1 /* DWARF2 EH unwinding support for PA Linux.
2 Copyright (C) 2004-2023 Free Software Foundation, Inc.
3
4 This file is part of GCC.
5
6 GCC is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 3, or (at your option)
9 any later version.
10
11 GCC is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
15
16 Under Section 7 of GPL version 3, you are granted additional
17 permissions described in the GCC Runtime Library Exception, version
18 3.1, as published by the Free Software Foundation.
19
20 You should have received a copy of the GNU General Public License and
21 a copy of the GCC Runtime Library Exception along with this program;
22 see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23 <http://www.gnu.org/licenses/>. */
24
25
26 /* Do code reading to identify a signal frame, and set the frame
27 state data appropriately. See unwind-dw2.c for the structs. */
28
29 /* Don't use this if inhibit_libc is set.
30 The build for this target will fail trying to include missing headers. */
31 #ifndef inhibit_libc
32 #include <signal.h>
33 #include <sys/ucontext.h>
34
35 /* Return TRUE if read access to *P is allowed. */
36
37 static inline long
38 pa32_read_access_ok (void *p)
39 {
40 long ret;
41
42 __asm__ ("proberi (%1),3,%0" : "=r" (ret) : "r" (p) :);
43 return ret;
44 }
45
46 /* Unfortunately, because of various bugs and changes to the kernel,
47 we have several cases to deal with.
48
49 In 2.4, the signal trampoline is 4 words, and (CONTEXT)->ra should
50 point directly at the beginning of the trampoline and struct rt_sigframe.
51
52 In <= 2.6.5-rc2-pa3, the signal trampoline is 9 words, and
53 (CONTEXT)->ra points at the 4th word in the trampoline structure. This
54 is wrong, it should point at the 5th word. This is fixed in 2.6.5-rc2-pa4.
55
56 To detect these cases, we first take (CONTEXT)->ra, align it to 64-bytes
57 to get the beginning of the signal frame, and then check offsets 0, 4
58 and 5 to see if we found the beginning of the trampoline. This will
59 tell us how to locate the sigcontext structure.
60
61 Note that with a 2.4 64-bit kernel, the signal context is not properly
62 passed back to userspace so the unwind will not work correctly.
63
64 There is also a bug in various glibc versions. The (CONTEXT)->ra
65 for the outermost frame is not marked as undefined, so we need to
66 check whether read access is allowed for all the accesses used in
67 searching for the signal trampoline. */
68
69 #define MD_FALLBACK_FRAME_STATE_FOR pa32_fallback_frame_state
70
71 static _Unwind_Reason_Code
72 pa32_fallback_frame_state (struct _Unwind_Context *context,
73 _Unwind_FrameState *fs)
74 {
75 unsigned long sp = (unsigned long)context->ra & ~63;
76 unsigned int *pc = (unsigned int *)sp;
77 unsigned long off;
78 _Unwind_Ptr new_cfa;
79 int i;
80 struct sigcontext *sc;
81 struct rt_sigframe {
82 siginfo_t info;
83 ucontext_t uc;
84 } *frame;
85
86 /* rt_sigreturn trampoline:
87 3419000x ldi 0, %r25 or ldi 1, %r25 (x = 0 or 2)
88 3414015a ldi __NR_rt_sigreturn, %r20
89 e4008200 be,l 0x100(%sr2, %r0), %sr0, %r31
90 08000240 nop */
91
92 if (pa32_read_access_ok (pc)
93 && (pc[0] == 0x34190000 || pc[0] == 0x34190002))
94 off = 4*4;
95 else if (pa32_read_access_ok (&pc[4])
96 && (pc[4] == 0x34190000 || pc[4] == 0x34190002))
97 {
98 pc += 4;
99 off = 10 * 4;
100 }
101 else if (pa32_read_access_ok (&pc[5])
102 && (pc[5] == 0x34190000 || pc[5] == 0x34190002))
103 {
104 pc += 5;
105 off = 10 * 4;
106 }
107 else
108 {
109 /* We may have to unwind through an alternate signal stack.
110 We assume that the alignment of the alternate signal stack
111 is BIGGEST_ALIGNMENT (i.e., that it has been allocated using
112 malloc). As a result, we can't distinguish trampolines
113 used prior to 2.6.5-rc2-pa4. However after 2.6.5-rc2-pa4,
114 the return address of a signal trampoline will be on an odd
115 word boundary and we can then determine the frame offset. */
116 sp = (unsigned long)context->ra;
117 pc = (unsigned int *)sp;
118 if ((sp & 4)
119 && pa32_read_access_ok (pc)
120 && (pc[0] == 0x34190000 || pc[0] == 0x34190002))
121 off = 5 * 4;
122 else
123 return _URC_END_OF_STACK;
124 }
125
126 if (!pa32_read_access_ok (&pc[3])
127 || pc[1] != 0x3414015a
128 || pc[2] != 0xe4008200
129 || pc[3] != 0x08000240)
130 return _URC_END_OF_STACK;
131
132 frame = (struct rt_sigframe *)(sp + off);
133 sc = (struct sigcontext *)&frame->uc.uc_mcontext;
134
135 new_cfa = sc->sc_gr[30];
136 fs->regs.cfa_how = CFA_REG_OFFSET;
137 fs->regs.cfa_reg = 30;
138 fs->regs.cfa_offset = new_cfa - (long) context->cfa;
139 for (i = 1; i <= 31; i++)
140 {
141 fs->regs.how[i] = REG_SAVED_OFFSET;
142 fs->regs.reg[i].loc.offset = (long)&sc->sc_gr[i] - new_cfa;
143 }
144 for (i = 4; i <= 31; i++)
145 {
146 /* FP regs have left and right halves */
147 fs->regs.how[2*i+24] = REG_SAVED_OFFSET;
148 fs->regs.reg[2*i+24].loc.offset
149 = (long)&sc->sc_fr[i] - new_cfa;
150 fs->regs.how[2*i+24+1] = REG_SAVED_OFFSET;
151 fs->regs.reg[2*i+24+1].loc.offset
152 = (long)&sc->sc_fr[i] + 4 - new_cfa;
153 }
154 fs->regs.how[88] = REG_SAVED_OFFSET;
155 fs->regs.reg[88].loc.offset = (long) &sc->sc_sar - new_cfa;
156 fs->regs.how[__LIBGCC_DWARF_ALT_FRAME_RETURN_COLUMN__]
157 = REG_SAVED_OFFSET;
158 fs->regs.reg[__LIBGCC_DWARF_ALT_FRAME_RETURN_COLUMN__].loc.offset
159 = (long) &sc->sc_iaoq[0] - new_cfa;
160 fs->retaddr_column = __LIBGCC_DWARF_ALT_FRAME_RETURN_COLUMN__;
161 fs->signal_frame = 1;
162 return _URC_NO_REASON;
163 }
164 #endif /* inhibit_libc */