diff options
| author | Vineet Gupta <vgupta@kernel.org> | 2020-05-12 22:18:08 -0700 |
|---|---|---|
| committer | Vineet Gupta <vgupta@kernel.org> | 2023-08-17 20:31:59 -0700 |
| commit | cfca4b5abe0cc13f9d9f45f760efd8260e31200f (patch) | |
| tree | bac7d51b9a322dbb17a9428c87aeae26aa5678ef /arch/arc/kernel/process.c | |
| parent | fad84e39f116035ae8d550c6020107b8ac113b45 (diff) | |
ARC: entry: use gp to cache task pointer (vs. r25)
The motivation is eventual ABI considerations for ARCv3 but even without
it this change us worthwhile as diffstat reduces 100 net lines
r25 is a callee saved register, normally not saved by entry code in
pt_regs. However because of its usage in CONFIG_ARC_CURR_IN_REG it needs
to be. This in turn requires a whole bunch of special casing when we
need to access r25. Then there is distinction between user mode r25 vs.
kernel mode r25 - hence distinct SAVE_CALLEE_SAVED_{USER,KERNEL}
Instead use gp which is a scratch register and thus saved already in entry
code. This cleans things up significantly and much nocer on eyes:
- SAVE_CALLEE_SAVED_{USER,KERNEL} are now exactly same
- no special user_r25 slot in pt_reggs
Note that typical global asm registers are callee-saved (r25), but gp is
not callee-saved thus needs additional -ffixed-<reg> toggle
Signed-off-by: Vineet Gupta <vgupta@kernel.org>
Diffstat (limited to 'arch/arc/kernel/process.c')
| -rw-r--r-- | arch/arc/kernel/process.c | 11 |
1 files changed, 0 insertions, 11 deletions
diff --git a/arch/arc/kernel/process.c b/arch/arc/kernel/process.c index 980b71da2f61..96f591508142 100644 --- a/arch/arc/kernel/process.c +++ b/arch/arc/kernel/process.c @@ -162,7 +162,6 @@ asmlinkage void ret_from_fork(void); * | SP | * | orig_r0 | * | event/ECR | - * | user_r25 | * ------------------ <===== END of PAGE */ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args) @@ -243,16 +242,6 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args) */ c_callee->r25 = task_thread_info(p)->thr_ptr; -#ifdef CONFIG_ARC_CURR_IN_REG - /* - * setup usermode thread pointer #2: - * however for this special use of r25 in kernel, __switch_to() sets - * r25 for kernel needs and only in the final return path is usermode - * r25 setup, from pt_regs->user_r25. So set that up as well - */ - c_regs->user_r25 = c_callee->r25; -#endif - return 0; } |