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>

5 files changed, 123 insertions, 60 deletions

diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 7f24fdb584e6..49c8a4c37d7c 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/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)
diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
index 6710dc78ac59..470474bafc4d 100644
--- a/arch/x86/boot/compressed/head_32.S
+++ b/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
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index 723c72dfd7bc..2b9f2510507b 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/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
 
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;
+}
diff --git a/arch/x86/boot/compressed/vmlinux.scr b/arch/x86/boot/compressed/vmlinux.scr
deleted file mode 100644
index f02382ae5c48..000000000000
--- a/arch/x86/boot/compressed/vmlinux.scr
+++ /dev/null
@@ -1,10 +0,0 @@
-SECTIONS
-{
-  .rodata.compressed : {
-        input_len = .;
-        LONG(input_data_end - input_data) input_data = .;
-        *(.data)
-        output_len = . - 4;
-        input_data_end = .;
-        }
-}