Merge branch 'x86-build-for-linus' of git://git.kernel.org/pub/scm/li…

…nux/kernel/git/tip/tip

Pull x86 build bits from Peter Anvin:
 "Various build-related minor bits.

  Most of this is work by David Woodhouse to be able to compile the
  early boot code with clang/llvm; we have also managed to push an
  actual -m16 option into gcc 4.9 so this makes us use that option if
  available instead of hacking it.

  The balance is a patch from Michael Davidson to the relocs program to
  help manual debugging.

  None of these should change the actual compiled binary with currently
  released compilers"

* 'x86-build-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86, build: Build 16-bit code with -m16 where possible
  x86, boot: Fix word-size assumptions in has_eflag() inline asm
  x86, boot: Use __attribute__((used)) to ensure videocard structs are emitted
  x86: Remove duplication of 16-bit CFLAGS
  x86, relocs: Add manual debug mode

arch/x86/Makefile

@@ -11,6 +11,28 @@ else
         KBUILD_DEFCONFIG := $(ARCH)_defconfig
 endif
 
+# How to compile the 16-bit code.  Note we always compile for -march=i386;
+# that way we can complain to the user if the CPU is insufficient.
+#
+# The -m16 option is supported by GCC >= 4.9 and clang >= 3.5. For
+# older versions of GCC, we need to play evil and unreliable tricks to
+# attempt to ensure that our asm(".code16gcc") is first in the asm
+# output.
+CODE16GCC_CFLAGS := -m32 -include $(srctree)/arch/x86/boot/code16gcc.h \
+		    $(call cc-option, -fno-toplevel-reorder,\
+		      $(call cc-option, -fno-unit-at-a-time))
+M16_CFLAGS	 := $(call cc-option, -m16, $(CODE16GCC_CFLAGS))
+
+REALMODE_CFLAGS	:= $(M16_CFLAGS) -g -Os -D__KERNEL__ \
+		   -DDISABLE_BRANCH_PROFILING \
+		   -Wall -Wstrict-prototypes -march=i386 -mregparm=3 \
+		   -fno-strict-aliasing -fomit-frame-pointer -fno-pic \
+		   -mno-mmx -mno-sse \
+		   $(call cc-option, -ffreestanding) \
+		   $(call cc-option, -fno-stack-protector) \
+		   $(call cc-option, -mpreferred-stack-boundary=2)
+export REALMODE_CFLAGS
+
 # BITS is used as extension for files which are available in a 32 bit
 # and a 64 bit version to simplify shared Makefiles.
 # e.g.: obj-y += foo_$(BITS).o

arch/x86/boot/Makefile

@@ -51,20 +51,7 @@ $(obj)/cpustr.h: $(obj)/mkcpustr FORCE
 
 # ---------------------------------------------------------------------------
 
-# How to compile the 16-bit code.  Note we always compile for -march=i386,
-# that way we can complain to the user if the CPU is insufficient.
-KBUILD_CFLAGS	:= $(USERINCLUDE) -m32 -g -Os -D_SETUP -D__KERNEL__ \
-		   -DDISABLE_BRANCH_PROFILING \
-		   -Wall -Wstrict-prototypes \
-		   -march=i386 -mregparm=3 \
-		   -include $(srctree)/$(src)/code16gcc.h \
-		   -fno-strict-aliasing -fomit-frame-pointer -fno-pic \
-		   -mno-mmx -mno-sse \
-		   $(call cc-option, -ffreestanding) \
-		   $(call cc-option, -fno-toplevel-reorder,\
-		   $(call cc-option, -fno-unit-at-a-time)) \
-		   $(call cc-option, -fno-stack-protector) \
-		   $(call cc-option, -mpreferred-stack-boundary=2)
+KBUILD_CFLAGS	:= $(USERINCLUDE) $(REALMODE_CFLAGS) -D_SETUP
 KBUILD_AFLAGS	:= $(KBUILD_CFLAGS) -D__ASSEMBLY__
 GCOV_PROFILE := n
 

arch/x86/boot/cpuflags.c

@@ -28,20 +28,35 @@ static int has_fpu(void)
 	return fsw == 0 && (fcw & 0x103f) == 0x003f;
 }
 
+/*
+ * For building the 16-bit code we want to explicitly specify 32-bit
+ * push/pop operations, rather than just saying 'pushf' or 'popf' and
+ * letting the compiler choose. But this is also included from the
+ * compressed/ directory where it may be 64-bit code, and thus needs
+ * to be 'pushfq' or 'popfq' in that case.
+ */
+#ifdef __x86_64__
+#define PUSHF "pushfq"
+#define POPF "popfq"
+#else
+#define PUSHF "pushfl"
+#define POPF "popfl"
+#endif
+
 int has_eflag(unsigned long mask)
 {
 	unsigned long f0, f1;
 
-	asm volatile("pushf	\n\t"
-		     "pushf	\n\t"
+	asm volatile(PUSHF "	\n\t"
+		     PUSHF "	\n\t"
 		     "pop %0	\n\t"
 		     "mov %0,%1	\n\t"
 		     "xor %2,%1	\n\t"
 		     "push %1	\n\t"
-		     "popf	\n\t"
-		     "pushf	\n\t"
+		     POPF "	\n\t"
+		     PUSHF "	\n\t"
 		     "pop %1	\n\t"
-		     "popf"
+		     POPF
 		     : "=&r" (f0), "=&r" (f1)
 		     : "ri" (mask));
 

arch/x86/boot/video.h

@@ -80,7 +80,7 @@ struct card_info {
 	u16 xmode_n;		/* Size of unprobed mode range */
 };
 
-#define __videocard struct card_info __attribute__((section(".videocards")))
+#define __videocard struct card_info __attribute__((used,section(".videocards")))
 extern struct card_info video_cards[], video_cards_end[];
 
 int mode_defined(u16 mode);	/* video.c */

arch/x86/realmode/rm/Makefile

@@ -64,20 +64,7 @@ $(obj)/realmode.relocs: $(obj)/realmode.elf FORCE
 
 # ---------------------------------------------------------------------------
 
-# How to compile the 16-bit code.  Note we always compile for -march=i386,
-# that way we can complain to the user if the CPU is insufficient.
-KBUILD_CFLAGS	:= $(LINUXINCLUDE) -m32 -g -Os -D_SETUP -D__KERNEL__ -D_WAKEUP \
-		   -I$(srctree)/arch/x86/boot \
-		   -DDISABLE_BRANCH_PROFILING \
-		   -Wall -Wstrict-prototypes \
-		   -march=i386 -mregparm=3 \
-		   -include $(srctree)/$(src)/../../boot/code16gcc.h \
-		   -fno-strict-aliasing -fomit-frame-pointer -fno-pic \
-		   -mno-mmx -mno-sse \
-		   $(call cc-option, -ffreestanding) \
-		   $(call cc-option, -fno-toplevel-reorder,\
-		   $(call cc-option, -fno-unit-at-a-time)) \
-		   $(call cc-option, -fno-stack-protector) \
-		   $(call cc-option, -mpreferred-stack-boundary=2)
+KBUILD_CFLAGS	:= $(LINUXINCLUDE) $(REALMODE_CFLAGS) -D_SETUP -D_WAKEUP \
+		   -I$(srctree)/arch/x86/boot
 KBUILD_AFLAGS	:= $(KBUILD_CFLAGS) -D__ASSEMBLY__
 GCOV_PROFILE := n

arch/x86/tools/relocs.c

@@ -1025,14 +1025,38 @@ static void emit_relocs(int as_text, int use_real_mode)
 	}
 }
 
+/*
+ * As an aid to debugging problems with different linkers
+ * print summary information about the relocs.
+ * Since different linkers tend to emit the sections in
+ * different orders we use the section names in the output.
+ */
+static int do_reloc_info(struct section *sec, Elf_Rel *rel, ElfW(Sym) *sym,
+				const char *symname)
+{
+	printf("%s\t%s\t%s\t%s\n",
+		sec_name(sec->shdr.sh_info),
+		rel_type(ELF_R_TYPE(rel->r_info)),
+		symname,
+		sec_name(sym->st_shndx));
+	return 0;
+}
+
+static void print_reloc_info(void)
+{
+	printf("reloc section\treloc type\tsymbol\tsymbol section\n");
+	walk_relocs(do_reloc_info);
+}
+
 #if ELF_BITS == 64
 # define process process_64
 #else
 # define process process_32
 #endif
 
 void process(FILE *fp, int use_real_mode, int as_text,
-	     int show_absolute_syms, int show_absolute_relocs)
+	     int show_absolute_syms, int show_absolute_relocs,
+	     int show_reloc_info)
 {
 	regex_init(use_real_mode);
 	read_ehdr(fp);
@@ -1050,5 +1074,9 @@ void process(FILE *fp, int use_real_mode, int as_text,
 		print_absolute_relocs();
 		return;
 	}
+	if (show_reloc_info) {
+		print_reloc_info();
+		return;
+	}
 	emit_relocs(as_text, use_real_mode);
 }

arch/x86/tools/relocs.h

@@ -29,8 +29,9 @@ enum symtype {
 };
 
 void process_32(FILE *fp, int use_real_mode, int as_text,
-		int show_absolute_syms, int show_absolute_relocs);
+		int show_absolute_syms, int show_absolute_relocs,
+		int show_reloc_info);
 void process_64(FILE *fp, int use_real_mode, int as_text,
-		int show_absolute_syms, int show_absolute_relocs);
-
+		int show_absolute_syms, int show_absolute_relocs,
+		int show_reloc_info);
 #endif /* RELOCS_H */

arch/x86/tools/relocs_common.c

@@ -11,12 +11,13 @@ void die(char *fmt, ...)
 
 static void usage(void)
 {
-	die("relocs [--abs-syms|--abs-relocs|--text|--realmode] vmlinux\n");
+	die("relocs [--abs-syms|--abs-relocs|--reloc-info|--text|--realmode]" \
+	    " vmlinux\n");
 }
 
 int main(int argc, char **argv)
 {
-	int show_absolute_syms, show_absolute_relocs;
+	int show_absolute_syms, show_absolute_relocs, show_reloc_info;
 	int as_text, use_real_mode;
 	const char *fname;
 	FILE *fp;
@@ -25,6 +26,7 @@ int main(int argc, char **argv)
 
 	show_absolute_syms = 0;
 	show_absolute_relocs = 0;
+	show_reloc_info = 0;
 	as_text = 0;
 	use_real_mode = 0;
 	fname = NULL;
@@ -39,6 +41,10 @@ int main(int argc, char **argv)
 				show_absolute_relocs = 1;
 				continue;
 			}
+			if (strcmp(arg, "--reloc-info") == 0) {
+				show_reloc_info = 1;
+				continue;
+			}
 			if (strcmp(arg, "--text") == 0) {
 				as_text = 1;
 				continue;
@@ -67,10 +73,12 @@ int main(int argc, char **argv)
 	rewind(fp);
 	if (e_ident[EI_CLASS] == ELFCLASS64)
 		process_64(fp, use_real_mode, as_text,
-			   show_absolute_syms, show_absolute_relocs);
+			   show_absolute_syms, show_absolute_relocs,
+			   show_reloc_info);
 	else
 		process_32(fp, use_real_mode, as_text,
-			   show_absolute_syms, show_absolute_relocs);
+			   show_absolute_syms, show_absolute_relocs,
+			   show_reloc_info);
 	fclose(fp);
 	return 0;
 }