1 /* Native-dependent code for OpenBSD/i386. 2 3 Copyright (C) 2002-2017 Free Software Foundation, Inc. 4 5 This file is part of GDB. 6 7 This program is free software; you can redistribute it and/or modify 8 it under the terms of the GNU General Public License as published by 9 the Free Software Foundation; either version 3 of the License, or 10 (at your option) any later version. 11 12 This program is distributed in the hope that it will be useful, 13 but WITHOUT ANY WARRANTY; without even the implied warranty of 14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 15 GNU General Public License for more details. 16 17 You should have received a copy of the GNU General Public License 18 along with this program. If not, see <http://www.gnu.org/licenses/>. */ 19 20 #include "defs.h" 21 #include "gdbcore.h" 22 #include "regcache.h" 23 #include "target.h" 24 25 #include <sys/sysctl.h> 26 #include <machine/frame.h> 27 #include <machine/pcb.h> 28 29 #include "i386-tdep.h" 30 #include "i386-bsd-nat.h" 31 #include "obsd-nat.h" 32 #include "bsd-kvm.h" 33 34 static int 35 i386obsd_supply_pcb (struct regcache *regcache, struct pcb *pcb) 36 { 37 struct gdbarch *gdbarch = get_regcache_arch (regcache); 38 enum bfd_endian byte_order = gdbarch_byte_order (gdbarch); 39 struct switchframe sf; 40 41 /* The following is true for OpenBSD 3.6: 42 43 The pcb contains %esp and %ebp at the point of the context switch 44 in cpu_switch(). At that point we have a stack frame as 45 described by `struct switchframe', which for OpenBSD 3.6 has the 46 following layout: 47 48 interrupt level 49 %edi 50 %esi 51 %ebx 52 %eip 53 54 we reconstruct the register state as it would look when we just 55 returned from cpu_switch(). */ 56 57 /* The stack pointer shouldn't be zero. */ 58 if (pcb->pcb_esp == 0) 59 return 0; 60 61 /* Read the stack frame, and check its validity. We do this by 62 checking if the saved interrupt priority level in the stack frame 63 looks reasonable.. */ 64 #ifdef PCB_SAVECTX 65 if ((pcb->pcb_flags & PCB_SAVECTX) == 0) 66 { 67 /* Yes, we have a frame that matches cpu_switch(). */ 68 read_memory (pcb->pcb_esp, (gdb_byte *) &sf, sizeof sf); 69 pcb->pcb_esp += sizeof (struct switchframe); 70 regcache_raw_supply (regcache, I386_EDI_REGNUM, &sf.sf_edi); 71 regcache_raw_supply (regcache, I386_ESI_REGNUM, &sf.sf_esi); 72 regcache_raw_supply (regcache, I386_EBX_REGNUM, &sf.sf_ebx); 73 regcache_raw_supply (regcache, I386_EIP_REGNUM, &sf.sf_eip); 74 } 75 else 76 #endif 77 { 78 /* No, the pcb must have been last updated by savectx(). */ 79 pcb->pcb_esp = pcb->pcb_ebp; 80 pcb->pcb_ebp = read_memory_integer(pcb->pcb_esp, 4, byte_order); 81 sf.sf_eip = read_memory_integer(pcb->pcb_esp + 4, 4, byte_order); 82 regcache_raw_supply (regcache, I386_EIP_REGNUM, &sf.sf_eip); 83 } 84 85 regcache_raw_supply (regcache, I386_EBP_REGNUM, &pcb->pcb_ebp); 86 regcache_raw_supply (regcache, I386_ESP_REGNUM, &pcb->pcb_esp); 87 88 return 1; 89 } 90 91 92 /* Prevent warning from -Wmissing-prototypes. */ 93 void _initialize_i386obsd_nat (void); 94 95 void 96 _initialize_i386obsd_nat (void) 97 { 98 /* Add some extra features to the common *BSD/i386 target. */ 99 obsd_add_target (i386bsd_target ()); 100 101 /* Support debugging kernel virtual memory images. */ 102 bsd_kvm_add_target (i386obsd_supply_pcb); 103 104 /* OpenBSD provides a vm.psstrings sysctl that we can use to locate 105 the sigtramp. That way we can still recognize a sigtramp if its 106 location is changed in a new kernel. This is especially 107 important for OpenBSD, since it uses a different memory layout 108 than NetBSD, yet we cannot distinguish between the two. 109 110 Of course this is still based on the assumption that the sigtramp 111 is placed directly under the location where the program arguments 112 and environment can be found. */ 113 #ifdef VM_PSSTRINGS 114 { 115 struct _ps_strings _ps; 116 int mib[2]; 117 size_t len; 118 119 mib[0] = CTL_VM; 120 mib[1] = VM_PSSTRINGS; 121 len = sizeof (_ps); 122 if (sysctl (mib, 2, &_ps, &len, NULL, 0) == 0) 123 { 124 i386obsd_sigtramp_start_addr = (u_long) _ps.val - 128; 125 i386obsd_sigtramp_end_addr = (u_long) _ps.val; 126 } 127 } 128 #endif 129 } 130