From 05df3bdbc259fb673716f3df6e307d761637d1a2 Mon Sep 17 00:00:00 2001 From: Miroslav Benes Date: Thu, 26 Mar 2020 10:26:03 +0100 Subject: [PATCH] x86/xen: Make the secondary CPU idle tasks reliable commit c3881eb58d56116c79ac4ee4f40fd15ead124c4b upstream. The unwinder reports the secondary CPU idle tasks' stack on XEN PV as unreliable, which affects at least live patching. cpu_initialize_context() sets up the context of the CPU through VCPUOP_initialise hypercall. After it is woken up, the idle task starts in cpu_bringup_and_idle() function and its stack starts at the offset right below pt_regs. The unwinder correctly detects the end of stack there but it is confused by NULL return address in the last frame. Introduce a wrapper in assembly, which just calls cpu_bringup_and_idle(). The return address is thus pushed on the stack and the wrapper contains the annotation hint for the unwinder regarding the stack state. Signed-off-by: Miroslav Benes Reviewed-by: Juergen Gross Signed-off-by: Juergen Gross Signed-off-by: Markus Boehme Signed-off-by: Greg Kroah-Hartman --- arch/x86/xen/smp_pv.c | 3 ++- arch/x86/xen/xen-head.S | 10 ++++++++++ 2 files changed, 12 insertions(+), 1 deletion(-) diff --git a/arch/x86/xen/smp_pv.c b/arch/x86/xen/smp_pv.c index 64e6ec2c32a7..9d9777ded5f7 100644 --- a/arch/x86/xen/smp_pv.c +++ b/arch/x86/xen/smp_pv.c @@ -53,6 +53,7 @@ static DEFINE_PER_CPU(struct xen_common_irq, xen_irq_work) = { .irq = -1 }; static DEFINE_PER_CPU(struct xen_common_irq, xen_pmu_irq) = { .irq = -1 }; static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id); +void asm_cpu_bringup_and_idle(void); static void cpu_bringup(void) { @@ -310,7 +311,7 @@ cpu_initialize_context(unsigned int cpu, struct task_struct *idle) * pointing just below where pt_regs would be if it were a normal * kernel entry. */ - ctxt->user_regs.eip = (unsigned long)cpu_bringup_and_idle; + ctxt->user_regs.eip = (unsigned long)asm_cpu_bringup_and_idle; ctxt->flags = VGCF_IN_KERNEL; ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */ ctxt->user_regs.ds = __USER_DS; diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S index deb6abe5d346..591544b4b85a 100644 --- a/arch/x86/xen/xen-head.S +++ b/arch/x86/xen/xen-head.S @@ -58,6 +58,16 @@ ENTRY(startup_xen) call xen_start_kernel END(startup_xen) __FINIT + +#ifdef CONFIG_XEN_PV_SMP +.pushsection .text +SYM_CODE_START(asm_cpu_bringup_and_idle) + UNWIND_HINT_EMPTY + + call cpu_bringup_and_idle +SYM_CODE_END(asm_cpu_bringup_and_idle) +.popsection +#endif #endif .pushsection .text