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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: Andy 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: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Andy Lutomirski 2015-10-05 17:48:10 -07:00 committed by Ingo Molnar
parent ee08c6bd31
commit 710246df58
1 changed files with 43 additions and 0 deletions
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43
arch/x86/entry/common.c
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@ -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