x86/fpu, sched: Introduce CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT and use it on x86

[linux-2.6-block.git] / arch / x86 / kernel / fpu / init.c

diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c
index fc878fee6a512a4485ac1d37db76da75f2501f25..0b39173dd9714ebed0eaca58b27af65e86dfbc0c 100644 (file)
--- a/arch/x86/kernel/fpu/init.c
+++ b/arch/x86/kernel/fpu/init.c
@@ -4,6 +4,8 @@
 #include <asm/fpu/internal.h>
 #include <asm/tlbflush.h>
 
+#include <linux/sched.h>
+
 /*
  * Initialize the TS bit in CR0 according to the style of context-switches
  * we are using:
@@ -95,11 +97,12 @@ static void __init fpu__init_system_mxcsr(void)
        unsigned int mask = 0;
 
        if (cpu_has_fxsr) {
-               struct fxregs_state fx_tmp __aligned(32) = { };
+               /* Static because GCC does not get 16-byte stack alignment right: */
+               static struct fxregs_state fxregs __initdata;
 
-               asm volatile("fxsave %0" : "+m" (fx_tmp));
+               asm volatile("fxsave %0" : "+m" (fxregs));
 
-               mask = fx_tmp.mxcsr_mask;
+               mask = fxregs.mxcsr_mask;
 
                /*
                 * If zero then use the default features mask,
@@ -135,6 +138,43 @@ static void __init fpu__init_system_generic(void)
 unsigned int xstate_size;
 EXPORT_SYMBOL_GPL(xstate_size);
 
+/* Enforce that 'MEMBER' is the last field of 'TYPE': */
+#define CHECK_MEMBER_AT_END_OF(TYPE, MEMBER) \
+       BUILD_BUG_ON(sizeof(TYPE) != offsetofend(TYPE, MEMBER))
+
+/*
+ * We append the 'struct fpu' to the task_struct:
+ */
+static void __init fpu__init_task_struct_size(void)
+{
+       int task_size = sizeof(struct task_struct);
+
+       /*
+        * Subtract off the static size of the register state.
+        * It potentially has a bunch of padding.
+        */
+       task_size -= sizeof(((struct task_struct *)0)->thread.fpu.state);
+
+       /*
+        * Add back the dynamically-calculated register state
+        * size.
+        */
+       task_size += xstate_size;
+
+       /*
+        * We dynamically size 'struct fpu', so we require that
+        * it be at the end of 'thread_struct' and that
+        * 'thread_struct' be at the end of 'task_struct'.  If
+        * you hit a compile error here, check the structure to
+        * see if something got added to the end.
+        */
+       CHECK_MEMBER_AT_END_OF(struct fpu, state);
+       CHECK_MEMBER_AT_END_OF(struct thread_struct, fpu);
+       CHECK_MEMBER_AT_END_OF(struct task_struct, thread);
+
+       arch_task_struct_size = task_size;
+}
+
 /*
  * Set up the xstate_size based on the legacy FPU context size.
  *
@@ -286,6 +326,7 @@ void __init fpu__init_system(struct cpuinfo_x86 *c)
        fpu__init_system_generic();
        fpu__init_system_xstate_size_legacy();
        fpu__init_system_xstate();
+       fpu__init_task_struct_size();
 
        fpu__init_system_ctx_switch();
 }