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From: Tony Luck <tony.luck@intel.com>
To: Borislav Petkov <bp@alien8.de>
Cc: Tony Luck <tony.luck@intel.com>,
	x86@kernel.org, Andrew Morton <akpm@linux-foundation.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Darren Hart <dvhart@infradead.org>,
	Andy Lutomirski <luto@kernel.org>,
	linux-kernel@vger.kernel.org, linux-edac@vger.kernel.org,
	linux-mm@kvack.org
Subject: [PATCH v2 2/3] x86/mce: Add new return value to get_user() for machine check
Date: Mon, 11 Jan 2021 13:44:51 -0800	[thread overview]
Message-ID: <20210111214452.1826-3-tony.luck@intel.com> (raw)
In-Reply-To: <20210111214452.1826-1-tony.luck@intel.com>

When an exception occurs during any of the get_user() functions
fixup_exception() passes the trap number of the exception in regs->ax
to the fixup code.

Check for X86_TRAP_MC and return -ENXIO ("No such device or address")
so that callers can take action to avoid repeating an access to an
address that has an uncorrectable error.

Signed-off-by: Tony Luck <tony.luck@intel.com>
---
 arch/x86/lib/getuser.S | 8 +++++++-
 arch/x86/mm/extable.c  | 1 +
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/x86/lib/getuser.S b/arch/x86/lib/getuser.S
index fa1bc2104b32..c49a449fced6 100644
--- a/arch/x86/lib/getuser.S
+++ b/arch/x86/lib/getuser.S
@@ -17,7 +17,7 @@
  *
  * Inputs:	%[r|e]ax contains the address.
  *
- * Outputs:	%[r|e]ax is error code (0 or -EFAULT)
+ * Outputs:	%[r|e]ax is error code (0 or -EFAULT or -ENXIO)
  *		%[r|e]dx contains zero-extended value
  *		%ecx contains the high half for 32-bit __get_user_8
  *
@@ -34,6 +34,7 @@
 #include <asm/asm.h>
 #include <asm/smap.h>
 #include <asm/export.h>
+#include <asm/trapnr.h>
 
 #define ASM_BARRIER_NOSPEC ALTERNATIVE "", "lfence", X86_FEATURE_LFENCE_RDTSC
 
@@ -168,8 +169,13 @@ SYM_CODE_START_LOCAL(.Lbad_get_user_clac)
 	ASM_CLAC
 bad_get_user:
 	xor %edx,%edx
+	cmpl $X86_TRAP_MC,%eax
+	je mce_get_user
 	mov $(-EFAULT),%_ASM_AX
 	ret
+mce_get_user:
+	mov $(-ENXIO),%_ASM_AX
+	ret
 SYM_CODE_END(.Lbad_get_user_clac)
 
 #ifdef CONFIG_X86_32
diff --git a/arch/x86/mm/extable.c b/arch/x86/mm/extable.c
index b93d6cd08a7f..ac4fcb820c40 100644
--- a/arch/x86/mm/extable.c
+++ b/arch/x86/mm/extable.c
@@ -77,6 +77,7 @@ __visible bool ex_handler_uaccess(const struct exception_table_entry *fixup,
 {
 	WARN_ONCE(trapnr == X86_TRAP_GP, "General protection fault in user access. Non-canonical address?");
 	regs->ip = ex_fixup_addr(fixup);
+	regs->ax = trapnr;
 	return true;
 }
 EXPORT_SYMBOL(ex_handler_uaccess);
-- 
2.21.1


  parent reply	other threads:[~2021-01-11 21:46 UTC|newest]

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-08 22:22 [PATCH 0/2] Fix infinite machine check loop in futex_wait_setup() Tony Luck
2021-01-08 22:22 ` [PATCH 1/2] x86/mce: Avoid infinite loop for copy from user recovery Tony Luck
2021-01-08 22:22 ` [PATCH 2/2] futex, x86/mce: Avoid double machine checks Tony Luck
2021-01-08 22:47   ` Peter Zijlstra
2021-01-08 23:08     ` Luck, Tony
2021-01-08 23:14       ` Peter Zijlstra
2021-01-08 23:20         ` Luck, Tony
2021-01-11 21:44 ` [PATCH v2 0/3] Fix infinite machine check loop in futex_wait_setup() Tony Luck
2021-01-11 21:44   ` [PATCH v2 1/3] x86/mce: Avoid infinite loop for copy from user recovery Tony Luck
2021-01-11 22:11     ` Andy Lutomirski
2021-01-11 22:20       ` Luck, Tony
2021-01-12 17:00         ` Andy Lutomirski
2021-01-12 17:16           ` Luck, Tony
2021-01-12 17:21             ` Andy Lutomirski
2021-01-12 18:23               ` Luck, Tony
2021-01-12 18:57                 ` Andy Lutomirski
2021-01-12 20:52                   ` Luck, Tony
2021-01-12 22:04                     ` Andy Lutomirski
2021-01-13  1:50                       ` Luck, Tony
2021-01-13  4:15                         ` Andy Lutomirski
2021-01-13 10:00                           ` Borislav Petkov
2021-01-13 16:06                             ` Luck, Tony
2021-01-13 16:19                               ` Borislav Petkov
2021-01-13 16:32                                 ` Luck, Tony
2021-01-13 17:35                                   ` Borislav Petkov
2021-01-14 20:22     ` Borislav Petkov
2021-01-14 21:05       ` Luck, Tony
2021-01-11 21:44   ` Tony Luck [this message]
2021-01-11 21:44   ` [PATCH v2 3/3] futex, x86/mce: Avoid double machine checks Tony Luck
2021-01-14 17:22   ` [PATCH v2 0/3] Fix infinite machine check loop in futex_wait_setup() Andy Lutomirski
2021-01-15  0:38   ` [PATCH v3] x86/mce: Avoid infinite loop for copy from user recovery Tony Luck
2021-01-15 15:27     ` Borislav Petkov
2021-01-15 19:34       ` Luck, Tony
2021-01-15 20:51         ` [PATCH v4] " Luck, Tony
2021-01-15 23:23           ` Luck, Tony
2021-01-19 10:56             ` Borislav Petkov
2021-01-19 23:57               ` Luck, Tony
2021-01-20 12:18                 ` Borislav Petkov
2021-01-20 17:17                   ` Luck, Tony
2021-01-21 21:09                   ` Luck, Tony
2021-01-25 22:55                     ` [PATCH v5] " Luck, Tony
2021-01-26 11:03                       ` Borislav Petkov
2021-01-26 22:36                         ` Luck, Tony
2021-01-28 17:57                           ` Borislav Petkov
2021-02-01 18:58                             ` Luck, Tony
2021-02-02 11:01                               ` Borislav Petkov
2021-02-02 16:04                                 ` Luck, Tony
2021-02-02 21:06                                   ` Borislav Petkov
2021-02-02 22:12                                     ` Luck, Tony
2021-01-18 15:39         ` [PATCH v3] " Borislav Petkov

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