Commit 071ccc96 authored Apr 03, 2018 by Andy Lutomirski Committed by Ingo Molnar Apr 09, 2018

x86/entry/64: Drop idtentry's manual stack switch for user entries



For non-paranoid entries, idtentry knows how to switch from the
kernel stack to the user stack, as does error_entry.  This results
in pointless duplication and code bloat.  Make idtentry stop
thinking about stacks for non-paranoid entries.

This reduces text size by 5377 bytes.

This goes back to the following commit:

  7f2590a1 ("x86/entry/64: Use a per-CPU trampoline stack for IDT entries")

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dominik Brodowski <linux@dominikbrodowski.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/90aab80c1f906e70742eaa4512e3c9b5e62d59d4.1522794757.git.luto@kernel.org


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 9820e1c3

arch/x86/entry/entry_64.S

+2 −2

Original line number	Diff line number	Diff line
		@@ -908,7 +908,7 @@ ENTRY(\sym)
		pushq $-1 /* ORIG_RAX: no syscall to restart */
		.endif

		.if \paranoid < 2
		.if \paranoid == 1
		testb $3, CS-ORIG_RAX(%rsp) /* If coming from userspace, switch stacks */
		jnz .Lfrom_usermode_switch_stack_\@
		.endif
		@@ -955,7 +955,7 @@ ENTRY(\sym)
		jmp error_exit
		.endif

		.if \paranoid < 2
		.if \paranoid == 1
		/*
		* Entry from userspace. Switch stacks and treat it
		* as a normal entry. This means that paranoid handlers