Commit 0788aa6a authored by Steven Rostedt's avatar Steven Rostedt Committed by H. Peter Anvin
Browse files

x86: Prepare removal of previous_esp from i386 thread_info structure 



The i386 thread_info contains a previous_esp field that is used
to daisy chain the different stacks for dump_stack()
(ie. irq, softirq, thread stacks).

The goal is to eventual make i386 handling of thread_info the same
as x86_64, which means that the thread_info will not be in the stack
but as a per_cpu variable. We will no longer depend on thread_info
being able to daisy chain different stacks as it will only exist
in one location (the thread stack).

By moving previous_esp to the end of thread_info and referencing
it as an offset instead of using a thread_info field, this becomes
a stepping stone to moving the thread_info.

The offset to get to the previous stack is rather ugly in this
patch, but this is only temporary and the prev_esp will be changed
in the next commit. This commit is more for sanity checks of the
change.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Robert Richter <rric@kernel.org>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20110806012353.891757693@goodmis.org
Link: http://lkml.kernel.org/r/20140206144321.608754481@goodmis.org


Signed-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
parent b807902a

arch/x86/include/asm/thread_info.h

+3 −2
Original line number Diff line number Diff line
@@ -32,13 +32,14 @@ struct thread_info { 
	mm_segment_t		addr_limit;

	struct restart_block    restart_block;

	void __user		*sysenter_return;

	unsigned int		sig_on_uaccess_error:1;

	unsigned int		uaccess_err:1;	/* uaccess failed */

#ifdef CONFIG_X86_32

	unsigned long           previous_esp;   /* ESP of the previous stack in

						   case of nested (IRQ) stacks

						   (Moved to end, to be removed soon)

						*/

#endif

	unsigned int		sig_on_uaccess_error:1;

	unsigned int		uaccess_err:1;	/* uaccess failed */

};



#define INIT_THREAD_INFO(tsk)			\

arch/x86/kernel/dumpstack_32.c

+10 −1
Original line number Diff line number Diff line
@@ -22,6 +22,7 @@ void dump_trace(struct task_struct *task, struct pt_regs *regs, 
		const struct stacktrace_ops *ops, void *data)

{

	int graph = 0;

	u32 *prev_esp;



	if (!task)

		task = current;
@@ -44,9 +45,17 @@ void dump_trace(struct task_struct *task, struct pt_regs *regs, 
			((unsigned long)stack & (~(THREAD_SIZE - 1)));

		bp = ops->walk_stack(context, stack, bp, ops, data, NULL, &graph);



		stack = (unsigned long *)context->previous_esp;

		/* Stop if not on irq stack */

		if (task_stack_page(task) == context)

			break;



		/* The previous esp is just above the context */

		prev_esp = (u32 *) ((char *)context + sizeof(struct thread_info) -

				    sizeof(long));

		stack = (unsigned long *)*prev_esp;

		if (!stack)

			break;



		if (ops->stack(data, "IRQ") < 0)

			break;

		touch_nmi_watchdog();

arch/x86/kernel/irq_32.c

+11 −4
Original line number Diff line number Diff line
@@ -81,7 +81,7 @@ static inline int 
execute_on_irq_stack(int overflow, struct irq_desc *desc, int irq)

{

	union irq_ctx *curctx, *irqctx;

	u32 *isp, arg1, arg2;

	u32 *isp, *prev_esp, arg1, arg2;



	curctx = (union irq_ctx *) current_thread_info();

	irqctx = __this_cpu_read(hardirq_ctx);
@@ -98,7 +98,10 @@ execute_on_irq_stack(int overflow, struct irq_desc *desc, int irq) 
	/* build the stack frame on the IRQ stack */

	isp = (u32 *) ((char *)irqctx + sizeof(*irqctx));

	irqctx->tinfo.task = curctx->tinfo.task;

	irqctx->tinfo.previous_esp = current_stack_pointer;

	/* Save the next esp after thread_info */

	prev_esp = (u32 *) ((char *)irqctx + sizeof(struct thread_info) -

			    sizeof(long));

	*prev_esp = current_stack_pointer;



	if (unlikely(overflow))

		call_on_stack(print_stack_overflow, isp);
@@ -149,16 +152,20 @@ void do_softirq_own_stack(void) 
{

	struct thread_info *curctx;

	union irq_ctx *irqctx;

	u32 *isp;

	u32 *isp, *prev_esp;



	curctx = current_thread_info();

	irqctx = __this_cpu_read(softirq_ctx);

	irqctx->tinfo.task = curctx->task;

	irqctx->tinfo.previous_esp = current_stack_pointer;



	/* build the stack frame on the softirq stack */

	isp = (u32 *) ((char *)irqctx + sizeof(*irqctx));



	/* Push the previous esp onto the stack */

	prev_esp = (u32 *) ((char *)irqctx + sizeof(struct thread_info) -

			    sizeof(long));

	*prev_esp = current_stack_pointer;



	call_on_stack(__do_softirq, isp);

}

arch/x86/kernel/ptrace.c

+4 −4
Original line number Diff line number Diff line
@@ -184,14 +184,14 @@ unsigned long kernel_stack_pointer(struct pt_regs *regs) 
{

	unsigned long context = (unsigned long)regs & ~(THREAD_SIZE - 1);

	unsigned long sp = (unsigned long)&regs->sp;

	struct thread_info *tinfo;

	u32 *prev_esp;



	if (context == (sp & ~(THREAD_SIZE - 1)))

		return sp;



	tinfo = (struct thread_info *)context;

	if (tinfo->previous_esp)

		return tinfo->previous_esp;

	prev_esp = (u32 *)(context + sizeof(struct thread_info) - sizeof(long));

	if (prev_esp)

		return (unsigned long)prev_esp;



	return (unsigned long)regs;

}

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