#include <asm/assembly.h>
#include <asm/processor.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
+
+#include <linux/config.h> /* for CONFIG_SMP */
+
#ifdef __LP64__
.level 2.0w
#else
.level 1.1
#endif
+
+#ifndef __LP64__
+ .macro fixup_branch,lbl
+ b \lbl
+ .endm
+#else
+ .macro fixup_branch,lbl
+ ldil L%\lbl, %r1
+ ldo R%\lbl(%r1), %r1
+ bv,n %r0(%r1)
+ .endm
+#endif
+
.text
.import syscall_exit,code
.align 4096
linux_gateway_page:
- .rept 56
- break 0,0
+ /* ADDRESS 0x00 to 0xb0 = 176 bytes / 4 bytes per insn = 44 insns */
+ .rept 44
+ KILL_INSN
.endr
+ /* ADDRESS 0xb0 to 0xb4, lws uses 1 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 (2)
+
+lws_entry:
+ /* Unconditional branch to lws_start, located on the
+ same gateway page */
+ b,n lws_start
+
+ /* Fill from 0xb4 to 0xe0 */
+ .rept 11
+ 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 3, 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
- break 0,0
+ KILL_INSN
.endr
-/* This address must remain fixed, or user binaries go splat. */
+/* This address must remain fixed at 0x100 for glibc's syscalls to work */
.align 256
linux_gateway_entry:
gate .+8, %r0 /* become privileged */
/* Are we being ptraced? */
mfctl %cr30, %r1
+ LDREG TI_TASK(%r1),%r1
LDREG TASK_PTRACE(%r1), %r1
bb,<,n %r1,31,.Ltracesys
comiclr,>>= __NR_Linux_syscalls, %r20, %r0
b,n .Lsyscall_nosys
-#ifdef __LP64__
- ldd,s %r20(%r19), %r19
-#else
- ldwx,s %r20(%r19), %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
comiclr,>>= __NR_Linux_syscalls, %r20, %r0
b,n .Lsyscall_nosys
-#ifdef __LP64__
- ldd,s %r20(%r19), %r19
-#else
- ldwx,s %r20(%r19), %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
ldil L%syscall_exit_rfi,%r1
be,n R%syscall_exit_rfi(%sr7,%r1)
+
+ /*********************************************************
+ Light-weight-syscall code
+
+ r20 - lws number
+ r26,r25,r24,r23,r22 - Input registers
+ r28 - Function return register
+ r21 - Error code.
+
+ Scracth: Any of the above that aren't being
+ currently used, including r1.
+
+ Return pointer: r31 (Not usable)
+
+ Error codes returned by entry path:
+
+ ENOSYS - r20 was an invalid LWS number.
+
+ *********************************************************/
+lws_start:
+ /* Gate and ensure we return to userspace */
+ gate .+8, %r0
+ depi 3, 31, 2, %r31 /* Ensure we return to userspace */
+
+#ifdef __LP64__
+ /* FIXME: If we are a 64-bit kernel just
+ * turn this on unconditionally.
+ */
+ 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
+
+ /* Clip LWS number to a 32-bit value always */
+ depdi 0, 31, 32, %r20
+#endif
+
+ /* Is the lws entry number valid? */
+ comiclr,>>= __NR_lws_entries, %r20, %r0
+ b,n lws_exit_nosys
+
+ /* WARNING: Trashing sr2 and sr3 */
+ mfsp %sr7,%r1 /* get userspace into sr3 */
+ mtsp %r1,%sr3
+ mtsp %r0,%sr2 /* get kernel space into sr2 */
+
+ /* 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_nosys:
+ ldo -ENOSYS(%r0),%r21 /* set errno */
+ /* Fall through: Return to userspace */
+
+lws_exit:
+#ifdef __LP64__
+ /* 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(%sr3, %r31)
+
+
+
+ /***************************************************
+ Implementing 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
+
+ If debugging is DISabled:
+
+ %r21 has the following meanings:
+
+ EAGAIN - CAS is busy, ldcw failed, try again.
+ EFAULT - Read or write failed.
+
+ If debugging is enabled:
+
+ EDEADLOCK - CAS called recursively.
+ EAGAIN && r28 == 1 - CAS is busy. Lock contended.
+ EAGAIN && r28 == 2 - CAS is busy. ldcw failed.
+ EFAULT - Read or write failed.
+
+ Scratch: r20, r28, r1
+
+ ****************************************************/
+
+ /* Do not enable LWS debugging */
+#define ENABLE_LWS_DEBUG 0
+
+ /* ELF64 Process entry path */
+lws_compare_and_swap64:
+#ifdef __LP64__
+ 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
+ */
+ b,n lws_exit_nosys
+#endif
+
+ /* ELF32 Process entry path */
+lws_compare_and_swap32:
+#ifdef __LP64__
+ /* Clip all the input registers */
+ depdi 0, 31, 32, %r26
+ depdi 0, 31, 32, %r25
+ depdi 0, 31, 32, %r24
+#endif
+
+lws_compare_and_swap:
+#ifdef CONFIG_SMP
+ /* Load start of lock table */
+ ldil L%lws_lock_start, %r20
+ ldo R%lws_lock_start(%r20), %r28
+
+ /* Extract four bits from r26 and hash lock (Bits 4-7) */
+ extru %r26, 27, 4, %r20
+
+ /* Find lock to use, the hash is either one of 0 to
+ 15, multiplied by 16 (keep it 16-byte aligned)
+ and add to the lock table offset. */
+ shlw %r20, 4, %r20
+ add %r20, %r28, %r20
+
+# ifdef ENABLE_LWS_DEBUG
+ /*
+ DEBUG, check for deadlock!
+ If the thread register values are the same
+ then we were the one that locked it last and
+ this is a recurisve call that will deadlock.
+ We *must* giveup this call and fail.
+ */
+ ldw 4(%sr2,%r20), %r28 /* Load thread register */
+ mfctl %cr27, %r21 /* Get current thread register */
+ cmpb,<>,n %r21, %r28, cas_lock /* Called recursive? */
+ b lws_exit /* Return error! */
+ ldo -EDEADLOCK(%r0), %r21
+cas_lock:
+ cmpb,=,n %r0, %r28, cas_nocontend /* Is nobody using it? */
+ ldo 1(%r0), %r28 /* 1st case */
+ b lws_exit /* Contended... */
+ ldo -EAGAIN(%r0), %r21 /* Spin in userspace */
+cas_nocontend:
+# endif
+/* ENABLE_LWS_DEBUG */
+
+ ldcw 0(%sr2,%r20), %r28 /* Try to acquire the lock */
+ cmpb,<>,n %r0, %r28, cas_action /* Did we get it? */
+cas_wouldblock:
+ ldo 2(%r0), %r28 /* 2nd case */
+ b lws_exit /* Contended... */
+ ldo -EAGAIN(%r0), %r21 /* Spin in userspace */
+#endif
+/* CONFIG_SMP */
+
+ /*
+ prev = *addr;
+ if ( prev == old )
+ *addr = new;
+ return prev;
+ */
+
+ /* NOTES:
+ This all works becuse 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 usrspaces
+ perspective
+ */
+cas_action:
+#if defined CONFIG_SMP && defined ENABLE_LWS_DEBUG
+ /* DEBUG */
+ mfctl %cr27, %r1
+ stw %r1, 4(%sr2,%r20)
+#endif
+ /* The load and store could fail */
+1: ldw 0(%sr3,%r26), %r28
+ sub,<> %r28, %r25, %r0
+2: stw %r24, 0(%sr3,%r26)
+#ifdef CONFIG_SMP
+ /* Free lock */
+ stw %r20, 0(%sr2,%r20)
+# ifdef ENABLE_LWS_DEBUG
+ /* Clear thread register indicator */
+ stw %r0, 4(%sr2,%r20)
+# endif
+#endif
+ /* Return to userspace, set no error */
+ b lws_exit
+ copy %r0, %r21
+
+3:
+ /* Error occured on load or store */
+#ifdef CONFIG_SMP
+ /* Free lock */
+ stw %r20, 0(%sr2,%r20)
+# ifdef ENABLE_LWS_DEBUG
+ stw %r0, 4(%sr2,%r20)
+# endif
+#endif
+ b lws_exit
+ ldo -EFAULT(%r0),%r21 /* set errno */
+ nop
+ nop
+ nop
+ nop
+
+ /* Two exception table entries, one for the load,
+ the other for the store. Either return -EFAULT.
+ Each of the entries must be relocated. */
+ .section __ex_table,"aw"
+#ifdef __LP64__
+ /* Pad the address calculation */
+ .word 0,(2b - linux_gateway_page)
+ .word 0,(3b - linux_gateway_page)
+#else
+ .word (2b - linux_gateway_page)
+ .word (3b - linux_gateway_page)
+#endif
+ .previous
+
+ .section __ex_table,"aw"
+#ifdef __LP64__
+ /* Pad the address calculation */
+ .word 0,(1b - linux_gateway_page)
+ .word 0,(3b - linux_gateway_page)
+#else
+ .word (1b - linux_gateway_page)
+ .word (3b - linux_gateway_page)
+#endif
+ .previous
+
+end_compare_and_swap:
+
+ /* Make sure nothing else is placed on this page */
+ .align 4096
+ .export end_linux_gateway_page
+end_linux_gateway_page:
+
+ /* Relocate symbols assuming linux_gateway_page is mapped
+ to virtual address 0x0 */
+#ifdef __LP64__
+ /* FIXME: The code will always be on the gateay page
+ and thus it will be on the first 4k, the
+ assembler seems to think that the final
+ subtraction result is only a word in
+ length, so we pad the value.
+ */
+#define LWS_ENTRY(_name_) .word 0,(lws_##_name_ - linux_gateway_page)
+#else
+#define LWS_ENTRY(_name_) .word (lws_##_name_ - linux_gateway_page)
+#endif
+
+ .align 4096
+ /* Light-weight-syscall table */
+ /* Start of lws table. */
+ .export lws_table
+.Llws_table:
+lws_table:
+ LWS_ENTRY(compare_and_swap32) /* 0 - ELF32 Atomic compare and swap */
+ LWS_ENTRY(compare_and_swap64) /* 1 - ELF64 Atomic compare and swap */
+ /* End of lws table */
+
.align 4096
.export sys_call_table
.Lsys_call_table:
sys_call_table:
#include "syscall_table.S"
-.end
+
#ifdef __LP64__
.align 4096
.export sys_call_table64
#include "syscall_table.S"
#endif
+#ifdef CONFIG_SMP
+ /*
+ All light-weight-syscall atomic operations
+ will use this set of locks
+ */
+ .section .data
+ .align 4096
+ .export lws_lock_start
+.Llws_lock_start:
+lws_lock_start:
+ /* lws locks */
+ .align 16
+ .rept 16
+ /* Keep locks aligned at 16-bytes */
+ .word 1
+ .word 0
+ .word 0
+ .word 0
+ .endr
+ .previous
+#endif
+/* CONFIG_SMP for lws_lock_start */
- /* Make sure nothing else is placed on this page */
+.end
- .align 4096
- .export end_linux_gateway_page
-end_linux_gateway_page:
git://git.onelab.eu / linux-2.6.git / blobdiff