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Diffstat (limited to 'gdb/ppc-linux-tdep.c')
| -rw-r--r-- | gdb/ppc-linux-tdep.c | 813 |
1 files changed, 0 insertions, 813 deletions
diff --git a/gdb/ppc-linux-tdep.c b/gdb/ppc-linux-tdep.c deleted file mode 100644 index 5c1fa2807c4..00000000000 --- a/gdb/ppc-linux-tdep.c +++ /dev/null @@ -1,813 +0,0 @@ -/* Target-dependent code for GDB, the GNU debugger. - - Copyright 1986, 1987, 1989, 1991, 1992, 1993, 1994, 1995, 1996, 1997, - 2000, 2001 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 "frame.h" -#include "inferior.h" -#include "symtab.h" -#include "target.h" -#include "gdbcore.h" -#include "gdbcmd.h" -#include "symfile.h" -#include "objfiles.h" -#include "regcache.h" -#include "value.h" - -#include "solib-svr4.h" -#include "ppc-tdep.h" - -/* The following two instructions are used in the signal trampoline - code on linux/ppc */ -#define INSTR_LI_R0_0x7777 0x38007777 -#define INSTR_SC 0x44000002 - -/* Since the *-tdep.c files are platform independent (i.e, they may be - used to build cross platform debuggers), we can't include system - headers. Therefore, details concerning the sigcontext structure - must be painstakingly rerecorded. What's worse, if these details - ever change in the header files, they'll have to be changed here - as well. */ - -/* __SIGNAL_FRAMESIZE from <asm/ptrace.h> */ -#define PPC_LINUX_SIGNAL_FRAMESIZE 64 - -/* From <asm/sigcontext.h>, offsetof(struct sigcontext_struct, regs) == 0x1c */ -#define PPC_LINUX_REGS_PTR_OFFSET (PPC_LINUX_SIGNAL_FRAMESIZE + 0x1c) - -/* From <asm/sigcontext.h>, - offsetof(struct sigcontext_struct, handler) == 0x14 */ -#define PPC_LINUX_HANDLER_PTR_OFFSET (PPC_LINUX_SIGNAL_FRAMESIZE + 0x14) - -/* From <asm/ptrace.h>, values for PT_NIP, PT_R1, and PT_LNK */ -#define PPC_LINUX_PT_R0 0 -#define PPC_LINUX_PT_R1 1 -#define PPC_LINUX_PT_R2 2 -#define PPC_LINUX_PT_R3 3 -#define PPC_LINUX_PT_R4 4 -#define PPC_LINUX_PT_R5 5 -#define PPC_LINUX_PT_R6 6 -#define PPC_LINUX_PT_R7 7 -#define PPC_LINUX_PT_R8 8 -#define PPC_LINUX_PT_R9 9 -#define PPC_LINUX_PT_R10 10 -#define PPC_LINUX_PT_R11 11 -#define PPC_LINUX_PT_R12 12 -#define PPC_LINUX_PT_R13 13 -#define PPC_LINUX_PT_R14 14 -#define PPC_LINUX_PT_R15 15 -#define PPC_LINUX_PT_R16 16 -#define PPC_LINUX_PT_R17 17 -#define PPC_LINUX_PT_R18 18 -#define PPC_LINUX_PT_R19 19 -#define PPC_LINUX_PT_R20 20 -#define PPC_LINUX_PT_R21 21 -#define PPC_LINUX_PT_R22 22 -#define PPC_LINUX_PT_R23 23 -#define PPC_LINUX_PT_R24 24 -#define PPC_LINUX_PT_R25 25 -#define PPC_LINUX_PT_R26 26 -#define PPC_LINUX_PT_R27 27 -#define PPC_LINUX_PT_R28 28 -#define PPC_LINUX_PT_R29 29 -#define PPC_LINUX_PT_R30 30 -#define PPC_LINUX_PT_R31 31 -#define PPC_LINUX_PT_NIP 32 -#define PPC_LINUX_PT_MSR 33 -#define PPC_LINUX_PT_CTR 35 -#define PPC_LINUX_PT_LNK 36 -#define PPC_LINUX_PT_XER 37 -#define PPC_LINUX_PT_CCR 38 -#define PPC_LINUX_PT_MQ 39 -#define PPC_LINUX_PT_FPR0 48 /* each FP reg occupies 2 slots in this space */ -#define PPC_LINUX_PT_FPR31 (PPC_LINUX_PT_FPR0 + 2*31) -#define PPC_LINUX_PT_FPSCR (PPC_LINUX_PT_FPR0 + 2*32 + 1) - -static int ppc_linux_at_sigtramp_return_path (CORE_ADDR pc); - -/* Determine if pc is in a signal trampoline... - - Ha! That's not what this does at all. wait_for_inferior in infrun.c - calls IN_SIGTRAMP in order to detect entry into a signal trampoline - just after delivery of a signal. But on linux, signal trampolines - are used for the return path only. The kernel sets things up so that - the signal handler is called directly. - - If we use in_sigtramp2() in place of in_sigtramp() (see below) - we'll (often) end up with stop_pc in the trampoline and prev_pc in - the (now exited) handler. The code there will cause a temporary - breakpoint to be set on prev_pc which is not very likely to get hit - again. - - If this is confusing, think of it this way... the code in - wait_for_inferior() needs to be able to detect entry into a signal - trampoline just after a signal is delivered, not after the handler - has been run. - - So, we define in_sigtramp() below to return 1 if the following is - true: - - 1) The previous frame is a real signal trampoline. - - - and - - - 2) pc is at the first or second instruction of the corresponding - handler. - - Why the second instruction? It seems that wait_for_inferior() - never sees the first instruction when single stepping. When a - signal is delivered while stepping, the next instruction that - would've been stepped over isn't, instead a signal is delivered and - the first instruction of the handler is stepped over instead. That - puts us on the second instruction. (I added the test for the - first instruction long after the fact, just in case the observed - behavior is ever fixed.) - - IN_SIGTRAMP is called from blockframe.c as well in order to set - the signal_handler_caller flag. Because of our strange definition - of in_sigtramp below, we can't rely on signal_handler_caller getting - set correctly from within blockframe.c. This is why we take pains - to set it in init_extra_frame_info(). */ - -int -ppc_linux_in_sigtramp (CORE_ADDR pc, char *func_name) -{ - CORE_ADDR lr; - CORE_ADDR sp; - CORE_ADDR tramp_sp; - char buf[4]; - CORE_ADDR handler; - - lr = read_register (gdbarch_tdep (current_gdbarch)->ppc_lr_regnum); - if (!ppc_linux_at_sigtramp_return_path (lr)) - return 0; - - sp = read_register (SP_REGNUM); - - if (target_read_memory (sp, buf, sizeof (buf)) != 0) - return 0; - - tramp_sp = extract_unsigned_integer (buf, 4); - - if (target_read_memory (tramp_sp + PPC_LINUX_HANDLER_PTR_OFFSET, buf, - sizeof (buf)) != 0) - return 0; - - handler = extract_unsigned_integer (buf, 4); - - return (pc == handler || pc == handler + 4); -} - -/* - * The signal handler trampoline is on the stack and consists of exactly - * two instructions. The easiest and most accurate way of determining - * whether the pc is in one of these trampolines is by inspecting the - * instructions. It'd be faster though if we could find a way to do this - * via some simple address comparisons. - */ -static int -ppc_linux_at_sigtramp_return_path (CORE_ADDR pc) -{ - char buf[12]; - unsigned long pcinsn; - if (target_read_memory (pc - 4, buf, sizeof (buf)) != 0) - return 0; - - /* extract the instruction at the pc */ - pcinsn = extract_unsigned_integer (buf + 4, 4); - - return ( - (pcinsn == INSTR_LI_R0_0x7777 - && extract_unsigned_integer (buf + 8, 4) == INSTR_SC) - || - (pcinsn == INSTR_SC - && extract_unsigned_integer (buf, 4) == INSTR_LI_R0_0x7777)); -} - -CORE_ADDR -ppc_linux_skip_trampoline_code (CORE_ADDR pc) -{ - char buf[4]; - struct obj_section *sect; - struct objfile *objfile; - unsigned long insn; - CORE_ADDR plt_start = 0; - CORE_ADDR symtab = 0; - CORE_ADDR strtab = 0; - int num_slots = -1; - int reloc_index = -1; - CORE_ADDR plt_table; - CORE_ADDR reloc; - CORE_ADDR sym; - long symidx; - char symname[1024]; - struct minimal_symbol *msymbol; - - /* Find the section pc is in; return if not in .plt */ - sect = find_pc_section (pc); - if (!sect || strcmp (sect->the_bfd_section->name, ".plt") != 0) - return 0; - - objfile = sect->objfile; - - /* Pick up the instruction at pc. It had better be of the - form - li r11, IDX - - where IDX is an index into the plt_table. */ - - if (target_read_memory (pc, buf, 4) != 0) - return 0; - insn = extract_unsigned_integer (buf, 4); - - if ((insn & 0xffff0000) != 0x39600000 /* li r11, VAL */ ) - return 0; - - reloc_index = (insn << 16) >> 16; - - /* Find the objfile that pc is in and obtain the information - necessary for finding the symbol name. */ - for (sect = objfile->sections; sect < objfile->sections_end; ++sect) - { - const char *secname = sect->the_bfd_section->name; - if (strcmp (secname, ".plt") == 0) - plt_start = sect->addr; - else if (strcmp (secname, ".rela.plt") == 0) - num_slots = ((int) sect->endaddr - (int) sect->addr) / 12; - else if (strcmp (secname, ".dynsym") == 0) - symtab = sect->addr; - else if (strcmp (secname, ".dynstr") == 0) - strtab = sect->addr; - } - - /* Make sure we have all the information we need. */ - if (plt_start == 0 || num_slots == -1 || symtab == 0 || strtab == 0) - return 0; - - /* Compute the value of the plt table */ - plt_table = plt_start + 72 + 8 * num_slots; - - /* Get address of the relocation entry (Elf32_Rela) */ - if (target_read_memory (plt_table + reloc_index, buf, 4) != 0) - return 0; - reloc = extract_address (buf, 4); - - sect = find_pc_section (reloc); - if (!sect) - return 0; - - if (strcmp (sect->the_bfd_section->name, ".text") == 0) - return reloc; - - /* Now get the r_info field which is the relocation type and symbol - index. */ - if (target_read_memory (reloc + 4, buf, 4) != 0) - return 0; - symidx = extract_unsigned_integer (buf, 4); - - /* Shift out the relocation type leaving just the symbol index */ - /* symidx = ELF32_R_SYM(symidx); */ - symidx = symidx >> 8; - - /* compute the address of the symbol */ - sym = symtab + symidx * 4; - - /* Fetch the string table index */ - if (target_read_memory (sym, buf, 4) != 0) - return 0; - symidx = extract_unsigned_integer (buf, 4); - - /* Fetch the string; we don't know how long it is. Is it possible - that the following will fail because we're trying to fetch too - much? */ - if (target_read_memory (strtab + symidx, symname, sizeof (symname)) != 0) - return 0; - - /* This might not work right if we have multiple symbols with the - same name; the only way to really get it right is to perform - the same sort of lookup as the dynamic linker. */ - msymbol = lookup_minimal_symbol_text (symname, NULL, NULL); - if (!msymbol) - return 0; - - return SYMBOL_VALUE_ADDRESS (msymbol); -} - -/* The rs6000 version of FRAME_SAVED_PC will almost work for us. The - signal handler details are different, so we'll handle those here - and call the rs6000 version to do the rest. */ -CORE_ADDR -ppc_linux_frame_saved_pc (struct frame_info *fi) -{ - if (fi->signal_handler_caller) - { - CORE_ADDR regs_addr = - read_memory_integer (fi->frame + PPC_LINUX_REGS_PTR_OFFSET, 4); - /* return the NIP in the regs array */ - return read_memory_integer (regs_addr + 4 * PPC_LINUX_PT_NIP, 4); - } - else if (fi->next && fi->next->signal_handler_caller) - { - CORE_ADDR regs_addr = - read_memory_integer (fi->next->frame + PPC_LINUX_REGS_PTR_OFFSET, 4); - /* return LNK in the regs array */ - return read_memory_integer (regs_addr + 4 * PPC_LINUX_PT_LNK, 4); - } - else - return rs6000_frame_saved_pc (fi); -} - -void -ppc_linux_init_extra_frame_info (int fromleaf, struct frame_info *fi) -{ - rs6000_init_extra_frame_info (fromleaf, fi); - - if (fi->next != 0) - { - /* We're called from get_prev_frame_info; check to see if - this is a signal frame by looking to see if the pc points - at trampoline code */ - if (ppc_linux_at_sigtramp_return_path (fi->pc)) - fi->signal_handler_caller = 1; - else - fi->signal_handler_caller = 0; - } -} - -int -ppc_linux_frameless_function_invocation (struct frame_info *fi) -{ - /* We'll find the wrong thing if we let - rs6000_frameless_function_invocation () search for a signal trampoline */ - if (ppc_linux_at_sigtramp_return_path (fi->pc)) - return 0; - else - return rs6000_frameless_function_invocation (fi); -} - -void -ppc_linux_frame_init_saved_regs (struct frame_info *fi) -{ - if (fi->signal_handler_caller) - { - CORE_ADDR regs_addr; - int i; - if (fi->saved_regs) - return; - - frame_saved_regs_zalloc (fi); - - regs_addr = - read_memory_integer (fi->frame + PPC_LINUX_REGS_PTR_OFFSET, 4); - fi->saved_regs[PC_REGNUM] = regs_addr + 4 * PPC_LINUX_PT_NIP; - fi->saved_regs[gdbarch_tdep (current_gdbarch)->ppc_ps_regnum] = - regs_addr + 4 * PPC_LINUX_PT_MSR; - fi->saved_regs[gdbarch_tdep (current_gdbarch)->ppc_cr_regnum] = - regs_addr + 4 * PPC_LINUX_PT_CCR; - fi->saved_regs[gdbarch_tdep (current_gdbarch)->ppc_lr_regnum] = - regs_addr + 4 * PPC_LINUX_PT_LNK; - fi->saved_regs[gdbarch_tdep (current_gdbarch)->ppc_ctr_regnum] = - regs_addr + 4 * PPC_LINUX_PT_CTR; - fi->saved_regs[gdbarch_tdep (current_gdbarch)->ppc_xer_regnum] = - regs_addr + 4 * PPC_LINUX_PT_XER; - fi->saved_regs[gdbarch_tdep (current_gdbarch)->ppc_mq_regnum] = - regs_addr + 4 * PPC_LINUX_PT_MQ; - for (i = 0; i < 32; i++) - fi->saved_regs[gdbarch_tdep (current_gdbarch)->ppc_gp0_regnum + i] = - regs_addr + 4 * PPC_LINUX_PT_R0 + 4 * i; - for (i = 0; i < 32; i++) - fi->saved_regs[FP0_REGNUM + i] = regs_addr + 4 * PPC_LINUX_PT_FPR0 + 8 * i; - } - else - rs6000_frame_init_saved_regs (fi); -} - -CORE_ADDR -ppc_linux_frame_chain (struct frame_info *thisframe) -{ - /* Kernel properly constructs the frame chain for the handler */ - if (thisframe->signal_handler_caller) - return read_memory_integer ((thisframe)->frame, 4); - else - return rs6000_frame_chain (thisframe); -} - -/* FIXME: Move the following to rs6000-tdep.c (or some other file where - it may be used generically by ports which use either the SysV ABI or - the EABI */ - -/* round2 rounds x up to the nearest multiple of s assuming that s is a - power of 2 */ - -#undef round2 -#define round2(x,s) ((((long) (x) - 1) & ~(long)((s)-1)) + (s)) - -/* Pass the arguments in either registers, or in the stack. Using the - ppc sysv ABI, the first eight words of the argument list (that might - be less than eight parameters if some parameters occupy more than one - word) are passed in r3..r10 registers. float and double parameters are - passed in fpr's, in addition to that. Rest of the parameters if any - are passed in user stack. - - If the function is returning a structure, then the return address is passed - in r3, then the first 7 words of the parametes can be passed in registers, - starting from r4. */ - -CORE_ADDR -ppc_sysv_abi_push_arguments (int nargs, struct value **args, CORE_ADDR sp, - int struct_return, CORE_ADDR struct_addr) -{ - int argno; - int greg, freg; - int argstkspace; - int structstkspace; - int argoffset; - int structoffset; - struct value *arg; - struct type *type; - int len; - char old_sp_buf[4]; - CORE_ADDR saved_sp; - - greg = struct_return ? 4 : 3; - freg = 1; - argstkspace = 0; - structstkspace = 0; - - /* Figure out how much new stack space is required for arguments - which don't fit in registers. Unlike the PowerOpen ABI, the - SysV ABI doesn't reserve any extra space for parameters which - are put in registers. */ - for (argno = 0; argno < nargs; argno++) - { - arg = args[argno]; - type = check_typedef (VALUE_TYPE (arg)); - len = TYPE_LENGTH (type); - - if (TYPE_CODE (type) == TYPE_CODE_FLT) - { - if (freg <= 8) - freg++; - else - { - /* SysV ABI converts floats to doubles when placed in - memory and requires 8 byte alignment */ - if (argstkspace & 0x4) - argstkspace += 4; - argstkspace += 8; - } - } - else if (TYPE_CODE (type) == TYPE_CODE_INT && len == 8) /* long long */ - { - if (greg > 9) - { - greg = 11; - if (argstkspace & 0x4) - argstkspace += 4; - argstkspace += 8; - } - else - { - if ((greg & 1) == 0) - greg++; - greg += 2; - } - } - else - { - if (len > 4 - || TYPE_CODE (type) == TYPE_CODE_STRUCT - || TYPE_CODE (type) == TYPE_CODE_UNION) - { - /* Rounding to the nearest multiple of 8 may not be necessary, - but it is safe. Particularly since we don't know the - field types of the structure */ - structstkspace += round2 (len, 8); - } - if (greg <= 10) - greg++; - else - argstkspace += 4; - } - } - - /* Get current SP location */ - saved_sp = read_sp (); - - sp -= argstkspace + structstkspace; - - /* Allocate space for backchain and callee's saved lr */ - sp -= 8; - - /* Make sure that we maintain 16 byte alignment */ - sp &= ~0x0f; - - /* Update %sp before proceeding any further */ - write_register (SP_REGNUM, sp); - - /* write the backchain */ - store_address (old_sp_buf, 4, saved_sp); - write_memory (sp, old_sp_buf, 4); - - argoffset = 8; - structoffset = argoffset + argstkspace; - freg = 1; - greg = 3; - /* Fill in r3 with the return structure, if any */ - if (struct_return) - { - char val_buf[4]; - store_address (val_buf, 4, struct_addr); - memcpy (®isters[REGISTER_BYTE (greg)], val_buf, 4); - greg++; - } - /* Now fill in the registers and stack... */ - for (argno = 0; argno < nargs; argno++) - { - arg = args[argno]; - type = check_typedef (VALUE_TYPE (arg)); - len = TYPE_LENGTH (type); - - if (TYPE_CODE (type) == TYPE_CODE_FLT) - { - if (freg <= 8) - { - if (len > 8) - printf_unfiltered ( - "Fatal Error: a floating point parameter #%d with a size > 8 is found!\n", argno); - memcpy (®isters[REGISTER_BYTE (FP0_REGNUM + freg)], - VALUE_CONTENTS (arg), len); - freg++; - } - else - { - /* SysV ABI converts floats to doubles when placed in - memory and requires 8 byte alignment */ - /* FIXME: Convert floats to doubles */ - if (argoffset & 0x4) - argoffset += 4; - write_memory (sp + argoffset, (char *) VALUE_CONTENTS (arg), len); - argoffset += 8; - } - } - else if (TYPE_CODE (type) == TYPE_CODE_INT && len == 8) /* long long */ - { - if (greg > 9) - { - greg = 11; - if (argoffset & 0x4) - argoffset += 4; - write_memory (sp + argoffset, (char *) VALUE_CONTENTS (arg), len); - argoffset += 8; - } - else - { - if ((greg & 1) == 0) - greg++; - - memcpy (®isters[REGISTER_BYTE (greg)], - VALUE_CONTENTS (arg), 4); - memcpy (®isters[REGISTER_BYTE (greg + 1)], - VALUE_CONTENTS (arg) + 4, 4); - greg += 2; - } - } - else - { - char val_buf[4]; - if (len > 4 - || TYPE_CODE (type) == TYPE_CODE_STRUCT - || TYPE_CODE (type) == TYPE_CODE_UNION) - { - write_memory (sp + structoffset, VALUE_CONTENTS (arg), len); - store_address (val_buf, 4, sp + structoffset); - structoffset += round2 (len, 8); - } - else - { - memset (val_buf, 0, 4); - memcpy (val_buf, VALUE_CONTENTS (arg), len); - } - if (greg <= 10) - { - *(int *) ®isters[REGISTER_BYTE (greg)] = 0; - memcpy (®isters[REGISTER_BYTE (greg)], val_buf, 4); - greg++; - } - else - { - write_memory (sp + argoffset, val_buf, 4); - argoffset += 4; - } - } - } - - target_store_registers (-1); - return sp; -} - -/* ppc_linux_memory_remove_breakpoints attempts to remove a breakpoint - in much the same fashion as memory_remove_breakpoint in mem-break.c, - but is careful not to write back the previous contents if the code - in question has changed in between inserting the breakpoint and - removing it. - - Here is the problem that we're trying to solve... - - Once upon a time, before introducing this function to remove - breakpoints from the inferior, setting a breakpoint on a shared - library function prior to running the program would not work - properly. In order to understand the problem, it is first - necessary to understand a little bit about dynamic linking on - this platform. - - A call to a shared library function is accomplished via a bl - (branch-and-link) instruction whose branch target is an entry - in the procedure linkage table (PLT). The PLT in the object - file is uninitialized. To gdb, prior to running the program, the - entries in the PLT are all zeros. - - Once the program starts running, the shared libraries are loaded - and the procedure linkage table is initialized, but the entries in - the table are not (necessarily) resolved. Once a function is - actually called, the code in the PLT is hit and the function is - resolved. In order to better illustrate this, an example is in - order; the following example is from the gdb testsuite. - - We start the program shmain. - - [kev@arroyo testsuite]$ ../gdb gdb.base/shmain - [...] - - We place two breakpoints, one on shr1 and the other on main. - - (gdb) b shr1 - Breakpoint 1 at 0x100409d4 - (gdb) b main - Breakpoint 2 at 0x100006a0: file gdb.base/shmain.c, line 44. - - Examine the instruction (and the immediatly following instruction) - upon which the breakpoint was placed. Note that the PLT entry - for shr1 contains zeros. - - (gdb) x/2i 0x100409d4 - 0x100409d4 <shr1>: .long 0x0 - 0x100409d8 <shr1+4>: .long 0x0 - - Now run 'til main. - - (gdb) r - Starting program: gdb.base/shmain - Breakpoint 1 at 0xffaf790: file gdb.base/shr1.c, line 19. - - Breakpoint 2, main () - at gdb.base/shmain.c:44 - 44 g = 1; - - Examine the PLT again. Note that the loading of the shared - library has initialized the PLT to code which loads a constant - (which I think is an index into the GOT) into r11 and then - branchs a short distance to the code which actually does the - resolving. - - (gdb) x/2i 0x100409d4 - 0x100409d4 <shr1>: li r11,4 - 0x100409d8 <shr1+4>: b 0x10040984 <sg+4> - (gdb) c - Continuing. - - Breakpoint 1, shr1 (x=1) - at gdb.base/shr1.c:19 - 19 l = 1; - - Now we've hit the breakpoint at shr1. (The breakpoint was - reset from the PLT entry to the actual shr1 function after the - shared library was loaded.) Note that the PLT entry has been - resolved to contain a branch that takes us directly to shr1. - (The real one, not the PLT entry.) - - (gdb) x/2i 0x100409d4 - 0x100409d4 <shr1>: b 0xffaf76c <shr1> - 0x100409d8 <shr1+4>: b 0x10040984 <sg+4> - - The thing to note here is that the PLT entry for shr1 has been - changed twice. - - Now the problem should be obvious. GDB places a breakpoint (a - trap instruction) on the zero value of the PLT entry for shr1. - Later on, after the shared library had been loaded and the PLT - initialized, GDB gets a signal indicating this fact and attempts - (as it always does when it stops) to remove all the breakpoints. - - The breakpoint removal was causing the former contents (a zero - word) to be written back to the now initialized PLT entry thus - destroying a portion of the initialization that had occurred only a - short time ago. When execution continued, the zero word would be - executed as an instruction an an illegal instruction trap was - generated instead. (0 is not a legal instruction.) - - The fix for this problem was fairly straightforward. The function - memory_remove_breakpoint from mem-break.c was copied to this file, - modified slightly, and renamed to ppc_linux_memory_remove_breakpoint. - In tm-linux.h, MEMORY_REMOVE_BREAKPOINT is defined to call this new - function. - - The differences between ppc_linux_memory_remove_breakpoint () and - memory_remove_breakpoint () are minor. All that the former does - that the latter does not is check to make sure that the breakpoint - location actually contains a breakpoint (trap instruction) prior - to attempting to write back the old contents. If it does contain - a trap instruction, we allow the old contents to be written back. - Otherwise, we silently do nothing. - - The big question is whether memory_remove_breakpoint () should be - changed to have the same functionality. The downside is that more - traffic is generated for remote targets since we'll have an extra - fetch of a memory word each time a breakpoint is removed. - - For the time being, we'll leave this self-modifying-code-friendly - version in ppc-linux-tdep.c, but it ought to be migrated somewhere - else in the event that some other platform has similar needs with - regard to removing breakpoints in some potentially self modifying - code. */ -int -ppc_linux_memory_remove_breakpoint (CORE_ADDR addr, char *contents_cache) -{ - unsigned char *bp; - int val; - int bplen; - char old_contents[BREAKPOINT_MAX]; - - /* Determine appropriate breakpoint contents and size for this address. */ - bp = BREAKPOINT_FROM_PC (&addr, &bplen); - if (bp == NULL) - error ("Software breakpoints not implemented for this target."); - - val = target_read_memory (addr, old_contents, bplen); - - /* If our breakpoint is no longer at the address, this means that the - program modified the code on us, so it is wrong to put back the - old value */ - if (val == 0 && memcmp (bp, old_contents, bplen) == 0) - val = target_write_memory (addr, contents_cache, bplen); - - return val; -} - -/* Fetch (and possibly build) an appropriate link_map_offsets - structure for Linux/PPC targets using the struct offsets - defined in link.h (but without actual reference to that file). - - This makes it possible to access Linux/PPC shared libraries from a - GDB that was not built on an Linux/PPC host (for cross debugging). */ - -struct link_map_offsets * -ppc_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 560 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; -} |