Commit 929b44eb authored Jul 18, 2018 by Joerg Roedel Committed by Thomas Gleixner Jul 20, 2018

x86/entry/32: Simplify debug entry point



The common exception entry code now handles the entry-from-sysenter stack
situation and makes sure to leave with the same stack as it entered the
kernel.

So there is no need anymore for the special handling in the debug entry
code.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Pavel Machek <pavel@ucw.cz>
Cc: "H . Peter Anvin" <hpa@zytor.com>
Cc: linux-mm@kvack.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: David Laight <David.Laight@aculab.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Eduardo Valentin <eduval@amazon.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: aliguori@amazon.com
Cc: daniel.gruss@iaik.tugraz.at
Cc: hughd@google.com
Cc: keescook@google.com
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Waiman Long <llong@redhat.com>
Cc: "David H . Gutteridge" <dhgutteridge@sympatico.ca>
Cc: joro@8bytes.org
Link: https://lkml.kernel.org/r/1531906876-13451-12-git-send-email-joro@8bytes.org

parent b92a165d

arch/x86/entry/entry_32.S

+3 −32

Original line number	Diff line number	Diff line
		@@ -1226,41 +1226,12 @@ END(common_exception)

		ENTRY(debug)
		/*
		* #DB can happen at the first instruction of
		* entry_SYSENTER_32 or in Xen's SYSENTER prologue. If this
		* happens, then we will be running on a very small stack. We
		* need to detect this condition and switch to the thread
		* stack before calling any C code at all.
		*
		* If you edit this code, keep in mind that NMIs can happen in here.
		* Entry from sysenter is now handled in common_exception
		*/
		ASM_CLAC
		pushl $-1 # mark this as an int

		SAVE_ALL
		ENCODE_FRAME_POINTER
		xorl %edx, %edx # error code 0
		movl %esp, %eax # pt_regs pointer

		/* Are we currently on the SYSENTER stack? */
		movl PER_CPU_VAR(cpu_entry_area), %ecx
		addl $CPU_ENTRY_AREA_entry_stack + SIZEOF_entry_stack, %ecx
		subl %eax, %ecx /* ecx = (end of entry_stack) - esp */
		cmpl $SIZEOF_entry_stack, %ecx
		jb .Ldebug_from_sysenter_stack

		TRACE_IRQS_OFF
		call do_debug
		jmp ret_from_exception

		.Ldebug_from_sysenter_stack:
		/* We're on the SYSENTER stack. Switch off. */
		movl %esp, %ebx
		movl PER_CPU_VAR(cpu_current_top_of_stack), %esp
		TRACE_IRQS_OFF
		call do_debug
		movl %ebx, %esp
		jmp ret_from_exception
		pushl $do_debug
		jmp common_exception
		END(debug)

		/*

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