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Commit efa70451 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Ingo Molnar
Browse files

x86/asm/entry: Make user_mode() work correctly if regs came from VM86 mode 



user_mode() is now identical to user_mode_vm().  Subsequent patches
will change all callers of user_mode_vm() to user_mode() and then
delete user_mode_vm().

Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brad Spengler <spender@grsecurity.net>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/0dd03eacb5f0a2b5ba0240de25347a31b493c289.1426728647.git.luto@kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent ae60f071

arch/x86/include/asm/ptrace.h

+7 −10
Original line number Diff line number Diff line
@@ -96,11 +96,13 @@ static inline unsigned long regs_return_value(struct pt_regs *regs) 
}



/*

 * user_mode_vm(regs) determines whether a register set came from user mode.

 * This is true if V8086 mode was enabled OR if the register set was from

 * protected mode with RPL-3 CS value.  This tricky test checks that with

 * one comparison.  Many places in the kernel can bypass this full check

 * if they have already ruled out V8086 mode, so user_mode(regs) can be used.

 * user_mode(regs) determines whether a register set came from user

 * mode.  On x86_32, this is true if V8086 mode was enabled OR if the

 * register set was from protected mode with RPL-3 CS value.  This

 * tricky test checks that with one comparison.

 *

 * On x86_64, vm86 mode is mercifully nonexistent, and we don't need

 * the extra check.

 */

static inline int user_mode(struct pt_regs *regs)

{
@@ -113,12 +115,7 @@ static inline int user_mode(struct pt_regs *regs) 


static inline int user_mode_vm(struct pt_regs *regs)

{

#ifdef CONFIG_X86_32

	return ((regs->cs & SEGMENT_RPL_MASK) | (regs->flags & X86_VM_MASK)) >=

		USER_RPL;

#else

	return user_mode(regs);

#endif

}



/*