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 <[email protected]> CC: Linus Torvalds <[email protected]> CC: Steven Rostedt <[email protected]> CC: Ingo Molnar <[email protected]> CC: Borislav Petkov <[email protected]> CC: "H. Peter Anvin" <[email protected]> CC: Andy Lutomirski <[email protected]> CC: Oleg Nesterov <[email protected]> CC: Frederic Weisbecker <[email protected]> CC: Alexei Starovoitov <[email protected]> CC: Will Drewry <[email protected]> CC: Kees Cook <[email protected]> CC: [email protected] CC: [email protected] --- Run-tested, including with PARAVIRT on. 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) movq_cfi rax,ORIG_RAX + /* + * No need to follow this irqs off/on section - it's straight + * and short: + */ + ENABLE_INTERRUPTS(CLBR_RAX) SAVE_C_REGS_EXCEPT_RAX_RCX_R11 movq $-ENOSYS,RAX(%rsp) CFI_REL_OFFSET rip,RIP -- 1.8.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
