Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 710246df authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Ingo Molnar
Browse files

x86/entry: Add C code for fast system call entries 



This handles both SYSENTER and SYSCALL.  The asm glue will take
care of the differences.

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/6041a58a9b8ef6d2522ab4350deb1a1945eb563f.1444091585.git.luto@kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent ee08c6bd

arch/x86/entry/common.c

+43 −0
Original line number Diff line number Diff line
@@ -24,6 +24,8 @@ 


#include <asm/desc.h>

#include <asm/traps.h>

#include <asm/vdso.h>

#include <asm/uaccess.h>



#define CREATE_TRACE_POINTS

#include <trace/events/syscalls.h>
@@ -360,4 +362,45 @@ __visible void do_int80_syscall_32(struct pt_regs *regs) 


	syscall_return_slowpath(regs);

}



__visible void do_fast_syscall_32(struct pt_regs *regs)

{

	/*

	 * Called using the internal vDSO SYSENTER/SYSCALL32 calling

	 * convention.  Adjust regs so it looks like we entered using int80.

	 */



	unsigned long landing_pad = (unsigned long)current->mm->context.vdso +

		vdso_image_32.sym_int80_landing_pad;



	/*

	 * SYSENTER loses EIP, and even SYSCALL32 needs us to skip forward

	 * so that 'regs->ip -= 2' lands back on an int $0x80 instruction.

	 * Fix it up.

	 */

	regs->ip = landing_pad;



	/*

	 * Fetch ECX from where the vDSO stashed it.

	 *

	 * WARNING: We are in CONTEXT_USER and RCU isn't paying attention!

	 */

	local_irq_enable();

	if (get_user(*(u32 *)&regs->cx,

		     (u32 __user __force *)(unsigned long)(u32)regs->sp)) {

		/* User code screwed up. */

		local_irq_disable();

		regs->ax = -EFAULT;

#ifdef CONFIG_CONTEXT_TRACKING

		enter_from_user_mode();

#endif

		prepare_exit_to_usermode(regs);

		return;

	}

	local_irq_disable();



	/* Now this is just like a normal syscall. */

	do_int80_syscall_32(regs);

	return;

}

#endif