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ARC: pt_regs update #1: Align pt_regs end with end of kernel stack page 

Historically, pt_regs would end at offset of 1 word from end of stack
page.

        -----------------  -> START of page (task->stack)
        |               |
        | thread_info   |
        -----------------
        |               |
   ^    ~               ~
   |    ~               ~
   |    |               |
   |    |               | <---- pt_regs used to END here
        -----------------
        | 1 word GUTTER |
        ----------------- -> End of page (START of kernel stack)

This required special "one-off" considerations in low level code.

The root cause is very likely assumption of "empty" SP by the original
ARC kernel hackers, despite ARC700 always been "full" SP.

So finally RIP one word gutter !

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
This commit is contained in:
Vineet Gupta 2013-05-28 09:34:45 +05:30
parent bed30976e7
commit 283237a04f
4 changed files with 3 additions and 5 deletions
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2
arch/arc/include/asm/entry.h
View File

@ -252,7 +252,7 @@
ld \out, [\tsk, TASK_THREAD_INFO]
/* Go to end of page where stack begins (grows upwards) */
add2 \out, \out, (THREAD_SIZE - 4)/4 /* one word GUTTER */
add2 \out, \out, (THREAD_SIZE)/4
.endm

2
arch/arc/include/asm/processor.h
View File

@ -50,7 +50,7 @@ struct task_struct;
unsigned long thread_saved_pc(struct task_struct *t);
#define task_pt_regs(p) \
((struct pt_regs *)(THREAD_SIZE - 4 + (void *)task_stack_page(p)) - 1)
((struct pt_regs *)(THREAD_SIZE + (void *)task_stack_page(p)) - 1)
/* Free all resources held by a thread. */
#define release_thread(thread) do { } while (0)

2
arch/arc/include/asm/ptrace.h
View File

@ -110,7 +110,7 @@ struct callee_regs {
/* open-coded current_thread_info() */ \
register unsigned long sp asm ("sp"); \
unsigned long pg_start = (sp & ~(THREAD_SIZE - 1)); \
(struct pt_regs *)(pg_start + THREAD_SIZE - 4) - 1; \
(struct pt_regs *)(pg_start + THREAD_SIZE) - 1; \
})
static inline long regs_return_value(struct pt_regs *regs)

2
arch/arc/kernel/process.c
View File

@ -75,8 +75,6 @@ asmlinkage void ret_from_fork(void);
* ~ ~
* | --to-- | (scratch Regs of user mode)
* | r0 |
* ------------------
* | UNUSED 1 word|
* ------------------ <===== END of PAGE
*/
int copy_thread(unsigned long clone_flags,