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Diffstat (limited to 'arch/metag/kernel/user_gateway.S')
| -rw-r--r-- | arch/metag/kernel/user_gateway.S | 97 |
1 files changed, 97 insertions, 0 deletions
diff --git a/arch/metag/kernel/user_gateway.S b/arch/metag/kernel/user_gateway.S new file mode 100644 index 00000000000..7167f3e8db6 --- /dev/null +++ b/arch/metag/kernel/user_gateway.S @@ -0,0 +1,97 @@ +/* + * Copyright (C) 2010 Imagination Technologies Ltd. + * + * This file contains code that can be accessed from userspace and can + * access certain kernel data structures without the overhead of a system + * call. + */ + +#include <asm/metag_regs.h> +#include <asm/user_gateway.h> + +/* + * User helpers. + * + * These are segment of kernel provided user code reachable from user space + * at a fixed address in kernel memory. This is used to provide user space + * with some operations which require kernel help because of unimplemented + * native feature and/or instructions in some Meta CPUs. The idea is for + * this code to be executed directly in user mode for best efficiency but + * which is too intimate with the kernel counter part to be left to user + * libraries. The kernel reserves the right to change this code as needed + * without warning. Only the entry points and their results are guaranteed + * to be stable. + * + * Each segment is 64-byte aligned. This mechanism should be used only for + * for things that are really small and justified, and not be abused freely. + */ + .text + .global ___user_gateway_start +___user_gateway_start: + + /* get_tls + * Offset: 0 + * Description: Get the TLS pointer for this process. + */ + .global ___kuser_get_tls + .type ___kuser_get_tls,function +___kuser_get_tls: + MOVT D1Ar1,#HI(USER_GATEWAY_PAGE + USER_GATEWAY_TLS) + ADD D1Ar1,D1Ar1,#LO(USER_GATEWAY_PAGE + USER_GATEWAY_TLS) + MOV D1Ar3,TXENABLE + AND D1Ar3,D1Ar3,#(TXENABLE_THREAD_BITS) + LSR D1Ar3,D1Ar3,#(TXENABLE_THREAD_S - 2) + GETD D0Re0,[D1Ar1+D1Ar3] +___kuser_get_tls_end: /* Beyond this point the read will complete */ + MOV PC,D1RtP + .size ___kuser_get_tls,.-___kuser_get_tls + .global ___kuser_get_tls_end + + /* cmpxchg + * Offset: 64 + * Description: Replace the value at 'ptr' with 'newval' if the current + * value is 'oldval'. Return zero if we succeeded, + * non-zero otherwise. + * + * Reference prototype: + * + * int __kuser_cmpxchg(int oldval, int newval, unsigned long *ptr) + * + */ + .balign 64 + .global ___kuser_cmpxchg + .type ___kuser_cmpxchg,function +___kuser_cmpxchg: +#ifdef CONFIG_SMP + /* + * We must use LNKGET/LNKSET with an SMP kernel because the other method + * does not provide atomicity across multiple CPUs. + */ +0: LNKGETD D0Re0,[D1Ar3] + CMP D0Re0,D1Ar1 + LNKSETDZ [D1Ar3],D0Ar2 + BNZ 1f + DEFR D0Re0,TXSTAT + ANDT D0Re0,D0Re0,#HI(0x3f000000) + CMPT D0Re0,#HI(0x02000000) + BNE 0b +#ifdef CONFIG_METAG_LNKGET_AROUND_CACHE + DCACHE [D1Ar3], D0Re0 +#endif +1: MOV D0Re0,#1 + XORZ D0Re0,D0Re0,D0Re0 + MOV PC,D1RtP +#else + GETD D0Re0,[D1Ar3] + CMP D0Re0,D1Ar1 + SETDZ [D1Ar3],D0Ar2 +___kuser_cmpxchg_end: /* Beyond this point the write will complete */ + MOV D0Re0,#1 + XORZ D0Re0,D0Re0,D0Re0 + MOV PC,D1RtP +#endif /* CONFIG_SMP */ + .size ___kuser_cmpxchg,.-___kuser_cmpxchg + .global ___kuser_cmpxchg_end + + .global ___user_gateway_end +___user_gateway_end: |