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ARC: stop using pt_regs->orig_r8 

Historically, pt_regs have had orig_r8, an overloaded container for
  (1) backup copy of r8 (syscall number Trap Exceptions)
  (2) additional system state: (syscall/Exception/Interrupt)

There is no point in keeping (1) since syscall number is never clobbered
in-place, in pt_regs, unlike r0 which duals as first syscall arg as well
as syscall return value and in case of syscall restart, the orig arg0
needs restoring (from orig_r0)  after having been updated in-place with
syscall ret value.

This further paves way to convert (2) to contain ECR itself (rather than
current madeup values)

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
This commit is contained in:
Vineet Gupta 2013-06-22 12:38:59 +05:30
parent 359105bdb0
commit 352c1d95e3
3 changed files with 4 additions and 16 deletions
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13
arch/arc/include/asm/entry.h
View File

@ -422,18 +422,7 @@
* Save scratch regs for sys calls
*-------------------------------------------------------------*/
.macro SAVE_ALL_TRAP
/*
* Setup pt_regs->orig_r8.
* Encode syscall number (r8) in upper short word of event type (r9)
* N.B. #1: This is already endian safe (see ptrace.h)
* #2: Only r9 can be used as scratch as it is already clobbered
* and it's contents are no longer needed by the latter part
* of exception prologue
*/
lsl r9, r8, 16
or r9, r9, orig_r8_IS_SCALL
SAVE_ALL_EXCEPTION r9
SAVE_ALL_EXCEPTION orig_r8_IS_SCALL
.endm
/*--------------------------------------------------------------

5
arch/arc/include/asm/syscall.h
View File

@ -18,7 +18,7 @@ static inline long
syscall_get_nr(struct task_struct *task, struct pt_regs *regs)
{
if (user_mode(regs) && in_syscall(regs))
return regs->orig_r8;
return regs->r8;
else
return -1;
}
@ -26,8 +26,7 @@ syscall_get_nr(struct task_struct *task, struct pt_regs *regs)
static inline void
syscall_rollback(struct task_struct *task, struct pt_regs *regs)
{
/* XXX: I can't fathom how pt_regs->r8 will be clobbered ? */
regs->r8 = regs->orig_r8;
regs->r0 = regs->orig_r0;
}
static inline long

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

@ -44,7 +44,7 @@ struct user_regs_struct {
long r19, r18, r17, r16, r15, r14, r13;
} callee;
long efa; /* break pt addr, for break points in delay slots */
long stop_pc; /* give dbg stop_pc directly after checking orig_r8 */
long stop_pc; /* give dbg stop_pc after ensuring brkpt trap */
};
#endif /* !__ASSEMBLY__ */