From 710246df58041106b7de645f4b45770f8a59a269 Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Mon, 5 Oct 2015 17:48:10 -0700 Subject: [PATCH] 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 Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-kernel@vger.kernel.org Link: http://lkml.kernel.org/r/6041a58a9b8ef6d2522ab4350deb1a1945eb563f.1444091585.git.luto@kernel.org Signed-off-by: Ingo Molnar --- arch/x86/entry/common.c | 43 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 43 insertions(+) diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c index 41d17508cf46..1b2606edc621 100644 --- a/arch/x86/entry/common.c +++ b/arch/x86/entry/common.c @@ -24,6 +24,8 @@ #include #include +#include +#include #define CREATE_TRACE_POINTS #include @@ -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 *)®s->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 -- 2.20.1