/* Intel 386 target-dependent stuff. Copyright (C) 1988, 1989, 1991 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., 675 Mass Ave, Cambridge, MA 02139, USA. */ #include "defs.h" #include "frame.h" #include "inferior.h" #include "gdbcore.h" #include "target.h" #ifdef USE_PROC_FS /* Target dependent support for /proc */ #include <sys/procfs.h> #endif static long i386_get_frame_setup PARAMS ((int)); static void i386_follow_jump PARAMS ((void)); static void codestream_read PARAMS ((unsigned char *, int)); static void codestream_seek PARAMS ((int)); static unsigned char codestream_fill PARAMS ((int)); /* helper functions for tm-i386.h */ /* Stdio style buffering was used to minimize calls to ptrace, but this buffering did not take into account that the code section being accessed may not be an even number of buffers long (even if the buffer is only sizeof(int) long). In cases where the code section size happened to be a non-integral number of buffers long, attempting to read the last buffer would fail. Simply using target_read_memory and ignoring errors, rather than read_memory, is not the correct solution, since legitimate access errors would then be totally ignored. To properly handle this situation and continue to use buffering would require that this code be able to determine the minimum code section size granularity (not the alignment of the section itself, since the actual failing case that pointed out this problem had a section alignment of 4 but was not a multiple of 4 bytes long), on a target by target basis, and then adjust it's buffer size accordingly. This is messy, but potentially feasible. It probably needs the bfd library's help and support. For now, the buffer size is set to 1. (FIXME -fnf) */ #define CODESTREAM_BUFSIZ 1 /* Was sizeof(int), see note above. */ static CORE_ADDR codestream_next_addr; static CORE_ADDR codestream_addr; static unsigned char codestream_buf[CODESTREAM_BUFSIZ]; static int codestream_off; static int codestream_cnt; #define codestream_tell() (codestream_addr + codestream_off) #define codestream_peek() (codestream_cnt == 0 ? \ codestream_fill(1): codestream_buf[codestream_off]) #define codestream_get() (codestream_cnt-- == 0 ? \ codestream_fill(0) : codestream_buf[codestream_off++]) static unsigned char codestream_fill (peek_flag) int peek_flag; { codestream_addr = codestream_next_addr; codestream_next_addr += CODESTREAM_BUFSIZ; codestream_off = 0; codestream_cnt = CODESTREAM_BUFSIZ; read_memory (codestream_addr, (unsigned char *)codestream_buf, CODESTREAM_BUFSIZ); if (peek_flag) return (codestream_peek()); else return (codestream_get()); } static void codestream_seek (place) int place; { codestream_next_addr = place / CODESTREAM_BUFSIZ; codestream_next_addr *= CODESTREAM_BUFSIZ; codestream_cnt = 0; codestream_fill (1); while (codestream_tell() != place) codestream_get (); } static void codestream_read (buf, count) unsigned char *buf; int count; { unsigned char *p; int i; p = buf; for (i = 0; i < count; i++) *p++ = codestream_get (); } /* next instruction is a jump, move to target */ static void i386_follow_jump () { int long_delta; short short_delta; char byte_delta; int data16; int pos; pos = codestream_tell (); data16 = 0; if (codestream_peek () == 0x66) { codestream_get (); data16 = 1; } switch (codestream_get ()) { case 0xe9: /* relative jump: if data16 == 0, disp32, else disp16 */ if (data16) { codestream_read ((unsigned char *)&short_delta, 2); /* include size of jmp inst (including the 0x66 prefix). */ pos += short_delta + 4; } else { codestream_read ((unsigned char *)&long_delta, 4); pos += long_delta + 5; } break; case 0xeb: /* relative jump, disp8 (ignore data16) */ codestream_read ((unsigned char *)&byte_delta, 1); pos += byte_delta + 2; break; } codestream_seek (pos); } /* * find & return amound a local space allocated, and advance codestream to * first register push (if any) * * if entry sequence doesn't make sense, return -1, and leave * codestream pointer random */ static long i386_get_frame_setup (pc) int pc; { unsigned char op; codestream_seek (pc); i386_follow_jump (); op = codestream_get (); if (op == 0x58) /* popl %eax */ { /* * this function must start with * * popl %eax 0x58 * xchgl %eax, (%esp) 0x87 0x04 0x24 * or xchgl %eax, 0(%esp) 0x87 0x44 0x24 0x00 * * (the system 5 compiler puts out the second xchg * inst, and the assembler doesn't try to optimize it, * so the 'sib' form gets generated) * * this sequence is used to get the address of the return * buffer for a function that returns a structure */ int pos; unsigned char buf[4]; static unsigned char proto1[3] = { 0x87,0x04,0x24 }; static unsigned char proto2[4] = { 0x87,0x44,0x24,0x00 }; pos = codestream_tell (); codestream_read (buf, 4); if (memcmp (buf, proto1, 3) == 0) pos += 3; else if (memcmp (buf, proto2, 4) == 0) pos += 4; codestream_seek (pos); op = codestream_get (); /* update next opcode */ } if (op == 0x55) /* pushl %ebp */ { /* check for movl %esp, %ebp - can be written two ways */ switch (codestream_get ()) { case 0x8b: if (codestream_get () != 0xec) return (-1); break; case 0x89: if (codestream_get () != 0xe5) return (-1); break; default: return (-1); } /* check for stack adjustment * * subl $XXX, %esp * * note: you can't subtract a 16 bit immediate * from a 32 bit reg, so we don't have to worry * about a data16 prefix */ op = codestream_peek (); if (op == 0x83) { /* subl with 8 bit immed */ codestream_get (); if (codestream_get () != 0xec) /* Some instruction starting with 0x83 other than subl. */ { codestream_seek (codestream_tell () - 2); return 0; } /* subl with signed byte immediate * (though it wouldn't make sense to be negative) */ return (codestream_get()); } else if (op == 0x81) { /* subl with 32 bit immed */ int locals; codestream_get(); if (codestream_get () != 0xec) /* Some instruction starting with 0x81 other than subl. */ { codestream_seek (codestream_tell () - 2); return 0; } /* subl with 32 bit immediate */ codestream_read ((unsigned char *)&locals, 4); SWAP_TARGET_AND_HOST (&locals, 4); return (locals); } else { return (0); } } else if (op == 0xc8) { /* enter instruction: arg is 16 bit unsigned immed */ unsigned short slocals; codestream_read ((unsigned char *)&slocals, 2); SWAP_TARGET_AND_HOST (&slocals, 2); codestream_get (); /* flush final byte of enter instruction */ return (slocals); } return (-1); } /* Return number of args passed to a frame. Can return -1, meaning no way to tell. */ /* on the 386, the instruction following the call could be: * popl %ecx - one arg * addl $imm, %esp - imm/4 args; imm may be 8 or 32 bits * anything else - zero args */ int i386_frame_num_args (fi) struct frame_info *fi; { int retpc; unsigned char op; struct frame_info *pfi; int frameless; FRAMELESS_FUNCTION_INVOCATION (fi, frameless); if (frameless) /* In the absence of a frame pointer, GDB doesn't get correct values for nameless arguments. Return -1, so it doesn't print any nameless arguments. */ return -1; pfi = get_prev_frame_info (fi); if (pfi == 0) { /* Note: this can happen if we are looking at the frame for main, because FRAME_CHAIN_VALID won't let us go into start. If we have debugging symbols, that's not really a big deal; it just means it will only show as many arguments to main as are declared. */ return -1; } else { retpc = pfi->pc; op = read_memory_integer (retpc, 1); if (op == 0x59) /* pop %ecx */ return 1; else if (op == 0x83) { op = read_memory_integer (retpc+1, 1); if (op == 0xc4) /* addl $<signed imm 8 bits>, %esp */ return (read_memory_integer (retpc+2,1)&0xff)/4; else return 0; } else if (op == 0x81) { /* add with 32 bit immediate */ op = read_memory_integer (retpc+1, 1); if (op == 0xc4) /* addl $<imm 32>, %esp */ return read_memory_integer (retpc+2, 4) / 4; else return 0; } else { return 0; } } } /* * parse the first few instructions of the function to see * what registers were stored. * * We handle these cases: * * The startup sequence can be at the start of the function, * or the function can start with a branch to startup code at the end. * * %ebp can be set up with either the 'enter' instruction, or * 'pushl %ebp, movl %esp, %ebp' (enter is too slow to be useful, * but was once used in the sys5 compiler) * * Local space is allocated just below the saved %ebp by either the * 'enter' instruction, or by 'subl $<size>, %esp'. 'enter' has * a 16 bit unsigned argument for space to allocate, and the * 'addl' instruction could have either a signed byte, or * 32 bit immediate. * * Next, the registers used by this function are pushed. In * the sys5 compiler they will always be in the order: %edi, %esi, %ebx * (and sometimes a harmless bug causes it to also save but not restore %eax); * however, the code below is willing to see the pushes in any order, * and will handle up to 8 of them. * * If the setup sequence is at the end of the function, then the * next instruction will be a branch back to the start. */ void i386_frame_find_saved_regs (fip, fsrp) struct frame_info *fip; struct frame_saved_regs *fsrp; { long locals; unsigned char op; CORE_ADDR dummy_bottom; CORE_ADDR adr; int i; (void) memset (fsrp, 0, sizeof *fsrp); /* if frame is the end of a dummy, compute where the * beginning would be */ dummy_bottom = fip->frame - 4 - REGISTER_BYTES - CALL_DUMMY_LENGTH; /* check if the PC is in the stack, in a dummy frame */ if (dummy_bottom <= fip->pc && fip->pc <= fip->frame) { /* all regs were saved by push_call_dummy () */ adr = fip->frame; for (i = 0; i < NUM_REGS; i++) { adr -= REGISTER_RAW_SIZE (i); fsrp->regs[i] = adr; } return; } locals = i386_get_frame_setup (get_pc_function_start (fip->pc)); if (locals >= 0) { adr = fip->frame - 4 - locals; for (i = 0; i < 8; i++) { op = codestream_get (); if (op < 0x50 || op > 0x57) break; fsrp->regs[op - 0x50] = adr; adr -= 4; } } fsrp->regs[PC_REGNUM] = fip->frame + 4; fsrp->regs[FP_REGNUM] = fip->frame; } /* return pc of first real instruction */ int i386_skip_prologue (pc) int pc; { unsigned char op; int i; if (i386_get_frame_setup (pc) < 0) return (pc); /* found valid frame setup - codestream now points to * start of push instructions for saving registers */ /* skip over register saves */ for (i = 0; i < 8; i++) { op = codestream_peek (); /* break if not pushl inst */ if (op < 0x50 || op > 0x57) break; codestream_get (); } i386_follow_jump (); return (codestream_tell ()); } void i386_push_dummy_frame () { CORE_ADDR sp = read_register (SP_REGNUM); int regnum; char regbuf[MAX_REGISTER_RAW_SIZE]; sp = push_word (sp, read_register (PC_REGNUM)); sp = push_word (sp, read_register (FP_REGNUM)); write_register (FP_REGNUM, sp); for (regnum = 0; regnum < NUM_REGS; regnum++) { read_register_gen (regnum, regbuf); sp = push_bytes (sp, regbuf, REGISTER_RAW_SIZE (regnum)); } write_register (SP_REGNUM, sp); } void i386_pop_frame () { FRAME frame = get_current_frame (); CORE_ADDR fp; int regnum; struct frame_saved_regs fsr; struct frame_info *fi; char regbuf[MAX_REGISTER_RAW_SIZE]; fi = get_frame_info (frame); fp = fi->frame; get_frame_saved_regs (fi, &fsr); for (regnum = 0; regnum < NUM_REGS; regnum++) { CORE_ADDR adr; adr = fsr.regs[regnum]; if (adr) { read_memory (adr, regbuf, REGISTER_RAW_SIZE (regnum)); write_register_bytes (REGISTER_BYTE (regnum), regbuf, REGISTER_RAW_SIZE (regnum)); } } write_register (FP_REGNUM, read_memory_integer (fp, 4)); write_register (PC_REGNUM, read_memory_integer (fp + 4, 4)); write_register (SP_REGNUM, fp + 8); flush_cached_frames (); set_current_frame ( create_new_frame (read_register (FP_REGNUM), read_pc ())); } #ifdef USE_PROC_FS /* Target dependent support for /proc */ /* The /proc interface divides the target machine's register set up into two different sets, the general register set (gregset) and the floating point register set (fpregset). For each set, there is an ioctl to get the current register set and another ioctl to set the current values. The actual structure passed through the ioctl interface is, of course, naturally machine dependent, and is different for each set of registers. For the i386 for example, the general register set is typically defined by: typedef int gregset_t[19]; (in <sys/regset.h>) #define GS 0 (in <sys/reg.h>) #define FS 1 ... #define UESP 17 #define SS 18 and the floating point set by: typedef struct fpregset { union { struct fpchip_state // fp extension state // { int state[27]; // 287/387 saved state // int status; // status word saved at exception // } fpchip_state; struct fp_emul_space // for emulators // { char fp_emul[246]; char fp_epad[2]; } fp_emul_space; int f_fpregs[62]; // union of the above // } fp_reg_set; long f_wregs[33]; // saved weitek state // } fpregset_t; These routines provide the packing and unpacking of gregset_t and fpregset_t formatted data. */ /* This is a duplicate of the table in i386-xdep.c. */ static int regmap[] = { EAX, ECX, EDX, EBX, UESP, EBP, ESI, EDI, EIP, EFL, CS, SS, DS, ES, FS, GS, }; /* Given a pointer to a general register set in /proc format (gregset_t *), unpack the register contents and supply them as gdb's idea of the current register values. */ void supply_gregset (gregsetp) gregset_t *gregsetp; { register int regno; register greg_t *regp = (greg_t *) gregsetp; extern int regmap[]; for (regno = 0 ; regno < NUM_REGS ; regno++) { supply_register (regno, (char *) (regp + regmap[regno])); } } void fill_gregset (gregsetp, regno) gregset_t *gregsetp; int regno; { int regi; register greg_t *regp = (greg_t *) gregsetp; extern char registers[]; extern int regmap[]; for (regi = 0 ; regi < NUM_REGS ; regi++) { if ((regno == -1) || (regno == regi)) { *(regp + regmap[regno]) = *(int *) ®isters[REGISTER_BYTE (regi)]; } } } #if defined (FP0_REGNUM) /* Given a pointer to a floating point register set in /proc format (fpregset_t *), unpack the register contents and supply them as gdb's idea of the current floating point register values. */ void supply_fpregset (fpregsetp) fpregset_t *fpregsetp; { register int regno; /* FIXME: see m68k-tdep.c for an example, for the m68k. */ } /* Given a pointer to a floating point register set in /proc format (fpregset_t *), update the register specified by REGNO from gdb's idea of the current floating point register set. If REGNO is -1, update them all. */ void fill_fpregset (fpregsetp, regno) fpregset_t *fpregsetp; int regno; { int regi; char *to; char *from; extern char registers[]; /* FIXME: see m68k-tdep.c for an example, for the m68k. */ } #endif /* defined (FP0_REGNUM) */ #endif /* USE_PROC_FS */ #ifdef GET_LONGJMP_TARGET /* Figure out where the longjmp will land. Slurp the args out of the stack. We expect the first arg to be a pointer to the jmp_buf structure from which we extract the pc (JB_PC) that we will land at. The pc is copied into PC. This routine returns true on success. */ int get_longjmp_target(pc) CORE_ADDR *pc; { CORE_ADDR sp, jb_addr; sp = read_register(SP_REGNUM); if (target_read_memory(sp + SP_ARG0, /* Offset of first arg on stack */ (char *) &jb_addr, sizeof(CORE_ADDR))) return 0; SWAP_TARGET_AND_HOST(&jb_addr, sizeof(CORE_ADDR)); if (target_read_memory(jb_addr + JB_PC * JB_ELEMENT_SIZE, (char *) pc, sizeof(CORE_ADDR))) return 0; SWAP_TARGET_AND_HOST(pc, sizeof(CORE_ADDR)); return 1; } #endif /* GET_LONGJMP_TARGET */