x86: move switch_to macro to system.h

This patch moves the switch_to() macro to system.h

As those macros are fundamentally different between i386 and x86_64,
they are enclosed around an ifdef.

Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 61 insertions, 0 deletions

diff --git a/include/asm-x86/system.h b/include/asm-x86/system.h
index 4c15eb11a917..ba3403f1d020 100644
--- a/include/asm-x86/system.h
+++ b/include/asm-x86/system.h
@@ -6,8 +6,69 @@
 #include <linux/kernel.h>
 
 #ifdef CONFIG_X86_32
+#define AT_VECTOR_SIZE_ARCH 2 /* entries in ARCH_DLINFO */
+
+struct task_struct; /* one of the stranger aspects of C forward declarations */
+extern struct task_struct *FASTCALL(__switch_to(struct task_struct *prev,
+                                                struct task_struct *next));
+
+/*
+ * Saving eflags is important. It switches not only IOPL between tasks,
+ * it also protects other tasks from NT leaking through sysenter etc.
+ */
+#define switch_to(prev, next, last) do {                                \
+        unsigned long esi, edi;                                         \
+        asm volatile("pushfl\n\t"               /* Save flags */        \
+                     "pushl %%ebp\n\t"                                  \
+                     "movl %%esp,%0\n\t"        /* save ESP */          \
+                     "movl %5,%%esp\n\t"        /* restore ESP */       \
+                     "movl $1f,%1\n\t"          /* save EIP */          \
+                     "pushl %6\n\t"             /* restore EIP */       \
+                     "jmp __switch_to\n"                                \
+                     "1:\t"                                             \
+                     "popl %%ebp\n\t"                                   \
+                     "popfl"                                            \
+                     :"=m" (prev->thread.sp), "=m" (prev->thread.ip),   \
+                      "=a" (last), "=S" (esi), "=D" (edi)               \
+                     :"m" (next->thread.sp), "m" (next->thread.ip),     \
+                      "2" (prev), "d" (next));                          \
+} while (0)
+
 # include "system_32.h"
 #else
+#define __SAVE(reg, offset) "movq %%" #reg ",(14-" #offset ")*8(%%rsp)\n\t"
+#define __RESTORE(reg, offset) "movq (14-" #offset ")*8(%%rsp),%%" #reg "\n\t"
+
+/* frame pointer must be last for get_wchan */
+#define SAVE_CONTEXT    "pushf ; pushq %%rbp ; movq %%rsi,%%rbp\n\t"
+#define RESTORE_CONTEXT "movq %%rbp,%%rsi ; popq %%rbp ; popf\t"
+
+#define __EXTRA_CLOBBER  \
+        , "rcx", "rbx", "rdx", "r8", "r9", "r10", "r11", \
+          "r12", "r13", "r14", "r15"
+
+/* Save restore flags to clear handle leaking NT */
+#define switch_to(prev, next, last) \
+        asm volatile(SAVE_CONTEXT                                         \
+             "movq %%rsp,%P[threadrsp](%[prev])\n\t" /* save RSP */       \
+             "movq %P[threadrsp](%[next]),%%rsp\n\t" /* restore RSP */    \
+             "call __switch_to\n\t"                                       \
+             ".globl thread_return\n"                                     \
+             "thread_return:\n\t"                                         \
+             "movq %%gs:%P[pda_pcurrent],%%rsi\n\t"                       \
+             "movq %P[thread_info](%%rsi),%%r8\n\t"                       \
+             LOCK_PREFIX "btr  %[tif_fork],%P[ti_flags](%%r8)\n\t"        \
+             "movq %%rax,%%rdi\n\t"                                       \
+             "jc   ret_from_fork\n\t"                                     \
+             RESTORE_CONTEXT                                              \
+             : "=a" (last)                                                \
+             : [next] "S" (next), [prev] "D" (prev),                      \
+               [threadrsp] "i" (offsetof(struct task_struct, thread.sp)), \
+               [ti_flags] "i" (offsetof(struct thread_info, flags)),      \
+               [tif_fork] "i" (TIF_FORK),                                 \
+               [thread_info] "i" (offsetof(struct task_struct, stack)),   \
+               [pda_pcurrent] "i" (offsetof(struct x8664_pda, pcurrent))  \
+             : "memory", "cc" __EXTRA_CLOBBER)
 # include "system_64.h"
 #endif