[PATCH v5 1/2] x86/boot: Extract error reporting functions

[Kees Cook]

Currently to use warn(), a caller would need to include misc.h. However,
this means they would get the (unavailable during compressed boot)
gcc built-in memcpy family of functions. But since string.c is defining
these memcpy functions for use by misc.c, we end up in a weird circular
dependency.

To break this loop, move the error reporting functions outside of misc.c
with their own header so that they can be independently included by
other sources. Since the screen-writing routines use memmove(), keep the
low-level *_putstr() functions in misc.c.

Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
 arch/x86/boot/compressed/Makefile |  2 +-
 arch/x86/boot/compressed/error.c  | 22 ++++++++++++++++++++++
 arch/x86/boot/compressed/error.h  |  7 +++++++
 arch/x86/boot/compressed/kaslr.c  |  1 +
 arch/x86/boot/compressed/misc.c   | 18 +-----------------
 arch/x86/boot/compressed/misc.h   |  1 -
 arch/x86/boot/compressed/string.c |  2 ++
 7 files changed, 34 insertions(+), 19 deletions(-)
 create mode 100644 arch/x86/boot/compressed/error.c
 create mode 100644 arch/x86/boot/compressed/error.h

diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 75f2233b8414..77ce3a04d46e 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -70,7 +70,7 @@ $(obj)/../voffset.h: vmlinux FORCE
 $(obj)/misc.o: $(obj)/../voffset.h
 
 vmlinux-objs-y := $(obj)/vmlinux.lds $(obj)/head_$(BITS).o $(obj)/misc.o \
-	$(obj)/string.o $(obj)/cmdline.o \
+	$(obj)/string.o $(obj)/cmdline.o $(obj)/error.o \
 	$(obj)/piggy.o $(obj)/cpuflags.o
 
 vmlinux-objs-$(CONFIG_EARLY_PRINTK) += $(obj)/early_serial_console.o
diff --git a/arch/x86/boot/compressed/error.c b/arch/x86/boot/compressed/error.c
new file mode 100644
index 000000000000..6248740b68b5
--- /dev/null
+++ b/arch/x86/boot/compressed/error.c
@@ -0,0 +1,22 @@
+/*
+ * Callers outside of misc.c need access to the error reporting routines,
+ * but the *_putstr() functions need to stay in misc.c because of how
+ * memcpy() and memmove() are defined for the compressed boot environment.
+ */
+#include "misc.h"
+
+void warn(char *m)
+{
+	error_putstr("\n\n");
+	error_putstr(m);
+	error_putstr("\n\n");
+}
+
+void error(char *m)
+{
+	warn(m);
+	error_putstr(" -- System halted");
+
+	while (1)
+		asm("hlt");
+}
diff --git a/arch/x86/boot/compressed/error.h b/arch/x86/boot/compressed/error.h
new file mode 100644
index 000000000000..2e59dac07f9e
--- /dev/null
+++ b/arch/x86/boot/compressed/error.h
@@ -0,0 +1,7 @@
+#ifndef BOOT_COMPRESSED_ERROR_H
+#define BOOT_COMPRESSED_ERROR_H
+
+void warn(char *m);
+void error(char *m);
+
+#endif /* BOOT_COMPRESSED_ERROR_H */
diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index 8741a6d83bfe..f1818d95d726 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -10,6 +10,7 @@
  *
  */
 #include "misc.h"
+#include "error.h"
 
 #include <asm/msr.h>
 #include <asm/archrandom.h>
diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index 8f0253d8c7ff..9536d778149e 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -12,6 +12,7 @@
  */
 
 #include "misc.h"
+#include "error.h"
 #include "../string.h"
 #include "../voffset.h"
 
@@ -36,7 +37,6 @@
 #define memmove		memmove
 
 /* Functions used by the included decompressor code below. */
-static void error(char *m);
 void *memmove(void *dest, const void *src, size_t n);
 
 /*
@@ -169,22 +169,6 @@ void __puthex(unsigned long value)
 	}
 }
 
-void warn(char *m)
-{
-	error_putstr("\n\n");
-	error_putstr(m);
-	error_putstr("\n\n");
-}
-
-static void error(char *m)
-{
-	warn(m);
-	error_putstr(" -- System halted");
-
-	while (1)
-		asm("hlt");
-}
-
 #if CONFIG_X86_NEED_RELOCS
 static void handle_relocations(void *output, unsigned long output_len)
 {
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index e75f6cf9caaf..9887e0d4aaeb 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -35,7 +35,6 @@ extern memptr free_mem_end_ptr;
 extern struct boot_params *boot_params;
 void __putstr(const char *s);
 void __puthex(unsigned long value);
-void warn(char *m);
 #define error_putstr(__x)  __putstr(__x)
 #define error_puthex(__x)  __puthex(__x)
 
diff --git a/arch/x86/boot/compressed/string.c b/arch/x86/boot/compressed/string.c
index 2befeca1aada..faa4dc7dc66b 100644
--- a/arch/x86/boot/compressed/string.c
+++ b/arch/x86/boot/compressed/string.c
@@ -5,6 +5,8 @@
  * trust the gcc built-in implementations as they may do unexpected things
  * (e.g. FPU ops) in the minimal decompression stub execution environment.
  */
+#include "error.h"
+
 #include "../string.c"
 
 #ifdef CONFIG_X86_32
-- 
2.6.3