Commit-ID: 710246df58041106b7de645f4b45770f8a59a269
Gitweb: http://git.kernel.org/tip/710246df58041106b7de645f4b45770f8a59a269
Author: Andy Lutomirski <luto@xxxxxxxxxx>
AuthorDate: Mon, 5 Oct 2015 17:48:10 -0700
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Fri, 9 Oct 2015 09:41:09 +0200
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@xxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/6041a58a9b8ef6d2522ab4350deb1a1945eb563f.1444091585.git.luto@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
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 41d1750..1b2606e 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -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 *)®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
--
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