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- /* Functions for manipulating expressions designed to be executed on the agent
- Copyright (C) 1998-2022 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 3 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, see <http://www.gnu.org/licenses/>. */
- /* Despite what the above comment says about this file being part of
- GDB, we would like to keep these functions free of GDB
- dependencies, since we want to be able to use them in contexts
- outside of GDB (test suites, the stub, etc.) */
- #include "defs.h"
- #include "ax.h"
- #include "gdbarch.h"
- #include "value.h"
- #include "user-regs.h"
- static void grow_expr (struct agent_expr *x, int n);
- static void append_const (struct agent_expr *x, LONGEST val, int n);
- static LONGEST read_const (struct agent_expr *x, int o, int n);
- static void generic_ext (struct agent_expr *x, enum agent_op op, int n);
- /* Functions for building expressions. */
- agent_expr::agent_expr (struct gdbarch *gdbarch, CORE_ADDR scope)
- {
- this->len = 0;
- this->size = 1; /* Change this to a larger value once
- reallocation code is tested. */
- this->buf = (unsigned char *) xmalloc (this->size);
- this->gdbarch = gdbarch;
- this->scope = scope;
- /* Bit vector for registers used. */
- this->reg_mask_len = 1;
- this->reg_mask = XCNEWVEC (unsigned char, this->reg_mask_len);
- this->tracing = 0;
- this->trace_string = 0;
- }
- agent_expr::~agent_expr ()
- {
- xfree (this->buf);
- xfree (this->reg_mask);
- }
- /* Make sure that X has room for at least N more bytes. This doesn't
- affect the length, just the allocated size. */
- static void
- grow_expr (struct agent_expr *x, int n)
- {
- if (x->len + n > x->size)
- {
- x->size *= 2;
- if (x->size < x->len + n)
- x->size = x->len + n + 10;
- x->buf = (unsigned char *) xrealloc (x->buf, x->size);
- }
- }
- /* Append the low N bytes of VAL as an N-byte integer to the
- expression X, in big-endian order. */
- static void
- append_const (struct agent_expr *x, LONGEST val, int n)
- {
- int i;
- grow_expr (x, n);
- for (i = n - 1; i >= 0; i--)
- {
- x->buf[x->len + i] = val & 0xff;
- val >>= 8;
- }
- x->len += n;
- }
- /* Extract an N-byte big-endian unsigned integer from expression X at
- offset O. */
- static LONGEST
- read_const (struct agent_expr *x, int o, int n)
- {
- int i;
- LONGEST accum = 0;
- /* Make sure we're not reading off the end of the expression. */
- if (o + n > x->len)
- error (_("GDB bug: ax-general.c (read_const): incomplete constant"));
- for (i = 0; i < n; i++)
- accum = (accum << 8) | x->buf[o + i];
- return accum;
- }
- /* See ax.h. */
- void
- ax_raw_byte (struct agent_expr *x, gdb_byte byte)
- {
- grow_expr (x, 1);
- x->buf[x->len++] = byte;
- }
- /* Append a simple operator OP to EXPR. */
- void
- ax_simple (struct agent_expr *x, enum agent_op op)
- {
- ax_raw_byte (x, op);
- }
- /* Append a pick operator to EXPR. DEPTH is the stack item to pick,
- with 0 being top of stack. */
- void
- ax_pick (struct agent_expr *x, int depth)
- {
- if (depth < 0 || depth > 255)
- error (_("GDB bug: ax-general.c (ax_pick): stack depth out of range"));
- ax_simple (x, aop_pick);
- append_const (x, 1, depth);
- }
- /* Append a sign-extension or zero-extension instruction to EXPR, to
- extend an N-bit value. */
- static void
- generic_ext (struct agent_expr *x, enum agent_op op, int n)
- {
- /* N must fit in a byte. */
- if (n < 0 || n > 255)
- error (_("GDB bug: ax-general.c (generic_ext): bit count out of range"));
- /* That had better be enough range. */
- if (sizeof (LONGEST) * 8 > 255)
- error (_("GDB bug: ax-general.c (generic_ext): "
- "opcode has inadequate range"));
- grow_expr (x, 2);
- x->buf[x->len++] = op;
- x->buf[x->len++] = n;
- }
- /* Append a sign-extension instruction to EXPR, to extend an N-bit value. */
- void
- ax_ext (struct agent_expr *x, int n)
- {
- generic_ext (x, aop_ext, n);
- }
- /* Append a zero-extension instruction to EXPR, to extend an N-bit value. */
- void
- ax_zero_ext (struct agent_expr *x, int n)
- {
- generic_ext (x, aop_zero_ext, n);
- }
- /* Append a trace_quick instruction to EXPR, to record N bytes. */
- void
- ax_trace_quick (struct agent_expr *x, int n)
- {
- /* N must fit in a byte. */
- if (n < 0 || n > 255)
- error (_("GDB bug: ax-general.c (ax_trace_quick): "
- "size out of range for trace_quick"));
- grow_expr (x, 2);
- x->buf[x->len++] = aop_trace_quick;
- x->buf[x->len++] = n;
- }
- /* Append a goto op to EXPR. OP is the actual op (must be aop_goto or
- aop_if_goto). We assume we don't know the target offset yet,
- because it's probably a forward branch, so we leave space in EXPR
- for the target, and return the offset in EXPR of that space, so we
- can backpatch it once we do know the target offset. Use ax_label
- to do the backpatching. */
- int
- ax_goto (struct agent_expr *x, enum agent_op op)
- {
- grow_expr (x, 3);
- x->buf[x->len + 0] = op;
- x->buf[x->len + 1] = 0xff;
- x->buf[x->len + 2] = 0xff;
- x->len += 3;
- return x->len - 2;
- }
- /* Suppose a given call to ax_goto returns some value PATCH. When you
- know the offset TARGET that goto should jump to, call
- ax_label (EXPR, PATCH, TARGET)
- to patch TARGET into the ax_goto instruction. */
- void
- ax_label (struct agent_expr *x, int patch, int target)
- {
- /* Make sure the value is in range. Don't accept 0xffff as an
- offset; that's our magic sentinel value for unpatched branches. */
- if (target < 0 || target >= 0xffff)
- error (_("GDB bug: ax-general.c (ax_label): label target out of range"));
- x->buf[patch] = (target >> 8) & 0xff;
- x->buf[patch + 1] = target & 0xff;
- }
- /* Assemble code to push a constant on the stack. */
- void
- ax_const_l (struct agent_expr *x, LONGEST l)
- {
- static enum agent_op ops[]
- =
- {aop_const8, aop_const16, aop_const32, aop_const64};
- int size;
- int op;
- /* How big is the number? 'op' keeps track of which opcode to use.
- Notice that we don't really care whether the original number was
- signed or unsigned; we always reproduce the value exactly, and
- use the shortest representation. */
- for (op = 0, size = 8; size < 64; size *= 2, op++)
- {
- LONGEST lim = ((LONGEST) 1) << (size - 1);
- if (-lim <= l && l <= lim - 1)
- break;
- }
- /* Emit the right opcode... */
- ax_simple (x, ops[op]);
- /* Emit the low SIZE bytes as an unsigned number. We know that
- sign-extending this will yield l. */
- append_const (x, l, size / 8);
- /* Now, if it was negative, and not full-sized, sign-extend it. */
- if (l < 0 && size < 64)
- ax_ext (x, size);
- }
- void
- ax_const_d (struct agent_expr *x, LONGEST d)
- {
- /* FIXME: floating-point support not present yet. */
- error (_("GDB bug: ax-general.c (ax_const_d): "
- "floating point not supported yet"));
- }
- /* Assemble code to push the value of register number REG on the
- stack. */
- void
- ax_reg (struct agent_expr *x, int reg)
- {
- if (reg >= gdbarch_num_regs (x->gdbarch))
- {
- /* This is a pseudo-register. */
- if (!gdbarch_ax_pseudo_register_push_stack_p (x->gdbarch))
- error (_("'%s' is a pseudo-register; "
- "GDB cannot yet trace its contents."),
- user_reg_map_regnum_to_name (x->gdbarch, reg));
- if (gdbarch_ax_pseudo_register_push_stack (x->gdbarch, x, reg))
- error (_("Trace '%s' failed."),
- user_reg_map_regnum_to_name (x->gdbarch, reg));
- }
- else
- {
- /* Get the remote register number. */
- reg = gdbarch_remote_register_number (x->gdbarch, reg);
- /* Make sure the register number is in range. */
- if (reg < 0 || reg > 0xffff)
- error (_("GDB bug: ax-general.c (ax_reg): "
- "register number out of range"));
- grow_expr (x, 3);
- x->buf[x->len] = aop_reg;
- x->buf[x->len + 1] = (reg >> 8) & 0xff;
- x->buf[x->len + 2] = (reg) & 0xff;
- x->len += 3;
- }
- }
- /* Assemble code to operate on a trace state variable. */
- void
- ax_tsv (struct agent_expr *x, enum agent_op op, int num)
- {
- /* Make sure the tsv number is in range. */
- if (num < 0 || num > 0xffff)
- internal_error (__FILE__, __LINE__,
- _("ax-general.c (ax_tsv): variable "
- "number is %d, out of range"), num);
- grow_expr (x, 3);
- x->buf[x->len] = op;
- x->buf[x->len + 1] = (num >> 8) & 0xff;
- x->buf[x->len + 2] = (num) & 0xff;
- x->len += 3;
- }
- /* Append a string to the expression. Note that the string is going
- into the bytecodes directly, not on the stack. As a precaution,
- include both length as prefix, and terminate with a NUL. (The NUL
- is counted in the length.) */
- void
- ax_string (struct agent_expr *x, const char *str, int slen)
- {
- int i;
- /* Make sure the string length is reasonable. */
- if (slen < 0 || slen > 0xffff)
- internal_error (__FILE__, __LINE__,
- _("ax-general.c (ax_string): string "
- "length is %d, out of allowed range"), slen);
- grow_expr (x, 2 + slen + 1);
- x->buf[x->len++] = ((slen + 1) >> 8) & 0xff;
- x->buf[x->len++] = (slen + 1) & 0xff;
- for (i = 0; i < slen; ++i)
- x->buf[x->len++] = str[i];
- x->buf[x->len++] = '\0';
- }
- /* Functions for disassembling agent expressions, and otherwise
- debugging the expression compiler. */
- struct aop_map aop_map[] =
- {
- {0, 0, 0, 0, 0}
- #define DEFOP(NAME, SIZE, DATA_SIZE, CONSUMED, PRODUCED, VALUE) \
- , { # NAME, SIZE, DATA_SIZE, CONSUMED, PRODUCED }
- #include "gdbsupport/ax.def"
- #undef DEFOP
- };
- /* Disassemble the expression EXPR, writing to F. */
- void
- ax_print (struct ui_file *f, struct agent_expr *x)
- {
- int i;
- gdb_printf (f, _("Scope: %s\n"), paddress (x->gdbarch, x->scope));
- gdb_printf (f, _("Reg mask:"));
- for (i = 0; i < x->reg_mask_len; ++i)
- gdb_printf (f, _(" %02x"), x->reg_mask[i]);
- gdb_printf (f, _("\n"));
- /* Check the size of the name array against the number of entries in
- the enum, to catch additions that people didn't sync. */
- if ((sizeof (aop_map) / sizeof (aop_map[0]))
- != aop_last)
- error (_("GDB bug: ax-general.c (ax_print): opcode map out of sync"));
- for (i = 0; i < x->len;)
- {
- enum agent_op op = (enum agent_op) x->buf[i];
- if (op >= (sizeof (aop_map) / sizeof (aop_map[0]))
- || !aop_map[op].name)
- {
- gdb_printf (f, _("%3d <bad opcode %02x>\n"), i, op);
- i++;
- continue;
- }
- if (i + 1 + aop_map[op].op_size > x->len)
- {
- gdb_printf (f, _("%3d <incomplete opcode %s>\n"),
- i, aop_map[op].name);
- break;
- }
- gdb_printf (f, "%3d %s", i, aop_map[op].name);
- if (aop_map[op].op_size > 0)
- {
- gdb_puts (" ", f);
- print_longest (f, 'd', 0,
- read_const (x, i + 1, aop_map[op].op_size));
- }
- /* Handle the complicated printf arguments specially. */
- else if (op == aop_printf)
- {
- int slen, nargs;
- i++;
- nargs = x->buf[i++];
- slen = x->buf[i++];
- slen = slen * 256 + x->buf[i++];
- gdb_printf (f, _(" \"%s\", %d args"),
- &(x->buf[i]), nargs);
- i += slen - 1;
- }
- gdb_printf (f, "\n");
- i += 1 + aop_map[op].op_size;
- }
- }
- /* Add register REG to the register mask for expression AX. */
- void
- ax_reg_mask (struct agent_expr *ax, int reg)
- {
- if (reg >= gdbarch_num_regs (ax->gdbarch))
- {
- /* This is a pseudo-register. */
- if (!gdbarch_ax_pseudo_register_collect_p (ax->gdbarch))
- error (_("'%s' is a pseudo-register; "
- "GDB cannot yet trace its contents."),
- user_reg_map_regnum_to_name (ax->gdbarch, reg));
- if (gdbarch_ax_pseudo_register_collect (ax->gdbarch, ax, reg))
- error (_("Trace '%s' failed."),
- user_reg_map_regnum_to_name (ax->gdbarch, reg));
- }
- else
- {
- int byte;
- /* Get the remote register number. */
- reg = gdbarch_remote_register_number (ax->gdbarch, reg);
- byte = reg / 8;
- /* Grow the bit mask if necessary. */
- if (byte >= ax->reg_mask_len)
- {
- /* It's not appropriate to double here. This isn't a
- string buffer. */
- int new_len = byte + 1;
- unsigned char *new_reg_mask
- = XRESIZEVEC (unsigned char, ax->reg_mask, new_len);
- memset (new_reg_mask + ax->reg_mask_len, 0,
- (new_len - ax->reg_mask_len) * sizeof (ax->reg_mask[0]));
- ax->reg_mask_len = new_len;
- ax->reg_mask = new_reg_mask;
- }
- ax->reg_mask[byte] |= 1 << (reg % 8);
- }
- }
- /* Given an agent expression AX, fill in requirements and other descriptive
- bits. */
- void
- ax_reqs (struct agent_expr *ax)
- {
- int i;
- int height;
- /* Jump target table. targets[i] is non-zero iff we have found a
- jump to offset i. */
- char *targets = (char *) alloca (ax->len * sizeof (targets[0]));
- /* Instruction boundary table. boundary[i] is non-zero iff our scan
- has reached an instruction starting at offset i. */
- char *boundary = (char *) alloca (ax->len * sizeof (boundary[0]));
- /* Stack height record. If either targets[i] or boundary[i] is
- non-zero, heights[i] is the height the stack should have before
- executing the bytecode at that point. */
- int *heights = (int *) alloca (ax->len * sizeof (heights[0]));
- /* Pointer to a description of the present op. */
- struct aop_map *op;
- memset (targets, 0, ax->len * sizeof (targets[0]));
- memset (boundary, 0, ax->len * sizeof (boundary[0]));
- ax->max_height = ax->min_height = height = 0;
- ax->flaw = agent_flaw_none;
- ax->max_data_size = 0;
- for (i = 0; i < ax->len; i += 1 + op->op_size)
- {
- if (ax->buf[i] > (sizeof (aop_map) / sizeof (aop_map[0])))
- {
- ax->flaw = agent_flaw_bad_instruction;
- return;
- }
- op = &aop_map[ax->buf[i]];
- if (!op->name)
- {
- ax->flaw = agent_flaw_bad_instruction;
- return;
- }
- if (i + 1 + op->op_size > ax->len)
- {
- ax->flaw = agent_flaw_incomplete_instruction;
- return;
- }
- /* If this instruction is a forward jump target, does the
- current stack height match the stack height at the jump
- source? */
- if (targets[i] && (heights[i] != height))
- {
- ax->flaw = agent_flaw_height_mismatch;
- return;
- }
- boundary[i] = 1;
- heights[i] = height;
- height -= op->consumed;
- if (height < ax->min_height)
- ax->min_height = height;
- height += op->produced;
- if (height > ax->max_height)
- ax->max_height = height;
- if (op->data_size > ax->max_data_size)
- ax->max_data_size = op->data_size;
- /* For jump instructions, check that the target is a valid
- offset. If it is, record the fact that that location is a
- jump target, and record the height we expect there. */
- if (aop_goto == op - aop_map
- || aop_if_goto == op - aop_map)
- {
- int target = read_const (ax, i + 1, 2);
- if (target < 0 || target >= ax->len)
- {
- ax->flaw = agent_flaw_bad_jump;
- return;
- }
- /* Do we have any information about what the stack height
- should be at the target? */
- if (targets[target] || boundary[target])
- {
- if (heights[target] != height)
- {
- ax->flaw = agent_flaw_height_mismatch;
- return;
- }
- }
- /* Record the target, along with the stack height we expect. */
- targets[target] = 1;
- heights[target] = height;
- }
- /* For unconditional jumps with a successor, check that the
- successor is a target, and pick up its stack height. */
- if (aop_goto == op - aop_map
- && i + 3 < ax->len)
- {
- if (!targets[i + 3])
- {
- ax->flaw = agent_flaw_hole;
- return;
- }
- height = heights[i + 3];
- }
- /* For reg instructions, record the register in the bit mask. */
- if (aop_reg == op - aop_map)
- {
- int reg = read_const (ax, i + 1, 2);
- ax_reg_mask (ax, reg);
- }
- }
- /* Check that all the targets are on boundaries. */
- for (i = 0; i < ax->len; i++)
- if (targets[i] && !boundary[i])
- {
- ax->flaw = agent_flaw_bad_jump;
- return;
- }
- ax->final_height = height;
- }
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