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minix/servers/vm/slaballoc.c
Ben Gras 565f13088f make vfs & filesystems use failable copying 
Change the kernel to add features to vircopy and safecopies so that
transparent copy fixing won't happen to avoid deadlocks, and such copies
fail with EFAULT.

Transparently making copying work from filesystems (as normally done by
the kernel & VM when copying fails because of missing/readonly memory)
is problematic as it can happen that, for file-mapped ranges, that that
same filesystem that is blocked on the copy request is needed to satisfy
the memory range, leading to deadlock. Dito for VFS itself, if done with
a blocking call.

This change makes the copying done from a filesystem fail in such cases
with EFAULT by VFS adding the CPF_TRY flag to the grants. If a FS call
fails with EFAULT, VFS will then request the range to be made available
to VM after the FS is unblocked, allowing it to be used to satisfy the
range if need be in another VFS thread.

Similarly, for datacopies that VFS itself does, it uses the failable
vircopy variant and callers use a wrapper that talk to VM if necessary
to get the copy to work.

	. kernel: add CPF_TRY flag to safecopies
	. kernel: only request writable ranges to VM for the
	  target buffer when copying fails
	. do copying in VFS TRY-first
	. some fixes in VM to build SANITYCHECK mode
	. add regression test for the cases where
	  - a FS system call needs memory mapped in a process that the
	    FS itself must map.
	  - such a range covers more than one file-mapped region.
	. add 'try' mode to vircopy, physcopy
	. add flags field to copy kernel call messages
	. if CP_FLAG_TRY is set, do not transparently try
	  to fix memory ranges
	. for use by VFS when accessing user buffers to avoid
	  deadlock
	. remove some obsolete backwards compatability assignments
        . VFS: let thread scheduling work for VM requests too
          Allows VFS to make calls to VM while suspending and resuming
          the currently running thread. Does currently not work for the
          main thread.
        . VM: add fix memory range call for use by VFS

Change-Id: I295794269cea51a3163519a9cfe5901301d90b32
2014-07-28 17:05:14 +02:00

528 lines
12 KiB
C
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#define _SYSTEM 1
#include <minix/callnr.h>
#include <minix/com.h>
#include <minix/config.h>
#include <minix/const.h>
#include <minix/ds.h>
#include <minix/endpoint.h>
#include <minix/minlib.h>
#include <minix/type.h>
#include <minix/ipc.h>
#include <minix/sysutil.h>
#include <minix/syslib.h>
#include <minix/bitmap.h>
#include <minix/debug.h>
#include <assert.h>
#include <errno.h>
#include <string.h>
#include <env.h>
#include <sys/param.h>
#include "glo.h"
#include "proto.h"
#include "util.h"
#include "sanitycheck.h"
#define SLABSIZES 200
#define ITEMSPERPAGE(bytes) (int)(DATABYTES / (bytes))
#define ELBITS (sizeof(element_t)*8)
#define BITPAT(b) (1UL << ((b) % ELBITS))
#define BITEL(f, b) (f)->sdh.usebits[(b)/ELBITS]
#define OFF(f, b) assert(!GETBIT(f, b))
#define ON(f, b) assert(GETBIT(f, b))
#if MEMPROTECT
#define SLABDATAWRITABLE(data, wr) do { \
assert(data->sdh.writable == WRITABLE_NONE); \
assert(wr != WRITABLE_NONE); \
vm_pagelock(data, 0); \
data->sdh.writable = wr; \
} while(0)
#define SLABDATAUNWRITABLE(data) do { \
assert(data->sdh.writable != WRITABLE_NONE); \
data->sdh.writable = WRITABLE_NONE; \
vm_pagelock(data, 1); \
} while(0)
#define SLABDATAUSE(data, code) do { \
SLABDATAWRITABLE(data, WRITABLE_HEADER); \
code \
SLABDATAUNWRITABLE(data); \
} while(0)
#else
#define SLABDATAWRITABLE(data, wr)
#define SLABDATAUNWRITABLE(data)
#define SLABDATAUSE(data, code) do { code } while(0)
#endif
#define GETBIT(f, b) (BITEL(f,b) & BITPAT(b))
#define SETBIT(f, b) {OFF(f,b); SLABDATAUSE(f, BITEL(f,b)|= BITPAT(b); (f)->sdh.nused++;); }
#define CLEARBIT(f, b) {ON(f, b); SLABDATAUSE(f, BITEL(f,b)&=~BITPAT(b); (f)->sdh.nused--; (f)->sdh.freeguess = (b);); }
#define OBJALIGN 8
#define MINSIZE 8
#define MAXSIZE (SLABSIZES-1+MINSIZE)
#define USEELEMENTS (1+(VM_PAGE_SIZE/MINSIZE/8))
static int pages = 0;
typedef u8_t element_t;
#define BITS_FULL (~(element_t)0)
typedef element_t elements_t[USEELEMENTS];
/* This file is too low-level to have global SANITYCHECKs everywhere,
* as the (other) data structures are often necessarily in an
* inconsistent state during a slaballoc() / slabfree(). So only do
* our own sanity checks here, with SLABSANITYCHECK.
*/
/* Special writable values. */
#define WRITABLE_NONE -2
#define WRITABLE_HEADER -1
struct sdh {
#if SANITYCHECKS
u32_t magic1;
#endif
int freeguess;
struct slabdata *next, *prev;
elements_t usebits;
phys_bytes phys;
#if SANITYCHECKS
int writable; /* data item number or WRITABLE_* */
u32_t magic2;
#endif
u16_t nused; /* Number of data items used in this slab. */
};
#define DATABYTES (VM_PAGE_SIZE-sizeof(struct sdh))
#define MAGIC1 0x1f5b842f
#define MAGIC2 0x8bb5a420
#define JUNK 0xdeadbeef
#define NOJUNK 0xc0ffee
static struct slabheader {
struct slabdata {
u8_t data[DATABYTES];
struct sdh sdh;
} *list_head;
} slabs[SLABSIZES];
static int objstats(void *, int, struct slabheader **, struct slabdata
**, int *);
#define GETSLAB(b, s) { \
int _gsi; \
assert((b) >= MINSIZE); \
_gsi = (b) - MINSIZE; \
assert((_gsi) < SLABSIZES); \
assert((_gsi) >= 0); \
s = &slabs[_gsi]; \
}
/* move slabdata nw to slabheader sl under list number l. */
#define ADDHEAD(nw, sl) { \
SLABDATAUSE(nw, \
(nw)->sdh.next = sl->list_head; \
(nw)->sdh.prev = NULL;); \
sl->list_head = nw; \
if((nw)->sdh.next) { \
SLABDATAUSE((nw)->sdh.next, \
(nw)->sdh.next->sdh.prev = (nw);); \
} \
}
#define UNLINKNODE(node) { \
struct slabdata *next, *prev; \
prev = (node)->sdh.prev; \
next = (node)->sdh.next; \
if(prev) { SLABDATAUSE(prev, prev->sdh.next = next;); } \
if(next) { SLABDATAUSE(next, next->sdh.prev = prev;); } \
}
static struct slabdata *newslabdata(void)
{
struct slabdata *n;
phys_bytes p;
assert(sizeof(*n) == VM_PAGE_SIZE);
if(!(n = vm_allocpage(&p, VMP_SLAB))) {
printf("newslabdata: vm_allocpage failed\n");
return NULL;
}
memset(n->sdh.usebits, 0, sizeof(n->sdh.usebits));
pages++;
n->sdh.phys = p;
#if SANITYCHECKS
n->sdh.magic1 = MAGIC1;
n->sdh.magic2 = MAGIC2;
#endif
n->sdh.nused = 0;
n->sdh.freeguess = 0;
#if SANITYCHECKS
n->sdh.writable = WRITABLE_HEADER;
SLABDATAUNWRITABLE(n);
#endif
return n;
}
#if SANITYCHECKS
/*===========================================================================*
* checklist *
*===========================================================================*/
static int checklist(const char *file, int line,
struct slabheader *s, int bytes)
{
struct slabdata *n = s->list_head;
int ch = 0;
while(n) {
int count = 0, i;
#if SANITYCHECKS
MYASSERT(n->sdh.magic1 == MAGIC1);
MYASSERT(n->sdh.magic2 == MAGIC2);
#endif
MYASSERT(usedpages_add(n->sdh.phys, VM_PAGE_SIZE) == OK);
if(n->sdh.prev)
MYASSERT(n->sdh.prev->sdh.next == n);
else
MYASSERT(s->list_head == n);
if(n->sdh.next) MYASSERT(n->sdh.next->sdh.prev == n);
for(i = 0; i < USEELEMENTS*8; i++)
if(i >= ITEMSPERPAGE(bytes))
MYASSERT(!GETBIT(n, i));
else
if(GETBIT(n,i))
count++;
MYASSERT(count == n->sdh.nused);
ch += count;
n = n->sdh.next;
}
return ch;
}
/*===========================================================================*
* void slab_sanitycheck *
*===========================================================================*/
void slab_sanitycheck(const char *file, int line)
{
int s;
for(s = 0; s < SLABSIZES; s++) {
checklist(file, line, &slabs[s], s + MINSIZE);
}
}
/*===========================================================================*
* int slabsane *
*===========================================================================*/
int slabsane_f(const char *file, int line, void *mem, int bytes)
{
struct slabheader *s;
struct slabdata *f;
int i;
bytes = roundup(bytes, OBJALIGN);
return (objstats(mem, bytes, &s, &f, &i) == OK);
}
#endif
#if SANITYCHECKS
static int nojunkwarning = 0;
#endif
/*===========================================================================*
* void *slaballoc *
*===========================================================================*/
void *slaballoc(int bytes)
{
int i;
int count = 0;
struct slabheader *s;
struct slabdata *newslab;
char *ret;
bytes = roundup(bytes, OBJALIGN);
SLABSANITYCHECK(SCL_FUNCTIONS);
/* Retrieve entry in slabs[]. */
GETSLAB(bytes, s);
assert(s);
if(!(newslab = s->list_head)) {
/* Make sure there is something on the freelist. */
newslab = newslabdata();
if(!newslab) return NULL;
ADDHEAD(newslab, s);
assert(newslab->sdh.nused == 0);
} else assert(newslab->sdh.nused > 0);
assert(newslab->sdh.nused < ITEMSPERPAGE(bytes));
SLABSANITYCHECK(SCL_DETAIL);
#if SANITYCHECKS
assert(newslab->sdh.magic1 == MAGIC1);
assert(newslab->sdh.magic2 == MAGIC2);
#endif
for(i = newslab->sdh.freeguess;
count < ITEMSPERPAGE(bytes); count++, i++) {
i = i % ITEMSPERPAGE(bytes);
if(!GETBIT(newslab, i))
break;
}
SLABSANITYCHECK(SCL_FUNCTIONS);
assert(count < ITEMSPERPAGE(bytes));
assert(i >= 0 && i < ITEMSPERPAGE(bytes));
SETBIT(newslab, i);
if(newslab->sdh.nused == ITEMSPERPAGE(bytes)) {
UNLINKNODE(newslab);
s->list_head = newslab->sdh.next;
}
ret = ((char *) newslab) + i*bytes;
#if SANITYCHECKS
#if MEMPROTECT
nojunkwarning++;
slabunlock(ret, bytes);
nojunkwarning--;
assert(!nojunkwarning);
#endif
*(u32_t *) ret = NOJUNK;
#if MEMPROTECT
slablock(ret, bytes);
#endif
#endif
SLABDATAUSE(newslab, newslab->sdh.freeguess = i+1;);
#if SANITYCHECKS
if(bytes >= SLABSIZES+MINSIZE) {
printf("slaballoc: odd, bytes %d?\n", bytes);
}
if(!slabsane_f(__FILE__, __LINE__, ret, bytes))
panic("slaballoc: slabsane failed");
#endif
assert(!((vir_bytes) ret % OBJALIGN));
return ret;
}
/*===========================================================================*
* int objstats *
*===========================================================================*/
static inline int objstats(void *mem, int bytes,
struct slabheader **sp, struct slabdata **fp, int *ip)
{
#if SANITYCHECKS
#define OBJSTATSCHECK(cond) \
if(!(cond)) { \
printf("VM: objstats: %s failed for ptr %p, %d bytes\n", \
#cond, mem, bytes); \
return EINVAL; \
}
#else
#define OBJSTATSCHECK(cond)
#endif
struct slabheader *s;
struct slabdata *f;
int i;
assert(!(bytes % OBJALIGN));
OBJSTATSCHECK((char *) mem >= (char *) VM_PAGE_SIZE);
#if SANITYCHECKS
if(*(u32_t *) mem == JUNK && !nojunkwarning) {
util_stacktrace();
printf("VM: WARNING: JUNK seen in slab object, likely freed\n");
}
#endif
/* Retrieve entry in slabs[]. */
GETSLAB(bytes, s);
/* Round address down to VM_PAGE_SIZE boundary to get header. */
f = (struct slabdata *) ((char *) mem - (vir_bytes) mem % VM_PAGE_SIZE);
#if SANITYCHECKS
OBJSTATSCHECK(f->sdh.magic1 == MAGIC1);
OBJSTATSCHECK(f->sdh.magic2 == MAGIC2);
#endif
/* Make sure it's in range. */
OBJSTATSCHECK((char *) mem >= (char *) f->data);
OBJSTATSCHECK((char *) mem < (char *) f->data + sizeof(f->data));
/* Get position. */
i = (char *) mem - (char *) f->data;
OBJSTATSCHECK(!(i % bytes));
i = i / bytes;
/* Make sure it is marked as allocated. */
OBJSTATSCHECK(GETBIT(f, i));
/* return values */
*ip = i;
*fp = f;
*sp = s;
return OK;
}
/*===========================================================================*
* void *slabfree *
*===========================================================================*/
void slabfree(void *mem, int bytes)
{
int i;
struct slabheader *s;
struct slabdata *f;
bytes = roundup(bytes, OBJALIGN);
SLABSANITYCHECK(SCL_FUNCTIONS);
if(objstats(mem, bytes, &s, &f, &i) != OK) {
panic("slabfree objstats failed");
}
#if SANITYCHECKS
if(*(u32_t *) mem == JUNK) {
printf("VM: WARNING: likely double free, JUNK seen\n");
}
#endif
#if SANITYCHECKS
#if MEMPROTECT
slabunlock(mem, bytes);
#endif
#if JUNKFREE
memset(mem, 0xa6, bytes);
#endif
*(u32_t *) mem = JUNK;
nojunkwarning++;
#if MEMPROTECT
slablock(mem, bytes);
#endif
nojunkwarning--;
assert(!nojunkwarning);
#endif
/* Free this data. */
CLEARBIT(f, i);
/* Check if this slab changes lists. */
if(f->sdh.nused == 0) {
UNLINKNODE(f);
if(f == s->list_head) s->list_head = f->sdh.next;
vm_freepages((vir_bytes) f, 1);
SLABSANITYCHECK(SCL_DETAIL);
} else if(f->sdh.nused == ITEMSPERPAGE(bytes)-1) {
ADDHEAD(f, s);
}
SLABSANITYCHECK(SCL_FUNCTIONS);
return;
}
#if MEMPROTECT
/*===========================================================================*
* void *slablock *
*===========================================================================*/
void slablock(void *mem, int bytes)
{
int i;
struct slabheader *s;
struct slabdata *f;
bytes = roundup(bytes, OBJALIGN);
if(objstats(mem, bytes, &s, &f, &i) != OK)
panic("slablock objstats failed");
SLABDATAUNWRITABLE(f);
return;
}
/*===========================================================================*
* void *slabunlock *
*===========================================================================*/
void slabunlock(void *mem, int bytes)
{
int i;
struct slabheader *s;
struct slabdata *f;
bytes = roundup(bytes, OBJALIGN);
if(objstats(mem, bytes, &s, &f, &i) != OK)
panic("slabunlock objstats failed");
SLABDATAWRITABLE(f, i);
return;
}
#endif
#if SANITYCHECKS
/*===========================================================================*
* void slabstats *
*===========================================================================*/
void slabstats(void)
{
int s, totalbytes = 0;
static int n;
n++;
if(n%1000) return;
for(s = 0; s < SLABSIZES; s++) {
int b, t;
b = s + MINSIZE;
t = checklist(__FILE__, __LINE__, &slabs[s], b);
if(t > 0) {
int bytes = t * b;
printf("VMSTATS: %2d slabs: %d (%dkB)\n", b, t, bytes/1024);
totalbytes += bytes;
}
}
if(pages > 0) {
printf("VMSTATS: %dK net used in slab objects in %d pages (%dkB): %d%% utilization\n",
totalbytes/1024, pages, pages*VM_PAGE_SIZE/1024,
100 * totalbytes / (pages*VM_PAGE_SIZE));
}
}
#endif
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