| Message ID | 20230320131845.3138015-13-ardb@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | ARM: vfp: Switch to C API to en/disable softirqs | expand |
On Mon, Mar 20, 2023 at 2:19 PM Ard Biesheuvel <ardb@kernel.org> wrote: > Now that we can dispatch all VFP and iWMMXT related undef exceptions > using undef hooks implemented in C code, we no longer need the asm entry > code that takes care of this unless we are using FPE. As this means it > is ARM only, we can also remove the Thumb2 specific decorations. > > It also means the non-standard, asm-only calling convention where > returning via LR means failure and returning via R9 means success is now > only used on legacy platforms that lack any kind of function return > prediction, avoiding the associated performance impact. > > Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Clearly makes things more compartmentalized. Reviewed-by: Linus Walleij <linus.walleij@linaro.org> > call_fpe: > - badr r9, ret_from_exception > - badr lr, __und_usr_fault_32 > +#ifdef CONFIG_FPE_NWFPE > + adr r9, ret_from_exception > + adr lr, __und_usr_fault_32 I actually have the NetWinder so if we want to refactor further I can test. Marc Zyngier has this machine too. Scott Bambrough wrote the NWFPE handling a long time ago I think, so putting him on CC for fun. Yours, Linus Walleij
diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S index 0367c9581c1f05a6..5552179faf7a469e 100644 --- a/arch/arm/kernel/entry-armv.S +++ b/arch/arm/kernel/entry-armv.S @@ -532,8 +532,9 @@ ENDPROC(__und_usr) * IRQs enabled, FIQs enabled. */ call_fpe: - badr r9, ret_from_exception - badr lr, __und_usr_fault_32 +#ifdef CONFIG_FPE_NWFPE + adr r9, ret_from_exception + adr lr, __und_usr_fault_32 sub r4, r2, #4 @ ARM instr at LR - 4 USERL( 4b, ldrt r0, [r4]) @@ -554,9 +555,7 @@ ARM_BE8(rev r0, r0) @ little endian instruction teqeq r5, #1 << TIF_USING_IWMMXT @ check whether it is set beq iwmmxt_task_enable @ branch if set #endif - ARM( add pc, pc, r8, lsr #6 ) - THUMB( lsr r8, r8, #6 ) - THUMB( add pc, r8 ) + add pc, pc, r8, lsr #6 nop ret.w lr @ CP#0 @@ -598,6 +597,7 @@ ENTRY(fp_enter) ENTRY(no_fp) ret lr ENDPROC(no_fp) +#endif __und_usr_fault_32: mov r1, #4
Now that we can dispatch all VFP and iWMMXT related undef exceptions using undef hooks implemented in C code, we no longer need the asm entry code that takes care of this unless we are using FPE. As this means it is ARM only, we can also remove the Thumb2 specific decorations. It also means the non-standard, asm-only calling convention where returning via LR means failure and returning via R9 means success is now only used on legacy platforms that lack any kind of function return prediction, avoiding the associated performance impact. Signed-off-by: Ard Biesheuvel <ardb@kernel.org> --- arch/arm/kernel/entry-armv.S | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-)