[PATCH] Make vm86 support optional

This adds an option to remove vm86 support under CONFIG_EMBEDDED. Saves
about 5k.

This version eliminates most of the #ifdefs of the previous version and
instead uses function stubs in vm86.h. Also, release_vm86_irqs is moved
from asm-i386/irq.h to a more appropriate home in vm86.h so that the stubs
can live together.

$ size vmlinux-baseline vmlinux-novm86
text data bss dec hex filename
2920821 523232 190652 3634705 377611 vmlinux-baseline
2916268 523100 190492 3629860 376324 vmlinux-novm86

Signed-off-by: Matt Mackall <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

arch/i386/kernel/Makefile

···
 
 extra-y := head.o init_task.o vmlinux.lds
 
-obj-y	:= process.o semaphore.o signal.o entry.o traps.o irq.o vm86.o \
+obj-y	:= process.o semaphore.o signal.o entry.o traps.o irq.o \
 		ptrace.o time.o ioport.o ldt.o setup.o i8259.o sys_i386.o \
 		pci-dma.o i386_ksyms.o i387.o dmi_scan.o bootflag.o \
 		quirks.o i8237.o
···
 obj-$(CONFIG_HPET_TIMER) 	+= time_hpet.o
 obj-$(CONFIG_EFI) 		+= efi.o efi_stub.o
 obj-$(CONFIG_DOUBLEFAULT) 	+= doublefault.o
+obj-$(CONFIG_VM86)		+= vm86.o
 obj-$(CONFIG_EARLY_PRINTK)	+= early_printk.o
 
 EXTRA_AFLAGS   := -traditional

arch/i386/kernel/entry.S

···
 
 	ALIGN
 work_notifysig_v86:
+#ifdef CONFIG_VM86
 	pushl %ecx			# save ti_flags for do_notify_resume
 	call save_v86_state		# %eax contains pt_regs pointer
 	popl %ecx
···
 	xorl %edx, %edx
 	call do_notify_resume
 	jmp resume_userspace
+#endif
 
 	# perform syscall exit tracing
 	ALIGN

arch/i386/kernel/process.c

···
 #include <asm/processor.h>
 #include <asm/i387.h>
 #include <asm/desc.h>
+#include <asm/vm86.h>
 #ifdef CONFIG_MATH_EMULATION
 #include <asm/math_emu.h>
 #endif

include/asm-i386/irq.h

···
 	return ((irq == 2) ? 9 : irq);
 }
 
-extern void release_vm86_irqs(struct task_struct *);
-
 #ifdef CONFIG_X86_LOCAL_APIC
 # define ARCH_HAS_NMI_WATCHDOG		/* See include/linux/nmi.h */
 #endif

include/asm-i386/vm86.h

···
 #define IF_MASK		0x00000200
 #define IOPL_MASK	0x00003000
 #define NT_MASK		0x00004000
+#ifdef CONFIG_VM86
 #define VM_MASK		0x00020000
+#else
+#define VM_MASK		0 /* ignored */
+#endif
 #define AC_MASK		0x00040000
 #define VIF_MASK	0x00080000	/* virtual interrupt flag */
 #define VIP_MASK	0x00100000	/* virtual interrupt pending */
···
  */
 };
 
+#ifdef CONFIG_VM86
+
 void handle_vm86_fault(struct kernel_vm86_regs *, long);
 int handle_vm86_trap(struct kernel_vm86_regs *, long, int);
+
+struct task_struct;
+void release_vm86_irqs(struct task_struct *);
+
+#else
+
+#define handle_vm86_fault(a, b)
+#define release_vm86_irqs(a)
+
+static inline int handle_vm86_trap(struct kernel_vm86_regs *a, long b, int c) {
+	return 0;
+}
+
+#endif /* CONFIG_VM86 */
 
 #endif /* __KERNEL__ */
 

init/Kconfig

···
 	help
 	  This enables the legacy 16-bit UID syscall wrappers.
 
+config VM86
+	depends X86
+	default y
+	bool "Enable VM86 support" if EMBEDDED
+	help
+          This option is required by programs like DOSEMU to run 16-bit legacy
+	  code on X86 processors. It also may be needed by software like
+          XFree86 to initialize some video cards via BIOS. Disabling this
+          option saves about 6k.
+
 config CC_OPTIMIZE_FOR_SIZE
 	bool "Optimize for size (Look out for broken compilers!)"
 	default y

kernel/sys_ni.c

···
 cond_syscall(sys_setresuid16);
 cond_syscall(sys_setreuid16);
 cond_syscall(sys_setuid16);
+cond_syscall(sys_vm86old);
+cond_syscall(sys_vm86);
 
 /* arch-specific weak syscall entries */
 cond_syscall(sys_pciconfig_read);