From: Miroslav Benes mbenes@suse.cz
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 mbenes@suse.cz Reviewed-by: Juergen Gross jgross@suse.com Signed-off-by: Juergen Gross jgross@suse.com Signed-off-by: Markus Boehme markubo@amazon.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/xen/smp_pv.c | 3 ++- arch/x86/xen/xen-head.S | 10 ++++++++++ 2 files changed, 12 insertions(+), 1 deletion(-)
--- 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_ 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, * 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; --- 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