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BCMath: Avoid using the heap for temporary objects by using arena allocations #14170

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Merged
merged 3 commits into from
May 8, 2024
Merged

BCMath: Avoid using the heap for temporary objects by using arena allocations #14170

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f465955
BCMath: Avoid using the heap for temporary objects by using arena all…
nielsdos May 7, 2024
6736982
Fix alignment
nielsdos May 7, 2024
00ebf24
Improve size computation
nielsdos May 7, 2024
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47 changes: 47 additions & 0 deletions ext/bcmath/bcmath.c
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Original file line number Diff line number Diff line change
Expand Up @@ -29,6 +29,16 @@
#include "php_bcmath.h"
#include "libbcmath/src/bcmath.h"

/* Always pair SETUP with TEARDOWN, and do so in the outer scope!
* Should not be used when data can escape the function. */
#define BC_ARENA_SETUP \
char bc_arena[BC_ARENA_SIZE]; \
BCG(arena) = bc_arena;

#define BC_ARENA_TEARDOWN \
BCG(arena) = NULL; \
BCG(arena_offset) = 0;

ZEND_DECLARE_MODULE_GLOBALS(bcmath)
static PHP_GINIT_FUNCTION(bcmath);
static PHP_GSHUTDOWN_FUNCTION(bcmath);
Expand Down Expand Up @@ -89,6 +99,8 @@ static PHP_GINIT_FUNCTION(bcmath)
ZEND_TSRMLS_CACHE_UPDATE();
#endif
bcmath_globals->bc_precision = 0;
bcmath_globals->arena = NULL;
bcmath_globals->arena_offset = 0;
bc_init_numbers();
}
/* }}} */
Expand All @@ -99,6 +111,8 @@ static PHP_GSHUTDOWN_FUNCTION(bcmath)
_bc_free_num_ex(&bcmath_globals->_zero_, 1);
_bc_free_num_ex(&bcmath_globals->_one_, 1);
_bc_free_num_ex(&bcmath_globals->_two_, 1);
bcmath_globals->arena = NULL;
bcmath_globals->arena_offset = 0;
}
/* }}} */

Expand Down Expand Up @@ -167,6 +181,8 @@ PHP_FUNCTION(bcadd)
scale = (int) scale_param;
}

BC_ARENA_SETUP;

if (php_str2num(&first, left) == FAILURE) {
zend_argument_value_error(1, "is not well-formed");
goto cleanup;
Expand All @@ -185,6 +201,7 @@ PHP_FUNCTION(bcadd)
bc_free_num(&first);
bc_free_num(&second);
bc_free_num(&result);
BC_ARENA_TEARDOWN;
};
}
/* }}} */
Expand Down Expand Up @@ -214,6 +231,8 @@ PHP_FUNCTION(bcsub)
scale = (int) scale_param;
}

BC_ARENA_SETUP;

if (php_str2num(&first, left) == FAILURE) {
zend_argument_value_error(1, "is not well-formed");
goto cleanup;
Expand All @@ -232,6 +251,7 @@ PHP_FUNCTION(bcsub)
bc_free_num(&first);
bc_free_num(&second);
bc_free_num(&result);
BC_ARENA_TEARDOWN;
};
}
/* }}} */
Expand Down Expand Up @@ -261,6 +281,8 @@ PHP_FUNCTION(bcmul)
scale = (int) scale_param;
}

BC_ARENA_SETUP;

if (php_str2num(&first, left) == FAILURE) {
zend_argument_value_error(1, "is not well-formed");
goto cleanup;
Expand All @@ -279,6 +301,7 @@ PHP_FUNCTION(bcmul)
bc_free_num(&first);
bc_free_num(&second);
bc_free_num(&result);
BC_ARENA_TEARDOWN;
};
}
/* }}} */
Expand Down Expand Up @@ -308,6 +331,8 @@ PHP_FUNCTION(bcdiv)
scale = (int) scale_param;
}

BC_ARENA_SETUP;

bc_init_num(&result);

if (php_str2num(&first, left) == FAILURE) {
Expand All @@ -331,6 +356,7 @@ PHP_FUNCTION(bcdiv)
bc_free_num(&first);
bc_free_num(&second);
bc_free_num(&result);
BC_ARENA_TEARDOWN;
};
}
/* }}} */
Expand Down Expand Up @@ -360,6 +386,8 @@ PHP_FUNCTION(bcmod)
scale = (int) scale_param;
}

BC_ARENA_SETUP;

bc_init_num(&result);

if (php_str2num(&first, left) == FAILURE) {
Expand All @@ -383,6 +411,7 @@ PHP_FUNCTION(bcmod)
bc_free_num(&first);
bc_free_num(&second);
bc_free_num(&result);
BC_ARENA_TEARDOWN;
};
}
/* }}} */
Expand Down Expand Up @@ -413,6 +442,8 @@ PHP_FUNCTION(bcpowmod)
scale = (int) scale_param;
}

BC_ARENA_SETUP;

bc_init_num(&result);

if (php_str2num(&bc_base, base_str) == FAILURE) {
Expand Down Expand Up @@ -458,6 +489,7 @@ PHP_FUNCTION(bcpowmod)
bc_free_num(&bc_expo);
bc_free_num(&bc_modulus);
bc_free_num(&result);
BC_ARENA_TEARDOWN;
};
}
/* }}} */
Expand Down Expand Up @@ -487,6 +519,8 @@ PHP_FUNCTION(bcpow)
scale = (int) scale_param;
}

BC_ARENA_SETUP;

bc_init_num(&result);

if (php_str2num(&first, base_str) == FAILURE) {
Expand Down Expand Up @@ -518,6 +552,7 @@ PHP_FUNCTION(bcpow)
bc_free_num(&first);
bc_free_num(&bc_exponent);
bc_free_num(&result);
BC_ARENA_TEARDOWN;
};
}
/* }}} */
Expand Down Expand Up @@ -546,6 +581,8 @@ PHP_FUNCTION(bcsqrt)
scale = (int) scale_param;
}

BC_ARENA_SETUP;

if (php_str2num(&result, left) == FAILURE) {
zend_argument_value_error(1, "is not well-formed");
goto cleanup;
Expand All @@ -559,6 +596,7 @@ PHP_FUNCTION(bcsqrt)

cleanup: {
bc_free_num(&result);
BC_ARENA_TEARDOWN;
};
}
/* }}} */
Expand Down Expand Up @@ -588,6 +626,8 @@ PHP_FUNCTION(bccomp)
scale = (int) scale_param;
}

BC_ARENA_SETUP;

if (!bc_str2num(&first, ZSTR_VAL(left), ZSTR_VAL(left) + ZSTR_LEN(left), scale, false)) {
zend_argument_value_error(1, "is not well-formed");
goto cleanup;
Expand All @@ -603,6 +643,7 @@ PHP_FUNCTION(bccomp)
cleanup: {
bc_free_num(&first);
bc_free_num(&second);
BC_ARENA_TEARDOWN;
};
}
/* }}} */
Expand All @@ -617,6 +658,8 @@ static void bcfloor_or_bcceil(INTERNAL_FUNCTION_PARAMETERS, bool is_floor)
Z_PARAM_STR(numstr)
ZEND_PARSE_PARAMETERS_END();

BC_ARENA_SETUP;

if (php_str2num(&num, numstr) == FAILURE) {
zend_argument_value_error(1, "is not well-formed");
goto cleanup;
Expand All @@ -628,6 +671,7 @@ static void bcfloor_or_bcceil(INTERNAL_FUNCTION_PARAMETERS, bool is_floor)
cleanup: {
bc_free_num(&num);
bc_free_num(&result);
BC_ARENA_TEARDOWN;
};
}
/* }}} */
Expand Down Expand Up @@ -676,6 +720,8 @@ PHP_FUNCTION(bcround)
return;
}

BC_ARENA_SETUP;

bc_init_num(&result);

if (php_str2num(&num, numstr) == FAILURE) {
Expand All @@ -689,6 +735,7 @@ PHP_FUNCTION(bcround)
cleanup: {
bc_free_num(&num);
bc_free_num(&result);
BC_ARENA_TEARDOWN;
};
}
/* }}} */
Expand Down
19 changes: 15 additions & 4 deletions ext/bcmath/libbcmath/src/init.c
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Original file line number Diff line number Diff line change
Expand Up @@ -35,14 +35,25 @@
#include <string.h>
#include "zend_alloc.h"

static zend_always_inline bc_num _bc_new_num_nonzeroed_ex_internal(size_t length, size_t scale, bool persistent)
static bc_num _bc_new_num_nonzeroed_ex_internal(size_t length, size_t scale, bool persistent)
{
/* PHP Change: malloc() -> pemalloc(), removed free_list code, merged n_ptr and n_value */
bc_num temp = safe_pemalloc(1, sizeof(bc_struct) + length, scale, persistent);
size_t required_size = zend_safe_address_guarded(1, sizeof(bc_struct) + (ZEND_MM_ALIGNMENT - 1) + length, scale);
required_size &= -ZEND_MM_ALIGNMENT;
bc_num temp;

if (!persistent && BCG(arena) && required_size <= BC_ARENA_SIZE - BCG(arena_offset)) {
temp = (bc_num) (BCG(arena) + BCG(arena_offset));
BCG(arena_offset) += required_size;
temp->n_refs = 2; /* prevent freeing */
} else {
/* PHP Change: malloc() -> pemalloc(), removed free_list code, merged n_ptr and n_value */
temp = pemalloc(required_size, persistent);
temp->n_refs = 1;
}

temp->n_sign = PLUS;
temp->n_len = length;
temp->n_scale = scale;
temp->n_refs = 1;
temp->n_value = (char *) temp + sizeof(bc_struct);
return temp;
}
Expand Down
4 changes: 4 additions & 0 deletions ext/bcmath/php_bcmath.h
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Original file line number Diff line number Diff line change
Expand Up @@ -27,11 +27,15 @@ extern zend_module_entry bcmath_module_entry;
#include "php_version.h"
#define PHP_BCMATH_VERSION PHP_VERSION

#define BC_ARENA_SIZE 256

ZEND_BEGIN_MODULE_GLOBALS(bcmath)
bc_num _zero_;
bc_num _one_;
bc_num _two_;
int bc_precision;
char *arena;
size_t arena_offset;
ZEND_END_MODULE_GLOBALS(bcmath)

#if defined(ZTS) && defined(COMPILE_DL_BCMATH)
Expand Down
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