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Subject[tip:x86/fpu] x86/fpu/xstate: Define and use 'fpu_user_xstate_size'
Commit-ID:  a1141e0b5ca6ee3e5e35d5f1a310a5ecb9c96ce5
Gitweb: http://git.kernel.org/tip/a1141e0b5ca6ee3e5e35d5f1a310a5ecb9c96ce5
Author: Fenghua Yu <fenghua.yu@intel.com>
AuthorDate: Fri, 20 May 2016 10:47:05 -0700
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Sat, 18 Jun 2016 10:10:18 +0200

x86/fpu/xstate: Define and use 'fpu_user_xstate_size'

The kernel xstate area can be in standard or compacted format;
it is always in standard format for user mode. When XSAVES is
enabled, the kernel uses the compacted format and it is necessary
to use a separate fpu_user_xstate_size for signal/ptrace frames.

Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
[ Rebased the patch and cleaned up the naming. ]
Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
Reviewed-by: Dave Hansen <dave.hansen@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: Ravi V. Shankar <ravi.v.shankar@intel.com>
Cc: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/8756ec34dabddfc727cda5743195eb81e8caf91c.1463760376.git.yu-cheng.yu@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/include/asm/fpu/xstate.h | 1 -
arch/x86/include/asm/processor.h | 1 +
arch/x86/kernel/fpu/init.c | 5 ++-
arch/x86/kernel/fpu/signal.c | 27 ++++++++++----
arch/x86/kernel/fpu/xstate.c | 76 ++++++++++++++++++++++++---------------
5 files changed, 73 insertions(+), 37 deletions(-)

diff --git a/arch/x86/include/asm/fpu/xstate.h b/arch/x86/include/asm/fpu/xstate.h
index 38951b0..16df2c4 100644
--- a/arch/x86/include/asm/fpu/xstate.h
+++ b/arch/x86/include/asm/fpu/xstate.h
@@ -39,7 +39,6 @@
#define REX_PREFIX
#endif

-extern unsigned int xstate_size;
extern u64 xfeatures_mask;
extern u64 xstate_fx_sw_bytes[USER_XSTATE_FX_SW_WORDS];

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 62c6cc3..0a16a16 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -368,6 +368,7 @@ DECLARE_PER_CPU(struct irq_stack *, softirq_stack);
#endif /* X86_64 */

extern unsigned int xstate_size;
+extern unsigned int fpu_user_xstate_size;

struct perf_event;

diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c
index aacfd7a..5b1928c 100644
--- a/arch/x86/kernel/fpu/init.c
+++ b/arch/x86/kernel/fpu/init.c
@@ -195,7 +195,7 @@ static void __init fpu__init_task_struct_size(void)
}

/*
- * Set up the xstate_size based on the legacy FPU context size.
+ * Set up the user and kernel xstate_size based on the legacy FPU context size.
*
* We set this up first, and later it will be overwritten by
* fpu__init_system_xstate() if the CPU knows about xstates.
@@ -226,6 +226,9 @@ static void __init fpu__init_system_xstate_size_legacy(void)
else
xstate_size = sizeof(struct fregs_state);
}
+
+ fpu_user_xstate_size = xstate_size;
+
/*
* Quirk: we don't yet handle the XSAVES* instructions
* correctly, as we don't correctly convert between
diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index c6f2a3c..0d29d4d 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -32,7 +32,7 @@ static inline int check_for_xstate(struct fxregs_state __user *buf,
/* Check for the first magic field and other error scenarios. */
if (fx_sw->magic1 != FP_XSTATE_MAGIC1 ||
fx_sw->xstate_size < min_xstate_size ||
- fx_sw->xstate_size > xstate_size ||
+ fx_sw->xstate_size > fpu_user_xstate_size ||
fx_sw->xstate_size > fx_sw->extended_size)
return -1;

@@ -89,7 +89,8 @@ static inline int save_xstate_epilog(void __user *buf, int ia32_frame)
if (!use_xsave())
return err;

- err |= __put_user(FP_XSTATE_MAGIC2, (__u32 *)(buf + xstate_size));
+ err |= __put_user(FP_XSTATE_MAGIC2,
+ (__u32 *)(buf + fpu_user_xstate_size));

/*
* Read the xfeatures which we copied (directly from the cpu or
@@ -126,7 +127,7 @@ static inline int copy_fpregs_to_sigframe(struct xregs_state __user *buf)
else
err = copy_fregs_to_user((struct fregs_state __user *) buf);

- if (unlikely(err) && __clear_user(buf, xstate_size))
+ if (unlikely(err) && __clear_user(buf, fpu_user_xstate_size))
err = -EFAULT;
return err;
}
@@ -176,8 +177,19 @@ int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
if (ia32_fxstate)
copy_fxregs_to_kernel(&tsk->thread.fpu);
} else {
+ /*
+ * It is a *bug* if kernel uses compacted-format for xsave
+ * area and we copy it out directly to a signal frame. It
+ * should have been handled above by saving the registers
+ * directly.
+ */
+ if (boot_cpu_has(X86_FEATURE_XSAVES)) {
+ WARN_ONCE(1, "x86/fpu: saving compacted-format xsave area to a signal frame!\n");
+ return -1;
+ }
+
fpstate_sanitize_xstate(&tsk->thread.fpu);
- if (__copy_to_user(buf_fx, xsave, xstate_size))
+ if (__copy_to_user(buf_fx, xsave, fpu_user_xstate_size))
return -1;
}

@@ -344,7 +356,8 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)

static inline int xstate_sigframe_size(void)
{
- return use_xsave() ? xstate_size + FP_XSTATE_MAGIC2_SIZE : xstate_size;
+ return use_xsave() ? fpu_user_xstate_size + FP_XSTATE_MAGIC2_SIZE :
+ fpu_user_xstate_size;
}

/*
@@ -388,12 +401,12 @@ fpu__alloc_mathframe(unsigned long sp, int ia32_frame,
*/
void fpu__init_prepare_fx_sw_frame(void)
{
- int size = xstate_size + FP_XSTATE_MAGIC2_SIZE;
+ int size = fpu_user_xstate_size + FP_XSTATE_MAGIC2_SIZE;

fx_sw_reserved.magic1 = FP_XSTATE_MAGIC1;
fx_sw_reserved.extended_size = size;
fx_sw_reserved.xfeatures = xfeatures_mask;
- fx_sw_reserved.xstate_size = xstate_size;
+ fx_sw_reserved.xstate_size = fpu_user_xstate_size;

if (config_enabled(CONFIG_IA32_EMULATION) ||
config_enabled(CONFIG_X86_32)) {
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 4ea2a59..9c4da35 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -44,6 +44,13 @@ static unsigned int xstate_sizes[XFEATURE_MAX] = { [ 0 ... XFEATURE_MAX - 1] =
static unsigned int xstate_comp_offsets[sizeof(xfeatures_mask)*8];

/*
+ * The XSAVE area of kernel can be in standard or compacted format;
+ * it is always in standard format for user mode. This is the user
+ * mode standard format size used for signal and ptrace frames.
+ */
+unsigned int fpu_user_xstate_size;
+
+/*
* Clear all of the X86_FEATURE_* bits that are unavailable
* when the CPU has no XSAVE support.
*/
@@ -171,7 +178,7 @@ void fpstate_sanitize_xstate(struct fpu *fpu)
*/
while (xfeatures) {
if (xfeatures & 0x1) {
- int offset = xstate_offsets[feature_bit];
+ int offset = xstate_comp_offsets[feature_bit];
int size = xstate_sizes[feature_bit];

memcpy((void *)fx + offset,
@@ -533,8 +540,9 @@ static void do_extra_xstate_size_checks(void)
XSTATE_WARN_ON(paranoid_xstate_size != xstate_size);
}

+
/*
- * Calculate total size of enabled xstates in XCR0/xfeatures_mask.
+ * Get total size of enabled xstates in XCR0/xfeatures_mask.
*
* Note the SDM's wording here. "sub-function 0" only enumerates
* the size of the *user* states. If we use it to size a buffer
@@ -544,34 +552,33 @@ static void do_extra_xstate_size_checks(void)
* Note that we do not currently set any bits on IA32_XSS so
* 'XCR0 | IA32_XSS == XCR0' for now.
*/
-static unsigned int __init calculate_xstate_size(void)
+static unsigned int __init get_xsaves_size(void)
{
unsigned int eax, ebx, ecx, edx;
- unsigned int calculated_xstate_size;
+ /*
+ * - CPUID function 0DH, sub-function 1:
+ * EBX enumerates the size (in bytes) required by
+ * the XSAVES instruction for an XSAVE area
+ * containing all the state components
+ * corresponding to bits currently set in
+ * XCR0 | IA32_XSS.
+ */
+ cpuid_count(XSTATE_CPUID, 1, &eax, &ebx, &ecx, &edx);
+ return ebx;
+}

- if (!boot_cpu_has(X86_FEATURE_XSAVES)) {
- /*
- * - CPUID function 0DH, sub-function 0:
- * EBX enumerates the size (in bytes) required by
- * the XSAVE instruction for an XSAVE area
- * containing all the *user* state components
- * corresponding to bits currently set in XCR0.
- */
- cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
- calculated_xstate_size = ebx;
- } else {
- /*
- * - CPUID function 0DH, sub-function 1:
- * EBX enumerates the size (in bytes) required by
- * the XSAVES instruction for an XSAVE area
- * containing all the state components
- * corresponding to bits currently set in
- * XCR0 | IA32_XSS.
- */
- cpuid_count(XSTATE_CPUID, 1, &eax, &ebx, &ecx, &edx);
- calculated_xstate_size = ebx;
- }
- return calculated_xstate_size;
+static unsigned int __init get_xsave_size(void)
+{
+ unsigned int eax, ebx, ecx, edx;
+ /*
+ * - CPUID function 0DH, sub-function 0:
+ * EBX enumerates the size (in bytes) required by
+ * the XSAVE instruction for an XSAVE area
+ * containing all the *user* state components
+ * corresponding to bits currently set in XCR0.
+ */
+ cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
+ return ebx;
}

/*
@@ -591,7 +598,15 @@ static bool is_supported_xstate_size(unsigned int test_xstate_size)
static int init_xstate_size(void)
{
/* Recompute the context size for enabled features: */
- unsigned int possible_xstate_size = calculate_xstate_size();
+ unsigned int possible_xstate_size;
+ unsigned int xsave_size;
+
+ xsave_size = get_xsave_size();
+
+ if (boot_cpu_has(X86_FEATURE_XSAVES))
+ possible_xstate_size = get_xsaves_size();
+ else
+ possible_xstate_size = xsave_size;

/* Ensure we have the space to store all enabled: */
if (!is_supported_xstate_size(possible_xstate_size))
@@ -603,6 +618,11 @@ static int init_xstate_size(void)
*/
xstate_size = possible_xstate_size;
do_extra_xstate_size_checks();
+
+ /*
+ * User space is always in standard format.
+ */
+ fpu_user_xstate_size = xsave_size;
return 0;
}

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