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loc2stap.cxx
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loc2stap.cxx
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// dwarf location-list-to-staptree translator
// Copyright (C) 2016 Red Hat Inc.
//
// This file is part of systemtap, and is free software. You can
// redistribute it and/or modify it under the terms of the GNU General
// Public License (GPL); either version 2, or (at your option) any
// later version.
#include "config.h"
#include <cinttypes>
#include <cassert>
#include <cstdlib>
#include <dwarf.h>
#include <elfutils/libdw.h>
#include <elfutils/version.h>
#include "loc2stap.h"
#include "dwflpp.h"
#if ! _ELFUTILS_PREREQ(0, 153)
#define DW_OP_GNU_entry_value 0xf3
#endif
#define N_(x) x
location_context::location_context(target_symbol *ee, expression *pp)
: e_orig(ee), e(deep_copy_visitor::deep_copy(ee)), pointer(0), value(0),
attr(0), dwbias(0), pc(0), fb_attr(0), cfa_ops(0),
dw(0), frame_base(0)
{
// If this code snippet uses a precomputed pointer, create an
// parameter variable to hold it.
if (pp)
{
vardecl *v = new vardecl;
v->type = pe_long;
v->name = "pointer";
v->tok = ee->tok;
this->pointer = v;
}
// Any non-literal indexes need to have parameter variables too.
for (unsigned i = 0; i < ee->components.size(); ++i)
if (ee->components[i].type == target_symbol::comp_expression_array_index)
{
vardecl *v = new vardecl;
v->type = pe_long;
v->name = "index" + lex_cast(i);
v->tok = e->tok;
this->indicies.push_back(v);
// substitute the [$exprN]->indexN in the target_symbol* copy,
// which will be used for expansion to kderef() etc.
symbol *s = new symbol;
s->type = pe_long;
s->name = v->name;
s->tok = v->tok;
e->components[i].expr_index = s;
}
}
expression *
location_context::translate_address(Dwarf_Addr addr)
{
if (dw == NULL)
return new literal_number(addr);
int n = dwfl_module_relocations (dw->module);
Dwarf_Addr reloc_addr = addr;
const char *secname = "";
if (n > 1)
{
int i = dwfl_module_relocate_address (dw->module, &reloc_addr);
secname = dwfl_module_relocation_info (dw->module, i, NULL);
}
if (n > 0 && !(n == 1 && secname == NULL))
{
std::string c;
if (n > 1 || secname[0] != 0)
{
// This gives us the module name and section name within the
// module, for a kernel module.
c = "({ unsigned long addr = 0; "
"addr = _stp_kmodule_relocate (\""
+ dw->module_name + "\", \"" + secname + "\", "
+ lex_cast_hex (reloc_addr)
+ "); addr; })";
}
else if (n == 1 && dw->module_name == "kernel" && secname[0] == 0)
{
// elfutils way of telling us that this is a relocatable kernel
// address, which we need to treat the same way here as
// dwarf_query::add_probe_point does.
c = "({ unsigned long addr = 0; "
"addr = _stp_kmodule_relocate (\"kernel\", \"_stext\", "
+ lex_cast_hex (addr - dw->sess.sym_stext)
+ "); addr; })";
}
else
{
c = "/* pragma:vma */ "
"({ unsigned long addr = 0; "
"addr = _stp_umodule_relocate (\""
+ resolve_path(dw->module_name.c_str()) + "\", "
+ lex_cast_hex (addr)
+ ", current); addr; })";
}
embedded_expr *r = new embedded_expr;
r->tok = e->tok;
r->code = c;
return r;
}
else
return new literal_number(addr);
}
location *
location_context::translate_constant(Dwarf_Attribute *attr)
{
location *loc;
switch (dwarf_whatform (attr))
{
case DW_FORM_addr:
{
Dwarf_Addr addr;
if (dwarf_formaddr (attr, &addr) != 0)
throw SEMANTIC_ERROR(std::string("cannot get constant address: ")
+ dwarf_errmsg (-1));
loc = new_location(loc_value);
loc->program = translate_address(this->dwbias + addr);
}
break;
case DW_FORM_block:
case DW_FORM_block1:
case DW_FORM_block2:
case DW_FORM_block4:
{
Dwarf_Block block;
if (dwarf_formblock (attr, &block) != 0)
throw SEMANTIC_ERROR(std::string("cannot get constant block :")
+ dwarf_errmsg (-1));
loc = new_location(loc_constant);
loc->byte_size = block.length;
loc->constant_block = block.data;
}
break;
case DW_FORM_string:
case DW_FORM_strp:
{
const char *string = dwarf_formstring (attr);
if (string == NULL)
throw SEMANTIC_ERROR(std::string("cannot get constant string:")
+ dwarf_errmsg (-1));
loc = new_location(loc_constant);
loc->byte_size = strlen(string) + 1;
loc->constant_block = string;
}
break;
default:
{
Dwarf_Sword value;
if (dwarf_formsdata (attr, &value) != 0)
throw SEMANTIC_ERROR (std::string("cannot get constant value: ")
+ dwarf_errmsg (-1));
loc = new_location(loc_value);
loc->program = new literal_number(this->dwbias + value);
}
break;
}
return loc;
}
/* Die in the middle of an expression. */
static void __attribute__((noreturn))
lose (const Dwarf_Op *lexpr, size_t len, const char *failure, size_t i)
{
if (lexpr == NULL || i >= len)
throw SEMANTIC_ERROR(failure);
else
throw SEMANTIC_ERROR(std::string(failure)
+ " in DWARF expression ["
+ lex_cast(i)
+ "] at " + lex_cast(lexpr[i].offset)
+ " (" + lex_cast(lexpr[i].atom)
+ ": " + lex_cast(lexpr[i].number)
+ ", " + lex_cast(lexpr[i].number2) + ")");
}
location *
location_context::new_location(location_type t)
{
location *n = new location(t);
this->locations.push_back(n);
return n;
}
location *
location_context::new_location(const location &o)
{
location *n = new location(o);
this->locations.push_back(n);
return n;
}
symbol *
location_context::new_symref(vardecl *var)
{
symbol *sym = new symbol;
sym->name = var->name;
// sym->referent = var;
return sym;
}
symbol *
location_context::new_local(const char *namebase)
{
static int counter;
vardecl *var = new vardecl;
var->name = std::string(namebase) + lex_cast(counter++);
var->type = pe_long;
var->arity = 0;
var->synthetic = true;
this->locals.push_back(var);
return new_symref(var);
}
expression *
location_context::new_target_reg(unsigned int regno)
{
target_register *reg = new target_register;
reg->tok = e->tok;
reg->regno = regno;
reg->userspace_p = this->userspace_p;
return reg;
}
expression *
location_context::new_plus_const(expression *l, int64_t r)
{
if (r == 0)
return l;
binary_expression *val = new binary_expression;
val->tok = e->tok;
val->op = "+";
val->left = l;
val->right = new literal_number(r);
return val;
}
// If VAL is cheaply copied, return it.
// Otherwise compute the expression to a temp.
expression *
location_context::save_expression(expression *val)
{
if (dynamic_cast<literal_number *>(val) || dynamic_cast<symbol *>(val))
return val;
symbol *sym = new_local("_tmp_");
assignment *set = new assignment;
set->tok = e->tok;
set->op = "=";
set->left = sym;
set->right = val;
this->evals.push_back(set);
return sym;
}
/* Translate a (constrained) DWARF expression into STAP trees.
If NEED_FB is null, fail on DW_OP_fbreg, else set *NEED_FB to the
variable that should be initialized with frame_base. */
location *
location_context::translate (const Dwarf_Op *expr, const size_t len,
const size_t piece_expr_start,
location *input, bool may_use_fb,
bool computing_value_orig)
{
#define DIE(msg) lose(expr, len, N_(msg), i)
#define POP(VAR) if (stack.empty()) goto underflow; \
expression *VAR = stack.back(); \
stack.pop_back(); \
tos_register = false;
#define PUSH(VAL) stack.push_back(VAL); \
tos_register = false;
bool saw_stack_value = false;
bool tos_register = false;
bool computing_value = computing_value_orig;
Dwarf_Word piece_size = 0;
Dwarf_Block implicit_value = Dwarf_Block();
const Dwarf_Op *implicit_pointer = NULL;
location temp_piece;
size_t i;
{
std::vector<expression *> stack;
if (input != NULL)
switch (input->type)
{
case loc_value:
assert(computing_value);
/* FALLTHRU */
case loc_address:
PUSH(input->program);
break;
case loc_register:
assert(computing_value);
PUSH(new_target_reg(input->regno));
tos_register = true;
break;
default:
abort();
}
for (i = piece_expr_start; i < len; ++i)
{
unsigned int reg;
uint_fast8_t sp;
Dwarf_Word value;
if (expr[i].atom != DW_OP_nop
&& expr[i].atom != DW_OP_piece
&& expr[i].atom != DW_OP_bit_piece)
{
if (saw_stack_value)
DIE("operations follow DW_OP_stack_value");
if (implicit_value.data != NULL)
DIE ("operations follow DW_OP_implicit_value");
if (implicit_pointer != NULL)
DIE ("operations follow DW_OP_GNU_implicit_pointer");
}
switch (expr[i].atom)
{
/* Basic stack operations. */
case DW_OP_nop:
break;
case DW_OP_drop:
{
POP(unused);
(void)unused;
}
break;
case DW_OP_dup:
sp = 0;
goto op_pick;
break;
case DW_OP_over:
sp = 1;
goto op_pick;
case DW_OP_pick:
sp = expr[i].number;
op_pick:
{
size_t stack_size = stack.size();
if (sp >= stack_size)
goto underflow;
expression *val = stack[stack_size - 1 - sp];
PUSH(save_expression(val));
}
break;
case DW_OP_swap:
{
POP(a);
POP(b);
PUSH(a);
PUSH(b);
}
break;
case DW_OP_rot:
{
POP(a);
POP(b);
POP(c);
PUSH(a);
PUSH(c);
PUSH(b);
}
break;
/* Control flow operations. */
case DW_OP_skip:
{
Dwarf_Off target = expr[i].offset + 3 + expr[i].number;
while (i + 1 < len && expr[i + 1].offset < target)
++i;
if (expr[i + 1].offset != target)
DIE ("invalid skip target");
break;
}
case DW_OP_bra:
// ??? Could copy the stack, recurse, and place both
// traces in arms of a ternary_expression. No point
// in doing that if this is never used, however.
DIE ("conditional branches not supported");
break;
/* Memory access. */
case DW_OP_deref:
// ??? Target sizeof, not host sizeof.
sp = sizeof(void *);
goto op_deref;
case DW_OP_deref_size:
sp = expr[i].number;
op_deref:
{
POP(addr);
target_deref *val = new target_deref;
val->addr = addr;
val->size = sp;
val->userspace_p = this->userspace_p;
val->tok = e->tok;
PUSH(val);
}
break;
case DW_OP_xderef:
case DW_OP_xderef_size:
// not yet
// POP (addr);
// POP (as);
// push (xderef expr[i].number, (unsigned)addr, (unsigned)as);
DIE ("address spaces not supported");
/* Constant-value operations. */
case DW_OP_addr:
PUSH(translate_address(this->dwbias + expr[i].number));
break;
case DW_OP_lit0 ... DW_OP_lit31:
value = expr[i].atom - DW_OP_lit0;
goto op_const;
case DW_OP_const1u:
case DW_OP_const1s:
case DW_OP_const2u:
case DW_OP_const2s:
case DW_OP_const4u:
case DW_OP_const4s:
case DW_OP_const8u:
case DW_OP_const8s:
case DW_OP_constu:
case DW_OP_consts:
value = expr[i].number;
op_const:
{
literal_number *ln = new literal_number(value);
ln->tok = e->tok;
PUSH(ln);
}
break;
/* Arithmetic operations. */
#define UNOP(dw_op, stap_op) \
case DW_OP_##dw_op: \
{ \
POP(arg); \
unary_expression *val = new unary_expression; \
val->tok = e->tok; \
val->op = #stap_op; \
val->operand = arg; \
PUSH(val); \
} \
break
UNOP (neg, -);
UNOP (not, ~);
#undef UNOP
#define BINOP(dw_op, type, stap_op) \
case DW_OP_##dw_op: \
{ \
POP(b); \
POP(a); \
type *val = new type; \
val->op = #stap_op; \
val->left = a; \
val->right = b; \
val->tok = e->tok; \
PUSH(val); \
} \
break
BINOP (and, binary_expression, &);
BINOP (minus, binary_expression, -);
BINOP (mul, binary_expression, *);
BINOP (or, binary_expression, |);
BINOP (plus, binary_expression, +);
BINOP (shl, binary_expression, <<);
BINOP (shr, binary_expression, >>>);
BINOP (shra, binary_expression, >>);
BINOP (xor, binary_expression, ^);
BINOP (div, binary_expression, /);
BINOP (mod, binary_expression, %);
/* Comparisons are binary operators too. */
BINOP (le, comparison, <=);
BINOP (ge, comparison, >=);
BINOP (eq, comparison, ==);
BINOP (lt, comparison, <);
BINOP (gt, comparison, >);
BINOP (ne, comparison, !=);
#undef BINOP
case DW_OP_abs:
{
// Form (arg < 0 ? -arg : arg).
POP(arg);
comparison *cmp = new comparison;
cmp->op = "<";
cmp->left = arg;
cmp->right = new literal_number(0);
unary_expression *neg = new unary_expression;
neg->op = "-";
neg->operand = arg;
ternary_expression *val = new ternary_expression;
val->cond = cmp;
val->truevalue = neg;
val->falsevalue = arg;
PUSH(val);
}
break;
case DW_OP_plus_uconst:
{
POP(arg);
PUSH(new_plus_const(arg, expr[i].number));
}
break;
/* Register-relative addressing. */
case DW_OP_breg0 ... DW_OP_breg31:
reg = expr[i].atom - DW_OP_breg0;
value = expr[i].number;
goto op_breg;
case DW_OP_bregx:
reg = expr[i].number;
value = expr[i].number2;
op_breg:
PUSH(new_plus_const(new_target_reg(reg), value));
break;
case DW_OP_fbreg:
if (!may_use_fb)
DIE ("DW_OP_fbreg from DW_AT_frame_base");
PUSH(new_plus_const(frame_location(), expr[i].number));
break;
/* Direct register contents. */
case DW_OP_reg0 ... DW_OP_reg31:
reg = expr[i].atom - DW_OP_reg0;
goto op_reg;
case DW_OP_regx:
reg = expr[i].number;
op_reg:
PUSH(new_target_reg(reg));
tos_register = true;
break;
/* Special magic. */
case DW_OP_piece:
if (stack.size() > 1)
// If this ever happens we could copy the program.
DIE ("DW_OP_piece left multiple values on stack");
piece_size = expr[i].number;
goto end_piece;
case DW_OP_stack_value:
if (stack.empty())
goto underflow;
if (stack.size() > 1)
DIE ("DW_OP_stack_value left multiple values on stack");
saw_stack_value = true;
computing_value = true;
break;
case DW_OP_implicit_value:
if (this->attr == NULL)
DIE ("DW_OP_implicit_value used in invalid context"
" (no DWARF attribute, ABI return value location?)");
/* It's supposed to appear by itself, except for DW_OP_piece. */
if (!stack.empty())
DIE ("DW_OP_implicit_value follows stack operations");
#if _ELFUTILS_PREREQ (0, 143)
if (dwarf_getlocation_implicit_value (this->attr,
(Dwarf_Op *) &expr[i],
&implicit_value) != 0)
DIE ("dwarf_getlocation_implicit_value failed");
/* Fake top of stack: implicit_value being set marks it. */
PUSH(NULL);
break;
#else
DIE ("DW_OP_implicit_value not supported");
break;
#endif
#if _ELFUTILS_PREREQ (0, 149)
case DW_OP_GNU_implicit_pointer:
implicit_pointer = &expr[i];
/* Fake top of stack: implicit_pointer being set marks it. */
PUSH(NULL);
break;
#endif
case DW_OP_call_frame_cfa:
// We pick this out when processing DW_AT_frame_base in
// so it really shouldn't turn up here.
if (!may_use_fb)
DIE ("DW_OP_call_frame_cfa while processing frame base");
// This is slightly weird/inefficient, but golang is known
// to produce DW_OP_call_frame_cfa; DW_OP_consts: 8; DW_OP_plus
// instead of a simple DW_OP_fbreg 8.
PUSH(frame_location());
break;
case DW_OP_push_object_address:
DIE ("unhandled DW_OP_push_object_address");
break;
case DW_OP_GNU_entry_value:
DIE ("unhandled DW_OP_GNU_entry_value");
break;
default:
DIE ("unhandled DW_OP operation");
break;
}
}
end_piece:
// Finish recognizing exceptions before allocating memory.
if (i == piece_expr_start)
{
assert(stack.empty());
assert(!tos_register);
temp_piece.type = loc_unavailable;
}
else if (stack.empty())
goto underflow;
else if (implicit_pointer != NULL)
{
temp_piece.type = loc_implicit_pointer;
temp_piece.offset = implicit_pointer->number2;
#if !_ELFUTILS_PREREQ (0, 149)
/* Then how did we get here? */
abort ();
#else
Dwarf_Attribute target;
if (dwarf_getlocation_implicit_pointer (this->attr, implicit_pointer,
&target) != 0)
DIE ("invalid implicit pointer");
switch (dwarf_whatattr (&target))
{
case DW_AT_const_value:
temp_piece.target = translate_constant(&target);
break;
case DW_AT_location:
{
Dwarf_Op *expr;
size_t len;
switch (dwarf_getlocation_addr(&target, pc, &expr, &len, 1))
{
case 1: /* Should always happen */
if (len > 0)
break;
/* fallthru */
case 0: /* Should never happen */
throw SEMANTIC_ERROR("not accessible at this address: "
+ lex_cast(pc));
default: /* Should never happen */
throw SEMANTIC_ERROR(std::string("dwarf_getlocation_addr: ")
+ dwarf_errmsg(-1));
}
temp_piece.target = location_from_address(expr, len, NULL);
}
break;
default:
DIE ("unexpected implicit pointer attribute!");
}
#endif
}
else if (implicit_value.data != NULL)
{
temp_piece.type = loc_constant;
temp_piece.byte_size = implicit_value.length;
temp_piece.constant_block = implicit_value.data;
}
else
{
expression *val = stack.back();
if (computing_value || tos_register)
{
if (target_register *reg = dynamic_cast<target_register *>(val))
{
temp_piece.type = loc_register;
temp_piece.regno = reg->regno;
}
else
temp_piece.type = loc_value;
}
else
temp_piece.type = loc_address;
temp_piece.program = val;
}
// stack goes out of scope here
}
if (piece_size != 0)
{
temp_piece.byte_size = piece_size;
temp_piece.piece_next = translate(expr, len, i + 1, input, may_use_fb,
computing_value_orig);
// For the first DW_OP_piece, create the loc_noncontiguous container.
// For subsequent pieces, fall through for normal location return.
if (piece_expr_start == 0)
{
location *pieces = new_location(temp_piece);
location *loc = new_location(loc_noncontiguous);
loc->pieces = pieces;
size_t total_size = 0;
for (location *p = pieces; p != NULL; p = p->piece_next)
total_size += p->byte_size;
loc->byte_size = total_size;
return loc;
}
}
else if (piece_expr_start && piece_expr_start != i)
DIE ("extra operations after last DW_OP_piece");
return new_location(temp_piece);
underflow:
DIE ("stack underflow");
#undef DIE
#undef PUSH
#undef POP
}
symbol *
location_context::frame_location()
{
if (this->frame_base == NULL)
{
// The main expression uses DW_OP_fbreg, so we need to compute
// the DW_AT_frame_base attribute expression's value first.
const Dwarf_Op *fb_ops;
Dwarf_Op *fb_expr;
size_t fb_len;
if (this->fb_attr == NULL)
{
// Lets just assume we want DW_OP_call_frame_cfa.
// Some (buggy golang) DWARF producers use that directly in
// location descriptions. And at least we should have a chance
// to get an actual call frame address that way.
goto use_cfa_ops;
}
else
{
switch (dwarf_getlocation_addr (this->fb_attr, this->pc,
&fb_expr, &fb_len, 1))
{
case 1: /* Should always happen. */
if (fb_len != 0)
break;
/* fallthru */
case 0: /* Shouldn't happen. */
throw SEMANTIC_ERROR("DW_AT_frame_base not accessible "
"at this address");
default: /* Shouldn't happen. */
case -1:
throw SEMANTIC_ERROR
("dwarf_getlocation_addr (form "
+ lex_cast(dwarf_whatform (this->fb_attr))
+ "): " + dwarf_errmsg (-1));
}
}
// If it is DW_OP_call_frame_cfa then get cfi cfa ops.
if (fb_len == 1 && fb_expr[0].atom == DW_OP_call_frame_cfa)
{
use_cfa_ops:
if (this->cfa_ops == NULL)
throw SEMANTIC_ERROR("No cfa_ops supplied, "
"but needed by DW_OP_call_frame_cfa");
fb_ops = this->cfa_ops;
}
else
fb_ops = fb_expr;
location *fb_loc = translate (fb_ops, fb_len, 0, NULL, false, false);
assert(fb_loc->type == loc_address);
this->frame_base = new_local("_fb_");
assignment *set = new assignment;
set->op = "=";
set->left = this->frame_base;
set->right = fb_loc->program;
this->evals.push_back(set);
}
return this->frame_base;
}
/* Translate a location starting from an address or nothing. */
location *
location_context::location_from_address (const Dwarf_Op *expr, size_t len,
struct location *input)
{
return translate (expr, len, 0, input, true, false);
}
location *
location_context::translate_offset (const Dwarf_Op *expr, size_t len,
size_t i, location *input,
Dwarf_Word offset)
{
#define DIE(msg) lose (expr, len, N_(msg), i)
while (input->type == loc_noncontiguous)
{
/* We are starting from a noncontiguous object (DW_OP_piece).
Find the piece we want. */
struct location *piece = input->pieces;
while (piece != NULL && offset >= piece->byte_size)
{
offset -= piece->byte_size;
piece = piece->piece_next;
}
if (piece == NULL)
DIE ("offset outside available pieces");
input = piece;
}
location *loc = new_location(*input);
switch (loc->type)
{
case loc_address:
/* The piece we want is actually in memory. Use the same
program to compute the address from the preceding input. */
loc->program = new_plus_const(loc->program, offset);
break;
case loc_register:
case loc_implicit_pointer:
loc->offset += offset;
break;
case loc_constant:
/* This piece has a constant offset. */
if (offset >= loc->byte_size)
DIE ("offset outside available constant block");
loc->constant_block = (void *)((char *)loc->constant_block + offset);
loc->byte_size -= offset;
break;
case loc_unavailable:
/* Let it be diagnosed later. */
break;
case loc_value:
/* The piece we want is part of a computed offset.
If it's the whole thing, we are done. */
if (offset == 0)
break;
DIE ("extract partial rematerialized value");
default:
abort ();
}
return loc;
#undef DIE
}
/* Translate a location starting from a non-address "on the top of the
stack". The *INPUT location is a register name or noncontiguous
object specification, and this expression wants to find the "address"
of an object (or the actual value) relative to that "address". */
location *
location_context::location_relative (const Dwarf_Op *expr, size_t len,
location *input)
{
#define DIE(msg) lose(expr, len, N_(msg), i)
#define POP(VAR) if (stack.empty()) \
goto underflow; \
Dwarf_Sword VAR = stack.back(); \
stack.pop_back()
#define PUSH(VAL) stack.push_back(VAL)
std::vector<Dwarf_Sword> stack;
size_t i;
for (i = 0; i < len; ++i)
{
uint_fast8_t sp;
Dwarf_Word value;
switch (expr[i].atom)
{
/* Basic stack operations. */
case DW_OP_nop:
break;
case DW_OP_drop:
if (stack.empty())
{
if (input == NULL)
goto underflow;
/* Mark that we have consumed the input. */
input = NULL;
}
else
stack.pop_back();
break;
case DW_OP_dup:
sp = 0;
goto op_pick;
case DW_OP_over:
sp = 1;
goto op_pick;
case DW_OP_pick:
sp = expr[i].number;
op_pick:
{
size_t stack_size = stack.size();
if (sp < stack_size)
PUSH(stack[stack_size - 1 - sp]);
else if (sp == stack_size)
goto underflow;
else
goto real_underflow;
}
break;
case DW_OP_swap:
{
POP(a);