/* Copyright (c) 2016, 2022, Oracle and/or its affiliates.

This program is free software; you can redistribute it and/or modify

it under the terms of the GNU General Public License, version 2.0,

as published by the Free Software Foundation.

This program is also distributed with certain software (including

but not limited to OpenSSL) that is licensed under separate terms,

as designated in a particular file or component or in included license

documentation. The authors of MySQL hereby grant you an additional

permission to link the program and your derivative works with the

separately licensed software that they have included with MySQL.

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, version 2.0, 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., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */

#include "sql/check_stack.h"

#include "my_config.h"

#include <stdio.h>

#include <algorithm>

#include <atomic>

#include <new>

#include "my_compiler.h"

#include "my_dbug.h"

#include "my_inttypes.h"

#include "my_sys.h"

#include "mysql_com.h"

#include "mysqld_error.h"

#include "sql/current_thd.h"

#include "sql/derror.h"

#include "sql/sql_class.h"

/****************************************************************************

Check stack size; Send error if there isn't enough stack to continue

****************************************************************************/

#if STACK_DIRECTION < 0

#define used_stack(A, B) (long)(A - B)

#else

#define used_stack(A, B) (long)(B - A)

#endif

#ifndef NDEBUG

std::atomic<long> max_stack_used;

#endif

/**

Check stack for a overrun

@param thd Thread handler.

@param margin Minimal acceptable unused space in the stack.

@param buf See a note below.

@returns false if success, true if error (reported).

@note

Note: The 'buf' parameter is necessary, and we must have code which uses it.

- Some of the fix_fields functions have a "dummy" buffer large enough for the

corresponding execution. (Thus we only have to check in fix_fields.)

- Passing the buffer to check_stack_overrun() prevents the compiler from

removing it.

- For -flto builds, the dummy buffer may be optimized away,

so we need to write something into it.

*/

bool check_stack_overrun(const THD *thd, long margin, unsigned char *buf) {

assert(thd == current_thd);

long stack_used =

used_stack(thd->thread_stack, reinterpret_cast<char *>(&stack_used));

if (stack_used >= static_cast<long>(my_thread_stack_size - margin) ||

DBUG_EVALUATE_IF("simulate_stack_overrun", true, false)) {

// Touch the buffer, so that it is not optimized away by -flto.

if (buf != nullptr) buf[0] = '\0';

/*

Do not use stack for the message buffer to ensure correct

behaviour in cases we have close to no stack left.

*/

char *ebuff = new (std::nothrow) char[MYSQL_ERRMSG_SIZE];

if (ebuff) {

snprintf(ebuff, MYSQL_ERRMSG_SIZE,

ER_THD(thd, ER_STACK_OVERRUN_NEED_MORE), stack_used,

my_thread_stack_size, margin);

my_message(ER_STACK_OVERRUN_NEED_MORE, ebuff, MYF(ME_FATALERROR));

delete[] ebuff;

}

return true;

}

#ifndef NDEBUG

max_stack_used = std::max(max_stack_used.load(), stack_used);

#endif

return false;

}