mksh/aalloc.c

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#include "sh.h"
__RCSID("$MirOS: src/bin/mksh/aalloc.c,v 1.25 2008/11/12 23:34:02 tg Exp $");
/* mksh integration of aalloc */
#ifndef AALLOC_ABORT
#define AALLOC_ABORT internal_errorf
#endif
#ifndef AALLOC_WARN
#define AALLOC_WARN internal_warningf
#endif
#define AALLOC_LEAK_SILENT /* the code does not yet clean up at exit */
#ifndef AALLOC_RANDOM
#if HAVE_ARC4RANDOM
#define AALLOC_RANDOM() arc4random()
#else
#define AALLOC_RANDOM() (rand() * RAND_MAX + rand())
#endif
#endif
#ifdef DEBUG
#define AALLOC_DEBUG
#endif
/* generic area-based allocator built for mmap malloc or omalloc */
#define PVALIGN (sizeof (void *))
#define PVMASK (sizeof (void *) - 1)
#ifndef AALLOC_INITSZ
#define AALLOC_INITSZ (64 * PVALIGN) /* at least 4 pointers */
#endif
typedef /* unsigned */ ptrdiff_t TCookie;
typedef union {
TCookie iv;
char *pv;
} TPtr;
/*
* The separation between TBlock and TArea does not seem to make
* sense at first, especially in the !AALLOC_TRACK case, but is
* necessary to keep PArea values constant even if the storage is
* enlarged. While we could use an extensible array to keep track
* of the TBlock instances, kind of like we use TBlock.storage to
* track the allocations, it would require another TBlock member
* and a fair amount of backtracking; since omalloc can optimise
* pointer sized allocations like a !AALLOC_TRACK TArea, we don't
* do that then.
*/
struct TBlock {
TCookie cookie;
char *endp;
char *last;
void *storage;
};
typedef struct TBlock *PBlock;
struct TArea {
TPtr bp;
#ifdef AALLOC_TRACK
TPtr prev;
TCookie ocookie;
#endif
};
static TCookie global_cookie;
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#ifdef AALLOC_NO_COOKIES
#define gcookie 0
#else
#define gcookie global_cookie
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#endif
#ifdef AALLOC_TRACK
static PArea track;
static void track_check(void);
#endif
#ifdef AALLOC_MPROTECT
#undef AALLOC_INITSZ
#define AALLOC_INITSZ pagesz
static long pagesz;
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#define AALLOC_ALLOW(bp) mprotect((bp), (bp)->endp - (char *)(bp), \
PROT_READ | PROT_WRITE)
#define AALLOC_DENY(bp) mprotect((bp), (bp)->endp - (char *)(bp), \
PROT_NONE)
#define AALLOC_PEEK(bp) mprotect((bp), sizeof (struct TArea), \
PROT_READ | PROT_WRITE)
#else
#define AALLOC_ALLOW(bp) /* nothing */
#define AALLOC_DENY(bp) /* nothing */
#define AALLOC_PEEK(bp) /* nothing */
#endif
/*
* Some nice properties: allocations are always PVALIGNed, which
* includes the pointers seen by our user, the forward and back
* pointers, the AALLOC_TRACK prev pointer, etc.
*/
#define safe_malloc(dest, len) do { \
(dest) = malloc((len)); \
safe_xalloc_common((dest), (len)); \
} while (/* CONSTCOND */ 0)
#define safe_realloc(dest, len) do { \
(dest) = realloc((dest), (len)); \
safe_xalloc_common((dest), (len)); \
} while (/* CONSTCOND */ 0)
#define safe_xalloc_common(dest, len) do { \
if ((dest) == NULL) \
AALLOC_ABORT("unable to allocate %lu bytes: %s", \
(unsigned long)(len), strerror(errno)); \
if ((ptrdiff_t)(dest) & PVMASK) \
AALLOC_ABORT("unaligned malloc result: %p", (dest)); \
} while (/* CONSTCOND */ 0)
#define MUL_NO_OVERFLOW (1UL << (sizeof (size_t) * 8 / 2))
#define safe_muladd(nmemb, size, extra) do { \
if ((nmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) && \
nmemb > 0 && SIZE_MAX / nmemb < size) \
AALLOC_ABORT("attempted integer overflow: %lu * %lu", \
(unsigned long)nmemb, (unsigned long)size); \
size *= nmemb; \
if (size >= SIZE_MAX - extra) \
AALLOC_ABORT("unable to allocate %lu bytes: %s", \
(unsigned long)size, "value plus extra too big"); \
size += extra; \
} while (/* CONSTCOND */ 0)
static void adelete_leak(PArea, PBlock, bool, const char *);
static PBlock check_bp(PArea, const char *, TCookie);
static TPtr *check_ptr(void *, PArea, PBlock *, const char *, const char *);
PArea
anew(void)
{
PArea ap;
PBlock bp;
#ifdef AALLOC_MPROTECT
if (!pagesz) {
if ((pagesz = sysconf(_SC_PAGESIZE)) == -1 ||
(size_t)pagesz < (size_t)PVALIGN)
AALLOC_ABORT("sysconf(_SC_PAGESIZE) failed: %ld %s",
pagesz, strerror(errno));
}
#endif
#ifdef AALLOC_DEBUG
if (PVALIGN != 2 && PVALIGN != 4 && PVALIGN != 8 && PVALIGN != 16)
AALLOC_ABORT("PVALIGN not a power of two: %lu",
(unsigned long)PVALIGN);
if (sizeof (TPtr) != sizeof (TCookie) || sizeof (TPtr) != PVALIGN)
AALLOC_ABORT("TPtr sizes do not match: %lu, %lu, %lu",
(unsigned long)sizeof (TPtr),
(unsigned long)sizeof (TCookie), (unsigned long)PVALIGN);
if ((size_t)AALLOC_INITSZ < sizeof (struct TBlock))
AALLOC_ABORT("AALLOC_INITSZ constant too small: %lu < %lu",
(unsigned long)AALLOC_INITSZ,
(unsigned long)sizeof (struct TBlock));
#endif
if (!global_cookie) {
size_t v;
/* ensure unaligned cookie */
do {
global_cookie = AALLOC_RANDOM();
v = AALLOC_RANDOM() & 7;
} while (!(global_cookie & PVMASK) || !v);
/* randomise seed afterwards */
while (v--)
AALLOC_RANDOM();
#ifdef AALLOC_TRACK
atexit(track_check);
#endif
}
safe_malloc(ap, sizeof (struct TArea));
safe_malloc(bp, AALLOC_INITSZ);
/* ensure unaligned cookie */
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#ifdef AALLOC_NO_COOKIES
bp->cookie = 0;
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#else
do {
bp->cookie = AALLOC_RANDOM();
} while (!(bp->cookie & PVMASK));
#endif
/* first byte after block */
bp->endp = (char *)bp + AALLOC_INITSZ; /* bp + size of the block */
/* next entry (forward pointer) available for new allocation */
bp->last = (char *)&bp->storage; /* first entry */
ap->bp.pv = (char *)bp;
ap->bp.iv ^= gcookie;
#ifdef AALLOC_TRACK
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ap->prev.pv = (char *)track;
ap->prev.iv ^= gcookie;
ap->ocookie = bp->cookie ^ gcookie;
track = ap;
#endif
AALLOC_DENY(bp);
return (ap);
}
/*
* Validate block in Area ap, return unlocked block pointer.
* If ocookie is not 0, make sure block cookie is equal.
*/
static PBlock
check_bp(PArea ap, const char *funcname, TCookie ocookie)
{
TPtr p;
PBlock bp;
if (ap->bp.pv == NULL) {
AALLOC_WARN("%s: area %p already freed", funcname, ap);
return (NULL);
}
p.iv = ap->bp.iv ^ gcookie;
if ((ptrdiff_t)(bp = (PBlock)p.pv) & PVMASK) {
AALLOC_WARN("%s: area %p block pointer destroyed: %p",
funcname, ap, p.pv);
return (NULL);
}
AALLOC_PEEK(bp);
if (ocookie && bp->cookie != ocookie) {
AALLOC_WARN("%s: block %p cookie destroyed: %p, %p",
funcname, bp, (void *)ocookie, (void *)bp->cookie);
return (NULL);
}
if (((ptrdiff_t)bp->endp & PVMASK) || ((ptrdiff_t)bp->last & PVMASK)) {
AALLOC_WARN("%s: block %p data structure destroyed: %p, %p",
funcname, bp, bp->endp, bp->last);
return (NULL);
}
if (bp->endp < (char *)bp) {
AALLOC_WARN("%s: block %p end pointer out of bounds: %p",
funcname, bp, bp->endp);
return (NULL);
}
if ((bp->last < (char *)&bp->storage) || (bp->last > bp->endp)) {
AALLOC_WARN("%s: block %p last pointer out of bounds: "
"%p < %p < %p", funcname, bp, &bp->storage, bp->last,
bp->endp);
return (NULL);
}
AALLOC_ALLOW(bp);
return (bp);
}
#ifdef AALLOC_TRACK
/*
* At exit, dump and free any leaked allocations, blocks and areas.
*/
static void
track_check(void)
{
PArea tp;
TPtr lp;
PBlock bp;
while (track) {
tp = track;
tp->ocookie ^= gcookie;
lp.iv = tp->prev.iv ^ gcookie;
if ((lp.iv & PVMASK)
#ifndef AALLOC_NO_COOKIES
|| !(tp->ocookie & PVMASK)
#endif
) {
/* buffer overflow or something? */
AALLOC_WARN("AALLOC_TRACK data structure %p destroyed:"
" %p, %p, %p; exiting", tp, lp.pv, tp->bp.pv,
(void *)tp->ocookie);
return;
}
if (!(bp = check_bp(tp, "atexit:track_check", tp->ocookie)))
goto track_next;
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if (bp->last != (char *)&bp->storage)
#ifdef AALLOC_LEAK_SILENT
adelete_leak(tp, bp, false, "at exit");
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#else
adelete_leak(tp, bp, true, "at exit");
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else
AALLOC_WARN("leaking empty area %p (%p %lu)", tp,
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bp, (unsigned long)(bp->endp - (char *)bp));
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#endif
free(bp);
track_next:
track = (PArea)lp.pv;
free(tp);
}
}
#endif
static void
adelete_leak(PArea ap, PBlock bp, bool always_warn, const char *when)
{
TPtr *cp;
while (bp->last > (char *)&bp->storage) {
bp->last -= PVALIGN;
cp = *((void **)bp->last);
cp->iv ^= bp->cookie;
if (always_warn || cp->pv != bp->last)
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AALLOC_WARN("leaking %s pointer %p in area %p (%p %lu) %s",
cp->pv == bp->last ? "valid" : "underflown",
(char *)cp + PVALIGN, ap, bp,
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(unsigned long)(bp->endp - (char *)bp), when);
free(cp);
}
}
void
adelete(PArea *pap)
{
#ifdef AALLOC_TRACK
PArea tp;
TPtr lp;
#endif
PBlock bp;
/* ignore invalid areas */
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if ((bp = check_bp(*pap, "adelete", 0)) != NULL) {
if (bp->last != (char *)&bp->storage)
adelete_leak(*pap, bp, false, "in adelete");
free(bp);
}
#ifdef AALLOC_TRACK
if (track == *pap) {
(*pap)->prev.iv ^= gcookie;
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track = (PArea)((*pap)->prev.pv);
goto adelete_tracked;
}
/* find the TArea whose prev is *pap */
tp = track;
while (tp) {
lp.iv = tp->prev.iv ^ gcookie;
if ((lp.iv & PVMASK)
#ifndef AALLOC_NO_COOKIES
|| !((tp->ocookie ^ gcookie) & PVMASK)
#endif
) {
/* buffer overflow or something? */
AALLOC_WARN("AALLOC_TRACK data structure %p destroyed:"
" %p, %p, %p; exiting", tp, lp.pv, tp->bp.pv,
(void *)(tp->ocookie ^ gcookie));
tp = NULL;
break;
}
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if (lp.pv == (char *)*pap)
break;
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tp = (PArea)lp.pv;
}
if (tp)
tp->prev.iv = (*pap)->prev.iv; /* decouple *pap */
else
AALLOC_WARN("area %p not in found AALLOC_TRACK data structure",
*pap);
adelete_tracked:
#endif
free(*pap);
*pap = NULL;
}
void *
alloc(size_t nmemb, size_t size, PArea ap)
{
PBlock bp;
TPtr *ptr;
/* obtain the memory region requested, retaining guards */
safe_muladd(nmemb, size, sizeof (TPtr));
safe_malloc(ptr, size);
/* chain into area */
if ((bp = check_bp(ap, "alloc", 0)) == NULL)
AALLOC_ABORT("cannot continue");
if (bp->last == bp->endp) {
TPtr **tp;
size_t bsz;
/* make room for more forward ptrs in the block allocation */
bsz = bp->endp - (char *)bp;
safe_muladd(2, bsz, 0);
safe_realloc(bp, bsz);
bp->last = (char *)bp + (bsz / 2);
bp->endp = (char *)bp + bsz;
/* all backpointers have to be adjusted */
for (tp = (TPtr **)&bp->storage; tp < (TPtr **)bp->last; ++tp) {
(*tp)->pv = (char *)tp;
(*tp)->iv ^= bp->cookie;
}
/* “bp” has possibly changed, enter its new value into ap */
ap->bp.pv = (char *)bp;
ap->bp.iv ^= gcookie;
}
*((void **)bp->last) = ptr; /* next available forward ptr */
ptr->pv = bp->last; /* backpointer to fwdptr storage */
ptr->iv ^= bp->cookie; /* apply block cookie */
bp->last += PVALIGN; /* advance next-avail pointer */
AALLOC_DENY(bp);
/* return aligned storage just after the cookied backpointer */
return ((char *)ptr + PVALIGN);
}
void *
aresize(void *vp, size_t nmemb, size_t size, PArea ap)
{
PBlock bp;
TPtr *ptr;
if (vp == NULL)
return (alloc(nmemb, size, ap));
/* validate allocation and backpointer against forward pointer */
if ((ptr = check_ptr(vp, ap, &bp, "aresize", "")) == NULL)
AALLOC_ABORT("cannot continue");
/* move allocation to size and possibly new location */
safe_muladd(nmemb, size, sizeof (TPtr));
safe_realloc(ptr, size);
/* write new address of allocation into the block forward pointer */
memcpy(ptr->pv, &ptr, PVALIGN);
/* apply the cookie on the backpointer again */
ptr->iv ^= bp->cookie;
AALLOC_DENY(bp);
return ((char *)ptr + PVALIGN);
}
/*
* Try to find vp inside Area ap, use what and extra for error msgs.
*
* If an error occurs, returns NULL with no side effects.
* Otherwise, returns address of the allocation, with the cookie on the
* backpointer unapplied; *bpp contains the unlocked block pointer.
*/
static TPtr *
check_ptr(void *vp, PArea ap, PBlock *bpp, const char *what, const char *extra)
{
PBlock bp;
TPtr *ptr;
if ((ptrdiff_t)vp & PVMASK) {
AALLOC_WARN("trying to %s rogue unaligned pointer %p from "
"area %p%s", what + 1, vp, ap, extra);
return (NULL);
}
ptr = (TPtr *)((char *)vp - PVALIGN);
if (!ptr->iv) {
AALLOC_WARN("trying to %s already freed pointer %p from "
"area %p%s", what + 1, vp, ap, extra);
return (NULL);
}
if ((bp = check_bp(ap, what, 0)) == NULL)
AALLOC_ABORT("cannot continue");
ptr->iv ^= bp->cookie;
if (ptr->pv < (char *)&bp->storage || ptr->pv >= bp->last) {
AALLOC_WARN("trying to %s rogue pointer %p from area %p "
"(block %p..%p), backpointer %p out of bounds%s",
what + 1, vp, ap, bp, bp->last, ptr->pv, extra);
AALLOC_DENY(bp);
return (NULL);
}
if (*((void **)ptr->pv) != ptr) {
AALLOC_WARN("trying to %s rogue pointer %p from area %p "
"(block %p..%p), backpointer %p, forward pointer to "
"%p instead%s", what + 1, vp, ap, bp, bp->last,
ptr->pv, *((void **)ptr->pv), extra);
AALLOC_DENY(bp);
return (NULL);
}
*bpp = bp;
return (ptr);
}
void
afree(void *vp, PArea ap)
{
PBlock bp;
TPtr *ptr;
if (vp == NULL)
return;
/* validate allocation and backpointer, ignore rogues */
if ((ptr = check_ptr(vp, ap, &bp, "afree", ", ignoring")) == NULL)
return;
/* note: the block allocation does not ever shrink */
bp->last -= PVALIGN; /* mark the last forward pointer as free */
/* if our forward pointer was not the last one, relocate the latter */
if (ptr->pv < bp->last) {
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TPtr *tmp = *((TPtr **)bp->last);
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/* tmp is the former last forward pointer */
tmp->pv = ptr->pv; /* its backpointer to former our … */
tmp->iv ^= bp->cookie; /* … forward pointer, and cookie it */
memcpy(ptr->pv, bp->last, PVALIGN); /* relocate fwd ptr */
}
ptr->iv = 0; /* our backpointer, just in case, for double frees */
free(ptr);
AALLOC_DENY(bp);
return;
}