All manipulations of PER_CPU(old_rsp) in C code are removed:
it is not used on SYSRET return, storing anything there is pointless.
This also allows to get rid of thread_struct::usersp,
which was needed only to set PER_CPU(old_rsp) for
correct return from fork/clone.
Tweak a few comments (we no longer have "partial stack frame", ever).
Signed-off-by: Denys Vlasenko <dvlas...@redhat.com>
CC: Linus Torvalds <torva...@linux-foundation.org>
CC: Steven Rostedt <rost...@goodmis.org>
CC: Ingo Molnar <mi...@kernel.org>
CC: Borislav Petkov <b...@alien8.de>
CC: "H. Peter Anvin" <h...@zytor.com>
CC: Oleg Nesterov <o...@redhat.com>
CC: Frederic Weisbecker <fweis...@gmail.com>
CC: Alexei Starovoitov <a...@plumgrid.com>
CC: Will Drewry <w...@chromium.org>
CC: Kees Cook <keesc...@chromium.org>
CC: x...@kernel.org
CC: linux-kernel@vger.kernel.org
---
arch/x86/include/asm/processor.h | 6 ------
arch/x86/kernel/entry_64.S | 4 ++--
arch/x86/kernel/process_64.c | 5 -----
3 files changed, 2 insertions(+), 13 deletions(-)
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 48a61c1..c77605d 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -478,7 +478,6 @@ struct thread_struct {
#ifdef CONFIG_X86_32
unsigned long sysenter_cs;
#else
- unsigned long usersp; /* Copy from PDA */
unsigned short es;
unsigned short ds;
unsigned short fsindex;
@@ -894,11 +893,6 @@ 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/entry_64.S b/arch/x86/kernel/entry_64.S
index d86788c..9e37b36 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -303,7 +303,7 @@ int_ret_from_sys_call_fixup:
FIXUP_TOP_OF_STACK %r11
jmp int_ret_from_sys_call
- /* Do syscall tracing */
+ /* Do syscall entry tracing */
tracesys:
movq %rsp, %rdi
movq $AUDIT_ARCH_X86_64, %rsi
@@ -343,7 +343,7 @@ tracesys_phase2:
/*
* Syscall return path ending with IRET.
- * Has correct top of stack, but partial stack frame.
+ * Has correct iret frame.
*/
GLOBAL(int_ret_from_sys_call)
DISABLE_INTERRUPTS(CLBR_NONE)
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index e8c124a..14df2be 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -161,7 +161,6 @@ int copy_thread(unsigned long clone_flags, unsigned long sp,
p->thread.sp0 = (unsigned long)task_stack_page(p) + THREAD_SIZE;
childregs = task_pt_regs(p);
p->thread.sp = (unsigned long) childregs;
- p->thread.usersp = me->thread.usersp;
set_tsk_thread_flag(p, TIF_FORK);
p->thread.io_bitmap_ptr = NULL;
@@ -235,10 +234,8 @@ start_thread_common(struct pt_regs *regs, unsigned long
new_ip,
loadsegment(es, _ds);
loadsegment(ds, _ds);
load_gs_index(0);
- 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;
@@ -398,8 +395,6 @@ __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);
/*
--
1.8.1.4
--
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