[tip:x86/pti] x86/entry/64: Drop idtentry's manual stack switch for user entries
From: tip-bot for Andy Lutomirski
Date: Mon Apr 09 2018 - 13:12:14 EST
Commit-ID: 071ccc966ba5db1ac8f5c24b0faebb37698f68db
Gitweb: https://git.kernel.org/tip/071ccc966ba5db1ac8f5c24b0faebb37698f68db
Author: Andy Lutomirski <luto@xxxxxxxxxx>
AuthorDate: Tue, 3 Apr 2018 15:39:26 -0700
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Mon, 9 Apr 2018 18:23:50 +0200
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:
7f2590a110b8 ("x86/entry/64: Use a per-CPU trampoline stack for IDT entries")
Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Dominik Brodowski <linux@xxxxxxxxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/90aab80c1f906e70742eaa4512e3c9b5e62d59d4.1522794757.git.luto@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
arch/x86/entry/entry_64.S | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 9b114675fbc0..e237913a056b 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -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