On Tue, Jul 15, 2008 at 1:32 PM, Helge Deller <deller@xxxxxx> wrote: >> The LWS interface *already* has a 64-bit runtime entry point, see >> arch/parisc/kernel/syscall.S: >> [....] > > Sure. I thought the discussion was about adding a 64-bit runtime entry point > which operates on a 64-bit pointer. But this can be done discussed when > 64-bit userspace is coming... The entry point is already there. It's LWS #1. Apparnetly I created it with a 64-bit userspace in mind. >> Helge, please review. I rolled in your fix for the superfluous .align >> 16. I would like your signed-off-by if you think the patch is good. >> >> [PARISC] Document LWS ABI and LWS cleanups. >> >> Document the LWS ABI including implementation notes for >> userspace, and comment cleanup. >> >> Remove extraneous .align 16 after lws_lock_start. >> >> Signed-off-by: Carlos O'Donell <carlos@xxxxxxxxxxxxxxxx> > > Signed-off-by: Helge Deller <deller@xxxxxx> Thanks. Kyle, Please apply the patch and send it upstream? Cheers, Carlos.
[PARISC] Document LWS ABI and LWS cleanups. Document the LWS ABI including implementation notes for userspace, and comment cleanup. Remove extraneous .align 16 after lws_lock_start. Signed-off-by: Carlos O'Donell <carlos@xxxxxxxxxxxxxxxx> Signed-off-by: Helge Deller <deller@xxxxxx> diff --git a/arch/parisc/kernel/syscall.S b/arch/parisc/kernel/syscall.S index 69b6eeb..3fc73ad 100644 --- a/arch/parisc/kernel/syscall.S +++ b/arch/parisc/kernel/syscall.S @@ -365,17 +365,51 @@ tracesys_sigexit: /********************************************************* - Light-weight-syscall code + 32/64-bit Light-Weight-Syscall ABI - r20 - lws number - r26,r25,r24,r23,r22 - Input registers - r28 - Function return register - r21 - Error code. + * - Indicates a hint for userspace inline asm + implementations. - Scracth: Any of the above that aren't being - currently used, including r1. + Syscall number (caller-saves) + - %r20 + * In asm clobber. - Return pointer: r31 (Not usable) + Argument registers (caller-saves) + - %r26, %r25, %r24, %r23, %r22 + * In asm input. + + Return registers (caller-saves) + - %r28 (return), %r21 (errno) + * In asm output. + + Caller-saves registers + - %r1, %r27, %r29 + - %r2 (return pointer) + - %r31 (ble link register) + * In asm clobber. + + Callee-saves registers + - %r3-%r18 + - %r30 (stack pointer) + * Not in asm clobber. + + If userspace is 32-bit: + Callee-saves registers + - %r19 (32-bit PIC register) + + Differences from 32-bit calling convention: + - Syscall number in %r20 + - Additional argument register %r22 (arg4) + - Callee-saves %r19. + + If userspace is 64-bit: + Callee-saves registers + - %r27 (64-bit PIC register) + + Differences from 64-bit calling convention: + - Syscall number in %r20 + - Additional argument register %r22 (arg4) + - Callee-saves %r27. Error codes returned by entry path: @@ -473,7 +507,8 @@ lws_compare_and_swap64: b,n lws_compare_and_swap #else /* If we are not a 64-bit kernel, then we don't - * implement having 64-bit input registers + * have 64-bit input registers, and calling + * the 64-bit LWS CAS returns ENOSYS. */ b,n lws_exit_nosys #endif @@ -635,12 +670,15 @@ END(sys_call_table64) /* All light-weight-syscall atomic operations will use this set of locks + + NOTE: The lws_lock_start symbol must be + at least 16-byte aligned for safe use + with ldcw. */ .section .data .align PAGE_SIZE ENTRY(lws_lock_start) /* lws locks */ - .align 16 .rept 16 /* Keep locks aligned at 16-bytes */ .word 1
