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From: Thomas Gleixner <tglx@linutronix.de>
To: LKML <linux-kernel@vger.kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Fenghua Yu <fenghua.yu@intel.com>,
	Tony Luck <tony.luck@intel.com>,
	Yu-cheng Yu <yu-cheng.yu@intel.com>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Borislav Petkov <bp@suse.de>,
	Peter Zijlstra <peterz@infradead.org>,
	Kan Liang <kan.liang@linux.intel.com>,
	"Chang Seok Bae" <chang.seok.bae@intel.com>,
	Megha Dey <megha.dey@linux.intel.com>,
	Oliver Sang <oliver.sang@intel.com>
Subject: [patch V4 63/65] x86/fpu: Return proper error codes from user access functions
Date: Wed, 23 Jun 2021 14:02:30 +0200
Message-ID: <20210623121457.601480369@linutronix.de> (raw)
In-Reply-To: <20210623120127.327154589@linutronix.de>

When *RSTOR from user memory raises an exception there is no way to
differentiate them. That's bad because it forces the slow path even when
the failure was not a fault. If the operation raised eg. #GP then going
through the slow path is pointless.

Use _ASM_EXTABLE_FAULT() which stores the trap number and let the exception
fixup return the negated trap number as error.

This allows to separate the fast path and let it handle faults directly and
avoid the slow path for all other exceptions.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
V4: Fixup XSTATE_OP() as well (Boris)
---
 arch/x86/include/asm/fpu/internal.h |   19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -88,6 +88,7 @@ static inline void fpstate_init_soft(str
 #endif
 extern void save_fpregs_to_fpstate(struct fpu *fpu);
 
+/* Returns 0 or the negated trap number, which results in -EFAULT for #PF */
 #define user_insn(insn, output, input...)				\
 ({									\
 	int err;							\
@@ -95,14 +96,14 @@ extern void save_fpregs_to_fpstate(struc
 	might_fault();							\
 									\
 	asm volatile(ASM_STAC "\n"					\
-		     "1:" #insn "\n\t"					\
+		     "1: " #insn "\n"					\
 		     "2: " ASM_CLAC "\n"				\
 		     ".section .fixup,\"ax\"\n"				\
-		     "3:  movl $-1,%[err]\n"				\
+		     "3:  negl %%eax\n"					\
 		     "    jmp  2b\n"					\
 		     ".previous\n"					\
-		     _ASM_EXTABLE(1b, 3b)				\
-		     : [err] "=r" (err), output				\
+		     _ASM_EXTABLE_FAULT(1b, 3b)				\
+		     : [err] "=a" (err), output				\
 		     : "0"(0), input);					\
 	err;								\
 })
@@ -196,16 +197,20 @@ static inline void fxsave(struct fxregs_
 #define XRSTOR		".byte " REX_PREFIX "0x0f,0xae,0x2f"
 #define XRSTORS		".byte " REX_PREFIX "0x0f,0xc7,0x1f"
 
+/*
+ * After this @err contains 0 on success or the negated trap number when
+ * the operation raises an exception. For faults this results in -EFAULT.
+ */
 #define XSTATE_OP(op, st, lmask, hmask, err)				\
 	asm volatile("1:" op "\n\t"					\
 		     "xor %[err], %[err]\n"				\
 		     "2:\n\t"						\
 		     ".pushsection .fixup,\"ax\"\n\t"			\
-		     "3: movl $-2,%[err]\n\t"				\
+		     "3: negl %%eax\n\t"				\
 		     "jmp 2b\n\t"					\
 		     ".popsection\n\t"					\
-		     _ASM_EXTABLE(1b, 3b)				\
-		     : [err] "=r" (err)					\
+		     _ASM_EXTABLE_FAULT(1b, 3b)				\
+		     : [err] "=a" (err)					\
 		     : "D" (st), "m" (*st), "a" (lmask), "d" (hmask)	\
 		     : "memory")
 


  parent reply index

Thread overview: 134+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-23 12:01 [patch V4 00/65] x86/fpu: Spring cleaning and PKRU sanitizing Thomas Gleixner
2021-06-23 12:01 ` [patch V4 01/65] x86/fpu: Fix copy_xstate_to_kernel() gap handling Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:01 ` [patch V4 02/65] x86/pkeys: Revert a5eff7259790 ("x86/pkeys: Add PKRU value to init_fpstate") Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:01 ` [patch V4 03/65] x86/fpu: Mark various FPU states __ro_after_init Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] x86/fpu: Mark various FPU state variables __ro_after_init tip-bot2 for Thomas Gleixner
2021-06-23 12:01 ` [patch V4 04/65] x86/fpu: Make xfeatures_mask_all __ro_after_init Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:01 ` [patch V4 05/65] x86/fpu: Get rid of fpu__get_supported_xfeatures_mask() Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:01 ` [patch V4 06/65] x86/fpu: Remove unused get_xsave_field_ptr() Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:01 ` [patch V4 07/65] x86/fpu: Move inlines where they belong Thomas Gleixner
2021-06-23 18:43   ` Bae, Chang Seok
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:01 ` [patch V4 08/65] x86/fpu: Limit xstate copy size in xstateregs_set() Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:01 ` [patch V4 09/65] x86/fpu: Sanitize xstateregs_set() Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:01 ` [patch V4 10/65] x86/fpu: Reject invalid MXCSR values in copy_kernel_to_xstate() Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:01 ` [patch V4 11/65] x86/fpu: Simplify PTRACE_GETREGS code Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Dave Hansen
2021-06-23 12:01 ` [patch V4 12/65] x86/fpu: Rewrite xfpregs_set() Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Andy Lutomirski
2021-06-23 12:01 ` [patch V4 13/65] x86/fpu: Fail ptrace() requests that try to set invalid MXCSR values Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Andy Lutomirski
2021-06-23 12:01 ` [patch V4 14/65] x86/fpu: Clean up fpregs_set() Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Andy Lutomirski
2021-06-23 12:01 ` [patch V4 15/65] x86/fpu: Make copy_xstate_to_kernel() usable for [x]fpregs_get() Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-24 15:09   ` [PATCH] x86/fpu/xstate: Clear xstate header in copy_xstate_to_uabi_buf() again Thomas Gleixner
2021-06-24 15:41     ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:01 ` [patch V4 16/65] x86/fpu: Use copy_xstate_to_uabi_buf() in xfpregs_get() Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:01 ` [patch V4 17/65] x86/fpu: Use copy_xstate_to_uabi_buf() in fpregs_get() Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:01 ` [patch V4 18/65] x86/fpu: Remove fpstate_sanitize_xstate() Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:01 ` [patch V4 19/65] x86/fpu/regset: Move fpu__read_begin() into regset Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:01 ` [patch V4 20/65] x86/fpu: Move fpu__write_begin() to regset Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:01 ` [patch V4 21/65] x86/fpu: Get rid of using_compacted_format() Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:01 ` [patch V4 22/65] x86/kvm: Avoid looking up PKRU in XSAVE buffer Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Dave Hansen
2021-06-23 12:01 ` [patch V4 23/65] x86/fpu: Cleanup arch_set_user_pkey_access() Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:01 ` [patch V4 24/65] x86/fpu: Get rid of copy_supervisor_to_kernel() Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:01 ` [patch V4 25/65] x86/fpu: Rename copy_xregs_to_kernel() and copy_kernel_to_xregs() Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:01 ` [patch V4 26/65] x86/fpu: Rename copy_user_to_xregs() and copy_xregs_to_user() Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:01 ` [patch V4 27/65] x86/fpu: Rename fxregs related copy functions Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] x86/fpu: Rename fxregs-related " tip-bot2 for Thomas Gleixner
2021-06-23 12:01 ` [patch V4 28/65] x86/math-emu: Rename frstor() Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:01 ` [patch V4 29/65] x86/fpu: Rename fregs related copy functions Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] x86/fpu: Rename fregs-related " tip-bot2 for Thomas Gleixner
2021-06-23 12:01 ` [patch V4 30/65] x86/fpu: Rename xstate copy functions which are related to UABI Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:01 ` [patch V4 31/65] x86/fpu: Deduplicate copy_uabi_from_user/kernel_to_xstate() Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:01 ` [patch V4 32/65] x86/fpu: Rename copy_fpregs_to_fpstate() to save_fpregs_to_fpstate() Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:02 ` [patch V4 33/65] x86/fpu: Get rid of the FNSAVE optimization Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:02 ` [patch V4 34/65] x86/fpu: Rename copy_kernel_to_fpregs() to restore_fpregs_from_fpstate() Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:02 ` [patch V4 35/65] x86/fpu: Rename initstate copy functions Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:02 ` [patch V4 36/65] x86/fpu: Rename "dynamic" XSTATEs to "independent" Thomas Gleixner
2021-06-23 12:02 ` [patch V4 37/65] x86/fpu/xstate: Sanitize handling of independent features Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:02 ` [patch V4 38/65] x86/pkeys: Move read_pkru() and write_pkru() Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Dave Hansen
2021-06-23 12:02 ` [patch V4 39/65] x86/fpu: Rename and sanitize fpu__save/copy() Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:02 ` [patch V4 40/65] x86/cpu: Sanitize X86_FEATURE_OSPKE Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:02 ` [patch V4 41/65] x86/pkru: Provide pkru_get_init_value() Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:02 ` [patch V4 42/65] x86/pkru: Provide pkru_write_default() Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:02 ` [patch V4 43/65] x86/cpu: Write the default PKRU value when enabling PKE Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:02 ` [patch V4 44/65] x86/fpu: Use pkru_write_default() in copy_init_fpstate_to_fpregs() Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:02 ` [patch V4 45/65] x86/fpu: Rename fpu__clear_all() to fpu_flush_thread() Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:02 ` [patch V4 46/65] x86/fpu: Clean up the fpu__clear() variants Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Andy Lutomirski
2021-06-23 12:02 ` [patch V4 47/65] x86/fpu: Rename __fpregs_load_activate() to fpregs_restore_userregs() Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:02 ` [patch V4 48/65] x86/fpu: Move FXSAVE_LEAK quirk info __copy_kernel_to_fpregs() Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:02 ` [patch V4 49/65] x86/fpu: Rename xfeatures_mask_user() to xfeatures_mask_uabi() Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:02 ` [patch V4 50/65] x86/fpu: Dont restore PKRU in fpregs_restore_userspace() Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:02 ` [patch V4 51/65] x86/fpu: Add PKRU storage outside of task XSAVE buffer Thomas Gleixner
2021-06-23 22:09   ` [tip: x86/fpu] " tip-bot2 for Dave Hansen
2021-06-23 12:02 ` [patch V4 52/65] x86/fpu: Hook up PKRU into ptrace() Thomas Gleixner
2021-06-23 22:08   ` [tip: x86/fpu] " tip-bot2 for Dave Hansen
2021-06-23 12:02 ` [patch V4 53/65] x86/fpu: Mask PKRU from kernel XRSTOR[S] operations Thomas Gleixner
2021-06-23 22:08   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:02 ` [patch V4 54/65] x86/fpu: Remove PKRU handling from switch_fpu_finish() Thomas Gleixner
2021-06-23 22:08   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:02 ` [patch V4 55/65] x86/fpu: Dont store PKRU in xstate in fpu_reset_fpstate() Thomas Gleixner
2021-06-23 22:08   ` [tip: x86/fpu] x86/fpu: Don't " tip-bot2 for Thomas Gleixner
2021-06-23 12:02 ` [patch V4 56/65] x86/pkru: Remove xstate fiddling from write_pkru() Thomas Gleixner
2021-06-23 22:08   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:02 ` [patch V4 57/65] x86/fpu: Mark init_fpstate __ro_after_init Thomas Gleixner
2021-06-23 22:08   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:02 ` [patch V4 58/65] x86/fpu/signal: Move initial checks into fpu__sig_restore() Thomas Gleixner
2021-06-23 22:08   ` [tip: x86/fpu] x86/fpu/signal: Move initial checks into fpu__restore_sig() tip-bot2 for Thomas Gleixner
2021-06-23 12:02 ` [patch V4 59/65] x86/fpu/signal: Remove the legacy alignment check Thomas Gleixner
2021-06-23 22:08   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:02 ` [patch V4 60/65] x86/fpu/signal: Sanitize the xstate check on sigframe Thomas Gleixner
2021-06-23 22:08   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:02 ` [patch V4 61/65] x86/fpu/signal: Sanitize copy_user_to_fpregs_zeroing() Thomas Gleixner
2021-06-23 22:08   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:02 ` [patch V4 62/65] x86/fpu/signal: Split out the direct restore code Thomas Gleixner
2021-06-23 22:08   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:02 ` Thomas Gleixner [this message]
2021-06-23 22:08   ` [tip: x86/fpu] x86/fpu: Return proper error codes from user access functions tip-bot2 for Thomas Gleixner
2021-06-23 12:02 ` [patch V4 64/65] x86/fpu/signal: Handle #PF in the direct restore path Thomas Gleixner
2021-06-23 22:08   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-23 12:02 ` [patch V4 65/65] x86/fpu/signal: Let xrstor handle the features to init Thomas Gleixner
2021-06-23 22:08   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-06-25 14:50 ` [patch V4 00/65] x86/fpu: Spring cleaning and PKRU sanitizing Oliver Sang

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