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Diffstat (limited to 'arch/parisc/kernel/syscall.S')
| -rw-r--r-- | arch/parisc/kernel/syscall.S | 1341 |
1 files changed, 1341 insertions, 0 deletions
diff --git a/arch/parisc/kernel/syscall.S b/arch/parisc/kernel/syscall.S new file mode 100644 index 000000000..1373e5129 --- /dev/null +++ b/arch/parisc/kernel/syscall.S @@ -0,0 +1,1341 @@ +/* + * Linux/PA-RISC Project (http://www.parisc-linux.org/) + * + * System call entry code / Linux gateway page + * Copyright (c) Matthew Wilcox 1999 <willy@infradead.org> + * Licensed under the GNU GPL. + * thanks to Philipp Rumpf, Mike Shaver and various others + * sorry about the wall, puffin.. + */ + +/* +How does the Linux gateway page on PA-RISC work? +------------------------------------------------ +The Linux gateway page on PA-RISC is "special". +It actually has PAGE_GATEWAY bits set (this is linux terminology; in parisc +terminology it's Execute, promote to PL0) in the page map. So anything +executing on this page executes with kernel level privilege (there's more to it +than that: to have this happen, you also have to use a branch with a ,gate +completer to activate the privilege promotion). The upshot is that everything +that runs on the gateway page runs at kernel privilege but with the current +user process address space (although you have access to kernel space via %sr2). +For the 0x100 syscall entry, we redo the space registers to point to the kernel +address space (preserving the user address space in %sr3), move to wide mode if +required, save the user registers and branch into the kernel syscall entry +point. For all the other functions, we execute at kernel privilege but don't +flip address spaces. The basic upshot of this is that these code snippets are +executed atomically (because the kernel can't be pre-empted) and they may +perform architecturally forbidden (to PL3) operations (like setting control +registers). +*/ + + +#include <asm/asm-offsets.h> +#include <asm/unistd.h> +#include <asm/errno.h> +#include <asm/page.h> +#include <asm/psw.h> +#include <asm/thread_info.h> +#include <asm/assembly.h> +#include <asm/processor.h> +#include <asm/cache.h> + +#include <linux/linkage.h> + + /* We fill the empty parts of the gateway page with + * something that will kill the kernel or a + * userspace application. + */ +#define KILL_INSN break 0,0 + + .level PA_ASM_LEVEL + + .macro lws_pagefault_disable reg1,reg2 + mfctl %cr30, \reg2 + ldo TASK_PAGEFAULT_DISABLED(\reg2), \reg2 + ldw 0(%sr2,\reg2), \reg1 + ldo 1(\reg1), \reg1 + stw \reg1, 0(%sr2,\reg2) + .endm + + .macro lws_pagefault_enable reg1,reg2 + mfctl %cr30, \reg2 + ldo TASK_PAGEFAULT_DISABLED(\reg2), \reg2 + ldw 0(%sr2,\reg2), \reg1 + ldo -1(\reg1), \reg1 + stw \reg1, 0(%sr2,\reg2) + .endm + + .text + + .import syscall_exit,code + .import syscall_exit_rfi,code + + /* Linux gateway page is aliased to virtual page 0 in the kernel + * address space. Since it is a gateway page it cannot be + * dereferenced, so null pointers will still fault. We start + * the actual entry point at 0x100. We put break instructions + * at the beginning of the page to trap null indirect function + * pointers. + */ + + .align PAGE_SIZE +ENTRY(linux_gateway_page) + + /* ADDRESS 0x00 to 0xb0 = 176 bytes / 4 bytes per insn = 44 insns */ + .rept 44 + KILL_INSN + .endr + + /* ADDRESS 0xb0 to 0xb8, lws uses two insns for entry */ + /* Light-weight-syscall entry must always be located at 0xb0 */ + /* WARNING: Keep this number updated with table size changes */ +#define __NR_lws_entries (5) + +lws_entry: + gate lws_start, %r0 /* increase privilege */ + depi PRIV_USER, 31, 2, %r31 /* Ensure we return into user mode. */ + + /* Fill from 0xb8 to 0xe0 */ + .rept 10 + KILL_INSN + .endr + + /* This function MUST be located at 0xe0 for glibc's threading + mechanism to work. DO NOT MOVE THIS CODE EVER! */ +set_thread_pointer: + gate .+8, %r0 /* increase privilege */ + depi PRIV_USER, 31, 2, %r31 /* Ensure we return into user mode. */ + be 0(%sr7,%r31) /* return to user space */ + mtctl %r26, %cr27 /* move arg0 to the control register */ + + /* Increase the chance of trapping if random jumps occur to this + address, fill from 0xf0 to 0x100 */ + .rept 4 + KILL_INSN + .endr + +/* This address must remain fixed at 0x100 for glibc's syscalls to work */ + .align LINUX_GATEWAY_ADDR +linux_gateway_entry: + gate .+8, %r0 /* become privileged */ + mtsp %r0,%sr4 /* get kernel space into sr4 */ + mtsp %r0,%sr5 /* get kernel space into sr5 */ + mtsp %r0,%sr6 /* get kernel space into sr6 */ + +#ifdef CONFIG_64BIT + /* Store W bit on entry to the syscall in case it's a wide userland + * process. */ + ssm PSW_SM_W, %r1 + extrd,u %r1,PSW_W_BIT,1,%r1 + /* sp must be aligned on 4, so deposit the W bit setting into + * the bottom of sp temporarily */ + or,ev %r1,%r30,%r30 + b,n 1f + /* The top halves of argument registers must be cleared on syscall + * entry from narrow executable. + */ + depdi 0, 31, 32, %r26 + depdi 0, 31, 32, %r25 + depdi 0, 31, 32, %r24 + depdi 0, 31, 32, %r23 + depdi 0, 31, 32, %r22 + depdi 0, 31, 32, %r21 +1: +#endif + + /* We use a rsm/ssm pair to prevent sr3 from being clobbered + * by external interrupts. + */ + mfsp %sr7,%r1 /* save user sr7 */ + rsm PSW_SM_I, %r0 /* disable interrupts */ + mtsp %r1,%sr3 /* and store it in sr3 */ + + mfctl %cr30,%r1 + xor %r1,%r30,%r30 /* ye olde xor trick */ + xor %r1,%r30,%r1 + xor %r1,%r30,%r30 + + LDREG TASK_STACK(%r30),%r30 /* set up kernel stack */ + ldo FRAME_SIZE(%r30),%r30 + /* N.B.: It is critical that we don't set sr7 to 0 until r30 + * contains a valid kernel stack pointer. It is also + * critical that we don't start using the kernel stack + * until after sr7 has been set to 0. + */ + + mtsp %r0,%sr7 /* get kernel space into sr7 */ + ssm PSW_SM_I, %r0 /* enable interrupts */ + STREGM %r1,FRAME_SIZE(%r30) /* save r1 (usp) here for now */ + mfctl %cr30,%r1 /* get task ptr in %r1 */ + + /* Save some registers for sigcontext and potential task + switch (see entry.S for the details of which ones are + saved/restored). TASK_PT_PSW is zeroed so we can see whether + a process is on a syscall or not. For an interrupt the real + PSW value is stored. This is needed for gdb and sys_ptrace. */ + STREG %r0, TASK_PT_PSW(%r1) + STREG %r2, TASK_PT_GR2(%r1) /* preserve rp */ + STREG %r19, TASK_PT_GR19(%r1) + + LDREGM -FRAME_SIZE(%r30), %r2 /* get users sp back */ +#ifdef CONFIG_64BIT + extrd,u %r2,63,1,%r19 /* W hidden in bottom bit */ +#if 0 + xor %r19,%r2,%r2 /* clear bottom bit */ + depd,z %r19,1,1,%r19 + std %r19,TASK_PT_PSW(%r1) +#endif +#endif + STREG %r2, TASK_PT_GR30(%r1) /* ... and save it */ + + STREG %r20, TASK_PT_GR20(%r1) /* Syscall number */ + STREG %r21, TASK_PT_GR21(%r1) + STREG %r22, TASK_PT_GR22(%r1) + STREG %r23, TASK_PT_GR23(%r1) /* 4th argument */ + STREG %r24, TASK_PT_GR24(%r1) /* 3rd argument */ + STREG %r25, TASK_PT_GR25(%r1) /* 2nd argument */ + STREG %r26, TASK_PT_GR26(%r1) /* 1st argument */ + STREG %r27, TASK_PT_GR27(%r1) /* user dp */ + STREG %r28, TASK_PT_GR28(%r1) /* return value 0 */ + STREG %r0, TASK_PT_ORIG_R28(%r1) /* don't prohibit restarts */ + STREG %r29, TASK_PT_GR29(%r1) /* return value 1 */ + STREG %r31, TASK_PT_GR31(%r1) /* preserve syscall return ptr */ + + ldo TASK_PT_FR0(%r1), %r27 /* save fpregs from the kernel */ + save_fp %r27 /* or potential task switch */ + + mfctl %cr11, %r27 /* i.e. SAR */ + STREG %r27, TASK_PT_SAR(%r1) + + loadgp + +#ifdef CONFIG_64BIT + ldo -16(%r30),%r29 /* Reference param save area */ + copy %r19,%r2 /* W bit back to r2 */ +#else + /* no need to save these on stack in wide mode because the first 8 + * args are passed in registers */ + stw %r22, -52(%r30) /* 5th argument */ + stw %r21, -56(%r30) /* 6th argument */ +#endif + + /* Are we being ptraced? */ + mfctl %cr30, %r1 + LDREG TASK_TI_FLAGS(%r1),%r1 + ldi _TIF_SYSCALL_TRACE_MASK, %r19 + and,COND(=) %r1, %r19, %r0 + b,n .Ltracesys + + /* Note! We cannot use the syscall table that is mapped + nearby since the gateway page is mapped execute-only. */ + +#ifdef CONFIG_64BIT + ldil L%sys_call_table, %r1 + or,= %r2,%r2,%r2 + addil L%(sys_call_table64-sys_call_table), %r1 + ldo R%sys_call_table(%r1), %r19 + or,= %r2,%r2,%r2 + ldo R%sys_call_table64(%r1), %r19 +#else + load32 sys_call_table, %r19 +#endif + comiclr,>> __NR_Linux_syscalls, %r20, %r0 + b,n .Lsyscall_nosys + + LDREGX %r20(%r19), %r19 + + /* If this is a sys_rt_sigreturn call, and the signal was received + * when not in_syscall, then we want to return via syscall_exit_rfi, + * not syscall_exit. Signal no. in r20, in_syscall in r25 (see + * trampoline code in signal.c). + */ + ldi __NR_rt_sigreturn,%r2 + comb,= %r2,%r20,.Lrt_sigreturn +.Lin_syscall: + ldil L%syscall_exit,%r2 + be 0(%sr7,%r19) + ldo R%syscall_exit(%r2),%r2 +.Lrt_sigreturn: + comib,<> 0,%r25,.Lin_syscall + ldil L%syscall_exit_rfi,%r2 + be 0(%sr7,%r19) + ldo R%syscall_exit_rfi(%r2),%r2 + + /* Note! Because we are not running where we were linked, any + calls to functions external to this file must be indirect. To + be safe, we apply the opposite rule to functions within this + file, with local labels given to them to ensure correctness. */ + +.Lsyscall_nosys: +syscall_nosys: + ldil L%syscall_exit,%r1 + be R%syscall_exit(%sr7,%r1) + ldo -ENOSYS(%r0),%r28 /* set errno */ + + +/* Warning! This trace code is a virtual duplicate of the code above so be + * sure to maintain both! */ +.Ltracesys: +tracesys: + /* Need to save more registers so the debugger can see where we + * are. This saves only the lower 8 bits of PSW, so that the C + * bit is still clear on syscalls, and the D bit is set if this + * full register save path has been executed. We check the D + * bit on syscall_return_rfi to determine which registers to + * restore. An interrupt results in a full PSW saved with the + * C bit set, a non-straced syscall entry results in C and D clear + * in the saved PSW. + */ + mfctl %cr30,%r1 /* get task ptr */ + ssm 0,%r2 + STREG %r2,TASK_PT_PSW(%r1) /* Lower 8 bits only!! */ + mfsp %sr0,%r2 + STREG %r2,TASK_PT_SR0(%r1) + mfsp %sr1,%r2 + STREG %r2,TASK_PT_SR1(%r1) + mfsp %sr2,%r2 + STREG %r2,TASK_PT_SR2(%r1) + mfsp %sr3,%r2 + STREG %r2,TASK_PT_SR3(%r1) + STREG %r2,TASK_PT_SR4(%r1) + STREG %r2,TASK_PT_SR5(%r1) + STREG %r2,TASK_PT_SR6(%r1) + STREG %r2,TASK_PT_SR7(%r1) + STREG %r2,TASK_PT_IASQ0(%r1) + STREG %r2,TASK_PT_IASQ1(%r1) + LDREG TASK_PT_GR31(%r1),%r2 + STREG %r2,TASK_PT_IAOQ0(%r1) + ldo 4(%r2),%r2 + STREG %r2,TASK_PT_IAOQ1(%r1) + ldo TASK_REGS(%r1),%r2 + /* reg_save %r2 */ + STREG %r3,PT_GR3(%r2) + STREG %r4,PT_GR4(%r2) + STREG %r5,PT_GR5(%r2) + STREG %r6,PT_GR6(%r2) + STREG %r7,PT_GR7(%r2) + STREG %r8,PT_GR8(%r2) + STREG %r9,PT_GR9(%r2) + STREG %r10,PT_GR10(%r2) + STREG %r11,PT_GR11(%r2) + STREG %r12,PT_GR12(%r2) + STREG %r13,PT_GR13(%r2) + STREG %r14,PT_GR14(%r2) + STREG %r15,PT_GR15(%r2) + STREG %r16,PT_GR16(%r2) + STREG %r17,PT_GR17(%r2) + STREG %r18,PT_GR18(%r2) + /* Finished saving things for the debugger */ + + copy %r2,%r26 + ldil L%do_syscall_trace_enter,%r1 + ldil L%tracesys_next,%r2 + be R%do_syscall_trace_enter(%sr7,%r1) + ldo R%tracesys_next(%r2),%r2 + +tracesys_next: + /* do_syscall_trace_enter either returned the syscallno, or -1L, + * so we skip restoring the PT_GR20 below, since we pulled it from + * task->thread.regs.gr[20] above. + */ + copy %ret0,%r20 + + mfctl %cr30,%r1 /* get task ptr */ + LDREG TASK_PT_GR28(%r1), %r28 /* Restore return value */ + LDREG TASK_PT_GR26(%r1), %r26 /* Restore the users args */ + LDREG TASK_PT_GR25(%r1), %r25 + LDREG TASK_PT_GR24(%r1), %r24 + LDREG TASK_PT_GR23(%r1), %r23 + LDREG TASK_PT_GR22(%r1), %r22 + LDREG TASK_PT_GR21(%r1), %r21 +#ifdef CONFIG_64BIT + ldo -16(%r30),%r29 /* Reference param save area */ +#else + stw %r22, -52(%r30) /* 5th argument */ + stw %r21, -56(%r30) /* 6th argument */ +#endif + + cmpib,COND(=),n -1,%r20,tracesys_exit /* seccomp may have returned -1 */ + comiclr,>> __NR_Linux_syscalls, %r20, %r0 + b,n .Ltracesys_nosys + + /* Note! We cannot use the syscall table that is mapped + nearby since the gateway page is mapped execute-only. */ + +#ifdef CONFIG_64BIT + LDREG TASK_PT_GR30(%r1), %r19 /* get users sp back */ + extrd,u %r19,63,1,%r2 /* W hidden in bottom bit */ + + ldil L%sys_call_table, %r1 + or,= %r2,%r2,%r2 + addil L%(sys_call_table64-sys_call_table), %r1 + ldo R%sys_call_table(%r1), %r19 + or,= %r2,%r2,%r2 + ldo R%sys_call_table64(%r1), %r19 +#else + load32 sys_call_table, %r19 +#endif + + LDREGX %r20(%r19), %r19 + + /* If this is a sys_rt_sigreturn call, and the signal was received + * when not in_syscall, then we want to return via syscall_exit_rfi, + * not syscall_exit. Signal no. in r20, in_syscall in r25 (see + * trampoline code in signal.c). + */ + ldi __NR_rt_sigreturn,%r2 + comb,= %r2,%r20,.Ltrace_rt_sigreturn +.Ltrace_in_syscall: + ldil L%tracesys_exit,%r2 + be 0(%sr7,%r19) + ldo R%tracesys_exit(%r2),%r2 + +.Ltracesys_nosys: + ldo -ENOSYS(%r0),%r28 /* set errno */ + + /* Do *not* call this function on the gateway page, because it + makes a direct call to syscall_trace. */ + +tracesys_exit: + mfctl %cr30,%r1 /* get task ptr */ +#ifdef CONFIG_64BIT + ldo -16(%r30),%r29 /* Reference param save area */ +#endif + ldo TASK_REGS(%r1),%r26 + BL do_syscall_trace_exit,%r2 + STREG %r28,TASK_PT_GR28(%r1) /* save return value now */ + mfctl %cr30,%r1 /* get task ptr */ + LDREG TASK_PT_GR28(%r1), %r28 /* Restore return val. */ + + ldil L%syscall_exit,%r1 + be,n R%syscall_exit(%sr7,%r1) + +.Ltrace_rt_sigreturn: + comib,<> 0,%r25,.Ltrace_in_syscall + ldil L%tracesys_sigexit,%r2 + be 0(%sr7,%r19) + ldo R%tracesys_sigexit(%r2),%r2 + +tracesys_sigexit: + mfctl %cr30,%r1 /* get task ptr */ +#ifdef CONFIG_64BIT + ldo -16(%r30),%r29 /* Reference param save area */ +#endif + BL do_syscall_trace_exit,%r2 + ldo TASK_REGS(%r1),%r26 + + ldil L%syscall_exit_rfi,%r1 + be,n R%syscall_exit_rfi(%sr7,%r1) + + + /********************************************************* + 32/64-bit Light-Weight-Syscall ABI + + * - Indicates a hint for userspace inline asm + implementations. + + Syscall number (caller-saves) + - %r20 + * In asm clobber. + + 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: + + ENOSYS - r20 was an invalid LWS number. + + *********************************************************/ +lws_start: + +#ifdef CONFIG_64BIT + ssm PSW_SM_W, %r1 + extrd,u %r1,PSW_W_BIT,1,%r1 + /* sp must be aligned on 4, so deposit the W bit setting into + * the bottom of sp temporarily */ + or,od %r1,%r30,%r30 + + /* Clip LWS number to a 32-bit value for 32-bit processes */ + depdi 0, 31, 32, %r20 +#endif + + /* Is the lws entry number valid? */ + comiclr,>> __NR_lws_entries, %r20, %r0 + b,n lws_exit_nosys + + /* Load table start */ + ldil L%lws_table, %r1 + ldo R%lws_table(%r1), %r28 /* Scratch use of r28 */ + LDREGX %r20(%sr2,r28), %r21 /* Scratch use of r21 */ + + /* Jump to lws, lws table pointers already relocated */ + be,n 0(%sr2,%r21) + +lws_exit_noerror: + lws_pagefault_enable %r1,%r21 + stw,ma %r20, 0(%sr2,%r20) + ssm PSW_SM_I, %r0 + b lws_exit + copy %r0, %r21 + +lws_wouldblock: + ssm PSW_SM_I, %r0 + ldo 2(%r0), %r28 + b lws_exit + ldo -EAGAIN(%r0), %r21 + +lws_pagefault: + lws_pagefault_enable %r1,%r21 + stw,ma %r20, 0(%sr2,%r20) + ssm PSW_SM_I, %r0 + ldo 3(%r0),%r28 + b lws_exit + ldo -EAGAIN(%r0),%r21 + +lws_fault: + ldo 1(%r0),%r28 + b lws_exit + ldo -EFAULT(%r0),%r21 + +lws_exit_nosys: + ldo -ENOSYS(%r0),%r21 + /* Fall through: Return to userspace */ + +lws_exit: +#ifdef CONFIG_64BIT + /* decide whether to reset the wide mode bit + * + * For a syscall, the W bit is stored in the lowest bit + * of sp. Extract it and reset W if it is zero */ + extrd,u,*<> %r30,63,1,%r1 + rsm PSW_SM_W, %r0 + /* now reset the lowest bit of sp if it was set */ + xor %r30,%r1,%r30 +#endif + be,n 0(%sr7, %r31) + + + + /*************************************************** + Implementing 32bit CAS as an atomic operation: + + %r26 - Address to examine + %r25 - Old value to check (old) + %r24 - New value to set (new) + %r28 - Return prev through this register. + %r21 - Kernel error code + + %r21 returns the following error codes: + EAGAIN - CAS is busy, ldcw failed, try again. + EFAULT - Read or write failed. + + If EAGAIN is returned, %r28 indicates the busy reason: + r28 == 1 - CAS is busy. lock contended. + r28 == 2 - CAS is busy. ldcw failed. + r28 == 3 - CAS is busy. page fault. + + Scratch: r20, r28, r1 + + ****************************************************/ + + /* ELF64 Process entry path */ +lws_compare_and_swap64: +#ifdef CONFIG_64BIT + b,n lws_compare_and_swap +#else + /* If we are not a 64-bit kernel, then we don't + * have 64-bit input registers, and calling + * the 64-bit LWS CAS returns ENOSYS. + */ + b,n lws_exit_nosys +#endif + + /* ELF32/ELF64 Process entry path */ +lws_compare_and_swap32: +#ifdef CONFIG_64BIT + /* Wide mode user process? */ + bb,<,n %sp, 31, lws_compare_and_swap + + /* Clip all the input registers for 32-bit processes */ + depdi 0, 31, 32, %r26 + depdi 0, 31, 32, %r25 + depdi 0, 31, 32, %r24 +#endif + +lws_compare_and_swap: + /* Trigger memory reference interruptions without writing to memory */ +1: ldw 0(%r26), %r28 +2: stbys,e %r0, 0(%r26) + + /* Calculate 8-bit hash index from virtual address */ + extru_safe %r26, 27, 8, %r20 + + /* Load start of lock table */ + ldil L%lws_lock_start, %r28 + ldo R%lws_lock_start(%r28), %r28 + + /* Find lock to use, the hash index is one of 0 to + 255, multiplied by 16 (keep it 16-byte aligned) + and add to the lock table offset. */ + shlw %r20, 4, %r20 + add %r20, %r28, %r20 + + rsm PSW_SM_I, %r0 /* Disable interrupts */ + + /* Try to acquire the lock */ + LDCW 0(%sr2,%r20), %r28 + comclr,<> %r0, %r28, %r0 + b,n lws_wouldblock + + /* Disable page faults to prevent sleeping in critical region */ + lws_pagefault_disable %r21,%r28 + + /* + prev = *addr; + if ( prev == old ) + *addr = new; + return prev; + */ + + /* NOTES: + This all works because intr_do_signal + and schedule both check the return iasq + and see that we are on the kernel page + so this process is never scheduled off + or is ever sent any signal of any sort, + thus it is wholly atomic from usrspace's + perspective + */ + /* The load and store could fail */ +3: ldw 0(%r26), %r28 + sub,<> %r28, %r25, %r0 +4: stw %r24, 0(%r26) + b,n lws_exit_noerror + + /* A fault occurred on load or stbys,e store */ +5: b,n lws_fault + ASM_EXCEPTIONTABLE_ENTRY(1b-linux_gateway_page, 5b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(2b-linux_gateway_page, 5b-linux_gateway_page) + + /* A page fault occurred in critical region */ +6: b,n lws_pagefault + ASM_EXCEPTIONTABLE_ENTRY(3b-linux_gateway_page, 6b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(4b-linux_gateway_page, 6b-linux_gateway_page) + + + /*************************************************** + New CAS implementation which uses pointers and variable size + information. The value pointed by old and new MUST NOT change + while performing CAS. The lock only protects the value at %r26. + + %r26 - Address to examine + %r25 - Pointer to the value to check (old) + %r24 - Pointer to the value to set (new) + %r23 - Size of the variable (0/1/2/3 for 8/16/32/64 bit) + %r28 - Return non-zero on failure + %r21 - Kernel error code + + %r21 returns the following error codes: + EAGAIN - CAS is busy, ldcw failed, try again. + EFAULT - Read or write failed. + + If EAGAIN is returned, %r28 indicates the busy reason: + r28 == 1 - CAS is busy. lock contended. + r28 == 2 - CAS is busy. ldcw failed. + r28 == 3 - CAS is busy. page fault. + + Scratch: r20, r22, r28, r29, r1, fr4 (32bit for 64bit CAS only) + + ****************************************************/ + +lws_compare_and_swap_2: +#ifdef CONFIG_64BIT + /* Wide mode user process? */ + bb,<,n %sp, 31, cas2_begin + + /* Clip the input registers for 32-bit processes. We don't + need to clip %r23 as we only use it for word operations */ + depdi 0, 31, 32, %r26 + depdi 0, 31, 32, %r25 + depdi 0, 31, 32, %r24 +#endif + +cas2_begin: + /* Check the validity of the size pointer */ + subi,>>= 3, %r23, %r0 + b,n lws_exit_nosys + + /* Jump to the functions which will load the old and new values into + registers depending on the their size */ + shlw %r23, 2, %r29 + blr %r29, %r0 + nop + + /* 8-bit load */ +1: ldb 0(%r25), %r25 + b cas2_lock_start +2: ldb 0(%r24), %r24 + nop + nop + nop + nop + nop + + /* 16-bit load */ +3: ldh 0(%r25), %r25 + b cas2_lock_start +4: ldh 0(%r24), %r24 + nop + nop + nop + nop + nop + + /* 32-bit load */ +5: ldw 0(%r25), %r25 + b cas2_lock_start +6: ldw 0(%r24), %r24 + nop + nop + nop + nop + nop + + /* 64-bit load */ +#ifdef CONFIG_64BIT +7: ldd 0(%r25), %r25 +8: ldd 0(%r24), %r24 +#else + /* Load old value into r22/r23 - high/low */ +7: ldw 0(%r25), %r22 +8: ldw 4(%r25), %r23 + /* Load new value into fr4 for atomic store later */ +9: flddx 0(%r24), %fr4 +#endif + +cas2_lock_start: + /* Trigger memory reference interruptions without writing to memory */ + copy %r26, %r28 + depi_safe 0, 31, 2, %r28 +10: ldw 0(%r28), %r1 +11: stbys,e %r0, 0(%r28) + + /* Calculate 8-bit hash index from virtual address */ + extru_safe %r26, 27, 8, %r20 + + /* Load start of lock table */ + ldil L%lws_lock_start, %r28 + ldo R%lws_lock_start(%r28), %r28 + + /* Find lock to use, the hash index is one of 0 to + 255, multiplied by 16 (keep it 16-byte aligned) + and add to the lock table offset. */ + shlw %r20, 4, %r20 + add %r20, %r28, %r20 + + rsm PSW_SM_I, %r0 /* Disable interrupts */ + + /* Try to acquire the lock */ + LDCW 0(%sr2,%r20), %r28 + comclr,<> %r0, %r28, %r0 + b,n lws_wouldblock + + /* Disable page faults to prevent sleeping in critical region */ + lws_pagefault_disable %r21,%r28 + + /* + prev = *addr; + if ( prev == old ) + *addr = new; + return prev; + */ + + /* NOTES: + This all works because intr_do_signal + and schedule both check the return iasq + and see that we are on the kernel page + so this process is never scheduled off + or is ever sent any signal of any sort, + thus it is wholly atomic from usrspace's + perspective + */ + + /* Jump to the correct function */ + blr %r29, %r0 + /* Set %r28 as non-zero for now */ + ldo 1(%r0),%r28 + + /* 8-bit CAS */ +12: ldb 0(%r26), %r29 + sub,= %r29, %r25, %r0 + b,n lws_exit_noerror +13: stb %r24, 0(%r26) + b lws_exit_noerror + copy %r0, %r28 + nop + nop + + /* 16-bit CAS */ +14: ldh 0(%r26), %r29 + sub,= %r29, %r25, %r0 + b,n lws_exit_noerror +15: sth %r24, 0(%r26) + b lws_exit_noerror + copy %r0, %r28 + nop + nop + + /* 32-bit CAS */ +16: ldw 0(%r26), %r29 + sub,= %r29, %r25, %r0 + b,n lws_exit_noerror +17: stw %r24, 0(%r26) + b lws_exit_noerror + copy %r0, %r28 + nop + nop + + /* 64-bit CAS */ +#ifdef CONFIG_64BIT +18: ldd 0(%r26), %r29 + sub,*= %r29, %r25, %r0 + b,n lws_exit_noerror +19: std %r24, 0(%r26) + copy %r0, %r28 +#else + /* Compare first word */ +18: ldw 0(%r26), %r29 + sub,= %r29, %r22, %r0 + b,n lws_exit_noerror + /* Compare second word */ +19: ldw 4(%r26), %r29 + sub,= %r29, %r23, %r0 + b,n lws_exit_noerror + /* Perform the store */ +20: fstdx %fr4, 0(%r26) + copy %r0, %r28 +#endif + b lws_exit_noerror + copy %r0, %r28 + + /* A fault occurred on load or stbys,e store */ +30: b,n lws_fault + ASM_EXCEPTIONTABLE_ENTRY(1b-linux_gateway_page, 30b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(2b-linux_gateway_page, 30b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(3b-linux_gateway_page, 30b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(4b-linux_gateway_page, 30b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(5b-linux_gateway_page, 30b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(6b-linux_gateway_page, 30b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(7b-linux_gateway_page, 30b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(8b-linux_gateway_page, 30b-linux_gateway_page) +#ifndef CONFIG_64BIT + ASM_EXCEPTIONTABLE_ENTRY(9b-linux_gateway_page, 30b-linux_gateway_page) +#endif + + ASM_EXCEPTIONTABLE_ENTRY(10b-linux_gateway_page, 30b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(11b-linux_gateway_page, 30b-linux_gateway_page) + + /* A page fault occurred in critical region */ +31: b,n lws_pagefault + ASM_EXCEPTIONTABLE_ENTRY(12b-linux_gateway_page, 31b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(13b-linux_gateway_page, 31b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(14b-linux_gateway_page, 31b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(15b-linux_gateway_page, 31b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(16b-linux_gateway_page, 31b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(17b-linux_gateway_page, 31b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(18b-linux_gateway_page, 31b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(19b-linux_gateway_page, 31b-linux_gateway_page) +#ifndef CONFIG_64BIT + ASM_EXCEPTIONTABLE_ENTRY(20b-linux_gateway_page, 31b-linux_gateway_page) +#endif + + + /*************************************************** + LWS atomic exchange. + + %r26 - Exchange address + %r25 - Size of the variable (0/1/2/3 for 8/16/32/64 bit) + %r24 - Address of new value + %r23 - Address of old value + %r28 - Return non-zero on failure + %r21 - Kernel error code + + %r21 returns the following error codes: + EAGAIN - CAS is busy, ldcw failed, try again. + EFAULT - Read or write failed. + + If EAGAIN is returned, %r28 indicates the busy reason: + r28 == 1 - CAS is busy. lock contended. + r28 == 2 - CAS is busy. ldcw failed. + r28 == 3 - CAS is busy. page fault. + + Scratch: r20, r1 + + ****************************************************/ + +lws_atomic_xchg: +#ifdef CONFIG_64BIT + /* Wide mode user process? */ + bb,<,n %sp, 31, atomic_xchg_begin + + /* Clip the input registers for 32-bit processes. We don't + need to clip %r23 as we only use it for word operations */ + depdi 0, 31, 32, %r26 + depdi 0, 31, 32, %r25 + depdi 0, 31, 32, %r24 + depdi 0, 31, 32, %r23 +#endif + +atomic_xchg_begin: + /* Check the validity of the size pointer */ + subi,>>= 3, %r25, %r0 + b,n lws_exit_nosys + + /* Jump to the functions which will load the old and new values into + registers depending on the their size */ + shlw %r25, 2, %r1 + blr %r1, %r0 + nop + + /* Perform exception checks */ + + /* 8-bit exchange */ +1: ldb 0(%r24), %r20 + copy %r23, %r20 + depi_safe 0, 31, 2, %r20 + b atomic_xchg_start +2: stbys,e %r0, 0(%r20) + nop + nop + nop + + /* 16-bit exchange */ +3: ldh 0(%r24), %r20 + copy %r23, %r20 + depi_safe 0, 31, 2, %r20 + b atomic_xchg_start +4: stbys,e %r0, 0(%r20) + nop + nop + nop + + /* 32-bit exchange */ +5: ldw 0(%r24), %r20 + b atomic_xchg_start +6: stbys,e %r0, 0(%r23) + nop + nop + nop + nop + nop + + /* 64-bit exchange */ +#ifdef CONFIG_64BIT +7: ldd 0(%r24), %r20 +8: stdby,e %r0, 0(%r23) +#else +7: ldw 0(%r24), %r20 +8: ldw 4(%r24), %r20 + copy %r23, %r20 + depi_safe 0, 31, 2, %r20 +9: stbys,e %r0, 0(%r20) +10: stbys,e %r0, 4(%r20) +#endif + +atomic_xchg_start: + /* Trigger memory reference interruptions without writing to memory */ + copy %r26, %r28 + depi_safe 0, 31, 2, %r28 +11: ldw 0(%r28), %r1 +12: stbys,e %r0, 0(%r28) + + /* Calculate 8-bit hash index from virtual address */ + extru_safe %r26, 27, 8, %r20 + + /* Load start of lock table */ + ldil L%lws_lock_start, %r28 + ldo R%lws_lock_start(%r28), %r28 + + /* Find lock to use, the hash index is one of 0 to + 255, multiplied by 16 (keep it 16-byte aligned) + and add to the lock table offset. */ + shlw %r20, 4, %r20 + add %r20, %r28, %r20 + + rsm PSW_SM_I, %r0 /* Disable interrupts */ + + /* Try to acquire the lock */ + LDCW 0(%sr2,%r20), %r28 + comclr,<> %r0, %r28, %r0 + b,n lws_wouldblock + + /* Disable page faults to prevent sleeping in critical region */ + lws_pagefault_disable %r21,%r28 + + /* NOTES: + This all works because intr_do_signal + and schedule both check the return iasq + and see that we are on the kernel page + so this process is never scheduled off + or is ever sent any signal of any sort, + thus it is wholly atomic from userspace's + perspective + */ + + /* Jump to the correct function */ + blr %r1, %r0 + /* Set %r28 as non-zero for now */ + ldo 1(%r0),%r28 + + /* 8-bit exchange */ +14: ldb 0(%r26), %r1 +15: stb %r1, 0(%r23) +15: ldb 0(%r24), %r1 +17: stb %r1, 0(%r26) + b lws_exit_noerror + copy %r0, %r28 + nop + nop + + /* 16-bit exchange */ +18: ldh 0(%r26), %r1 +19: sth %r1, 0(%r23) +20: ldh 0(%r24), %r1 +21: sth %r1, 0(%r26) + b lws_exit_noerror + copy %r0, %r28 + nop + nop + + /* 32-bit exchange */ +22: ldw 0(%r26), %r1 +23: stw %r1, 0(%r23) +24: ldw 0(%r24), %r1 +25: stw %r1, 0(%r26) + b lws_exit_noerror + copy %r0, %r28 + nop + nop + + /* 64-bit exchange */ +#ifdef CONFIG_64BIT +26: ldd 0(%r26), %r1 +27: std %r1, 0(%r23) +28: ldd 0(%r24), %r1 +29: std %r1, 0(%r26) +#else +26: flddx 0(%r26), %fr4 +27: fstdx %fr4, 0(%r23) +28: flddx 0(%r24), %fr4 +29: fstdx %fr4, 0(%r26) +#endif + b lws_exit_noerror + copy %r0, %r28 + + /* A fault occurred on load or stbys,e store */ +30: b,n lws_fault + ASM_EXCEPTIONTABLE_ENTRY(1b-linux_gateway_page, 30b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(2b-linux_gateway_page, 30b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(3b-linux_gateway_page, 30b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(4b-linux_gateway_page, 30b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(5b-linux_gateway_page, 30b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(6b-linux_gateway_page, 30b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(7b-linux_gateway_page, 30b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(8b-linux_gateway_page, 30b-linux_gateway_page) +#ifndef CONFIG_64BIT + ASM_EXCEPTIONTABLE_ENTRY(9b-linux_gateway_page, 30b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(10b-linux_gateway_page, 30b-linux_gateway_page) +#endif + + ASM_EXCEPTIONTABLE_ENTRY(11b-linux_gateway_page, 30b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(12b-linux_gateway_page, 30b-linux_gateway_page) + + /* A page fault occurred in critical region */ +31: b,n lws_pagefault + ASM_EXCEPTIONTABLE_ENTRY(14b-linux_gateway_page, 31b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(15b-linux_gateway_page, 31b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(16b-linux_gateway_page, 31b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(17b-linux_gateway_page, 31b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(18b-linux_gateway_page, 31b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(19b-linux_gateway_page, 31b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(20b-linux_gateway_page, 31b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(21b-linux_gateway_page, 31b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(22b-linux_gateway_page, 31b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(23b-linux_gateway_page, 31b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(24b-linux_gateway_page, 31b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(25b-linux_gateway_page, 31b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(26b-linux_gateway_page, 31b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(27b-linux_gateway_page, 31b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(28b-linux_gateway_page, 31b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(29b-linux_gateway_page, 31b-linux_gateway_page) + + /*************************************************** + LWS atomic store. + + %r26 - Address to store + %r25 - Size of the variable (0/1/2/3 for 8/16/32/64 bit) + %r24 - Address of value to store + %r28 - Return non-zero on failure + %r21 - Kernel error code + + %r21 returns the following error codes: + EAGAIN - CAS is busy, ldcw failed, try again. + EFAULT - Read or write failed. + + If EAGAIN is returned, %r28 indicates the busy reason: + r28 == 1 - CAS is busy. lock contended. + r28 == 2 - CAS is busy. ldcw failed. + r28 == 3 - CAS is busy. page fault. + + Scratch: r20, r1 + + ****************************************************/ + +lws_atomic_store: +#ifdef CONFIG_64BIT + /* Wide mode user process? */ + bb,<,n %sp, 31, atomic_store_begin + + /* Clip the input registers for 32-bit processes. We don't + need to clip %r23 as we only use it for word operations */ + depdi 0, 31, 32, %r26 + depdi 0, 31, 32, %r25 + depdi 0, 31, 32, %r24 +#endif + +atomic_store_begin: + /* Check the validity of the size pointer */ + subi,>>= 3, %r25, %r0 + b,n lws_exit_nosys + + shlw %r25, 1, %r1 + blr %r1, %r0 + nop + + /* Perform exception checks */ + + /* 8-bit store */ +1: ldb 0(%r24), %r20 + b,n atomic_store_start + nop + nop + + /* 16-bit store */ +2: ldh 0(%r24), %r20 + b,n atomic_store_start + nop + nop + + /* 32-bit store */ +3: ldw 0(%r24), %r20 + b,n atomic_store_start + nop + nop + + /* 64-bit store */ +#ifdef CONFIG_64BIT +4: ldd 0(%r24), %r20 +#else +4: ldw 0(%r24), %r20 +5: ldw 4(%r24), %r20 +#endif + +atomic_store_start: + /* Trigger memory reference interruptions without writing to memory */ + copy %r26, %r28 + depi_safe 0, 31, 2, %r28 +6: ldw 0(%r28), %r1 +7: stbys,e %r0, 0(%r28) + + /* Calculate 8-bit hash index from virtual address */ + extru_safe %r26, 27, 8, %r20 + + /* Load start of lock table */ + ldil L%lws_lock_start, %r28 + ldo R%lws_lock_start(%r28), %r28 + + /* Find lock to use, the hash index is one of 0 to + 255, multiplied by 16 (keep it 16-byte aligned) + and add to the lock table offset. */ + shlw %r20, 4, %r20 + add %r20, %r28, %r20 + + rsm PSW_SM_I, %r0 /* Disable interrupts */ + + /* Try to acquire the lock */ + LDCW 0(%sr2,%r20), %r28 + comclr,<> %r0, %r28, %r0 + b,n lws_wouldblock + + /* Disable page faults to prevent sleeping in critical region */ + lws_pagefault_disable %r21,%r28 + + /* NOTES: + This all works because intr_do_signal + and schedule both check the return iasq + and see that we are on the kernel page + so this process is never scheduled off + or is ever sent any signal of any sort, + thus it is wholly atomic from userspace's + perspective + */ + + /* Jump to the correct function */ + blr %r1, %r0 + /* Set %r28 as non-zero for now */ + ldo 1(%r0),%r28 + + /* 8-bit store */ +9: ldb 0(%r24), %r1 +10: stb %r1, 0(%r26) + b lws_exit_noerror + copy %r0, %r28 + + /* 16-bit store */ +11: ldh 0(%r24), %r1 +12: sth %r1, 0(%r26) + b lws_exit_noerror + copy %r0, %r28 + + /* 32-bit store */ +13: ldw 0(%r24), %r1 +14: stw %r1, 0(%r26) + b lws_exit_noerror + copy %r0, %r28 + + /* 64-bit store */ +#ifdef CONFIG_64BIT +15: ldd 0(%r24), %r1 +16: std %r1, 0(%r26) +#else +15: flddx 0(%r24), %fr4 +16: fstdx %fr4, 0(%r26) +#endif + b lws_exit_noerror + copy %r0, %r28 + + /* A fault occurred on load or stbys,e store */ +30: b,n lws_fault + ASM_EXCEPTIONTABLE_ENTRY(1b-linux_gateway_page, 30b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(2b-linux_gateway_page, 30b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(3b-linux_gateway_page, 30b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(4b-linux_gateway_page, 30b-linux_gateway_page) +#ifndef CONFIG_64BIT + ASM_EXCEPTIONTABLE_ENTRY(5b-linux_gateway_page, 30b-linux_gateway_page) +#endif + + ASM_EXCEPTIONTABLE_ENTRY(6b-linux_gateway_page, 30b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(7b-linux_gateway_page, 30b-linux_gateway_page) + + /* A page fault occurred in critical region */ +31: b,n lws_pagefault + ASM_EXCEPTIONTABLE_ENTRY(9b-linux_gateway_page, 31b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(10b-linux_gateway_page, 31b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(11b-linux_gateway_page, 31b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(12b-linux_gateway_page, 31b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(13b-linux_gateway_page, 31b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(14b-linux_gateway_page, 31b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(15b-linux_gateway_page, 31b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(16b-linux_gateway_page, 31b-linux_gateway_page) + + /* Make sure nothing else is placed on this page */ + .align PAGE_SIZE +END(linux_gateway_page) +ENTRY(end_linux_gateway_page) + + /* Relocate symbols assuming linux_gateway_page is mapped + to virtual address 0x0 */ + +#define LWS_ENTRY(_name_) ASM_ULONG_INSN (lws_##_name_ - linux_gateway_page) + + .section .rodata,"a" + + .align 8 + /* Light-weight-syscall table */ + /* Start of lws table. */ +ENTRY(lws_table) + LWS_ENTRY(compare_and_swap32) /* 0 - ELF32 Atomic 32bit CAS */ + LWS_ENTRY(compare_and_swap64) /* 1 - ELF64 Atomic 32bit CAS */ + LWS_ENTRY(compare_and_swap_2) /* 2 - Atomic 64bit CAS */ + LWS_ENTRY(atomic_xchg) /* 3 - Atomic Exchange */ + LWS_ENTRY(atomic_store) /* 4 - Atomic Store */ +END(lws_table) + /* End of lws table */ + +#ifdef CONFIG_64BIT +#define __SYSCALL_WITH_COMPAT(nr, native, compat) __SYSCALL(nr, compat) +#else +#define __SYSCALL_WITH_COMPAT(nr, native, compat) __SYSCALL(nr, native) +#endif +#define __SYSCALL(nr, entry) ASM_ULONG_INSN entry + .align 8 +ENTRY(sys_call_table) + .export sys_call_table,data +#include <asm/syscall_table_32.h> /* 32-bit syscalls */ +END(sys_call_table) + +#ifdef CONFIG_64BIT + .align 8 +ENTRY(sys_call_table64) +#include <asm/syscall_table_64.h> /* 64-bit syscalls */ +END(sys_call_table64) +#endif + + /* + 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 L1_CACHE_BYTES +ENTRY(lws_lock_start) + /* lws locks */ + .rept 256 + /* Keep locks aligned at 16-bytes */ + .word 1 + .word 0 + .word 0 + .word 0 + .endr +END(lws_lock_start) + .previous + +.end |