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From: Thomas Gleixner <tglx@linutronix.de>
To: Andy Lutomirski <luto@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>, X86 ML <x86@kernel.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Brian Gerst <brgerst@gmail.com>, Juergen Gross <jgross@suse.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Arnd Bergmann <arnd@arndb.de>
Subject: [patch V2 08/10] x86/entry/32: Remove the 0/-1 distinction from exception entries
Date: Thu, 27 Feb 2020 15:24:29 +0100	[thread overview]
Message-ID: <87mu94m7ky.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <87y2spb1nr.fsf@nanos.tec.linutronix.de>

Nothing cares about the -1 "mark as interrupt" in the errorcode of
exception entries. It's only used to fill the error code when a signal
is delivered, but this is already inconsistent vs. 64 bit as there all
exceptions which do not have an error code set it to 0. So if 32bit
applications would care about this, then they would have noticed more
than a decade ago.

Just use 0 for all excpetions which do not have an errorcode consistently.

This does neither break /proc/$PID/syscall because this interface
examines the error code / syscall number which is on the stack and that
is set to -1 (no syscall) in common_exception unconditionally for all
exceptions. The push in the entry stub is just there to fill the
hardware error code slot on the stack for consistency of the stack
layout.

A transient observation of 0 is possible, but that's true for the other
exceptions which use 0 already as well and that interface is an unreliable
snapshot of dubious correctness anyway.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
---
V2: Amend changelog. Rebased on top of tip x86/entry 
---
 arch/x86/entry/entry_32.S |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -1290,7 +1290,7 @@ SYM_CODE_END(simd_coprocessor_error)
 
 SYM_CODE_START(device_not_available)
 	ASM_CLAC
-	pushl	$-1				# mark this as an int
+	pushl	$0
 	pushl	$do_device_not_available
 	jmp	common_exception
 SYM_CODE_END(device_not_available)
@@ -1531,7 +1531,7 @@ SYM_CODE_START(debug)
 	 * Entry from sysenter is now handled in common_exception
 	 */
 	ASM_CLAC
-	pushl	$-1				# mark this as an int
+	pushl	$0
 	pushl	$do_debug
 	jmp	common_exception
 SYM_CODE_END(debug)
@@ -1682,7 +1682,7 @@ SYM_CODE_END(nmi)
 
 SYM_CODE_START(int3)
 	ASM_CLAC
-	pushl	$-1				# mark this as an int
+	pushl	$0
 	pushl	$do_int3
 	jmp	common_exception
 SYM_CODE_END(int3)

  reply	other threads:[~2020-02-27 14:24 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-25 21:36 [patch 00/10] x86/entry: Consolidation - Part I Thomas Gleixner
2020-02-25 21:36 ` [patch 01/10] x86/entry/32: Add missing ASM_CLAC to general_protection entry Thomas Gleixner
2020-02-26  1:00   ` Frederic Weisbecker
2020-02-27 14:15   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-02-25 21:36 ` [patch 02/10] x86/mce: Disable tracing and kprobes on do_machine_check() Thomas Gleixner
2020-02-26  1:13   ` Frederic Weisbecker
2020-02-26  5:29     ` Andy Lutomirski
2020-02-26 13:28       ` Peter Zijlstra
2020-02-26 15:10         ` Andy Lutomirski
2020-02-26 16:08           ` Peter Zijlstra
2020-02-26 17:28             ` Andy Lutomirski
2020-02-26 18:42               ` Borislav Petkov
2020-02-26 18:59                 ` Peter Zijlstra
2020-02-26 19:09                   ` Andy Lutomirski
2020-02-26 20:59                     ` Steven Rostedt
2020-02-26 11:18   ` Borislav Petkov
2020-02-27 14:15   ` [tip: x86/entry] " tip-bot2 for Andy Lutomirski
2020-02-25 21:36 ` [patch 03/10] x86/entry/32: Force MCE through do_mce() Thomas Gleixner
2020-02-26  1:11   ` Frederic Weisbecker
2020-02-27 14:15   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-02-25 21:36 ` [patch 04/10] x86/traps: Remove pointless irq enable from do_spurious_interrupt_bug() Thomas Gleixner
2020-02-26  1:19   ` Frederic Weisbecker
2020-02-25 21:36 ` [patch 05/10] x86/traps: Document do_spurious_interrupt_bug() Thomas Gleixner
2020-02-26 17:08   ` Frederic Weisbecker
2020-02-27 14:15   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-02-25 21:36 ` [patch 06/10] x86/traps: Remove redundant declaration of do_double_fault() Thomas Gleixner
2020-02-27 14:15   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-02-25 21:36 ` [patch 07/10] x86/irq: Remove useless return value from do_IRQ() Thomas Gleixner
2020-02-27 14:15   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-02-25 21:36 ` [patch 08/10] x86/entry/32: Remove the 0/-1 distinction from exception entries Thomas Gleixner
2020-02-26  5:34   ` Andy Lutomirski
2020-02-26 18:42     ` Thomas Gleixner
2020-02-26 18:57       ` Andy Lutomirski
2020-02-26 19:15         ` Thomas Gleixner
2020-02-27 14:24           ` Thomas Gleixner [this message]
2020-02-29 11:49             ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-02-25 21:36 ` [patch 09/10] x86/entry/entry_32: Route int3 through common_exception Thomas Gleixner
2020-02-26 17:35   ` Frederic Weisbecker
2020-02-27 14:15   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-02-25 21:36 ` [patch 10/10] x86/traps: Stop using ist_enter/exit() in do_int3() Thomas Gleixner
2020-02-27 14:15   ` [tip: x86/entry] " tip-bot2 for Thomas Gleixner
2020-02-27 14:33   ` tip-bot2 for Andy Lutomirski
2020-02-26  5:26 ` [patch 00/10] x86/entry: Consolidation - Part I Andy Lutomirski
2020-02-26  5:35 ` Andy Lutomirski
2020-02-27 11:01 ` Alexandre Chartre

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