relocate to for decompression */
+	leaq	z_extract_offset(%rbp), %rbx
 
 	/* Set up the stack */
 	leaq	boot_stack_end(%rbx), %rsp
@@ -292,13 +278,12 @@ relocated:
 /*
  * Do the decompression, and jump to the new kernel..
  */
-	pushq	%rsi			# Save the real mode argument
-	movq	%rsi, %rdi		# real mode address
-	leaq	boot_heap(%rip), %rsi	# malloc area for uncompression
-	leaq	input_data(%rip), %rdx  # input_data
-	movl	input_len(%rip), %eax
-	movq	%rax, %rcx		# input_len
-	movq	%rbp, %r8		# output
+	pushq	%rsi			/* Save the real mode argument */
+	movq	%rsi, %rdi		/* real mode address */
+	leaq	boot_heap(%rip), %rsi	/* malloc area for uncompression */
+	leaq	input_data(%rip), %rdx  /* input_data */
+	movl	$z_input_len, %ecx	/* input_len */
+	movq	%rbp, %r8		/* output target address */
 	call	decompress_kernel
 	popq	%rsi
 

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;
+}

arch/x86/boot/compressed/vmlinux.scr

@@ -1,10 +0,0 @@
-SECTIONS
-{
-  .rodata.compressed : {
-	input_len = .;
-	LONG(input_data_end - input_data) input_data = .;
-	*(.data)
-	output_len = . - 4;
-	input_data_end = .;
-	}
-}