x86/xen: Make the secondary CPU idle tasks reliable (c3881eb5) · Commits · 戴 / test

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 <mbenes@suse.cz> Reviewed-by:

Juergen Gross <jgross@suse.com> Signed-off-by:

Juergen Gross <jgross@suse.com>

arch/x86/xen/smp_pv.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -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)
		{
		@@ -309,7 +310,7 @@ 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;

arch/x86/xen/xen-head.S

+10 −0

Original line number	Diff line number	Diff line
		@@ -58,6 +58,16 @@ SYM_CODE_START(startup_xen)
		call xen_start_kernel
		SYM_CODE_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

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