diff options
Diffstat (limited to 'arch/parisc/kernel/syscall.S')
| -rw-r--r-- | arch/parisc/kernel/syscall.S | 68 |
1 files changed, 50 insertions, 18 deletions
diff --git a/arch/parisc/kernel/syscall.S b/arch/parisc/kernel/syscall.S index 68e75ce838d..83878601103 100644 --- a/arch/parisc/kernel/syscall.S +++ b/arch/parisc/kernel/syscall.S @@ -1,12 +1,35 @@ /* * Linux/PA-RISC Project (http://www.parisc-linux.org/) * - * System call entry code Copyright (c) Matthew Wilcox 1999 <willy@bofh.ai> + * System call entry code / Linux gateway page + * Copyright (c) Matthew Wilcox 1999 <willy@bofh.ai> * 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> @@ -15,6 +38,7 @@ #include <asm/thread_info.h> #include <asm/assembly.h> #include <asm/processor.h> +#include <asm/cache.h> #include <linux/linkage.h> @@ -156,7 +180,7 @@ linux_gateway_entry: 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 %r28, TASK_PT_ORIG_R28(%r1) /* return value 0 (saved for signals) */ + 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 */ @@ -180,9 +204,10 @@ linux_gateway_entry: /* Are we being ptraced? */ mfctl %cr30, %r1 - LDREG TI_TASK(%r1),%r1 - ldw TASK_PTRACE(%r1), %r1 - bb,<,n %r1,31,.Ltracesys + LDREG 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. */ @@ -308,10 +333,13 @@ tracesys_next: LDREG TASK_PT_GR25(%r1), %r25 LDREG TASK_PT_GR24(%r1), %r24 LDREG TASK_PT_GR23(%r1), %r23 -#ifdef CONFIG_64BIT 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 comiclr,>>= __NR_Linux_syscalls, %r20, %r0 @@ -561,10 +589,13 @@ cas_nocontend: # endif /* ENABLE_LWS_DEBUG */ + rsm PSW_SM_I, %r0 /* Disable interrupts */ + /* COW breaks can cause contention on UP systems */ 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 */ + ssm PSW_SM_I, %r0 b lws_exit /* Contended... */ ldo -EAGAIN(%r0), %r21 /* Spin in userspace */ @@ -591,26 +622,29 @@ cas_action: stw %r1, 4(%sr2,%r20) #endif /* The load and store could fail */ -1: ldw 0(%sr3,%r26), %r28 +1: ldw,ma 0(%sr3,%r26), %r28 sub,<> %r28, %r25, %r0 -2: stw %r24, 0(%sr3,%r26) +2: stw,ma %r24, 0(%sr3,%r26) /* Free lock */ - stw %r20, 0(%sr2,%r20) + stw,ma %r20, 0(%sr2,%r20) #if ENABLE_LWS_DEBUG /* Clear thread register indicator */ stw %r0, 4(%sr2,%r20) #endif + /* Enable interrupts */ + ssm PSW_SM_I, %r0 /* Return to userspace, set no error */ b lws_exit copy %r0, %r21 3: - /* Error occured on load or store */ + /* Error occurred on load or store */ /* Free lock */ stw %r20, 0(%sr2,%r20) #if ENABLE_LWS_DEBUG stw %r0, 4(%sr2,%r20) #endif + ssm PSW_SM_I, %r0 b lws_exit ldo -EFAULT(%r0),%r21 /* set errno */ nop @@ -621,10 +655,8 @@ cas_action: /* 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" - ASM_ULONG_INSN (1b - linux_gateway_page), (3b - linux_gateway_page) - ASM_ULONG_INSN (2b - linux_gateway_page), (3b - linux_gateway_page) - .previous + ASM_EXCEPTIONTABLE_ENTRY(1b-linux_gateway_page, 3b-linux_gateway_page) + ASM_EXCEPTIONTABLE_ENTRY(2b-linux_gateway_page, 3b-linux_gateway_page) /* Make sure nothing else is placed on this page */ @@ -639,7 +671,7 @@ ENTRY(end_linux_gateway_page) .section .rodata,"a" - .align PAGE_SIZE + .align 8 /* Light-weight-syscall table */ /* Start of lws table. */ ENTRY(lws_table) @@ -648,13 +680,13 @@ ENTRY(lws_table) END(lws_table) /* End of lws table */ - .align PAGE_SIZE + .align 8 ENTRY(sys_call_table) #include "syscall_table.S" END(sys_call_table) #ifdef CONFIG_64BIT - .align PAGE_SIZE + .align 8 ENTRY(sys_call_table64) #define SYSCALL_TABLE_64BIT #include "syscall_table.S" @@ -670,7 +702,7 @@ END(sys_call_table64) with ldcw. */ .section .data - .align PAGE_SIZE + .align L1_CACHE_BYTES ENTRY(lws_lock_start) /* lws locks */ .rept 16 |