diff options
Diffstat (limited to 'contrib/gdb/gdb/i386-linux-tdep.c')
| -rw-r--r-- | contrib/gdb/gdb/i386-linux-tdep.c | 530 |
1 files changed, 530 insertions, 0 deletions
diff --git a/contrib/gdb/gdb/i386-linux-tdep.c b/contrib/gdb/gdb/i386-linux-tdep.c new file mode 100644 index 0000000..d67c01c --- /dev/null +++ b/contrib/gdb/gdb/i386-linux-tdep.c @@ -0,0 +1,530 @@ +/* Target-dependent code for GNU/Linux running on i386's, for GDB. + + Copyright 2000, 2001, 2002 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., 59 Temple Place - Suite 330, + Boston, MA 02111-1307, USA. */ + +#include "defs.h" +#include "gdbcore.h" +#include "frame.h" +#include "value.h" +#include "regcache.h" +#include "inferior.h" + +/* For i386_linux_skip_solib_resolver. */ +#include "symtab.h" +#include "symfile.h" +#include "objfiles.h" + +#include "solib-svr4.h" /* For struct link_map_offsets. */ + +/* Return the name of register REG. */ + +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); +} + +int +i386_linux_register_byte (int reg) +{ + /* Deal with the extra "orig_eax" pseudo register. */ + if (reg == I386_LINUX_ORIG_EAX_REGNUM) + return (i386_register_byte (I386_LINUX_ORIG_EAX_REGNUM - 1) + + i386_register_raw_size (I386_LINUX_ORIG_EAX_REGNUM - 1)); + + return i386_register_byte (reg); +} + +int +i386_linux_register_raw_size (int reg) +{ + /* Deal with the extra "orig_eax" pseudo register. */ + if (reg == I386_LINUX_ORIG_EAX_REGNUM) + return 4; + + return i386_register_raw_size (reg); +} + +/* 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 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. The IN_SIGTRAMP macro in tm-linux.h arranges to + only call us 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 unsigned char 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 PC is in a sigtramp routine, return the address of the start of + the routine. Otherwise, return 0. */ + +static CORE_ADDR +i386_linux_sigtramp_start (CORE_ADDR pc) +{ + unsigned char 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 (read_memory_nobpt (pc, (char *) buf, LINUX_SIGTRAMP_LEN) != 0) + 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 (read_memory_nobpt (pc, (char *) buf, LINUX_SIGTRAMP_LEN) != 0) + 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 unsigned char 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 PC is in a RT sigtramp routine, return the address of the start + of the routine. Otherwise, return 0. */ + +static CORE_ADDR +i386_linux_rt_sigtramp_start (CORE_ADDR pc) +{ + unsigned char 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 (read_memory_nobpt (pc, (char *) buf, LINUX_RT_SIGTRAMP_LEN) != 0) + return 0; + + if (buf[0] != LINUX_RT_SIGTRAMP_INSN0) + { + if (buf[0] != LINUX_RT_SIGTRAMP_INSN1) + return 0; + + pc -= LINUX_RT_SIGTRAMP_OFFSET1; + + if (read_memory_nobpt (pc, (char *) buf, LINUX_RT_SIGTRAMP_LEN) != 0) + return 0; + } + + if (memcmp (buf, linux_rt_sigtramp_code, LINUX_RT_SIGTRAMP_LEN) != 0) + return 0; + + return pc; +} + +/* Return whether PC is in a GNU/Linux sigtramp routine. */ + +int +i386_linux_in_sigtramp (CORE_ADDR pc, char *name) +{ + if (name) + return STREQ ("__restore", name) || STREQ ("__restore_rt", name); + + return (i386_linux_sigtramp_start (pc) != 0 + || i386_linux_rt_sigtramp_start (pc) != 0); +} + +/* Assuming FRAME is for a GNU/Linux sigtramp routine, return the + address of the associated sigcontext structure. */ + +CORE_ADDR +i386_linux_sigcontext_addr (struct frame_info *frame) +{ + CORE_ADDR pc; + + pc = i386_linux_sigtramp_start (frame->pc); + if (pc) + { + CORE_ADDR sp; + + if (frame->next) + /* If this isn't the top frame, the next frame must be for the + signal handler itself. The sigcontext structure lives on + the stack, right after the signum argument. */ + return frame->next->frame + 12; + + /* This is the top frame. We'll have to find the address of the + sigcontext structure by looking at the stack pointer. Keep + in mind that the first instruction of the sigtramp code is + "pop %eax". If the PC is at this instruction, adjust the + returned value accordingly. */ + sp = read_register (SP_REGNUM); + if (pc == frame->pc) + return sp + 4; + return sp; + } + + pc = i386_linux_rt_sigtramp_start (frame->pc); + if (pc) + { + if (frame->next) + /* If this isn't the top frame, the next frame must be for the + signal handler itself. 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. */ + return read_memory_integer (frame->next->frame + 16, 4) + 20; + + /* This is the top frame. Again, use the stack pointer to find + the address of the sigcontext structure. */ + return read_memory_integer (read_register (SP_REGNUM) + 8, 4) + 20; + } + + error ("Couldn't recognize signal trampoline."); + return 0; +} + +/* Offset to saved PC in sigcontext, from <asm/sigcontext.h>. */ +#define LINUX_SIGCONTEXT_PC_OFFSET (56) + +/* Assuming FRAME is for a GNU/Linux sigtramp routine, return the + saved program counter. */ + +static CORE_ADDR +i386_linux_sigtramp_saved_pc (struct frame_info *frame) +{ + CORE_ADDR addr; + addr = i386_linux_sigcontext_addr (frame); + return read_memory_integer (addr + LINUX_SIGCONTEXT_PC_OFFSET, 4); +} + +/* Offset to saved SP in sigcontext, from <asm/sigcontext.h>. */ +#define LINUX_SIGCONTEXT_SP_OFFSET (28) + +/* Assuming FRAME is for a GNU/Linux sigtramp routine, return the + saved stack pointer. */ + +static CORE_ADDR +i386_linux_sigtramp_saved_sp (struct frame_info *frame) +{ + CORE_ADDR addr; + addr = i386_linux_sigcontext_addr (frame); + return read_memory_integer (addr + LINUX_SIGCONTEXT_SP_OFFSET, 4); +} + +/* Signal trampolines don't have a meaningful frame. As in + "i386/tm-i386.h", the frame pointer value we use is actually the + frame pointer of the calling frame -- that is, the frame which was + in progress when the signal trampoline was entered. GDB mostly + treats this frame pointer value as a magic cookie. We detect the + case of a signal trampoline by looking at the SIGNAL_HANDLER_CALLER + field, which is set based on IN_SIGTRAMP. + + When a signal trampoline is invoked from a frameless function, we + essentially have two frameless functions in a row. In this case, + we use the same magic cookie for three frames in a row. We detect + this case by seeing whether the next frame has + SIGNAL_HANDLER_CALLER set, and, if it does, checking whether the + current frame is actually frameless. In this case, we need to get + the PC by looking at the SP register value stored in the signal + context. + + This should work in most cases except in horrible situations where + a signal occurs just as we enter a function but before the frame + has been set up. */ + +#define FRAMELESS_SIGNAL(frame) \ + ((frame)->next != NULL \ + && (frame)->next->signal_handler_caller \ + && frameless_look_for_prologue (frame)) + +CORE_ADDR +i386_linux_frame_chain (struct frame_info *frame) +{ + if (frame->signal_handler_caller || FRAMELESS_SIGNAL (frame)) + return frame->frame; + + if (! inside_entry_file (frame->pc)) + return read_memory_unsigned_integer (frame->frame, 4); + + return 0; +} + +/* Return the saved program counter for FRAME. */ + +CORE_ADDR +i386_linux_frame_saved_pc (struct frame_info *frame) +{ + if (frame->signal_handler_caller) + return i386_linux_sigtramp_saved_pc (frame); + + if (FRAMELESS_SIGNAL (frame)) + { + CORE_ADDR sp = i386_linux_sigtramp_saved_sp (frame->next); + return read_memory_unsigned_integer (sp, 4); + } + + return read_memory_unsigned_integer (frame->frame + 4, 4); +} + +/* Immediately after a function call, return the saved pc. */ + +CORE_ADDR +i386_linux_saved_pc_after_call (struct frame_info *frame) +{ + if (frame->signal_handler_caller) + return i386_linux_sigtramp_saved_pc (frame); + + return read_memory_unsigned_integer (read_register (SP_REGNUM), 4); +} + +/* Set the program counter for process PTID to PC. */ + +void +i386_linux_write_pc (CORE_ADDR pc, ptid_t ptid) +{ + write_register_pid (PC_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); +} + +/* Calling functions in shared libraries. */ + +/* Find the minimal symbol named NAME, and return both the minsym + struct and its objfile. This probably ought to be in minsym.c, but + everything there is trying to deal with things like C++ and + SOFUN_ADDRESS_MAYBE_TURQUOISE, ... Since this is so simple, it may + be considered too special-purpose for general consumption. */ + +static struct minimal_symbol * +find_minsym_and_objfile (char *name, struct objfile **objfile_p) +{ + struct objfile *objfile; + + ALL_OBJFILES (objfile) + { + struct minimal_symbol *msym; + + ALL_OBJFILE_MSYMBOLS (objfile, msym) + { + if (SYMBOL_NAME (msym) + && STREQ (SYMBOL_NAME (msym), name)) + { + *objfile_p = objfile; + return msym; + } + } + } + + return 0; +} + +static CORE_ADDR +skip_hurd_resolver (CORE_ADDR pc) +{ + /* The HURD dynamic linker is part of the GNU C library, so many + GNU/Linux distributions use it. (All ELF versions, as far as I + know.) An unresolved PLT entry points to "_dl_runtime_resolve", + which calls "fixup" to patch the PLT, and then passes control to + the function. + + We look for the symbol `_dl_runtime_resolve', and find `fixup' in + the same objfile. If we are at the entry point of `fixup', then + we set a breakpoint at the return address (at the top of the + stack), and continue. + + It's kind of gross to do all these checks every time we're + called, since they don't change once the executable has gotten + started. But this is only a temporary hack --- upcoming versions + of GNU/Linux will provide a portable, efficient interface for + debugging programs that use shared libraries. */ + + struct objfile *objfile; + struct minimal_symbol *resolver + = find_minsym_and_objfile ("_dl_runtime_resolve", &objfile); + + if (resolver) + { + struct minimal_symbol *fixup + = lookup_minimal_symbol ("fixup", NULL, objfile); + + if (fixup && SYMBOL_VALUE_ADDRESS (fixup) == pc) + return (SAVED_PC_AFTER_CALL (get_current_frame ())); + } + + return 0; +} + +/* See the comments for SKIP_SOLIB_RESOLVER at the top of infrun.c. + This function: + 1) decides whether a PLT has sent us into the linker to resolve + a function reference, and + 2) if so, tells us where to set a temporary breakpoint that will + trigger when the dynamic linker is done. */ + +CORE_ADDR +i386_linux_skip_solib_resolver (CORE_ADDR pc) +{ + CORE_ADDR result; + + /* Plug in functions for other kinds of resolvers here. */ + result = skip_hurd_resolver (pc); + if (result) + return result; + + return 0; +} + +/* Fetch (and possibly build) an appropriate link_map_offsets + structure for native GNU/Linux x86 targets using the struct offsets + defined in link.h (but without actual reference to that file). + + This makes it possible to access GNU/Linux x86 shared libraries + from a GDB that was not built on an GNU/Linux x86 host (for cross + debugging). */ + +struct link_map_offsets * +i386_linux_svr4_fetch_link_map_offsets (void) +{ + static struct link_map_offsets lmo; + static struct link_map_offsets *lmp = NULL; + + if (lmp == NULL) + { + lmp = &lmo; + + lmo.r_debug_size = 8; /* The actual size is 20 bytes, but + this is all we need. */ + lmo.r_map_offset = 4; + lmo.r_map_size = 4; + + lmo.link_map_size = 20; /* The actual size is 552 bytes, but + this is all we need. */ + lmo.l_addr_offset = 0; + lmo.l_addr_size = 4; + + lmo.l_name_offset = 4; + lmo.l_name_size = 4; + + lmo.l_next_offset = 12; + lmo.l_next_size = 4; + + lmo.l_prev_offset = 16; + lmo.l_prev_size = 4; + } + + return lmp; +} |
