| 1 | /* Native-dependent code for OpenBSD/i386. |
| 2 | |
| 3 | Copyright (C) 2002-2016 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 "i386bsd-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 | \f |
| 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 | } |