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Commit 657c1eea authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Ingo Molnar
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x86/entry/32: Fix entry_INT80_32() to expect interrupts to be on 



When I rewrote entry_INT80_32, I thought that int80 was an
interrupt gate.  It's a trap gate.  *facepalm*

Thanks to Brian Gerst for pointing out that it's better to
change the entry code than to change the gate type.

Suggested-by: default avatarBrian Gerst <brgerst@gmail.com>
Reported-and-tested-by: default avatarBorislav Petkov <bp@suse.de>
Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 150ac78d ("x86/entry/32: Switch INT80 to the new C syscall path")
Link: http://lkml.kernel.org/r/dc09d9b574a5c1dcca996847875c73f8341ce0ad.1445035014.git.luto@kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 612bece6

arch/x86/entry/common.c

+12 −3
Original line number Diff line number Diff line
@@ -351,7 +351,14 @@ __visible inline void syscall_return_slowpath(struct pt_regs *regs) 
 * in workloads that use it, and it's usually called from

 * do_fast_syscall_32, so forcibly inline it to improve performance.

 */

static __always_inline void do_syscall_32_irqs_on(struct pt_regs *regs)

#ifdef CONFIG_X86_32

/* 32-bit kernels use a trap gate for INT80, and the asm code calls here. */

__visible

#else

/* 64-bit kernels use do_syscall_32_irqs_off() instead. */

static

#endif

__always_inline void do_syscall_32_irqs_on(struct pt_regs *regs)

{

	struct thread_info *ti = pt_regs_to_thread_info(regs);

	unsigned int nr = (unsigned int)regs->orig_ax;
@@ -386,12 +393,14 @@ static __always_inline void do_syscall_32_irqs_on(struct pt_regs *regs) 
	syscall_return_slowpath(regs);

}



/* Handles int $0x80 */

__visible void do_int80_syscall_32(struct pt_regs *regs)

#ifdef CONFIG_X86_64

/* Handles INT80 on 64-bit kernels */

__visible void do_syscall_32_irqs_off(struct pt_regs *regs)

{

	local_irq_enable();

	do_syscall_32_irqs_on(regs);

}

#endif



/* Returns 0 to return using IRET or 1 to return using SYSEXIT/SYSRETL. */

__visible long do_fast_syscall_32(struct pt_regs *regs)

arch/x86/entry/entry_32.S

+4 −4
Original line number Diff line number Diff line
@@ -345,13 +345,13 @@ ENTRY(entry_INT80_32) 
	SAVE_ALL pt_regs_ax=$-ENOSYS	/* save rest */



	/*

	 * User mode is traced as though IRQs are on, and the interrupt gate

	 * turned them off.

	 * User mode is traced as though IRQs are on.  Unlike the 64-bit

	 * case, INT80 is a trap gate on 32-bit kernels, so interrupts

	 * are already on (unless user code is messing around with iopl).

	 */

	TRACE_IRQS_OFF



	movl	%esp, %eax

	call	do_int80_syscall_32

	call	do_syscall_32_irqs_on

.Lsyscall_32_done:



restore_all:

arch/x86/entry/entry_64_compat.S

+1 −1
Original line number Diff line number Diff line
@@ -303,7 +303,7 @@ ENTRY(entry_INT80_compat) 
	TRACE_IRQS_OFF



	movq	%rsp, %rdi

	call	do_int80_syscall_32

	call	do_syscall_32_irqs_off

.Lsyscall_32_done:



	/* Go back to user mode. */