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/include/asm/entry-compact.h | |
| 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/include/asm/entry-compact.h')
| -rw-r--r-- | arch/arc/include/asm/entry-compact.h | 35 |
1 files changed, 11 insertions, 24 deletions
diff --git a/arch/arc/include/asm/entry-compact.h b/arch/arc/include/asm/entry-compact.h index 67ff06e15cea..e3383e1cb040 100644 --- a/arch/arc/include/asm/entry-compact.h +++ b/arch/arc/include/asm/entry-compact.h @@ -151,14 +151,6 @@ /* ARC700 doesn't provide auto-stack switching */ SWITCH_TO_KERNEL_STK -#ifdef CONFIG_ARC_CURR_IN_REG - /* Treat r25 as scratch reg (save on stack) and load with "current" */ - PUSH r25 - GET_CURR_TASK_ON_CPU r25 -#else - sub sp, sp, 4 -#endif - st.a r0, [sp, -8] /* orig_r0 needed for syscall (skip ECR slot) */ sub sp, sp, 4 /* skip pt_regs->sp, already saved above */ @@ -179,6 +171,11 @@ lr r10, [ecr] st r10, [sp, PT_event] /* EV_Trap expects r10 to have ECR */ + +#ifdef CONFIG_ARC_CURR_IN_REG + /* gp already saved on stack: now load with "current" */ + GET_CURR_TASK_ON_CPU gp +#endif .endm /*-------------------------------------------------------------- @@ -208,11 +205,8 @@ POP gp RESTORE_R12_TO_R0 -#ifdef CONFIG_ARC_CURR_IN_REG - ld r25, [sp, 12] -#endif ld sp, [sp] /* restore original sp */ - /* orig_r0, ECR, user_r25 skipped automatically */ + /* orig_r0, ECR skipped automatically */ .endm /* Dummy ECR values for Interrupts */ @@ -229,13 +223,6 @@ SWITCH_TO_KERNEL_STK -#ifdef CONFIG_ARC_CURR_IN_REG - /* Treat r25 as scratch reg (save on stack) and load with "current" */ - PUSH r25 - GET_CURR_TASK_ON_CPU r25 -#else - sub sp, sp, 4 -#endif PUSH 0x003\LVL\()abcd /* Dummy ECR */ sub sp, sp, 8 /* skip orig_r0 (not needed) @@ -255,6 +242,10 @@ PUSHAX lp_start PUSHAX bta_l\LVL\() +#ifdef CONFIG_ARC_CURR_IN_REG + /* gp already saved on stack: now load with "current" */ + GET_CURR_TASK_ON_CPU gp +#endif .endm /*-------------------------------------------------------------- @@ -282,11 +273,7 @@ POP gp RESTORE_R12_TO_R0 -#ifdef CONFIG_ARC_CURR_IN_REG - ld r25, [sp, 12] -#endif - ld sp, [sp] /* restore original sp */ - /* orig_r0, ECR, user_r25 skipped automatically */ + ld sp, [sp] /* restore original sp; orig_r0, ECR skipped implicitly */ .endm /* Get thread_info of "current" tsk */ |