x86, ptrace: regset extensions to support xstate

Add the xstate regset support which helps extend the kernel ptrace and the
core-dump interfaces to support AVX state etc.

This regset interface is designed to support all the future state that gets
supported using xsave/xrstor infrastructure.

Looking at the memory layout saved by "xsave", one can't say which state
is represented in the memory layout. This is because if a particular state is
in init state, in the xsave hdr it can be represented by bit '0'. And hence
we can't really say by the xsave header wether a state is in init state or
the state is not saved in the memory layout.

And hence the xsave memory layout available through this regset
interface uses SW usable bytes [464..511] to convey what state is represented
in the memory layout.

First 8 bytes of the sw_usable_bytes[464..467] will be set to OS enabled xstate
mask(which is same as the 64bit mask returned by the xgetbv's xCR0).

The note NT_X86_XSTATE represents the extended state information in the
core file, using the above mentioned memory layout.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
LKML-Reference: <20100211195614.802495327@sbs-t61.sc.intel.com>
Signed-off-by: Hongjiu Lu <hjl.tools@gmail.com>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

1 files changed, 83 insertions, 0 deletions

diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
index f2f8540a7f3d..7a8a193b5144 100644
--- a/arch/x86/kernel/i387.c
+++ b/arch/x86/kernel/i387.c
@@ -164,6 +164,11 @@ int init_fpu(struct task_struct *tsk)
         return 0;
 }
 
+/*
+ * The xstateregs_active() routine is the same as the fpregs_active() routine,
+ * as the "regset->n" for the xstate regset will be updated based on the feature
+ * capabilites supported by the xsave.
+ */
 int fpregs_active(struct task_struct *target, const struct user_regset *regset)
 {
         return tsk_used_math(target) ? regset->n : 0;
@@ -224,6 +229,84 @@ int xfpregs_set(struct task_struct *target, const struct user_regset *regset,
         return ret;
 }
 
+int xstateregs_get(struct task_struct *target, const struct user_regset *regset,
+                unsigned int pos, unsigned int count,
+                void *kbuf, void __user *ubuf)
+{
+        int ret;
+
+        if (!cpu_has_xsave)
+                return -ENODEV;
+
+        ret = init_fpu(target);
+        if (ret)
+                return ret;
+
+        /*
+         * First copy the fxsave bytes 0..463.
+         */
+        ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf,
+                                  &target->thread.xstate->xsave, 0,
+                                  offsetof(struct user_xstateregs,
+                                           i387.xstate_fx_sw));
+        if (ret)
+                return ret;
+
+        /*
+         * Copy the 48bytes defined by software.
+         */
+        ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf,
+                                  xstate_fx_sw_bytes,
+                                  offsetof(struct user_xstateregs,
+                                           i387.xstate_fx_sw),
+                                  offsetof(struct user_xstateregs,
+                                           xsave_hdr));
+        if (ret)
+                return ret;
+
+        /*
+         * Copy the rest of xstate memory layout.
+         */
+        ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf,
+                                  &target->thread.xstate->xsave.xsave_hdr,
+                                  offsetof(struct user_xstateregs,
+                                           xsave_hdr), -1);
+        return ret;
+}
+
+int xstateregs_set(struct task_struct *target, const struct user_regset *regset,
+                  unsigned int pos, unsigned int count,
+                  const void *kbuf, const void __user *ubuf)
+{
+        int ret;
+        struct xsave_hdr_struct *xsave_hdr;
+
+        if (!cpu_has_xsave)
+                return -ENODEV;
+
+        ret = init_fpu(target);
+        if (ret)
+                return ret;
+
+        ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
+                                 &target->thread.xstate->xsave, 0, -1);
+
+        /*
+         * mxcsr reserved bits must be masked to zero for security reasons.
+         */
+        target->thread.xstate->fxsave.mxcsr &= mxcsr_feature_mask;
+
+        xsave_hdr = &target->thread.xstate->xsave.xsave_hdr;
+
+        xsave_hdr->xstate_bv &= pcntxt_mask;
+        /*
+         * These bits must be zero.
+         */
+        xsave_hdr->reserved1[0] = xsave_hdr->reserved1[1] = 0;
+
+        return ret;
+}
+
 #if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION
 
 /*