[tip:x86/asm] x86/asm/entry/64: Simplify 'old_rsp' usage
From: tip-bot for Ingo Molnar
Date: Tue Mar 17 2015 - 12:43:40 EST
Commit-ID: 9854dd74c3f6af8d9d527de86c6074b7ed0495f1
Gitweb: http://git.kernel.org/tip/9854dd74c3f6af8d9d527de86c6074b7ed0495f1
Author: Ingo Molnar <mingo@xxxxxxxxxx>
AuthorDate: Tue, 17 Mar 2015 14:42:59 +0100
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Tue, 17 Mar 2015 16:01:41 +0100
x86/asm/entry/64: Simplify 'old_rsp' usage
Remove all manipulations of PER_CPU(old_rsp) in C code:
- it is not used on SYSRET return anymore, and system entries
are atomic, so updating it from the fork and context switch
paths is pointless.
- Tweak a few related comments as well: we no longer have a
"partial stack frame" on entry, ever.
Based on (split out of) patch from Denys Vlasenko.
Originally-from: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Tested-by: Borislav Petkov <bp@xxxxxxxxx>
Acked-by: Borislav Petkov <bp@xxxxxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Will Drewry <wad@xxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1426599779-8010-2-git-send-email-dvlasenk@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
arch/x86/include/asm/processor.h | 5 -----
arch/x86/kernel/process_64.c | 2 --
2 files changed, 7 deletions(-)
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 5abd9a5..3ac5092 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -905,11 +905,6 @@ extern unsigned long thread_saved_pc(struct task_struct *tsk);
#define task_pt_regs(tsk) ((struct pt_regs *)(tsk)->thread.sp0 - 1)
extern unsigned long KSTK_ESP(struct task_struct *task);
-/*
- * User space RSP while inside the SYSCALL fast path
- */
-DECLARE_PER_CPU(unsigned long, old_rsp);
-
#endif /* CONFIG_X86_64 */
extern void start_thread(struct pt_regs *regs, unsigned long new_ip,
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index e8c124a..59696d7 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -238,7 +238,6 @@ start_thread_common(struct pt_regs *regs, unsigned long new_ip,
current->thread.usersp = new_sp;
regs->ip = new_ip;
regs->sp = new_sp;
- this_cpu_write(old_rsp, new_sp);
regs->cs = _cs;
regs->ss = _ss;
regs->flags = X86_EFLAGS_IF;
@@ -399,7 +398,6 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
* Switch the PDA and FPU contexts.
*/
prev->usersp = this_cpu_read(old_rsp);
- this_cpu_write(old_rsp, next->usersp);
this_cpu_write(current_task, next_p);
/*
--
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