There has been a 64-byte gap at the end of the irq stack for at least 12 years. It predates git history, and I can't find any good reason for it. Remove it. What's the worst that could happen?
Signed-off-by: Josh Poimboeuf <[email protected]> --- arch/x86/include/asm/page_64_types.h | 3 --- arch/x86/kernel/cpu/common.c | 2 +- arch/x86/kernel/dumpstack_64.c | 4 ++-- arch/x86/kernel/setup_percpu.c | 2 +- 4 files changed, 4 insertions(+), 7 deletions(-) diff --git a/arch/x86/include/asm/page_64_types.h b/arch/x86/include/asm/page_64_types.h index 6256baf..3c0be3b 100644 --- a/arch/x86/include/asm/page_64_types.h +++ b/arch/x86/include/asm/page_64_types.h @@ -24,9 +24,6 @@ #define IRQ_STACK_ORDER (2 + KASAN_STACK_ORDER) #define IRQ_STACK_SIZE (PAGE_SIZE << IRQ_STACK_ORDER) -/* FIXME: why? */ -#define IRQ_USABLE_STACK_SIZE (IRQ_STACK_SIZE - 64) - #define DOUBLEFAULT_STACK 1 #define NMI_STACK 2 #define DEBUG_STACK 3 diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 55684b1..ce7a4c1 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -1286,7 +1286,7 @@ DEFINE_PER_CPU(struct task_struct *, current_task) ____cacheline_aligned = EXPORT_PER_CPU_SYMBOL(current_task); DEFINE_PER_CPU(char *, irq_stack_ptr) = - init_per_cpu_var(irq_stack_union.irq_stack) + IRQ_USABLE_STACK_SIZE; + init_per_cpu_var(irq_stack_union.irq_stack) + IRQ_STACK_SIZE; DEFINE_PER_CPU(unsigned int, irq_count) __visible = -1; diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c index 9f7a9f9..001a75d 100644 --- a/arch/x86/kernel/dumpstack_64.c +++ b/arch/x86/kernel/dumpstack_64.c @@ -78,7 +78,7 @@ static bool in_exception_stack(unsigned long *stack, struct stack_info *info) static bool in_irq_stack(unsigned long *stack, struct stack_info *info) { unsigned long *end = (unsigned long *)this_cpu_read(irq_stack_ptr); - unsigned long *begin = end - (IRQ_USABLE_STACK_SIZE / sizeof(long)); + unsigned long *begin = end - (IRQ_STACK_SIZE / sizeof(long)); if (stack < begin || stack >= end) return false; @@ -145,7 +145,7 @@ void show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs, int i; irq_stack_end = (unsigned long *)this_cpu_read(irq_stack_ptr); - irq_stack = irq_stack_end - (IRQ_USABLE_STACK_SIZE / sizeof(long)); + irq_stack = irq_stack_end - (IRQ_STACK_SIZE / sizeof(long)); sp = sp ? : get_stack_pointer(task, regs); diff --git a/arch/x86/kernel/setup_percpu.c b/arch/x86/kernel/setup_percpu.c index a2a0eae..2bbd27f 100644 --- a/arch/x86/kernel/setup_percpu.c +++ b/arch/x86/kernel/setup_percpu.c @@ -246,7 +246,7 @@ void __init setup_per_cpu_areas(void) #ifdef CONFIG_X86_64 per_cpu(irq_stack_ptr, cpu) = per_cpu(irq_stack_union.irq_stack, cpu) + - IRQ_USABLE_STACK_SIZE; + IRQ_STACK_SIZE; #endif #ifdef CONFIG_NUMA per_cpu(x86_cpu_to_node_map, cpu) = -- 2.7.4
