| /* Target-dependent code for GNU/Linux i386. |
| |
| Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005 |
| Free Software Foundation, Inc. |
| |
| This file is part of GDB. |
| |
| This program is free software; you can redistribute it and/or modify |
| it under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 2 of the License, or |
| (at your option) any later version. |
| |
| This program is distributed in the hope that it will be useful, |
| but WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| GNU General Public License for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with this program; if not, write to the Free Software |
| Foundation, Inc., 51 Franklin Street, Fifth Floor, |
| Boston, MA 02110-1301, USA. */ |
| |
| #include "defs.h" |
| #include "gdbcore.h" |
| #include "frame.h" |
| #include "value.h" |
| #include "regcache.h" |
| #include "inferior.h" |
| #include "osabi.h" |
| #include "reggroups.h" |
| #include "dwarf2-frame.h" |
| #include "gdb_string.h" |
| |
| #include "i386-tdep.h" |
| #include "i386-linux-tdep.h" |
| #include "glibc-tdep.h" |
| #include "solib-svr4.h" |
| |
| /* Return the name of register REG. */ |
| |
| static const char * |
| i386_linux_register_name (int reg) |
| { |
| /* Deal with the extra "orig_eax" pseudo register. */ |
| if (reg == I386_LINUX_ORIG_EAX_REGNUM) |
| return "orig_eax"; |
| |
| return i386_register_name (reg); |
| } |
| |
| /* Return non-zero, when the register is in the corresponding register |
| group. Put the LINUX_ORIG_EAX register in the system group. */ |
| static int |
| i386_linux_register_reggroup_p (struct gdbarch *gdbarch, int regnum, |
| struct reggroup *group) |
| { |
| if (regnum == I386_LINUX_ORIG_EAX_REGNUM) |
| return (group == system_reggroup |
| || group == save_reggroup |
| || group == restore_reggroup); |
| return i386_register_reggroup_p (gdbarch, regnum, group); |
| } |
| |
| |
| /* Recognizing signal handler frames. */ |
| |
| /* GNU/Linux has two flavors of signals. Normal signal handlers, and |
| "realtime" (RT) signals. The RT signals can provide additional |
| information to the signal handler if the SA_SIGINFO flag is set |
| when establishing a signal handler using `sigaction'. It is not |
| unlikely that future versions of GNU/Linux will support SA_SIGINFO |
| for normal signals too. */ |
| |
| /* When the i386 Linux kernel calls a signal handler and the |
| SA_RESTORER flag isn't set, the return address points to a bit of |
| code on the stack. This function returns whether the PC appears to |
| be within this bit of code. |
| |
| The instruction sequence for normal signals is |
| pop %eax |
| mov $0x77, %eax |
| int $0x80 |
| or 0x58 0xb8 0x77 0x00 0x00 0x00 0xcd 0x80. |
| |
| Checking for the code sequence should be somewhat reliable, because |
| the effect is to call the system call sigreturn. This is unlikely |
| to occur anywhere other than in a signal trampoline. |
| |
| It kind of sucks that we have to read memory from the process in |
| order to identify a signal trampoline, but there doesn't seem to be |
| any other way. Therefore we only do the memory reads if no |
| function name could be identified, which should be the case since |
| the code is on the stack. |
| |
| Detection of signal trampolines for handlers that set the |
| SA_RESTORER flag is in general not possible. Unfortunately this is |
| what the GNU C Library has been doing for quite some time now. |
| However, as of version 2.1.2, the GNU C Library uses signal |
| trampolines (named __restore and __restore_rt) that are identical |
| to the ones used by the kernel. Therefore, these trampolines are |
| supported too. */ |
| |
| #define LINUX_SIGTRAMP_INSN0 0x58 /* pop %eax */ |
| #define LINUX_SIGTRAMP_OFFSET0 0 |
| #define LINUX_SIGTRAMP_INSN1 0xb8 /* mov $NNNN, %eax */ |
| #define LINUX_SIGTRAMP_OFFSET1 1 |
| #define LINUX_SIGTRAMP_INSN2 0xcd /* int */ |
| #define LINUX_SIGTRAMP_OFFSET2 6 |
| |
| static const gdb_byte linux_sigtramp_code[] = |
| { |
| LINUX_SIGTRAMP_INSN0, /* pop %eax */ |
| LINUX_SIGTRAMP_INSN1, 0x77, 0x00, 0x00, 0x00, /* mov $0x77, %eax */ |
| LINUX_SIGTRAMP_INSN2, 0x80 /* int $0x80 */ |
| }; |
| |
| #define LINUX_SIGTRAMP_LEN (sizeof linux_sigtramp_code) |
| |
| /* If NEXT_FRAME unwinds into a sigtramp routine, return the address |
| of the start of the routine. Otherwise, return 0. */ |
| |
| static CORE_ADDR |
| i386_linux_sigtramp_start (struct frame_info *next_frame) |
| { |
| CORE_ADDR pc = frame_pc_unwind (next_frame); |
| gdb_byte buf[LINUX_SIGTRAMP_LEN]; |
| |
| /* We only recognize a signal trampoline if PC is at the start of |
| one of the three instructions. We optimize for finding the PC at |
| the start, as will be the case when the trampoline is not the |
| first frame on the stack. We assume that in the case where the |
| PC is not at the start of the instruction sequence, there will be |
| a few trailing readable bytes on the stack. */ |
| |
| if (!safe_frame_unwind_memory (next_frame, pc, buf, LINUX_SIGTRAMP_LEN)) |
| return 0; |
| |
| if (buf[0] != LINUX_SIGTRAMP_INSN0) |
| { |
| int adjust; |
| |
| switch (buf[0]) |
| { |
| case LINUX_SIGTRAMP_INSN1: |
| adjust = LINUX_SIGTRAMP_OFFSET1; |
| break; |
| case LINUX_SIGTRAMP_INSN2: |
| adjust = LINUX_SIGTRAMP_OFFSET2; |
| break; |
| default: |
| return 0; |
| } |
| |
| pc -= adjust; |
| |
| if (!safe_frame_unwind_memory (next_frame, pc, buf, LINUX_SIGTRAMP_LEN)) |
| return 0; |
| } |
| |
| if (memcmp (buf, linux_sigtramp_code, LINUX_SIGTRAMP_LEN) != 0) |
| return 0; |
| |
| return pc; |
| } |
| |
| /* This function does the same for RT signals. Here the instruction |
| sequence is |
| mov $0xad, %eax |
| int $0x80 |
| or 0xb8 0xad 0x00 0x00 0x00 0xcd 0x80. |
| |
| The effect is to call the system call rt_sigreturn. */ |
| |
| #define LINUX_RT_SIGTRAMP_INSN0 0xb8 /* mov $NNNN, %eax */ |
| #define LINUX_RT_SIGTRAMP_OFFSET0 0 |
| #define LINUX_RT_SIGTRAMP_INSN1 0xcd /* int */ |
| #define LINUX_RT_SIGTRAMP_OFFSET1 5 |
| |
| static const gdb_byte linux_rt_sigtramp_code[] = |
| { |
| LINUX_RT_SIGTRAMP_INSN0, 0xad, 0x00, 0x00, 0x00, /* mov $0xad, %eax */ |
| LINUX_RT_SIGTRAMP_INSN1, 0x80 /* int $0x80 */ |
| }; |
| |
| #define LINUX_RT_SIGTRAMP_LEN (sizeof linux_rt_sigtramp_code) |
| |
| /* If NEXT_FRAME unwinds into an RT sigtramp routine, return the |
| address of the start of the routine. Otherwise, return 0. */ |
| |
| static CORE_ADDR |
| i386_linux_rt_sigtramp_start (struct frame_info *next_frame) |
| { |
| CORE_ADDR pc = frame_pc_unwind (next_frame); |
| gdb_byte buf[LINUX_RT_SIGTRAMP_LEN]; |
| |
| /* We only recognize a signal trampoline if PC is at the start of |
| one of the two instructions. We optimize for finding the PC at |
| the start, as will be the case when the trampoline is not the |
| first frame on the stack. We assume that in the case where the |
| PC is not at the start of the instruction sequence, there will be |
| a few trailing readable bytes on the stack. */ |
| |
| if (!safe_frame_unwind_memory (next_frame, pc, buf, LINUX_RT_SIGTRAMP_LEN)) |
| return 0; |
| |
| if (buf[0] != LINUX_RT_SIGTRAMP_INSN0) |
| { |
| if (buf[0] != LINUX_RT_SIGTRAMP_INSN1) |
| return 0; |
| |
| pc -= LINUX_RT_SIGTRAMP_OFFSET1; |
| |
| if (!safe_frame_unwind_memory (next_frame, pc, buf, |
| LINUX_RT_SIGTRAMP_LEN)) |
| return 0; |
| } |
| |
| if (memcmp (buf, linux_rt_sigtramp_code, LINUX_RT_SIGTRAMP_LEN) != 0) |
| return 0; |
| |
| return pc; |
| } |
| |
| /* Return whether the frame preceding NEXT_FRAME corresponds to a |
| GNU/Linux sigtramp routine. */ |
| |
| static int |
| i386_linux_sigtramp_p (struct frame_info *next_frame) |
| { |
| CORE_ADDR pc = frame_pc_unwind (next_frame); |
| char *name; |
| |
| find_pc_partial_function (pc, &name, NULL, NULL); |
| |
| /* If we have NAME, we can optimize the search. The trampolines are |
| named __restore and __restore_rt. However, they aren't dynamically |
| exported from the shared C library, so the trampoline may appear to |
| be part of the preceding function. This should always be sigaction, |
| __sigaction, or __libc_sigaction (all aliases to the same function). */ |
| if (name == NULL || strstr (name, "sigaction") != NULL) |
| return (i386_linux_sigtramp_start (next_frame) != 0 |
| || i386_linux_rt_sigtramp_start (next_frame) != 0); |
| |
| return (strcmp ("__restore", name) == 0 |
| || strcmp ("__restore_rt", name) == 0); |
| } |
| |
| /* Return one if the unwound PC from NEXT_FRAME is in a signal trampoline |
| which may have DWARF-2 CFI. */ |
| |
| static int |
| i386_linux_dwarf_signal_frame_p (struct gdbarch *gdbarch, |
| struct frame_info *next_frame) |
| { |
| CORE_ADDR pc = frame_pc_unwind (next_frame); |
| char *name; |
| |
| find_pc_partial_function (pc, &name, NULL, NULL); |
| |
| /* If a vsyscall DSO is in use, the signal trampolines may have these |
| names. */ |
| if (name && (strcmp (name, "__kernel_sigreturn") == 0 |
| || strcmp (name, "__kernel_rt_sigreturn") == 0)) |
| return 1; |
| |
| return 0; |
| } |
| |
| /* Offset to struct sigcontext in ucontext, from <asm/ucontext.h>. */ |
| #define I386_LINUX_UCONTEXT_SIGCONTEXT_OFFSET 20 |
| |
| /* Assuming NEXT_FRAME is a frame following a GNU/Linux sigtramp |
| routine, return the address of the associated sigcontext structure. */ |
| |
| static CORE_ADDR |
| i386_linux_sigcontext_addr (struct frame_info *next_frame) |
| { |
| CORE_ADDR pc; |
| CORE_ADDR sp; |
| gdb_byte buf[4]; |
| |
| frame_unwind_register (next_frame, I386_ESP_REGNUM, buf); |
| sp = extract_unsigned_integer (buf, 4); |
| |
| pc = i386_linux_sigtramp_start (next_frame); |
| if (pc) |
| { |
| /* The sigcontext structure lives on the stack, right after |
| the signum argument. We determine the address of the |
| sigcontext structure by looking at the frame's stack |
| pointer. Keep in mind that the first instruction of the |
| sigtramp code is "pop %eax". If the PC is after this |
| instruction, adjust the returned value accordingly. */ |
| if (pc == frame_pc_unwind (next_frame)) |
| return sp + 4; |
| return sp; |
| } |
| |
| pc = i386_linux_rt_sigtramp_start (next_frame); |
| if (pc) |
| { |
| CORE_ADDR ucontext_addr; |
| |
| /* The sigcontext structure is part of the user context. A |
| pointer to the user context is passed as the third argument |
| to the signal handler. */ |
| read_memory (sp + 8, buf, 4); |
| ucontext_addr = extract_unsigned_integer (buf, 4); |
| return ucontext_addr + I386_LINUX_UCONTEXT_SIGCONTEXT_OFFSET; |
| } |
| |
| error (_("Couldn't recognize signal trampoline.")); |
| return 0; |
| } |
| |
| /* Set the program counter for process PTID to PC. */ |
| |
| static void |
| i386_linux_write_pc (CORE_ADDR pc, ptid_t ptid) |
| { |
| write_register_pid (I386_EIP_REGNUM, pc, ptid); |
| |
| /* We must be careful with modifying the program counter. If we |
| just interrupted a system call, the kernel might try to restart |
| it when we resume the inferior. On restarting the system call, |
| the kernel will try backing up the program counter even though it |
| no longer points at the system call. This typically results in a |
| SIGSEGV or SIGILL. We can prevent this by writing `-1' in the |
| "orig_eax" pseudo-register. |
| |
| Note that "orig_eax" is saved when setting up a dummy call frame. |
| This means that it is properly restored when that frame is |
| popped, and that the interrupted system call will be restarted |
| when we resume the inferior on return from a function call from |
| within GDB. In all other cases the system call will not be |
| restarted. */ |
| write_register_pid (I386_LINUX_ORIG_EAX_REGNUM, -1, ptid); |
| } |
| |
| |
| /* The register sets used in GNU/Linux ELF core-dumps are identical to |
| the register sets in `struct user' that are used for a.out |
| core-dumps. These are also used by ptrace(2). The corresponding |
| types are `elf_gregset_t' for the general-purpose registers (with |
| `elf_greg_t' the type of a single GP register) and `elf_fpregset_t' |
| for the floating-point registers. |
| |
| Those types used to be available under the names `gregset_t' and |
| `fpregset_t' too, and GDB used those names in the past. But those |
| names are now used for the register sets used in the `mcontext_t' |
| type, which have a different size and layout. */ |
| |
| /* Mapping between the general-purpose registers in `struct user' |
| format and GDB's register cache layout. */ |
| |
| /* From <sys/reg.h>. */ |
| static int i386_linux_gregset_reg_offset[] = |
| { |
| 6 * 4, /* %eax */ |
| 1 * 4, /* %ecx */ |
| 2 * 4, /* %edx */ |
| 0 * 4, /* %ebx */ |
| 15 * 4, /* %esp */ |
| 5 * 4, /* %ebp */ |
| 3 * 4, /* %esi */ |
| 4 * 4, /* %edi */ |
| 12 * 4, /* %eip */ |
| 14 * 4, /* %eflags */ |
| 13 * 4, /* %cs */ |
| 16 * 4, /* %ss */ |
| 7 * 4, /* %ds */ |
| 8 * 4, /* %es */ |
| 9 * 4, /* %fs */ |
| 10 * 4, /* %gs */ |
| -1, -1, -1, -1, -1, -1, -1, -1, |
| -1, -1, -1, -1, -1, -1, -1, -1, |
| -1, -1, -1, -1, -1, -1, -1, -1, |
| -1, |
| 11 * 4 /* "orig_eax" */ |
| }; |
| |
| /* Mapping between the general-purpose registers in `struct |
| sigcontext' format and GDB's register cache layout. */ |
| |
| /* From <asm/sigcontext.h>. */ |
| static int i386_linux_sc_reg_offset[] = |
| { |
| 11 * 4, /* %eax */ |
| 10 * 4, /* %ecx */ |
| 9 * 4, /* %edx */ |
| 8 * 4, /* %ebx */ |
| 7 * 4, /* %esp */ |
| 6 * 4, /* %ebp */ |
| 5 * 4, /* %esi */ |
| 4 * 4, /* %edi */ |
| 14 * 4, /* %eip */ |
| 16 * 4, /* %eflags */ |
| 15 * 4, /* %cs */ |
| 18 * 4, /* %ss */ |
| 3 * 4, /* %ds */ |
| 2 * 4, /* %es */ |
| 1 * 4, /* %fs */ |
| 0 * 4 /* %gs */ |
| }; |
| |
| static void |
| i386_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch) |
| { |
| struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch); |
| |
| /* GNU/Linux uses ELF. */ |
| i386_elf_init_abi (info, gdbarch); |
| |
| /* Since we have the extra "orig_eax" register on GNU/Linux, we have |
| to adjust a few things. */ |
| |
| set_gdbarch_write_pc (gdbarch, i386_linux_write_pc); |
| set_gdbarch_num_regs (gdbarch, I386_LINUX_NUM_REGS); |
| set_gdbarch_register_name (gdbarch, i386_linux_register_name); |
| set_gdbarch_register_reggroup_p (gdbarch, i386_linux_register_reggroup_p); |
| |
| tdep->gregset_reg_offset = i386_linux_gregset_reg_offset; |
| tdep->gregset_num_regs = ARRAY_SIZE (i386_linux_gregset_reg_offset); |
| tdep->sizeof_gregset = 17 * 4; |
| |
| tdep->jb_pc_offset = 20; /* From <bits/setjmp.h>. */ |
| |
| tdep->sigtramp_p = i386_linux_sigtramp_p; |
| tdep->sigcontext_addr = i386_linux_sigcontext_addr; |
| tdep->sc_reg_offset = i386_linux_sc_reg_offset; |
| tdep->sc_num_regs = ARRAY_SIZE (i386_linux_sc_reg_offset); |
| |
| /* GNU/Linux uses SVR4-style shared libraries. */ |
| set_solib_svr4_fetch_link_map_offsets |
| (gdbarch, svr4_ilp32_fetch_link_map_offsets); |
| |
| /* GNU/Linux uses the dynamic linker included in the GNU C Library. */ |
| set_gdbarch_skip_solib_resolver (gdbarch, glibc_skip_solib_resolver); |
| |
| dwarf2_frame_set_signal_frame_p (gdbarch, i386_linux_dwarf_signal_frame_p); |
| |
| /* Enable TLS support. */ |
| set_gdbarch_fetch_tls_load_module_address (gdbarch, |
| svr4_fetch_objfile_link_map); |
| } |
| |
| /* Provide a prototype to silence -Wmissing-prototypes. */ |
| extern void _initialize_i386_linux_tdep (void); |
| |
| void |
| _initialize_i386_linux_tdep (void) |
| { |
| gdbarch_register_osabi (bfd_arch_i386, 0, GDB_OSABI_LINUX, |
| i386_linux_init_abi); |
| } |