7 files changed, 172 insertions, 2 deletions

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 61a0cb15067e..bf79c461bd2c 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -2005,6 +2005,17 @@ config XIP_PHYS_ADDR
           be linked for and stored to.  This address is dependent on your
           own flash usage.
 
+config XIP_DEFLATED_DATA
+        bool "Store kernel .data section compressed in ROM"
+        depends on XIP_KERNEL
+        select ZLIB_INFLATE
+        help
+          Before the kernel is actually executed, its .data section has to be
+          copied to RAM from ROM. This option allows for storing that data
+          in compressed form and decompressed to RAM rather than merely being
+          copied, saving some precious ROM space. A possible drawback is a
+          slightly longer boot delay.
+
 config KEXEC
         bool "Kexec system call (EXPERIMENTAL)"
         depends on (!SMP || PM_SLEEP_SMP)
diff --git a/arch/arm/boot/Makefile b/arch/arm/boot/Makefile
index 50f8d1be7fcb..a3af4dc08c3e 100644
--- a/arch/arm/boot/Makefile
+++ b/arch/arm/boot/Makefile
@@ -31,8 +31,19 @@ targets := Image zImage xipImage bootpImage uImage
 
 ifeq ($(CONFIG_XIP_KERNEL),y)
 
+cmd_deflate_xip_data = $(CONFIG_SHELL) -c \
+        '$(srctree)/$(src)/deflate_xip_data.sh $< $@ || { rm -f $@; false; }'
+
+ifeq ($(CONFIG_XIP_DEFLATED_DATA),y)
+quiet_cmd_mkxip = XIPZ    $@
+cmd_mkxip = $(cmd_objcopy) && $(cmd_deflate_xip_data)
+else
+quiet_cmd_mkxip = $(quiet_cmd_objcopy)
+cmd_mkxip = $(cmd_objcopy)
+endif
+
 $(obj)/xipImage: vmlinux FORCE
-        $(call if_changed,objcopy)
+        $(call if_changed,mkxip)
         @$(kecho) '  Physical Address of xipImage: $(CONFIG_XIP_PHYS_ADDR)'
 
 $(obj)/Image $(obj)/zImage: FORCE
diff --git a/arch/arm/boot/deflate_xip_data.sh b/arch/arm/boot/deflate_xip_data.sh
new file mode 100755
index 000000000000..1189598a25eb
--- /dev/null
+++ b/arch/arm/boot/deflate_xip_data.sh
@@ -0,0 +1,64 @@
+#!/bin/sh
+
+# XIP kernel .data segment compressor
+#
+# Created by:   Nicolas Pitre, August 2017
+# Copyright:    (C) 2017  Linaro Limited
+#
+# 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 script locates the start of the .data section in xipImage and
+# substitutes it with a compressed version. The needed offsets are obtained
+# from symbol addresses in vmlinux. It is expected that .data extends to
+# the end of xipImage.
+
+set -e
+
+VMLINUX="$1"
+XIPIMAGE="$2"
+
+DD="dd status=none"
+
+# Use "make V=1" to debug this script.
+case "$KBUILD_VERBOSE" in
+*1*)
+        set -x
+        ;;
+esac
+
+sym_val() {
+        # extract hex value for symbol in $1
+        local val=$($NM "$VMLINUX" | sed -n "/ $1$/{s/ .*$//p;q}")
+        [ "$val" ] || { echo "can't find $1 in $VMLINUX" 1>&2; exit 1; }
+        # convert from hex to decimal
+        echo $((0x$val))
+}
+
+__data_loc=$(sym_val __data_loc)
+_edata_loc=$(sym_val _edata_loc)
+base_offset=$(sym_val _xiprom)
+
+# convert to file based offsets
+data_start=$(($__data_loc - $base_offset))
+data_end=$(($_edata_loc - $base_offset))
+
+# Make sure data occupies the last part of the file.
+file_end=$(stat -c "%s" "$XIPIMAGE")
+if [ "$file_end" != "$data_end" ]; then
+        printf "end of xipImage doesn't match with _edata_loc (%#x vs %#x)\n" \
+               $(($file_end + $base_offset)) $_edata_loc 2>&1
+        exit 1;
+fi
+
+# be ready to clean up
+trap 'rm -f "$XIPIMAGE.tmp"' 0 1 2 3
+
+# substitute the data section by a compressed version
+$DD if="$XIPIMAGE" count=$data_start iflag=count_bytes of="$XIPIMAGE.tmp"
+$DD if="$XIPIMAGE"  skip=$data_start iflag=skip_bytes |
+gzip -9 >> "$XIPIMAGE.tmp"
+
+# replace kernel binary
+mv -f "$XIPIMAGE.tmp" "$XIPIMAGE"
diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
index ad325a8c7e1e..52f437997cc6 100644
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@@ -87,6 +87,11 @@ head-y			:= head$(MMUEXT).o
 obj-$(CONFIG_DEBUG_LL)  += debug.o
 obj-$(CONFIG_EARLY_PRINTK)      += early_printk.o
 
+# This is executed very early using a temporary stack when no memory allocator
+# nor global data is available. Everything has to be allocated on the stack.
+CFLAGS_head-inflate-data.o := $(call cc-option,-Wframe-larger-than=10240)
+obj-$(CONFIG_XIP_DEFLATED_DATA) += head-inflate-data.o
+
 obj-$(CONFIG_ARM_VIRT_EXT)      += hyp-stub.o
 AFLAGS_hyp-stub.o               :=-Wa,-march=armv7-a
 ifeq ($(CONFIG_ARM_PSCI),y)
diff --git a/arch/arm/kernel/head-common.S b/arch/arm/kernel/head-common.S
index bf9c4e38eced..a25027b87a60 100644
--- a/arch/arm/kernel/head-common.S
+++ b/arch/arm/kernel/head-common.S
@@ -87,7 +87,14 @@ __mmap_switched:
         adr     r4, __mmap_switched_data
         mov     fp, #0
 
-#ifdef CONFIG_XIP_KERNEL
+#if defined(CONFIG_XIP_DEFLATED_DATA)
+   ARM( ldr     sp, [r4], #4 )
+ THUMB( ldr     sp, [r4] )
+ THUMB( add     r4, #4 )
+        bl      __inflate_kernel_data           @ decompress .data to RAM
+        teq     r0, #0
+        bne     __error
+#elif defined(CONFIG_XIP_KERNEL)
    ARM( ldmia   r4!, {r0, r1, r2, sp} )
  THUMB( ldmia   r4!, {r0, r1, r2, r3} )
  THUMB( mov     sp, r3 )
@@ -114,9 +121,11 @@ ENDPROC(__mmap_switched)
         .type   __mmap_switched_data, %object
 __mmap_switched_data:
 #ifdef CONFIG_XIP_KERNEL
+#ifndef CONFIG_XIP_DEFLATED_DATA
         .long   _sdata                          @ r0
         .long   __data_loc                      @ r1
         .long   _edata_loc                      @ r2
+#endif
         .long   __bss_stop                      @ sp (temporary stack in .bss)
 #endif
 
diff --git a/arch/arm/kernel/head-inflate-data.c b/arch/arm/kernel/head-inflate-data.c
new file mode 100644
index 000000000000..6dd0ce5e6058
--- /dev/null
+++ b/arch/arm/kernel/head-inflate-data.c
@@ -0,0 +1,62 @@
+/*
+ * XIP kernel .data segment decompressor
+ *
+ * Created by:  Nicolas Pitre, August 2017
+ * Copyright:   (C) 2017  Linaro Limited
+ *
+ * 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.
+ */
+
+#include <linux/init.h>
+#include <linux/zutil.h>
+
+/* for struct inflate_state */
+#include "../../../lib/zlib_inflate/inftrees.h"
+#include "../../../lib/zlib_inflate/inflate.h"
+#include "../../../lib/zlib_inflate/infutil.h"
+
+extern char __data_loc[];
+extern char _edata_loc[];
+extern char _sdata[];
+
+/*
+ * This code is called very early during the boot process to decompress
+ * the .data segment stored compressed in ROM. Therefore none of the global
+ * variables are valid yet, hence no kernel services such as memory
+ * allocation is available. Everything must be allocated on the stack and
+ * we must avoid any global data access. We use a temporary stack located
+ * in the .bss area. The linker script makes sure the .bss is big enough
+ * to hold our stack frame plus some room for called functions.
+ *
+ * We mimic the code in lib/decompress_inflate.c to use the smallest work
+ * area possible. And because everything is statically allocated on the
+ * stack then there is no need to clean up before returning.
+ */
+
+int __init __inflate_kernel_data(void)
+{
+        struct z_stream_s stream, *strm = &stream;
+        struct inflate_state state;
+        char *in = __data_loc;
+        int rc;
+
+        /* Check and skip gzip header (assume no filename) */
+        if (in[0] != 0x1f || in[1] != 0x8b || in[2] != 0x08 || in[3] & ~3)
+                return -1;
+        in += 10;
+
+        strm->workspace = &state;
+        strm->next_in = in;
+        strm->avail_in = _edata_loc - __data_loc;  /* upper bound */
+        strm->next_out = _sdata;
+        strm->avail_out = _edata_loc - __data_loc;
+        zlib_inflateInit2(strm, -MAX_WBITS);
+        WS(strm)->inflate_state.wsize = 0;
+        WS(strm)->inflate_state.window = NULL;
+        rc = zlib_inflate(strm, Z_FINISH);
+        if (rc == Z_OK || rc == Z_STREAM_END)
+                rc = strm->avail_out;  /* should be 0 */
+        return rc;
+}
diff --git a/arch/arm/kernel/vmlinux-xip.lds.S b/arch/arm/kernel/vmlinux-xip.lds.S
index 39b1fb470a0a..7a844310085e 100644
--- a/arch/arm/kernel/vmlinux-xip.lds.S
+++ b/arch/arm/kernel/vmlinux-xip.lds.S
@@ -306,3 +306,11 @@ ASSERT((__arch_info_end - __arch_info_begin), "no machine record defined")
  */
 ASSERT(__hyp_idmap_text_end - (__hyp_idmap_text_start & PAGE_MASK) <= PAGE_SIZE,
         "HYP init code too big or misaligned")
+
+#ifdef CONFIG_XIP_DEFLATED_DATA
+/*
+ * The .bss is used as a stack area for __inflate_kernel_data() whose stack
+ * frame is 9568 bytes. Make sure it has extra room left.
+ */
+ASSERT((_end - __bss_start) >= 12288, ".bss too small for CONFIG_XIP_DEFLATED_DATA")
+#endif