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/* Helper class for handling a call with specific arguments.
Copyright (C) 2020-2024 Free Software Foundation, Inc.
Contributed by David Malcolm <dmalcolm@redhat.com>.
This file is part of GCC.
GCC 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, or (at your option)
any later version.
GCC 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 GCC; see the file COPYING3. If not see
<http://www.gnu.org/licenses/>. */
#include "config.h"
#define INCLUDE_MEMORY
#define INCLUDE_VECTOR
#include "system.h"
#include "coretypes.h"
#include "tree.h"
#include "function.h"
#include "basic-block.h"
#include "gimple.h"
#include "diagnostic-core.h"
#include "analyzer/analyzer.h"
#include "analyzer/analyzer-logging.h"
#include "diagnostic.h"
#include "tree-diagnostic.h" /* for default_tree_printer. */
#include "gimple-pretty-print.h"
#include "analyzer/region-model.h"
#include "analyzer/call-details.h"
#include "analyzer/ranges.h"
#include "stringpool.h"
#include "attribs.h"
#include "make-unique.h"
#include "diagnostic-format-sarif.h"
#if ENABLE_ANALYZER
namespace ana {
/* class call_details. */
/* call_details's ctor. */
call_details::call_details (const gcall *call, region_model *model,
region_model_context *ctxt)
: m_call (call), m_model (model), m_ctxt (ctxt),
m_lhs_type (NULL_TREE), m_lhs_region (NULL)
{
m_lhs_type = NULL_TREE;
if (tree lhs = gimple_call_lhs (call))
{
m_lhs_region = model->get_lvalue (lhs, ctxt);
m_lhs_type = TREE_TYPE (lhs);
}
}
/* call_details's ctor: copy CD, but override the context,
using CTXT instead. */
call_details::call_details (const call_details &cd,
region_model_context *ctxt)
{
*this = cd;
m_ctxt = ctxt;
}
/* Get the manager from m_model. */
region_model_manager *
call_details::get_manager () const
{
return m_model->get_manager ();
}
/* Get any logger associated with this object. */
logger *
call_details::get_logger () const
{
if (m_ctxt)
return m_ctxt->get_logger ();
else
return NULL;
}
/* Get any uncertainty_t associated with the region_model_context. */
uncertainty_t *
call_details::get_uncertainty () const
{
if (m_ctxt)
return m_ctxt->get_uncertainty ();
else
return NULL;
}
/* If the callsite has a left-hand-side region, set it to RESULT
and return true.
Otherwise do nothing and return false. */
bool
call_details::maybe_set_lhs (const svalue *result) const
{
gcc_assert (result);
if (m_lhs_region)
{
m_model->set_value (m_lhs_region, result, m_ctxt);
return true;
}
else
return false;
}
/* Return true if CD is known to be a call to a function with
__attribute__((const)). */
static bool
const_fn_p (const call_details &cd)
{
tree fndecl = cd.get_fndecl_for_call ();
if (!fndecl)
return false;
gcc_assert (DECL_P (fndecl));
return TREE_READONLY (fndecl);
}
/* If this CD is known to be a call to a function with
__attribute__((const)), attempt to get a const_fn_result_svalue
based on the arguments, or return NULL otherwise. */
static const svalue *
maybe_get_const_fn_result (const call_details &cd)
{
if (!const_fn_p (cd))
return NULL;
unsigned num_args = cd.num_args ();
if (num_args > const_fn_result_svalue::MAX_INPUTS)
/* Too many arguments. */
return NULL;
auto_vec<const svalue *> inputs (num_args);
for (unsigned arg_idx = 0; arg_idx < num_args; arg_idx++)
{
const svalue *arg_sval = cd.get_arg_svalue (arg_idx);
if (!arg_sval->can_have_associated_state_p ())
return NULL;
inputs.quick_push (arg_sval);
}
region_model_manager *mgr = cd.get_manager ();
const svalue *sval
= mgr->get_or_create_const_fn_result_svalue (cd.get_lhs_type (),
cd.get_fndecl_for_call (),
inputs);
return sval;
}
/* Look for attribute "alloc_size" on the called function and, if found,
return a symbolic value of type size_type_node for the allocation size
based on the call's parameters.
Otherwise, return null. */
static const svalue *
get_result_size_in_bytes (const call_details &cd)
{
const tree attr = cd.lookup_function_attribute ("alloc_size");
if (!attr)
return nullptr;
const tree atval_1 = TREE_VALUE (attr);
if (!atval_1)
return nullptr;
unsigned argidx1 = TREE_INT_CST_LOW (TREE_VALUE (atval_1)) - 1;
if (cd.num_args () <= argidx1)
return nullptr;
const svalue *sval_arg1 = cd.get_arg_svalue (argidx1);
if (const tree atval_2 = TREE_CHAIN (atval_1))
{
/* Two arguments. */
unsigned argidx2 = TREE_INT_CST_LOW (TREE_VALUE (atval_2)) - 1;
if (cd.num_args () <= argidx2)
return nullptr;
const svalue *sval_arg2 = cd.get_arg_svalue (argidx2);
/* TODO: ideally we shouldn't need this cast here;
see PR analyzer/110902. */
return cd.get_manager ()->get_or_create_cast
(size_type_node,
cd.get_manager ()->get_or_create_binop (size_type_node,
MULT_EXPR,
sval_arg1, sval_arg2));
}
else
/* Single argument. */
return cd.get_manager ()->get_or_create_cast (size_type_node, sval_arg1);
}
/* If this call has an LHS, assign a value to it based on attributes
of the function:
- if __attribute__((const)), use a const_fn_result_svalue,
- if __attribute__((malloc)), use a heap-allocated region with
unknown content
- otherwise, use a conjured_svalue.
If __attribute__((alloc_size), set the dynamic extents on the region
pointed to. */
void
call_details::set_any_lhs_with_defaults () const
{
if (!m_lhs_region)
return;
const svalue *sval = maybe_get_const_fn_result (*this);
if (!sval)
{
region_model_manager *mgr = get_manager ();
if (lookup_function_attribute ("malloc"))
{
const region *new_reg
= m_model->get_or_create_region_for_heap_alloc (NULL, m_ctxt);
m_model->mark_region_as_unknown (new_reg, NULL);
sval = mgr->get_ptr_svalue (get_lhs_type (), new_reg);
}
else
/* For the common case of functions without __attribute__((const)),
use a conjured value, and purge any prior state involving that
value (in case this is in a loop). */
sval = get_or_create_conjured_svalue (m_lhs_region);
if (const svalue *size_in_bytes = get_result_size_in_bytes (*this))
{
const region *reg
= m_model->deref_rvalue (sval, NULL_TREE, m_ctxt, false);
m_model->set_dynamic_extents (reg, size_in_bytes, m_ctxt);
}
}
maybe_set_lhs (sval);
}
/* Return the number of arguments used by the call statement. */
unsigned
call_details::num_args () const
{
return gimple_call_num_args (m_call);
}
/* Return true if argument IDX is a size_t (or compatible with it). */
bool
call_details::arg_is_size_p (unsigned idx) const
{
return types_compatible_p (get_arg_type (idx), size_type_node);
}
/* Get the location of the call statement. */
location_t
call_details::get_location () const
{
return m_call->location;
}
/* Get argument IDX at the callsite as a tree. */
tree
call_details::get_arg_tree (unsigned idx) const
{
return gimple_call_arg (m_call, idx);
}
/* Get the type of argument IDX. */
tree
call_details::get_arg_type (unsigned idx) const
{
return TREE_TYPE (gimple_call_arg (m_call, idx));
}
/* Get argument IDX at the callsite as an svalue. */
const svalue *
call_details::get_arg_svalue (unsigned idx) const
{
tree arg = get_arg_tree (idx);
return m_model->get_rvalue (arg, m_ctxt);
}
/* If argument IDX's svalue at the callsite is of pointer type,
return the region it points to.
Otherwise return NULL. */
const region *
call_details::deref_ptr_arg (unsigned idx) const
{
const svalue *ptr_sval = get_arg_svalue (idx);
return m_model->deref_rvalue (ptr_sval, get_arg_tree (idx), m_ctxt);
}
/* Attempt to get the string literal for argument IDX, or return NULL
otherwise.
For use when implementing "__analyzer_*" functions that take
string literals. */
const char *
call_details::get_arg_string_literal (unsigned idx) const
{
const svalue *str_arg = get_arg_svalue (idx);
if (const region *pointee = str_arg->maybe_get_region ())
if (const string_region *string_reg = pointee->dyn_cast_string_region ())
{
tree string_cst = string_reg->get_string_cst ();
return TREE_STRING_POINTER (string_cst);
}
return NULL;
}
/* Attempt to get the fndecl used at this call, if known, or NULL_TREE
otherwise. */
tree
call_details::get_fndecl_for_call () const
{
return m_model->get_fndecl_for_call (m_call, m_ctxt);
}
/* Dump a multiline representation of this call to PP. */
void
call_details::dump_to_pp (pretty_printer *pp, bool simple) const
{
pp_string (pp, "gcall: ");
pp_gimple_stmt_1 (pp, m_call, 0 /* spc */, TDF_NONE /* flags */);
pp_newline (pp);
pp_string (pp, "return region: ");
if (m_lhs_region)
m_lhs_region->dump_to_pp (pp, simple);
else
pp_string (pp, "NULL");
pp_newline (pp);
for (unsigned i = 0; i < gimple_call_num_args (m_call); i++)
{
const svalue *arg_sval = get_arg_svalue (i);
pp_printf (pp, "arg %i: ", i);
arg_sval->dump_to_pp (pp, simple);
pp_newline (pp);
}
}
/* Dump a multiline representation of this call to stderr. */
DEBUG_FUNCTION void
call_details::dump (bool simple) const
{
pretty_printer pp;
pp_format_decoder (&pp) = default_tree_printer;
pp_show_color (&pp) = pp_show_color (global_dc->printer);
pp.buffer->stream = stderr;
dump_to_pp (&pp, simple);
pp_flush (&pp);
}
/* Get a conjured_svalue for this call for REG,
and purge any state already relating to that conjured_svalue. */
const svalue *
call_details::get_or_create_conjured_svalue (const region *reg) const
{
region_model_manager *mgr = m_model->get_manager ();
return mgr->get_or_create_conjured_svalue (reg->get_type (), m_call, reg,
conjured_purge (m_model, m_ctxt));
}
/* Look for a function attribute with name ATTR_NAME on the called
function (or on its type).
Return the attribute if one is found, otherwise return NULL_TREE. */
tree
call_details::lookup_function_attribute (const char *attr_name) const
{
tree allocfntype;
if (tree fndecl = get_fndecl_for_call ())
allocfntype = TREE_TYPE (fndecl);
else
allocfntype = gimple_call_fntype (m_call);
if (!allocfntype)
return NULL_TREE;
return lookup_attribute (attr_name, TYPE_ATTRIBUTES (allocfntype));
}
void
call_details::check_for_null_terminated_string_arg (unsigned arg_idx) const
{
check_for_null_terminated_string_arg (arg_idx, false, nullptr);
}
const svalue *
call_details::
check_for_null_terminated_string_arg (unsigned arg_idx,
bool include_terminator,
const svalue **out_sval) const
{
region_model *model = get_model ();
return model->check_for_null_terminated_string_arg (*this,
arg_idx,
include_terminator,
out_sval);
}
/* A subclass of pending_diagnostic for complaining about overlapping
buffers. */
class overlapping_buffers
: public pending_diagnostic_subclass<overlapping_buffers>
{
public:
overlapping_buffers (tree fndecl,
const symbolic_byte_range &byte_range_a,
const symbolic_byte_range &byte_range_b,
const svalue *num_bytes_read_sval)
: m_fndecl (fndecl),
m_byte_range_a (byte_range_a),
m_byte_range_b (byte_range_b),
m_num_bytes_read_sval (num_bytes_read_sval)
{
}
const char *get_kind () const final override
{
return "overlapping_buffers";
}
bool operator== (const overlapping_buffers &other) const
{
return m_fndecl == other.m_fndecl;
}
int get_controlling_option () const final override
{
return OPT_Wanalyzer_overlapping_buffers;
}
bool emit (diagnostic_emission_context &ctxt) final override
{
auto_diagnostic_group d;
bool warned = ctxt.warn ("overlapping buffers passed as arguments to %qD",
m_fndecl);
// TODO: draw a picture?
if (warned)
inform (DECL_SOURCE_LOCATION (m_fndecl),
"the behavior of %qD is undefined for overlapping buffers",
m_fndecl);
return warned;
}
label_text describe_final_event (const evdesc::final_event &ev) final override
{
return ev.formatted_print
("overlapping buffers passed as arguments to %qD",
m_fndecl);
}
void maybe_add_sarif_properties (sarif_object &result_obj)
const final override
{
sarif_property_bag &props = result_obj.get_or_create_properties ();
#define PROPERTY_PREFIX "gcc/analyzer/overlapping_buffers/"
props.set (PROPERTY_PREFIX "bytes_range_a",
m_byte_range_a.to_json ());
props.set (PROPERTY_PREFIX "bytes_range_b",
m_byte_range_b.to_json ());
props.set (PROPERTY_PREFIX "num_bytes_read_sval",
m_num_bytes_read_sval->to_json ());
#undef PROPERTY_PREFIX
}
private:
tree m_fndecl;
symbolic_byte_range m_byte_range_a;
symbolic_byte_range m_byte_range_b;
const svalue *m_num_bytes_read_sval;
};
/* Check if the buffers pointed to by arguments ARG_IDX_A and ARG_IDX_B
(zero-based) overlap, when considering them both to be of size
NUM_BYTES_READ_SVAL.
If they do overlap, complain to the context. */
void
call_details::complain_about_overlap (unsigned arg_idx_a,
unsigned arg_idx_b,
const svalue *num_bytes_read_sval) const
{
region_model_context *ctxt = get_ctxt ();
if (!ctxt)
return;
region_model *model = get_model ();
region_model_manager *mgr = model->get_manager ();
const svalue *arg_a_ptr_sval = get_arg_svalue (arg_idx_a);
if (arg_a_ptr_sval->get_kind () == SK_UNKNOWN)
return;
const region *arg_a_reg = model->deref_rvalue (arg_a_ptr_sval,
get_arg_tree (arg_idx_a),
ctxt);
const svalue *arg_b_ptr_sval = get_arg_svalue (arg_idx_b);
if (arg_b_ptr_sval->get_kind () == SK_UNKNOWN)
return;
const region *arg_b_reg = model->deref_rvalue (arg_b_ptr_sval,
get_arg_tree (arg_idx_b),
ctxt);
if (arg_a_reg->get_base_region () != arg_b_reg->get_base_region ())
return;
/* Are they within NUM_BYTES_READ_SVAL of each other? */
symbolic_byte_range byte_range_a (arg_a_reg->get_offset (mgr),
num_bytes_read_sval,
*mgr);
symbolic_byte_range byte_range_b (arg_b_reg->get_offset (mgr),
num_bytes_read_sval,
*mgr);
if (!byte_range_a.intersection (byte_range_b, *model).is_true ())
return;
ctxt->warn (make_unique<overlapping_buffers> (get_fndecl_for_call (),
byte_range_a,
byte_range_b,
num_bytes_read_sval));
}
} // namespace ana
#endif /* #if ENABLE_ANALYZER */
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