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sched/x86: Fix thread_saved_pc()

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thread_saved_pc() was using a completely bogus method to get the return
address.  Since switch_to() was previously inlined, there was no sane way
to know where on the stack the return address was stored.  Now with the
frame of a sleeping thread well defined, this can be implemented correctly.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1471106302-10159-7-git-send-email-brgerst@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Brian Gerst 2016-08-13 12:38:21 -04:00 committed by Ingo Molnar
parent 616d24835e
commit ffcb043ba5
3 changed files with 13 additions and 16 deletions
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10
arch/x86/include/asm/processor.h
View File

@ -721,8 +721,6 @@ static inline void spin_lock_prefetch(const void *x)
.addr_limit = KERNEL_DS, \
}
extern unsigned long thread_saved_pc(struct task_struct *tsk);
/*
* TOP_OF_KERNEL_STACK_PADDING reserves 8 bytes on top of the ring0 stack.
* This is necessary to guarantee that the entire "struct pt_regs"
@ -773,17 +771,13 @@ extern unsigned long thread_saved_pc(struct task_struct *tsk);
.addr_limit = KERNEL_DS, \
}
/*
* Return saved PC of a blocked thread.
* What is this good for? it will be always the scheduler or ret_from_fork.
*/
#define thread_saved_pc(t) READ_ONCE_NOCHECK(*(unsigned long *)((t)->thread.sp - 8))
#define task_pt_regs(tsk) ((struct pt_regs *)(tsk)->thread.sp0 - 1)
extern unsigned long KSTK_ESP(struct task_struct *task);
#endif /* CONFIG_X86_64 */
extern unsigned long thread_saved_pc(struct task_struct *tsk);
extern void start_thread(struct pt_regs *regs, unsigned long new_ip,
unsigned long new_sp);

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

@ -513,6 +513,17 @@ unsigned long arch_randomize_brk(struct mm_struct *mm)
return randomize_range(mm->brk, range_end, 0) ? : mm->brk;
}
/*
* Return saved PC of a blocked thread.
* What is this good for? it will be always the scheduler or ret_from_fork.
*/
unsigned long thread_saved_pc(struct task_struct *tsk)
{
struct inactive_task_frame *frame =
(struct inactive_task_frame *) READ_ONCE(tsk->thread.sp);
return READ_ONCE_NOCHECK(frame->ret_addr);
}
/*
* Called from fs/proc with a reference on @p to find the function
* which called into schedule(). This needs to be done carefully

8
arch/x86/kernel/process_32.c
View File

@ -55,14 +55,6 @@
#include <asm/switch_to.h>
#include <asm/vm86.h>
/*
* Return saved PC of a blocked thread.
*/
unsigned long thread_saved_pc(struct task_struct *tsk)
{
return ((unsigned long *)tsk->thread.sp)[3];
}
void __show_regs(struct pt_regs *regs, int all)
{
unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L;