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x86: Prepare removal of previous_esp from i386 thread_info structure

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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: Steven 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: H. Peter Anvin <hpa@linux.intel.com>
This commit is contained in:
Steven Rostedt 2014-02-06 09:41:30 -05:00 committed by H. Peter Anvin
parent b807902a88
commit 0788aa6a23
4 changed files with 28 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
arch/x86/include/asm/thread_info.h
View File

@ -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) \

11
arch/x86/kernel/dumpstack_32.c
View File

@ -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();

15
arch/x86/kernel/irq_32.c
View File

@ -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);
}

8
arch/x86/kernel/ptrace.c
View File

@ -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;
}