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/*++
/* NAME
/* mymalloc 3
/* SUMMARY
/* memory management wrappers
/* SYNOPSIS
/* #include <mymalloc.h>
/*
/* void *mymalloc(len)
/* ssize_t len;
/*
/* void *myrealloc(ptr, len)
/* void *ptr;
/* ssize_t len;
/*
/* void myfree(ptr)
/* void *ptr;
/*
/* char *mystrdup(str)
/* const char *str;
/*
/* char *mystrndup(str, len)
/* const char *str;
/* ssize_t len;
/*
/* char *mymemdup(ptr, len)
/* const char *ptr;
/* ssize_t len;
/* DESCRIPTION
/* This module performs low-level memory management with error
/* handling. A call of these functions either succeeds or it does
/* not return at all.
/*
/* To save memory, zero-length strings are shared and read-only.
/* The caller must not attempt to modify the null terminator.
/* This code is enabled unless NO_SHARED_EMPTY_STRINGS is
/* defined at compile time (for example, you have an sscanf()
/* routine that pushes characters back into its input).
/*
/* mymalloc() allocates the requested amount of memory. The memory
/* is not set to zero.
/*
/* myrealloc() resizes memory obtained from mymalloc() or myrealloc()
/* to the requested size. The result pointer value may differ from
/* that given via the \fIptr\fR argument.
/*
/* myfree() takes memory obtained from mymalloc() or myrealloc()
/* and makes it available for other use.
/*
/* mystrdup() returns a dynamic-memory copy of its null-terminated
/* argument. This routine uses mymalloc().
/*
/* mystrndup() returns a dynamic-memory copy of at most \fIlen\fR
/* leading characters of its null-terminated
/* argument. The result is null-terminated. This routine uses mymalloc().
/*
/* mymemdup() makes a copy of the memory pointed to by \fIptr\fR
/* with length \fIlen\fR. The result is NOT null-terminated.
/* This routine uses mymalloc().
/* SEE ALSO
/* msg(3) diagnostics interface
/* DIAGNOSTICS
/* Problems are reported via the msg(3) diagnostics routines:
/* the requested amount of memory is not available; improper use
/* is detected; other fatal errors.
/* LICENSE
/* .ad
/* .fi
/* The Secure Mailer license must be distributed with this software.
/* AUTHOR(S)
/* Wietse Venema
/* IBM T.J. Watson Research
/* P.O. Box 704
/* Yorktown Heights, NY 10598, USA
/*
/* Wietse Venema
/* Google, Inc.
/* 111 8th Avenue
/* New York, NY 10011, USA
/*--*/
/* System libraries. */
#include "sys_defs.h"
#include <stdlib.h>
#include <stddef.h>
#include <string.h>
/* Application-specific. */
#include "msg.h"
#include "mymalloc.h"
/*
* Structure of an annotated memory block. In order to detect spurious
* free() calls we prepend a signature to memory given to the application.
* In order to detect access to free()d blocks, overwrite each block as soon
* as it is passed to myfree(). With the code below, the user data has
* integer alignment or better.
*/
typedef struct MBLOCK {
int signature; /* set when block is active */
ssize_t length; /* user requested length */
union {
ALIGN_TYPE align;
char payload[1]; /* actually a bunch of bytes */
} u;
} MBLOCK;
#define SIGNATURE 0xdead
#define FILLER 0xff
#define CHECK_IN_PTR(ptr, real_ptr, len, fname) { \
if (ptr == 0) \
msg_panic("%s: null pointer input", fname); \
real_ptr = (MBLOCK *) (ptr - offsetof(MBLOCK, u.payload[0])); \
if (real_ptr->signature != SIGNATURE) \
msg_panic("%s: corrupt or unallocated memory block", fname); \
real_ptr->signature = 0; \
if ((len = real_ptr->length) < 1) \
msg_panic("%s: corrupt memory block length", fname); \
}
#define CHECK_OUT_PTR(ptr, real_ptr, len) { \
real_ptr->signature = SIGNATURE; \
real_ptr->length = len; \
ptr = real_ptr->u.payload; \
}
#define SPACE_FOR(len) (offsetof(MBLOCK, u.payload[0]) + len)
/*
* Optimization for short strings. We share one copy with multiple callers.
* This differs from normal heap memory in two ways, because the memory is
* shared:
*
* - It must be read-only to avoid horrible bugs. This is OK because there is
* no legitimate reason to modify the null terminator.
*
* - myfree() cannot overwrite the memory with a filler pattern like it can do
* with heap memory. Therefore, some dangling pointer bugs will be masked.
*/
#ifndef NO_SHARED_EMPTY_STRINGS
static const char empty_string[] = "";
#endif
/* mymalloc - allocate memory or bust */
void *mymalloc(ssize_t len)
{
void *ptr;
MBLOCK *real_ptr;
/*
* Note: for safety reasons the request length is a signed type. This
* allows us to catch integer overflow problems that weren't already
* caught up-stream.
*/
if (len < 1)
msg_panic("mymalloc: requested length %ld", (long) len);
#ifdef MYMALLOC_FUZZ
len += MYMALLOC_FUZZ;
#endif
if ((real_ptr = (MBLOCK *) malloc(SPACE_FOR(len))) == 0)
msg_fatal("mymalloc: insufficient memory for %ld bytes: %m",
(long) len);
CHECK_OUT_PTR(ptr, real_ptr, len);
memset(ptr, FILLER, len);
return (ptr);
}
/* myrealloc - reallocate memory or bust */
void *myrealloc(void *ptr, ssize_t len)
{
MBLOCK *real_ptr;
ssize_t old_len;
#ifndef NO_SHARED_EMPTY_STRINGS
if (ptr == empty_string)
return (mymalloc(len));
#endif
/*
* Note: for safety reasons the request length is a signed type. This
* allows us to catch integer overflow problems that weren't already
* caught up-stream.
*/
if (len < 1)
msg_panic("myrealloc: requested length %ld", (long) len);
#ifdef MYMALLOC_FUZZ
len += MYMALLOC_FUZZ;
#endif
CHECK_IN_PTR(ptr, real_ptr, old_len, "myrealloc");
if ((real_ptr = (MBLOCK *) realloc((void *) real_ptr, SPACE_FOR(len))) == 0)
msg_fatal("myrealloc: insufficient memory for %ld bytes: %m",
(long) len);
CHECK_OUT_PTR(ptr, real_ptr, len);
if (len > old_len)
memset(ptr + old_len, FILLER, len - old_len);
return (ptr);
}
/* myfree - release memory */
void myfree(void *ptr)
{
MBLOCK *real_ptr;
ssize_t len;
#ifndef NO_SHARED_EMPTY_STRINGS
if (ptr != empty_string) {
#endif
CHECK_IN_PTR(ptr, real_ptr, len, "myfree");
memset((void *) real_ptr, FILLER, SPACE_FOR(len));
free((void *) real_ptr);
#ifndef NO_SHARED_EMPTY_STRINGS
}
#endif
}
/* mystrdup - save string to heap */
char *mystrdup(const char *str)
{
size_t len;
if (str == 0)
msg_panic("mystrdup: null pointer argument");
#ifndef NO_SHARED_EMPTY_STRINGS
if (*str == 0)
return ((char *) empty_string);
#endif
if ((len = strlen(str) + 1) > SSIZE_T_MAX)
msg_panic("mystrdup: string length >= SSIZE_T_MAX");
return (memcpy(mymalloc(len), str, len));
}
/* mystrndup - save substring to heap */
char *mystrndup(const char *str, ssize_t len)
{
char *result;
char *cp;
if (str == 0)
msg_panic("mystrndup: null pointer argument");
if (len < 0)
msg_panic("mystrndup: requested length %ld", (long) len);
#ifndef NO_SHARED_EMPTY_STRINGS
if (*str == 0)
return ((char *) empty_string);
#endif
if ((cp = memchr(str, 0, len)) != 0)
len = cp - str;
result = memcpy(mymalloc(len + 1), str, len);
result[len] = 0;
return (result);
}
/* mymemdup - copy memory */
char *mymemdup(const void *ptr, ssize_t len)
{
if (ptr == 0)
msg_panic("mymemdup: null pointer argument");
return (memcpy(mymalloc(len), ptr, len));
}
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