x86/boot: Simplify pointer casting in choose_random_location()

Pass them down as 'unsigned long' directly and get rid of more casting and
assignments.

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: akpm@linux-foundation.org
Cc: bhe@redhat.com
Cc: dyoung@redhat.com
Cc: linux-tip-commits@vger.kernel.org
Cc: luto@kernel.org
Cc: vgoyal@redhat.com
Cc: yinghai@kernel.org
Link: http://lkml.kernel.org/r/20160506115015.GI24044@pd.tnic
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/boot/compressed/kaslr.c

@@ -350,20 +350,15 @@ static unsigned long find_random_addr(unsigned long minimum,
 	return slots_fetch_random();
 }
 
-unsigned char *choose_random_location(unsigned char *input_ptr,
+/*
+ * Since this function examines addresses much more numerically,
+ * it takes the input and output pointers as 'unsigned long'.
+ */
+unsigned char *choose_random_location(unsigned long input,
 				      unsigned long input_size,
-				      unsigned char *output_ptr,
+				      unsigned long output,
 				      unsigned long output_size)
 {
-	/*
-	 * The caller of choose_random_location() uses unsigned char * for
-	 * buffer pointers since it performs decompression, elf parsing, etc.
-	 * Since this code examines addresses much more numerically,
-	 * unsigned long is used internally here. Instead of sprinkling
-	 * more casts into extract_kernel, do them here and at return.
-	 */
-	unsigned long input = (unsigned long)input_ptr;
-	unsigned long output = (unsigned long)output_ptr;
 	unsigned long choice = output;
 	unsigned long random_addr;
 

arch/x86/boot/compressed/misc.c

@@ -366,7 +366,8 @@ asmlinkage __visible void *extract_kernel(void *rmode, memptr heap,
 	 * the entire decompressed kernel plus relocation table, or the
 	 * entire decompressed kernel plus .bss and .brk sections.
 	 */
-	output = choose_random_location(input_data, input_len, output,
+	output = choose_random_location((unsigned long)input_data, input_len,
+					(unsigned long)output,
 					max(output_len, kernel_total_size));
 
 	/* Validate memory location choices. */

arch/x86/boot/compressed/misc.h

@@ -67,20 +67,20 @@ int cmdline_find_option_bool(const char *option);
 
 #if CONFIG_RANDOMIZE_BASE
 /* kaslr.c */
-unsigned char *choose_random_location(unsigned char *input_ptr,
+unsigned char *choose_random_location(unsigned long input_ptr,
 				      unsigned long input_size,
-				      unsigned char *output_ptr,
+				      unsigned long output_ptr,
 				      unsigned long output_size);
 /* cpuflags.c */
 bool has_cpuflag(int flag);
 #else
 static inline
-unsigned char *choose_random_location(unsigned char *input_ptr,
+unsigned char *choose_random_location(unsigned long input_ptr,
 				      unsigned long input_size,
-				      unsigned char *output_ptr,
+				      unsigned long output_ptr,
 				      unsigned long output_size)
 {
-	return output_ptr;
+	return (unsigned char *)output_ptr;
 }
 #endif