From 8ef46a672a7d852709561d10672b6eaa8a4acd82 Mon Sep 17 00:00:00 2001
From: Andy Lutomirski <luto@amacapital.net>
Date: Thu, 5 Mar 2015 19:19:02 -0800
Subject: [PATCH] x86/asm/entry: Add this_cpu_sp0() to read sp0 for the current
cpu
We currently store references to the top of the kernel stack in
multiple places: kernel_stack (with an offset) and
init_tss.x86_tss.sp0 (no offset). The latter is defined by
hardware and is a clean canonical way to find the top of the
stack. Add an accessor so we can start using it.
This needs minor paravirt tweaks. On native, sp0 defines the
top of the kernel stack and is therefore always correct. On Xen
and lguest, the hypervisor tracks the top of the stack, but we
want to start reading sp0 in the kernel. Fixing this is simple:
just update our local copy of sp0 as well as the hypervisor's
copy on task switches.
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/8d675581859712bee09a055ed8f785d80dac1eca.1425611534.git.luto@amacapital.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/include/asm/processor.h | 5 +++++
arch/x86/kernel/process.c | 1 +
arch/x86/lguest/boot.c | 1 +
arch/x86/xen/enlighten.c | 1 +
4 files changed, 8 insertions(+)
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 7be2c9a6caba9..71c3a826a6901 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -564,6 +564,11 @@ static inline void native_swapgs(void)
#endif
}
+static inline unsigned long this_cpu_sp0(void)
+{
+ return this_cpu_read_stable(init_tss.x86_tss.sp0);
+}
+
#ifdef CONFIG_PARAVIRT
#include <asm/paravirt.h>
#else
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 046e2d620bbe7..ff5c9088b1c53 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -38,6 +38,7 @@
* on exact cacheline boundaries, to eliminate cacheline ping-pong.
*/
__visible DEFINE_PER_CPU_SHARED_ALIGNED(struct tss_struct, init_tss) = INIT_TSS;
+EXPORT_PER_CPU_SYMBOL_GPL(init_tss);
#ifdef CONFIG_X86_64
static DEFINE_PER_CPU(unsigned char, is_idle);
diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c
index ac4453d8520ef..8561585ee2c6a 100644
--- a/arch/x86/lguest/boot.c
+++ b/arch/x86/lguest/boot.c
@@ -1076,6 +1076,7 @@ static void lguest_load_sp0(struct tss_struct *tss,
{
lazy_hcall3(LHCALL_SET_STACK, __KERNEL_DS | 0x1, thread->sp0,
THREAD_SIZE / PAGE_SIZE);
+ tss->x86_tss.sp0 = thread->sp0;
}
/* Let's just say, I wouldn't do debugging under a Guest. */
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 5240f563076de..81665c9f21327 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -912,6 +912,7 @@ static void xen_load_sp0(struct tss_struct *tss,
mcs = xen_mc_entry(0);
MULTI_stack_switch(mcs.mc, __KERNEL_DS, thread->sp0);
xen_mc_issue(PARAVIRT_LAZY_CPU);
+ tss->x86_tss.sp0 = thread->sp0;
}
static void xen_set_iopl_mask(unsigned mask)
--
2.30.2