path: root/arch/arm64
diff options
authorMark Rutland <mark.rutland@arm.com>2017-07-31 21:17:03 +0100
committerMark Rutland <mark.rutland@arm.com>2017-08-15 18:35:54 +0100
commitf60fe78f133243e6de0f05fdefc3ed2f3c5085ca (patch)
tree3c507d62a32b88811d2c13bb8d70c5b5a2786001 /arch/arm64
parentarm64: assembler: allow adr_this_cpu to use the stack pointer (diff)
arm64: use an irq stack pointer
We allocate our IRQ stacks using a percpu array. This allows us to generate our IRQ stack pointers with adr_this_cpu, but bloats the kernel Image with the boot CPU's IRQ stack. Additionally, these are packed with other percpu variables, and aren't guaranteed to have guard pages. When we enable VMAP_STACK we'll want to vmap our IRQ stacks also, in order to provide guard pages and to permit more stringent alignment requirements. Doing so will require that we use a percpu pointer to each IRQ stack, rather than allocating a percpu IRQ stack in the kernel image. This patch updates our IRQ stack code to use a percpu pointer to the base of each IRQ stack. This will allow us to change the way the stack is allocated with minimal changes elsewhere. In some cases we may try to backtrace before the IRQ stack pointers are initialised, so on_irq_stack() is updated to account for this. In testing with cyclictest, there was no measureable difference between using adr_this_cpu (for irq_stack) and ldr_this_cpu (for irq_stack_ptr) in the IRQ entry path. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Reviewed-by: Will Deacon <will.deacon@arm.com> Tested-by: Laura Abbott <labbott@redhat.com> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: James Morse <james.morse@arm.com>
Diffstat (limited to '')
3 files changed, 16 insertions, 3 deletions
diff --git a/arch/arm64/include/asm/stacktrace.h b/arch/arm64/include/asm/stacktrace.h
index 000e24182a5c..4c68d8a81988 100644
--- a/arch/arm64/include/asm/stacktrace.h
+++ b/arch/arm64/include/asm/stacktrace.h
@@ -36,13 +36,16 @@ extern void walk_stackframe(struct task_struct *tsk, struct stackframe *frame,
int (*fn)(struct stackframe *, void *), void *data);
extern void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk);
-DECLARE_PER_CPU(unsigned long [IRQ_STACK_SIZE/sizeof(long)], irq_stack);
+DECLARE_PER_CPU(unsigned long *, irq_stack_ptr);
static inline bool on_irq_stack(unsigned long sp)
- unsigned long low = (unsigned long)raw_cpu_ptr(irq_stack);
+ unsigned long low = (unsigned long)raw_cpu_read(irq_stack_ptr);
unsigned long high = low + IRQ_STACK_SIZE;
+ if (!low)
+ return false;
return (low <= sp && sp < high);
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 58eba94279c5..52348869f82f 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -276,7 +276,7 @@ alternative_else_nop_endif
and x25, x25, #~(THREAD_SIZE - 1)
cbnz x25, 9998f
- adr_this_cpu x25, irq_stack, x26
+ ldr_this_cpu x25, irq_stack_ptr, x26
mov x26, #IRQ_STACK_SIZE
add x26, x25, x26
diff --git a/arch/arm64/kernel/irq.c b/arch/arm64/kernel/irq.c
index 2386b26c0712..5141282e47d5 100644
--- a/arch/arm64/kernel/irq.c
+++ b/arch/arm64/kernel/irq.c
@@ -32,6 +32,7 @@ unsigned long irq_err_count;
/* irq stack only needs to be 16 byte aligned - not IRQ_STACK_SIZE aligned. */
DEFINE_PER_CPU(unsigned long [IRQ_STACK_SIZE/sizeof(long)], irq_stack) __aligned(16);
+DEFINE_PER_CPU(unsigned long *, irq_stack_ptr);
int arch_show_interrupts(struct seq_file *p, int prec)
@@ -50,8 +51,17 @@ void __init set_handle_irq(void (*handle_irq)(struct pt_regs *))
handle_arch_irq = handle_irq;
+static void init_irq_stacks(void)
+ int cpu;
+ for_each_possible_cpu(cpu)
+ per_cpu(irq_stack_ptr, cpu) = per_cpu(irq_stack, cpu);
void __init init_IRQ(void)
+ init_irq_stacks();
if (!handle_arch_irq)
panic("No interrupt controller found.");