gdb/i386-fbsd-nat.c

   1 /* Native-dependent code for FreeBSD/i386.
   2
   3    Copyright (C) 2001-2020 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 "inferior.h"
  22 #include "regcache.h"
  23 #include "target.h"
  24
  25 #include <sys/types.h>
  26 #include <sys/ptrace.h>
  27 #include <sys/sysctl.h>
  28 #include <sys/user.h>
  29
  30 #include "fbsd-nat.h"
  31 #include "i386-tdep.h"
  32 #include "x86-nat.h"
  33 #include "gdbsupport/x86-xstate.h"
  34 #include "x86-bsd-nat.h"
  35 #include "i386-bsd-nat.h"
  36
  37 class i386_fbsd_nat_target final
  38   : public i386_bsd_nat_target<fbsd_nat_target>
  39 {
  40 public:
  41   /* Add some extra features to the common *BSD/i386 target.  */
  42 #ifdef PT_GETXSTATE_INFO
  43   const struct target_desc *read_description () override;
  44 #endif
  45
  46   void resume (ptid_t, int, enum gdb_signal) override;
  47
  48 #if defined(HAVE_PT_GETDBREGS) && defined(USE_SIGTRAP_SIGINFO)
  49   bool supports_stopped_by_hw_breakpoint () override;
  50 #endif
  51 };
  52
  53 static i386_fbsd_nat_target the_i386_fbsd_nat_target;
  54
  55 /* Resume execution of the inferior process.  If STEP is nonzero,
  56    single-step it.  If SIGNAL is nonzero, give it that signal.  */
  57
  58 void
  59 i386_fbsd_nat_target::resume (ptid_t ptid, int step, enum gdb_signal signal)
  60 {
  61   pid_t pid = ptid.pid ();
  62   int request = PT_STEP;
  63
  64   if (pid == -1)
  65     /* Resume all threads.  This only gets used in the non-threaded
  66        case, where "resume all threads" and "resume inferior_ptid" are
  67        the same.  */
  68     pid = inferior_ptid.pid ();
  69
  70   if (!step)
  71     {
  72       struct regcache *regcache = get_current_regcache ();
  73       ULONGEST eflags;
  74
  75       /* Workaround for a bug in FreeBSD.  Make sure that the trace
  76          flag is off when doing a continue.  There is a code path
  77          through the kernel which leaves the flag set when it should
  78          have been cleared.  If a process has a signal pending (such
  79          as SIGALRM) and we do a PT_STEP, the process never really has
  80          a chance to run because the kernel needs to notify the
  81          debugger that a signal is being sent.  Therefore, the process
  82          never goes through the kernel's trap() function which would
  83          normally clear it.  */
  84
  85       regcache_cooked_read_unsigned (regcache, I386_EFLAGS_REGNUM,
  86                                      &eflags);
  87       if (eflags & 0x0100)
  88         regcache_cooked_write_unsigned (regcache, I386_EFLAGS_REGNUM,
  89                                         eflags & ~0x0100);
  90
  91       request = PT_CONTINUE;
  92     }
  93
  94   /* An addres of (caddr_t) 1 tells ptrace to continue from where it
  95      was.  (If GDB wanted it to start some other way, we have already
  96      written a new PC value to the child.)  */
  97   if (ptrace (request, pid, (caddr_t) 1,
  98               gdb_signal_to_host (signal)) == -1)
  99     perror_with_name (("ptrace"));
 100 }
 101 \f
 102
 103 /* Support for debugging kernel virtual memory images.  */
 104
 105 #include <machine/pcb.h>
 106
 107 #include "bsd-kvm.h"
 108
 109 static int
 110 i386fbsd_supply_pcb (struct regcache *regcache, struct pcb *pcb)
 111 {
 112   /* The following is true for FreeBSD 4.7:
 113
 114      The pcb contains %eip, %ebx, %esp, %ebp, %esi, %edi and %gs.
 115      This accounts for all callee-saved registers specified by the
 116      psABI and then some.  Here %esp contains the stack pointer at the
 117      point just after the call to cpu_switch().  From this information
 118      we reconstruct the register state as it would look when we just
 119      returned from cpu_switch().  */
 120
 121   /* The stack pointer shouldn't be zero.  */
 122   if (pcb->pcb_esp == 0)
 123     return 0;
 124
 125   pcb->pcb_esp += 4;
 126   regcache->raw_supply (I386_EDI_REGNUM, &pcb->pcb_edi);
 127   regcache->raw_supply (I386_ESI_REGNUM, &pcb->pcb_esi);
 128   regcache->raw_supply (I386_EBP_REGNUM, &pcb->pcb_ebp);
 129   regcache->raw_supply (I386_ESP_REGNUM, &pcb->pcb_esp);
 130   regcache->raw_supply (I386_EBX_REGNUM, &pcb->pcb_ebx);
 131   regcache->raw_supply (I386_EIP_REGNUM, &pcb->pcb_eip);
 132   regcache->raw_supply (I386_GS_REGNUM, &pcb->pcb_gs);
 133
 134   return 1;
 135 }
 136 \f
 137
 138 #ifdef PT_GETXSTATE_INFO
 139 /* Implement the read_description method.  */
 140
 141 const struct target_desc *
 142 i386_fbsd_nat_target::read_description ()
 143 {
 144   static int xsave_probed;
 145   static uint64_t xcr0;
 146
 147   if (!xsave_probed)
 148     {
 149       struct ptrace_xstate_info info;
 150
 151       if (ptrace (PT_GETXSTATE_INFO, inferior_ptid.pid (),
 152                   (PTRACE_TYPE_ARG3) &info, sizeof (info)) == 0)
 153         {
 154           x86bsd_xsave_len = info.xsave_len;
 155           xcr0 = info.xsave_mask;
 156         }
 157       xsave_probed = 1;
 158     }
 159
 160   if (x86bsd_xsave_len == 0)
 161     xcr0 = X86_XSTATE_SSE_MASK;
 162
 163   return i386_target_description (xcr0, true);
 164 }
 165 #endif
 166
 167 #if defined(HAVE_PT_GETDBREGS) && defined(USE_SIGTRAP_SIGINFO)
 168 /* Implement the supports_stopped_by_hw_breakpoints method.  */
 169
 170 bool
 171 i386_fbsd_nat_target::supports_stopped_by_hw_breakpoint ()
 172 {
 173   return true;
 174 }
 175 #endif
 176
 177 void
 178 _initialize_i386fbsd_nat (void)
 179 {
 180   add_inf_child_target (&the_i386_fbsd_nat_target);
 181
 182   /* Support debugging kernel virtual memory images.  */
 183   bsd_kvm_add_target (i386fbsd_supply_pcb);
 184
 185 #ifdef KERN_PROC_SIGTRAMP
 186   /* Normally signal frames are detected via i386fbsd_sigtramp_p.
 187      However, FreeBSD 9.2 through 10.1 do not include the page holding
 188      the signal code in core dumps.  These releases do provide a
 189      kern.proc.sigtramp.<pid> sysctl that returns the location of the
 190      signal trampoline for a running process.  We fetch the location
 191      of the current (gdb) process and use this to identify signal
 192      frames in core dumps from these releases.  */
 193   {
 194     int mib[4];
 195     struct kinfo_sigtramp kst;
 196     size_t len;
 197
 198     mib[0] = CTL_KERN;
 199     mib[1] = KERN_PROC;
 200     mib[2] = KERN_PROC_SIGTRAMP;
 201     mib[3] = getpid ();
 202     len = sizeof (kst);
 203     if (sysctl (mib, 4, &kst, &len, NULL, 0) == 0)
 204       {
 205         i386fbsd_sigtramp_start_addr = (uintptr_t) kst.ksigtramp_start;
 206         i386fbsd_sigtramp_end_addr = (uintptr_t) kst.ksigtramp_end;
 207       }
 208   }
 209 #endif
 210 }