| Message ID | 20200326092603.7230-3-mbenes@suse.cz (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | c3881eb58d56116c79ac4ee4f40fd15ead124c4b |
| Headers | show |
| Series | x86/xen: Make idle tasks reliable | expand |
On 26.03.20 10:26, Miroslav Benes wrote: > 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> Juergen
diff --git a/arch/x86/xen/smp_pv.c b/arch/x86/xen/smp_pv.c index 802ee5bba66c..8fb8a50a28b4 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) { @@ -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; diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S index d63806e1ff7a..7d1c4fcbe8f7 100644 --- a/arch/x86/xen/xen-head.S +++ b/arch/x86/xen/xen-head.S @@ -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
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> --- arch/x86/xen/smp_pv.c | 3 ++- arch/x86/xen/xen-head.S | 10 ++++++++++ 2 files changed, 12 insertions(+), 1 deletion(-)