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Commit 05df3bdb authored by Miroslav Benes's avatar Miroslav Benes Committed by Greg Kroah-Hartman
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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: default avatarMiroslav Benes <mbenes@suse.cz>
Reviewed-by: default avatarJuergen Gross <jgross@suse.com>
Signed-off-by: default avatarJuergen Gross <jgross@suse.com>
Signed-off-by: default avatarMarkus Boehme <markubo@amazon.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 0d3817cb

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)

{
@@ -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;

arch/x86/xen/xen-head.S

+10 −0
Original line number Diff line number Diff line
@@ -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