ARM: Eliminate decompressor -Dstatic= PIC hack

We used to build decompressors with -Dstatic= to avoid any local data
being generated.  The problem is that local data generates GOTOFF
relocations, which means we can't relocate the data relative to the
text segment.

Global data, on the other hand, goes through the GOT, and can be
relocated anywhere.

Unfortunately, with the new decompressors, this presents a problem
since they declare static data within functions, and this leads to
stack overflow.

Fix this by separating out the decompressor code into a separate file,
and removing 'static' from BSS data in misc.c.

Also, discard the .data section - this means that should we end up
with read/write initialized data, the decompressor will fail to link
and the problem will be obvious.
Acked-by: Nicolas Pitre <nico@fluxnic.net>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/boot/compressed/Makefile

@@ -5,7 +5,7 @@
 #
 
 HEAD	= head.o
-OBJS	= misc.o
+OBJS	= misc.o decompress.o
 FONTC	= $(srctree)/drivers/video/console/font_acorn_8x8.c
 
 #
@@ -106,10 +106,6 @@ lib1funcs = $(obj)/lib1funcs.o
 $(obj)/lib1funcs.S: $(srctree)/arch/$(SRCARCH)/lib/lib1funcs.S FORCE
 	$(call cmd,shipped)
 
-# Don't allow any static data in misc.o, which
-# would otherwise mess up our GOT table
-CFLAGS_misc.o := -Dstatic=
-
 $(obj)/vmlinux: $(obj)/vmlinux.lds $(obj)/$(HEAD) $(obj)/piggy.$(suffix_y).o \
 	 	$(addprefix $(obj)/, $(OBJS)) $(lib1funcs) FORCE
 	$(call if_changed,ld)

arch/arm/boot/compressed/decompress.c

+#define _LINUX_STRING_H_
+
+#include <linux/compiler.h>	/* for inline */
+#include <linux/types.h>	/* for size_t */
+#include <linux/stddef.h>	/* for NULL */
+#include <linux/linkage.h>
+#include <asm/string.h>
+
+extern unsigned long free_mem_ptr;
+extern unsigned long free_mem_end_ptr;
+extern void error(char *);
+
+#define STATIC static
+
+#define ARCH_HAS_DECOMP_WDOG
+
+/* Diagnostic functions */
+#ifdef DEBUG
+#  define Assert(cond,msg) {if(!(cond)) error(msg);}
+#  define Trace(x) fprintf x
+#  define Tracev(x) {if (verbose) fprintf x ;}
+#  define Tracevv(x) {if (verbose>1) fprintf x ;}
+#  define Tracec(c,x) {if (verbose && (c)) fprintf x ;}
+#  define Tracecv(c,x) {if (verbose>1 && (c)) fprintf x ;}
+#else
+#  define Assert(cond,msg)
+#  define Trace(x)
+#  define Tracev(x)
+#  define Tracevv(x)
+#  define Tracec(c,x)
+#  define Tracecv(c,x)
+#endif
+
+#ifdef CONFIG_KERNEL_GZIP
+#include "../../../../lib/decompress_inflate.c"
+#endif
+
+#ifdef CONFIG_KERNEL_LZO
+#include "../../../../lib/decompress_unlzo.c"
+#endif
+
+void do_decompress(u8 *input, int len, u8 *output, void (*error)(char *x))
+{
+	decompress(input, len, NULL, NULL, output, NULL, error);
+}

arch/arm/boot/compressed/misc.c

@@ -23,8 +23,8 @@ unsigned int __machine_arch_type;
 #include <linux/compiler.h>	/* for inline */
 #include <linux/types.h>	/* for size_t */
 #include <linux/stddef.h>	/* for NULL */
-#include <asm/string.h>
 #include <linux/linkage.h>
+#include <asm/string.h>
 
 #include <asm/unaligned.h>
 
@@ -106,57 +106,7 @@ static void putstr(const char *ptr)
 
 #endif
 
-#define __ptr_t void *
-
-#define memzero(s,n) __memzero(s,n)
-
-/*
- * Optimised C version of memzero for the ARM.
- */
-void __memzero (__ptr_t s, size_t n)
-{
-	union { void *vp; unsigned long *ulp; unsigned char *ucp; } u;
-	int i;
-
-	u.vp = s;
-
-	for (i = n >> 5; i > 0; i--) {
-		*u.ulp++ = 0;
-		*u.ulp++ = 0;
-		*u.ulp++ = 0;
-		*u.ulp++ = 0;
-		*u.ulp++ = 0;
-		*u.ulp++ = 0;
-		*u.ulp++ = 0;
-		*u.ulp++ = 0;
-	}
-
-	if (n & 1 << 4) {
-		*u.ulp++ = 0;
-		*u.ulp++ = 0;
-		*u.ulp++ = 0;
-		*u.ulp++ = 0;
-	}
-
-	if (n & 1 << 3) {
-		*u.ulp++ = 0;
-		*u.ulp++ = 0;
-	}
-
-	if (n & 1 << 2)
-		*u.ulp++ = 0;
-
-	if (n & 1 << 1) {
-		*u.ucp++ = 0;
-		*u.ucp++ = 0;
-	}
-
-	if (n & 1)
-		*u.ucp++ = 0;
-}
-
-static inline __ptr_t memcpy(__ptr_t __dest, __const __ptr_t __src,
-			    size_t __n)
+void *memcpy(void *__dest, __const void *__src, size_t __n)
 {
 	int i = 0;
 	unsigned char *d = (unsigned char *)__dest, *s = (unsigned char *)__src;
@@ -193,59 +143,20 @@ static inline __ptr_t memcpy(__ptr_t __dest, __const __ptr_t __src,
 /*
  * gzip delarations
  */
-#define STATIC static
-
-/* Diagnostic functions */
-#ifdef DEBUG
-#  define Assert(cond,msg) {if(!(cond)) error(msg);}
-#  define Trace(x) fprintf x
-#  define Tracev(x) {if (verbose) fprintf x ;}
-#  define Tracevv(x) {if (verbose>1) fprintf x ;}
-#  define Tracec(c,x) {if (verbose && (c)) fprintf x ;}
-#  define Tracecv(c,x) {if (verbose>1 && (c)) fprintf x ;}
-#else
-#  define Assert(cond,msg)
-#  define Trace(x)
-#  define Tracev(x)
-#  define Tracevv(x)
-#  define Tracec(c,x)
-#  define Tracecv(c,x)
-#endif
-
-static void error(char *m);
-
 extern char input_data[];
 extern char input_data_end[];
 
-static unsigned char *output_data;
-static unsigned long output_ptr;
-
-static void error(char *m);
+unsigned char *output_data;
+unsigned long output_ptr;
 
-static void putstr(const char *);
-
-static unsigned long free_mem_ptr;
-static unsigned long free_mem_end_ptr;
-
-#ifdef STANDALONE_DEBUG
-#define NO_INFLATE_MALLOC
-#endif
-
-#define ARCH_HAS_DECOMP_WDOG
-
-#ifdef CONFIG_KERNEL_GZIP
-#include "../../../../lib/decompress_inflate.c"
-#endif
-
-#ifdef CONFIG_KERNEL_LZO
-#include "../../../../lib/decompress_unlzo.c"
-#endif
+unsigned long free_mem_ptr;
+unsigned long free_mem_end_ptr;
 
 #ifndef arch_error
 #define arch_error(x)
 #endif
 
-static void error(char *x)
+void error(char *x)
 {
 	arch_error(x);
 
@@ -261,6 +172,8 @@ asmlinkage void __div0(void)
 	error("Attempting division by 0!");
 }
 
+extern void do_decompress(u8 *input, int len, u8 *output, void (*error)(char *x));
+
 #ifndef STANDALONE_DEBUG
 
 unsigned long
@@ -281,8 +194,8 @@ decompress_kernel(unsigned long output_start, unsigned long free_mem_ptr_p,
 	output_ptr = get_unaligned_le32(tmp);
 
 	putstr("Uncompressing Linux...");
-	decompress(input_data, input_data_end - input_data,
-			NULL, NULL, output_data, NULL, error);
+	do_decompress(input_data, input_data_end - input_data,
+			output_data, error);
 	putstr(" done, booting the kernel.\n");
 	return output_ptr;
 }

arch/arm/boot/compressed/vmlinux.lds.in

@@ -14,6 +14,13 @@ SECTIONS
   /DISCARD/ : {
     *(.ARM.exidx*)
     *(.ARM.extab*)
+    /*
+     * Discard any r/w data - this produces a link error if we have any,
+     * which is required for PIC decompression.  Local data generates
+     * GOTOFF relocations, which prevents it being relocated independently
+     * of the text/got segments.
+     */
+    *(.data)
   }
 
   . = TEXT_START;
@@ -40,7 +47,6 @@ SECTIONS
   .got			: { *(.got) }
   _got_end = .;
   .got.plt		: { *(.got.plt) }
-  .data			: { *(.data) }
   _edata = .;
 
   . = BSS_START;