Without this change, it is still not possible to get rid of
PER_CPU_VAR(old_rsp) usage in switch_to: if preemption happens
while we did not fetch PER_CPU_VAR(old_rsp) and stored it in pt_regs->sp,
PER_CPU_VAR(old_rsp) gets corrupted by other task's user sp.
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: Andy Lutomirski <l...@amacapital.net>
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
---
Changes since v1: don't try to be clever and use CLBR_RAX
arch/x86/kernel/entry_64.S | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index d86788c..3054a9d 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -241,17 +241,17 @@ GLOBAL(system_call_after_swapgs)
movq %rsp,PER_CPU_VAR(old_rsp)
/* kernel_stack is set so that 5 slots (iret frame) are preallocated */
movq PER_CPU_VAR(kernel_stack),%rsp
- /*
- * No need to follow this irqs off/on section - it's straight
- * and short:
- */
- ENABLE_INTERRUPTS(CLBR_NONE)
ALLOC_PT_GPREGS_ON_STACK 8 /* +8: space for orig_ax */
movq %rcx,RIP(%rsp)
movq PER_CPU_VAR(old_rsp),%rcx
movq %r11,EFLAGS(%rsp)
movq %rcx,RSP(%rsp)
+ /*
+ * No need to follow this irqs off/on section - it's straight
+ * and short:
+ */
+ ENABLE_INTERRUPTS(CLBR_NONE)
movq_cfi rax,ORIG_RAX
SAVE_C_REGS_EXCEPT_RAX_RCX_R11
movq $-ENOSYS,RAX(%rsp)
CFI_REL_OFFSET rip,RIP
--
1.8.1.4
--
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