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1da177e4 LT |
1 | #include <linux/compiler.h> |
2 | #include <linux/mm.h> | |
3 | #include <linux/signal.h> | |
4 | #include <linux/smp.h> | |
1da177e4 LT |
5 | |
6 | #include <asm/asm.h> | |
7 | #include <asm/bootinfo.h> | |
8 | #include <asm/byteorder.h> | |
9 | #include <asm/cpu.h> | |
10 | #include <asm/inst.h> | |
11 | #include <asm/processor.h> | |
12 | #include <asm/uaccess.h> | |
13 | #include <asm/branch.h> | |
14 | #include <asm/mipsregs.h> | |
1da177e4 LT |
15 | #include <asm/cacheflush.h> |
16 | ||
17 | #include <asm/fpu_emulator.h> | |
18 | ||
19 | #include "ieee754.h" | |
1da177e4 LT |
20 | |
21 | /* Strap kernel emulator for full MIPS IV emulation */ | |
22 | ||
23 | #ifdef __mips | |
24 | #undef __mips | |
25 | #endif | |
26 | #define __mips 4 | |
27 | ||
1da177e4 LT |
28 | /* |
29 | * Emulate the arbritrary instruction ir at xcp->cp0_epc. Required when | |
30 | * we have to emulate the instruction in a COP1 branch delay slot. Do | |
31 | * not change cp0_epc due to the instruction | |
32 | * | |
33 | * According to the spec: | |
25985edc | 34 | * 1) it shouldn't be a branch :-) |
1da177e4 LT |
35 | * 2) it can be a COP instruction :-( |
36 | * 3) if we are tring to run a protected memory space we must take | |
37 | * special care on memory access instructions :-( | |
38 | */ | |
39 | ||
40 | /* | |
41 | * "Trampoline" return routine to catch exception following | |
42 | * execution of delay-slot instruction execution. | |
43 | */ | |
44 | ||
45 | struct emuframe { | |
46 | mips_instruction emul; | |
47 | mips_instruction badinst; | |
48 | mips_instruction cookie; | |
333d1f67 | 49 | unsigned long epc; |
1da177e4 LT |
50 | }; |
51 | ||
333d1f67 | 52 | int mips_dsemul(struct pt_regs *regs, mips_instruction ir, unsigned long cpc) |
1da177e4 LT |
53 | { |
54 | extern asmlinkage void handle_dsemulret(void); | |
5e0373b8 | 55 | struct emuframe __user *fr; |
1da177e4 LT |
56 | int err; |
57 | ||
58 | if (ir == 0) { /* a nop is easy */ | |
59 | regs->cp0_epc = cpc; | |
60 | regs->cp0_cause &= ~CAUSEF_BD; | |
61 | return 0; | |
62 | } | |
63 | #ifdef DSEMUL_TRACE | |
64 | printk("dsemul %lx %lx\n", regs->cp0_epc, cpc); | |
65 | ||
66 | #endif | |
67 | ||
68 | /* | |
69 | * The strategy is to push the instruction onto the user stack | |
70 | * and put a trap after it which we can catch and jump to | |
71 | * the required address any alternative apart from full | |
72 | * instruction emulation!!. | |
73 | * | |
74 | * Algorithmics used a system call instruction, and | |
75 | * borrowed that vector. MIPS/Linux version is a bit | |
76 | * more heavyweight in the interests of portability and | |
77 | * multiprocessor support. For Linux we generate a | |
78 | * an unaligned access and force an address error exception. | |
79 | * | |
80 | * For embedded systems (stand-alone) we prefer to use a | |
81 | * non-existing CP1 instruction. This prevents us from emulating | |
82 | * branches, but gives us a cleaner interface to the exception | |
83 | * handler (single entry point). | |
84 | */ | |
85 | ||
86 | /* Ensure that the two instructions are in the same cache line */ | |
5e0373b8 AN |
87 | fr = (struct emuframe __user *) |
88 | ((regs->regs[29] - sizeof(struct emuframe)) & ~0x7); | |
1da177e4 LT |
89 | |
90 | /* Verify that the stack pointer is not competely insane */ | |
91 | if (unlikely(!access_ok(VERIFY_WRITE, fr, sizeof(struct emuframe)))) | |
92 | return SIGBUS; | |
93 | ||
94 | err = __put_user(ir, &fr->emul); | |
ba3049ed | 95 | err |= __put_user((mips_instruction)BREAK_MATH, &fr->badinst); |
1da177e4 LT |
96 | err |= __put_user((mips_instruction)BD_COOKIE, &fr->cookie); |
97 | err |= __put_user(cpc, &fr->epc); | |
98 | ||
99 | if (unlikely(err)) { | |
b6ee75ed | 100 | MIPS_FPU_EMU_INC_STATS(errors); |
1da177e4 LT |
101 | return SIGBUS; |
102 | } | |
103 | ||
333d1f67 | 104 | regs->cp0_epc = (unsigned long) &fr->emul; |
1da177e4 LT |
105 | |
106 | flush_cache_sigtramp((unsigned long)&fr->badinst); | |
107 | ||
108 | return SIGILL; /* force out of emulation loop */ | |
109 | } | |
110 | ||
111 | int do_dsemulret(struct pt_regs *xcp) | |
112 | { | |
5e0373b8 | 113 | struct emuframe __user *fr; |
333d1f67 | 114 | unsigned long epc; |
1da177e4 LT |
115 | u32 insn, cookie; |
116 | int err = 0; | |
117 | ||
5e0373b8 AN |
118 | fr = (struct emuframe __user *) |
119 | (xcp->cp0_epc - sizeof(mips_instruction)); | |
1da177e4 LT |
120 | |
121 | /* | |
122 | * If we can't even access the area, something is very wrong, but we'll | |
123 | * leave that to the default handling | |
124 | */ | |
125 | if (!access_ok(VERIFY_READ, fr, sizeof(struct emuframe))) | |
126 | return 0; | |
127 | ||
128 | /* | |
129 | * Do some sanity checking on the stackframe: | |
130 | * | |
ba3049ed | 131 | * - Is the instruction pointed to by the EPC an BREAK_MATH? |
1da177e4 LT |
132 | * - Is the following memory word the BD_COOKIE? |
133 | */ | |
134 | err = __get_user(insn, &fr->badinst); | |
135 | err |= __get_user(cookie, &fr->cookie); | |
136 | ||
ba3049ed | 137 | if (unlikely(err || (insn != BREAK_MATH) || (cookie != BD_COOKIE))) { |
b6ee75ed | 138 | MIPS_FPU_EMU_INC_STATS(errors); |
1da177e4 LT |
139 | return 0; |
140 | } | |
141 | ||
142 | /* | |
143 | * At this point, we are satisfied that it's a BD emulation trap. Yes, | |
144 | * a user might have deliberately put two malformed and useless | |
145 | * instructions in a row in his program, in which case he's in for a | |
146 | * nasty surprise - the next instruction will be treated as a | |
147 | * continuation address! Alas, this seems to be the only way that we | |
148 | * can handle signals, recursion, and longjmps() in the context of | |
149 | * emulating the branch delay instruction. | |
150 | */ | |
151 | ||
152 | #ifdef DSEMUL_TRACE | |
153 | printk("dsemulret\n"); | |
154 | #endif | |
155 | if (__get_user(epc, &fr->epc)) { /* Saved EPC */ | |
156 | /* This is not a good situation to be in */ | |
157 | force_sig(SIGBUS, current); | |
158 | ||
159 | return 0; | |
160 | } | |
161 | ||
162 | /* Set EPC to return to post-branch instruction */ | |
163 | xcp->cp0_epc = epc; | |
164 | ||
165 | return 1; | |
166 | } |