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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
Download Patch File Download Diff File Expand all files Collapse all files

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);
}