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Commit bd2d3a3b authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Ingo Molnar
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x86/entry: Add do_syscall_32(), a C function to do 32-bit syscalls 



System calls are really quite simple.  Add a helper to call
a 32-bit system call.

Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
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>
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/a77ed179834c27da436fb4a7fb23c8ee77abc11c.1444091585.git.luto@kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent eb974c62

arch/x86/entry/common.c

+43 −0
Original line number Diff line number Diff line
@@ -318,3 +318,46 @@ __visible void syscall_return_slowpath(struct pt_regs *regs) 
	local_irq_disable();

	prepare_exit_to_usermode(regs);

}



#if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)

/*

 * Does a 32-bit syscall.  Called with IRQs off and does all entry and

 * exit work.

 */

__visible void do_int80_syscall_32(struct pt_regs *regs)

{

	struct thread_info *ti = pt_regs_to_thread_info(regs);

	unsigned int nr = (unsigned int)regs->orig_ax;



#ifdef CONFIG_IA32_EMULATION

	ti->status |= TS_COMPAT;

#endif



	local_irq_enable();



	if (READ_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY) {

		/*

		 * Subtlety here: if ptrace pokes something larger than

		 * 2^32-1 into orig_ax, this truncates it.  This may or

		 * may not be necessary, but it matches the old asm

		 * behavior.

		 */

		nr = syscall_trace_enter(regs);

	}



	if (nr < IA32_NR_syscalls) {

		/*

		 * It's possible that a 32-bit syscall implementation

		 * takes a 64-bit parameter but nonetheless assumes that

		 * the high bits are zero.  Make sure we zero-extend all

		 * of the args.

		 */

		regs->ax = ia32_sys_call_table[nr](

			(unsigned int)regs->bx, (unsigned int)regs->cx,

			(unsigned int)regs->dx, (unsigned int)regs->si,

			(unsigned int)regs->di, (unsigned int)regs->bp);

	}



	syscall_return_slowpath(regs);

}

#endif