From aca9c293d098292579e345b2b39b394778d41526 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Fri, 24 Jun 2016 16:55:53 -0700 Subject: [PATCH] x86: fix up a few misc stack pointer vs thread_info confusions As the actual pointer value is the same for the thread stack allocation and the thread_info, code that confused the two worked fine, but will break when the thread info is moved away from the stack allocation. It also looks very confusing. For example, the kprobe code wanted to know the current top of stack. To do that, it used this: (unsigned long)current_thread_info() + THREAD_SIZE which did indeed give the correct value. But it's not only a fairly nonsensical expression, it's also rather complex, especially since we actually have this: static inline unsigned long current_top_of_stack(void) which not only gives us the value we are interested in, but happens to be how "current_thread_info()" is currently defined as: (struct thread_info *)(current_top_of_stack() - THREAD_SIZE); so using current_thread_info() to figure out the top of the stack really is a very round-about thing to do. The other cases are just simpler confusion about task_thread_info() vs task_stack_page(), which currently return the same pointer - but if you want the stack page, you really should be using the latter one. And there was one entirely unused assignment of the current stack to a thread_info pointer. All cleaned up to make more sense today, and make it easier to move the thread_info away from the stack in the future. No semantic changes. Signed-off-by: Linus Torvalds --- arch/x86/include/asm/kprobes.h | 11 +++++------ arch/x86/kernel/dumpstack.c | 2 +- arch/x86/kernel/irq_32.c | 2 -- 3 files changed, 6 insertions(+), 9 deletions(-) diff --git a/arch/x86/include/asm/kprobes.h b/arch/x86/include/asm/kprobes.h index 4421b5da409d..d1d1e5094c28 100644 --- a/arch/x86/include/asm/kprobes.h +++ b/arch/x86/include/asm/kprobes.h @@ -38,12 +38,11 @@ typedef u8 kprobe_opcode_t; #define RELATIVECALL_OPCODE 0xe8 #define RELATIVE_ADDR_SIZE 4 #define MAX_STACK_SIZE 64 -#define MIN_STACK_SIZE(ADDR) \ - (((MAX_STACK_SIZE) < (((unsigned long)current_thread_info()) + \ - THREAD_SIZE - (unsigned long)(ADDR))) \ - ? (MAX_STACK_SIZE) \ - : (((unsigned long)current_thread_info()) + \ - THREAD_SIZE - (unsigned long)(ADDR))) +#define CUR_STACK_SIZE(ADDR) \ + (current_top_of_stack() - (unsigned long)(ADDR)) +#define MIN_STACK_SIZE(ADDR) \ + (MAX_STACK_SIZE < CUR_STACK_SIZE(ADDR) ? \ + MAX_STACK_SIZE : CUR_STACK_SIZE(ADDR)) #define flush_insn_slot(p) do { } while (0) diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c index d6209f3a69cb..ef8017ca5ba9 100644 --- a/arch/x86/kernel/dumpstack.c +++ b/arch/x86/kernel/dumpstack.c @@ -80,7 +80,7 @@ print_ftrace_graph_addr(unsigned long addr, void *data, static inline int valid_stack_ptr(struct task_struct *task, void *p, unsigned int size, void *end) { - void *t = task_thread_info(task); + void *t = task_stack_page(task); if (end) { if (p < end && p >= (end-THREAD_SIZE)) return 1; diff --git a/arch/x86/kernel/irq_32.c b/arch/x86/kernel/irq_32.c index 38da8f29a9c8..c627bf8d98ad 100644 --- a/arch/x86/kernel/irq_32.c +++ b/arch/x86/kernel/irq_32.c @@ -130,11 +130,9 @@ void irq_ctx_init(int cpu) void do_softirq_own_stack(void) { - struct thread_info *curstk; struct irq_stack *irqstk; u32 *isp, *prev_esp; - curstk = current_stack(); irqstk = __this_cpu_read(softirq_stack); /* build the stack frame on the softirq stack */ -- 2.20.1