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>

3 files changed, 116 insertions, 2 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
 
 /*
diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index 017d937639fe..16433a59b396 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -48,6 +48,7 @@ enum x86_regset {
         REGSET_FP,
         REGSET_XFP,
         REGSET_IOPERM64 = REGSET_XFP,
+        REGSET_XSTATE,
         REGSET_TLS,
         REGSET_IOPERM32,
 };
@@ -1584,7 +1585,7 @@ long compat_arch_ptrace(struct task_struct *child, compat_long_t request,
 
 #ifdef CONFIG_X86_64
 
-static const struct user_regset x86_64_regsets[] = {
+static struct user_regset x86_64_regsets[] __read_mostly = {
         [REGSET_GENERAL] = {
                 .core_note_type = NT_PRSTATUS,
                 .n = sizeof(struct user_regs_struct) / sizeof(long),
@@ -1597,6 +1598,12 @@ static const struct user_regset x86_64_regsets[] = {
                 .size = sizeof(long), .align = sizeof(long),
                 .active = xfpregs_active, .get = xfpregs_get, .set = xfpregs_set
         },
+        [REGSET_XSTATE] = {
+                .core_note_type = NT_X86_XSTATE,
+                .size = sizeof(u64), .align = sizeof(u64),
+                .active = xstateregs_active, .get = xstateregs_get,
+                .set = xstateregs_set
+        },
         [REGSET_IOPERM64] = {
                 .core_note_type = NT_386_IOPERM,
                 .n = IO_BITMAP_LONGS,
@@ -1622,7 +1629,7 @@ static const struct user_regset_view user_x86_64_view = {
 #endif  /* CONFIG_X86_64 */
 
 #if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION
-static const struct user_regset x86_32_regsets[] = {
+static struct user_regset x86_32_regsets[] __read_mostly = {
         [REGSET_GENERAL] = {
                 .core_note_type = NT_PRSTATUS,
                 .n = sizeof(struct user_regs_struct32) / sizeof(u32),
@@ -1641,6 +1648,12 @@ static const struct user_regset x86_32_regsets[] = {
                 .size = sizeof(u32), .align = sizeof(u32),
                 .active = xfpregs_active, .get = xfpregs_get, .set = xfpregs_set
         },
+        [REGSET_XSTATE] = {
+                .core_note_type = NT_X86_XSTATE,
+                .size = sizeof(u64), .align = sizeof(u64),
+                .active = xstateregs_active, .get = xstateregs_get,
+                .set = xstateregs_set
+        },
         [REGSET_TLS] = {
                 .core_note_type = NT_386_TLS,
                 .n = GDT_ENTRY_TLS_ENTRIES, .bias = GDT_ENTRY_TLS_MIN,
@@ -1663,6 +1676,23 @@ static const struct user_regset_view user_x86_32_view = {
 };
 #endif
 
+/*
+ * This represents bytes 464..511 in the memory layout exported through
+ * the REGSET_XSTATE interface.
+ */
+u64 xstate_fx_sw_bytes[USER_XSTATE_FX_SW_WORDS];
+
+void update_regset_xstate_info(unsigned int size, u64 xstate_mask)
+{
+#ifdef CONFIG_X86_64
+        x86_64_regsets[REGSET_XSTATE].n = size / sizeof(u64);
+#endif
+#if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION
+        x86_32_regsets[REGSET_XSTATE].n = size / sizeof(u64);
+#endif
+        xstate_fx_sw_bytes[USER_XSTATE_XCR0_WORD] = xstate_mask;
+}
+
 const struct user_regset_view *task_user_regset_view(struct task_struct *task)
 {
 #ifdef CONFIG_IA32_EMULATION
diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c
index c5ee17e8c6d9..782c3a362ec6 100644
--- a/arch/x86/kernel/xsave.c
+++ b/arch/x86/kernel/xsave.c
@@ -337,6 +337,7 @@ void __ref xsave_cntxt_init(void)
         cpuid_count(0xd, 0, &eax, &ebx, &ecx, &edx);
         xstate_size = ebx;
 
+        update_regset_xstate_info(xstate_size, pcntxt_mask);
         prepare_fx_sw_frame();
 
         setup_xstate_init();