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Subject[patch v2 2/4] 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>
Signed-off-by: Hongjiu Lu <hjl.tools@gmail.com>
---
arch/x86/include/asm/i387.h | 12 ++++-
arch/x86/include/asm/xsave.h | 2
arch/x86/kernel/i387.c | 88 ++++++++++++++++++++++++++++++++++++++++++-
arch/x86/kernel/ptrace.c | 29 +++++++++++++-
arch/x86/kernel/xsave.c | 1
include/linux/elf.h | 1
6 files changed, 127 insertions(+), 6 deletions(-)
Index: tip/arch/x86/include/asm/i387.h
===================================================================
--- tip.orig/arch/x86/include/asm/i387.h
+++ tip/arch/x86/include/asm/i387.h
@@ -33,8 +33,16 @@ extern void init_thread_xstate(void);
extern int dump_fpu(struct pt_regs *, struct user_i387_struct *);

extern user_regset_active_fn fpregs_active, xfpregs_active;
-extern user_regset_get_fn fpregs_get, xfpregs_get, fpregs_soft_get;
-extern user_regset_set_fn fpregs_set, xfpregs_set, fpregs_soft_set;
+extern user_regset_get_fn fpregs_get, xfpregs_get, fpregs_soft_get,
+ xstateregs_get;
+extern user_regset_set_fn fpregs_set, xfpregs_set, fpregs_soft_set,
+ xstateregs_set;
+
+/*
+ * xstateregs_active == fpregs_active. Please refer to the comment
+ * at the definition of fpregs_active.
+ */
+#define xstateregs_active fpregs_active

extern struct _fpx_sw_bytes fx_sw_reserved;
#ifdef CONFIG_IA32_EMULATION
Index: tip/arch/x86/include/asm/xsave.h
===================================================================
--- tip.orig/arch/x86/include/asm/xsave.h
+++ tip/arch/x86/include/asm/xsave.h
@@ -27,9 +27,11 @@
extern unsigned int xstate_size;
extern u64 pcntxt_mask;
extern struct xsave_struct *init_xstate_buf;
+extern u64 xstate_fx_sw_bytes[6];

extern void xsave_cntxt_init(void);
extern void xsave_init(void);
+extern void update_regset_xstate_info(unsigned int size, u64 xstate_mask);
extern int init_fpu(struct task_struct *child);
extern int check_for_xstate(struct i387_fxsave_struct __user *buf,
void __user *fpstate,
Index: tip/arch/x86/kernel/i387.c
===================================================================
--- tip.orig/arch/x86/kernel/i387.c
+++ tip/arch/x86/kernel/i387.c
@@ -164,6 +164,11 @@ int init_fpu(struct task_struct *tsk)
return 0;
}

+/*
+ * The xfpregs_active() routine is 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;
@@ -204,8 +209,6 @@ int xfpregs_set(struct task_struct *targ
if (ret)
return ret;

- set_stopped_child_used_math(target);
-
ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
&target->thread.xstate->fxsave, 0, -1);

@@ -224,6 +227,87 @@ int xfpregs_set(struct task_struct *targ
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;
+ int size = regset->n * regset->size;
+ struct xsave_hdr_struct *xsave_hdr =
+ &target->thread.xstate->xsave.xsave_hdr;
+
+ 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 i387_fxsave_struct,
+ sw_reserved));
+ if (!ret)
+ /*
+ * Copy the 48bytes defined by software
+ */
+ ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf,
+ xstate_fx_sw_bytes,
+ offsetof(struct i387_fxsave_struct,
+ sw_reserved),
+ offsetof(struct xsave_struct,
+ xsave_hdr));
+ if (!ret)
+ /*
+ * Copy the rest of xstate memory layout
+ */
+ ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf,
+ xsave_hdr,
+ offsetof(struct xsave_struct,
+ xsave_hdr), size);
+ 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;
+ int size = regset->n * regset->size;
+ struct xsave_hdr_struct *xsave_hdr =
+ &target->thread.xstate->xsave.xsave_hdr;
+
+
+ if (!cpu_has_xsave)
+ return -ENODEV;
+
+ ret = init_fpu(target);
+ if (ret)
+ return ret;
+
+ set_stopped_child_used_math(target);
+
+ ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
+ &target->thread.xstate->xsave, 0, size);
+
+ /*
+ * mxcsr reserved bits must be masked to zero for security reasons.
+ */
+ target->thread.xstate->fxsave.mxcsr &= mxcsr_feature_mask;
+
+ 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

/*
Index: tip/arch/x86/kernel/ptrace.c
===================================================================
--- tip.orig/arch/x86/kernel/ptrace.c
+++ tip/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,
};
@@ -1560,7 +1561,7 @@ long compat_arch_ptrace(struct task_stru

#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),
@@ -1573,6 +1574,12 @@ static const struct user_regset x86_64_r
.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(long), .align = sizeof(long),
+ .active = xstateregs_active, .get = xstateregs_get,
+ .set = xstateregs_set
+ },
[REGSET_IOPERM64] = {
.core_note_type = NT_386_IOPERM,
.n = IO_BITMAP_LONGS,
@@ -1598,7 +1605,7 @@ static const struct user_regset_view use
#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),
@@ -1617,6 +1624,12 @@ static const struct user_regset x86_32_r
.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(u32), .align = sizeof(u32),
+ .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,
@@ -1639,6 +1652,18 @@ static const struct user_regset_view use
};
#endif

+u64 xstate_fx_sw_bytes[6];
+void update_regset_xstate_info(unsigned int size, u64 xstate_mask)
+{
+#ifdef CONFIG_X86_64
+ x86_64_regsets[REGSET_XSTATE].n = size / sizeof(long);
+#endif
+#if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION
+ x86_32_regsets[REGSET_XSTATE].n = size / sizeof(u32);
+#endif
+ xstate_fx_sw_bytes[0] = xstate_mask;
+}
+
const struct user_regset_view *task_user_regset_view(struct task_struct *task)
{
#ifdef CONFIG_IA32_EMULATION
Index: tip/arch/x86/kernel/xsave.c
===================================================================
--- tip.orig/arch/x86/kernel/xsave.c
+++ tip/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();
Index: tip/include/linux/elf.h
===================================================================
--- tip.orig/include/linux/elf.h
+++ tip/include/linux/elf.h
@@ -361,6 +361,7 @@ typedef struct elf64_shdr {
#define NT_PPC_VSX 0x102 /* PowerPC VSX registers */
#define NT_386_TLS 0x200 /* i386 TLS slots (struct user_desc) */
#define NT_386_IOPERM 0x201 /* x86 io permission bitmap (1=deny) */
+#define NT_X86_XSTATE 0x202 /* x86 extended state using xsave */
#define NT_S390_HIGH_GPRS 0x300 /* s390 upper register halves */





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