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Date: Thu, 2 Apr 2015 15:11:22 +0200
From: Borislav Petkov <bp@...en8.de>
To: X86 ML <x86@...nel.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Quentin Casasnovas <quentin.casasnovas@...cle.com>,
Oleg Nesterov <oleg@...hat.com>,
Andy Lutomirski <luto@...capital.net>
Subject: [PATCH] x86/xsave: Robustify and merge macros
From: Borislav Petkov <bp@...e.de>
Previously, we did call an XSAVE/XRSTOR variant through alternatives
and did potential exception handling resulting from the instruction
execution in a second inline asm. Which was misleading and error prone,
see
06c8173eb92b ("x86/fpu/xsaves: Fix improper uses of __ex_table")
for an example.
Add single macros which combine the alternatives and the exception
handling.
While at it, remove the SYSTEM_BOOTING checks in favor of
static_cpu_has_safe() which works regardless of system state.
Cleanup comments.
Signed-off-by: Borislav Petkov <bp@...e.de>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Quentin Casasnovas <quentin.casasnovas@...cle.com>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: Andy Lutomirski <luto@...capital.net>
---
arch/x86/include/asm/xsave.h | 141 ++++++++++++++++++++++---------------------
1 file changed, 73 insertions(+), 68 deletions(-)
diff --git a/arch/x86/include/asm/xsave.h b/arch/x86/include/asm/xsave.h
index c9a6d68b8d62..e6c7986c95df 100644
--- a/arch/x86/include/asm/xsave.h
+++ b/arch/x86/include/asm/xsave.h
@@ -67,6 +67,66 @@ extern int init_fpu(struct task_struct *child);
_ASM_EXTABLE(1b, 3b) \
: [err] "=r" (err)
+#define XSTATE_OP(op, st, lmask, hmask, err) \
+ asm volatile("1:" op "\n\t" \
+ "2:\n\t" \
+ "xor %[err], %[err]\n" \
+ ".pushsection .fixup,\"ax\"\n\t" \
+ "3: movl $-1,%[err]\n\t" \
+ "jmp 2b\n\t" \
+ ".popsection\n\t" \
+ _ASM_EXTABLE(1b, 3b) \
+ : [err] "=r" (err) \
+ : "D" (st), "m" (*st), "a" (lmask), "d" (hmask) \
+ : "memory")
+
+/*
+ * If XSAVES is enabled, it replaces XSAVEOPT because it supports a compact
+ * format and supervisor states in addition to modified optimization in
+ * XSAVEOPT.
+ *
+ * Otherwise, if XSAVEOPT is enabled, XSAVEOPT replaces XSAVE because XSAVEOPT
+ * supports modified optimization which is not supported by XSAVE.
+ *
+ * We use XSAVE as a fallback.
+ *
+ * 661 and alt_end_marker labels below are defined in ALTERNATIVE* and we're
+ * reusing them here so as not to clutter this macro unnecessarily.
+ */
+#define XSTATE_XSAVE(st, lmask, hmask, err) \
+ asm volatile(ALTERNATIVE_2(XSAVE, \
+ XSAVEOPT, X86_FEATURE_XSAVEOPT, \
+ XSAVES, X86_FEATURE_XSAVES) \
+ "\n" \
+ "xor %[err], %[err]\n" \
+ ".pushsection .fixup,\"ax\"\n" \
+ "3: movl $-1, %[err]\n" \
+ "jmp " alt_end_marker "b\n" \
+ ".popsection\n" \
+ _ASM_EXTABLE(661b, 3b) \
+ : [err] "=r" (err) \
+ : "D" (st), "a" (lmask), "d" (hmask) \
+ : "memory")
+
+/*
+ * Use XRSTORS to restore context if it is enabled. XRSTORS supports compact
+ * XSAVE area format.
+ */
+#define XSTATE_XRESTORE(st, lmask, hmask, err) \
+ asm volatile(ALTERNATIVE(XRSTOR, \
+ XRSTORS, X86_FEATURE_XSAVES) \
+ "\n" \
+ "xor %[err], %[err]\n" \
+ ".pushsection .fixup,\"ax\"\n" \
+ "3: movl $-1, %[err]\n" \
+ "jmp 663b\n" \
+ ".popsection\n" \
+ _ASM_EXTABLE(661b, 3b) \
+ : [err] "=r" (err) \
+ : "D" (st), "m" (*st), "a" (lmask), "d" (hmask) \
+ : "memory")
+
+
/*
* This function is called only during boot time when x86 caps are not set
* up and alternative can not be used yet.
@@ -75,22 +135,13 @@ static inline int xsave_state_booting(struct xsave_struct *fx, u64 mask)
{
u32 lmask = mask;
u32 hmask = mask >> 32;
- int err = 0;
-
- WARN_ON(system_state != SYSTEM_BOOTING);
+ int err;
- if (boot_cpu_has(X86_FEATURE_XSAVES))
- asm volatile("1:"XSAVES"\n\t"
- "2:\n\t"
- xstate_fault
- : "D" (fx), "m" (*fx), "a" (lmask), "d" (hmask)
- : "memory");
+ if (static_cpu_has_safe(X86_FEATURE_XSAVES))
+ XSTATE_OP(XSAVES, fx, lmask, hmask, err);
else
- asm volatile("1:"XSAVE"\n\t"
- "2:\n\t"
- xstate_fault
- : "D" (fx), "m" (*fx), "a" (lmask), "d" (hmask)
- : "memory");
+ XSTATE_OP(XSAVE, fx, lmask, hmask, err);
+
return err;
}
@@ -102,22 +153,12 @@ static inline int xrstor_state_booting(struct xsave_struct *fx, u64 mask)
{
u32 lmask = mask;
u32 hmask = mask >> 32;
- int err = 0;
-
- WARN_ON(system_state != SYSTEM_BOOTING);
+ int err;
- if (boot_cpu_has(X86_FEATURE_XSAVES))
- asm volatile("1:"XRSTORS"\n\t"
- "2:\n\t"
- xstate_fault
- : "D" (fx), "m" (*fx), "a" (lmask), "d" (hmask)
- : "memory");
+ if (static_cpu_has_safe(X86_FEATURE_XSAVES))
+ XSTATE_OP(XRSTORS, fx, lmask, hmask, err);
else
- asm volatile("1:"XRSTOR"\n\t"
- "2:\n\t"
- xstate_fault
- : "D" (fx), "m" (*fx), "a" (lmask), "d" (hmask)
- : "memory");
+ XSTATE_OP(XRSTOR, fx, lmask, hmask, err);
return err;
}
@@ -128,31 +169,9 @@ static inline int xsave_state(struct xsave_struct *fx, u64 mask)
{
u32 lmask = mask;
u32 hmask = mask >> 32;
- int err = 0;
+ int err;
- /*
- * If xsaves is enabled, xsaves replaces xsaveopt because
- * it supports compact format and supervisor states in addition to
- * modified optimization in xsaveopt.
- *
- * Otherwise, if xsaveopt is enabled, xsaveopt replaces xsave
- * because xsaveopt supports modified optimization which is not
- * supported by xsave.
- *
- * If none of xsaves and xsaveopt is enabled, use xsave.
- */
- alternative_input_2(
- "1:"XSAVE,
- XSAVEOPT,
- X86_FEATURE_XSAVEOPT,
- XSAVES,
- X86_FEATURE_XSAVES,
- [fx] "D" (fx), "a" (lmask), "d" (hmask) :
- "memory");
- asm volatile("2:\n\t"
- xstate_fault
- : "0" (0)
- : "memory");
+ XSTATE_XSAVE(fx, lmask, hmask, err);
return err;
}
@@ -162,25 +181,11 @@ static inline int xsave_state(struct xsave_struct *fx, u64 mask)
*/
static inline int xrstor_state(struct xsave_struct *fx, u64 mask)
{
- int err = 0;
+ int err;
u32 lmask = mask;
u32 hmask = mask >> 32;
- /*
- * Use xrstors to restore context if it is enabled. xrstors supports
- * compacted format of xsave area which is not supported by xrstor.
- */
- alternative_input(
- "1: " XRSTOR,
- XRSTORS,
- X86_FEATURE_XSAVES,
- "D" (fx), "m" (*fx), "a" (lmask), "d" (hmask)
- : "memory");
-
- asm volatile("2:\n"
- xstate_fault
- : "0" (0)
- : "memory");
+ XSTATE_XRESTORE(fx, lmask, hmask, err);
return err;
}
--
2.3.3
--
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