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Change select() so that only as many words as necessary for the 'nfds'

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argument from the fd bitmasks are copied from and back to userspace. This
solves an ABI dependency on OPEN_MAX. If nfds is too big for the current
OPEN_MAX, select() fails (but that's relatively easy to fix by 'just'
recompiling the system and not the application binaries), but if it's
smaller, binaries keep working.
This commit is contained in:
Ben Gras 2006-10-04 13:28:38 +00:00
parent 1d4be8052f
commit cbfa0f4fb8
1 changed files with 24 additions and 11 deletions
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35
servers/fs/select.c
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@ -31,8 +31,8 @@ PRIVATE struct selectentry {
fd_set readfds, writefds, errorfds;
fd_set ready_readfds, ready_writefds, ready_errorfds;
fd_set *vir_readfds, *vir_writefds, *vir_errorfds;
struct filp *filps[FD_SETSIZE];
int type[FD_SETSIZE];
struct filp *filps[OPEN_MAX];
int type[OPEN_MAX];
int nfds, nreadyfds;
clock_t expiry;
timer_t timer; /* if expiry > 0 */
@ -164,15 +164,22 @@ PRIVATE void ops2tab(int ops, int fd, struct selectentry *e)
*===========================================================================*/
PRIVATE void copy_fdsets(struct selectentry *e)
{
int fd_setsize;
if(e->nfds < 0 || e->nfds > OPEN_MAX)
panic(__FILE__, "select copy_fdsets: e->nfds wrong", e->nfds);
/* Only copy back as many bits as the user expects. */
fd_setsize = _FDSETWORDS(e->nfds)*_FDSETBITSPERWORD/8;
if (e->vir_readfds)
sys_vircopy(SELF, D, (vir_bytes) &e->ready_readfds,
e->req_endpt, D, (vir_bytes) e->vir_readfds, sizeof(fd_set));
e->req_endpt, D, (vir_bytes) e->vir_readfds, fd_setsize);
if (e->vir_writefds)
sys_vircopy(SELF, D, (vir_bytes) &e->ready_writefds,
e->req_endpt, D, (vir_bytes) e->vir_writefds, sizeof(fd_set));
e->req_endpt, D, (vir_bytes) e->vir_writefds, fd_setsize);
if (e->vir_errorfds)
sys_vircopy(SELF, D, (vir_bytes) &e->ready_errorfds,
e->req_endpt, D, (vir_bytes) e->vir_errorfds, sizeof(fd_set));
e->req_endpt, D, (vir_bytes) e->vir_errorfds, fd_setsize);
return;
}
@ -183,11 +190,11 @@ PRIVATE void copy_fdsets(struct selectentry *e)
PUBLIC int do_select(void)
{
int r, nfds, is_timeout = 1, nonzero_timeout = 0,
fd, s, block = 0;
fd, s, block = 0, fd_setsize;
struct timeval timeout;
nfds = m_in.SEL_NFDS;
if (nfds < 0 || nfds > FD_SETSIZE)
if (nfds < 0 || nfds > OPEN_MAX)
return EINVAL;
for(s = 0; s < MAXSELECTS; s++)
@ -214,20 +221,26 @@ PUBLIC int do_select(void)
selecttab[s].vir_writefds = (fd_set *) m_in.SEL_WRITEFDS;
selecttab[s].vir_errorfds = (fd_set *) m_in.SEL_ERRORFDS;
/* copy args */
/* Copy args. Our storage size is zeroed above. Only copy
* as many bits as user has supplied (nfds).
* Could be compiled with a different OPEN_MAX or FD_SETSIZE.
* If nfds is too large, we have already returned above.
*/
fd_setsize = _FDSETWORDS(nfds)*_FDSETBITSPERWORD/8;
if (selecttab[s].vir_readfds
&& (r=sys_vircopy(who_e, D, (vir_bytes) m_in.SEL_READFDS,
SELF, D, (vir_bytes) &selecttab[s].readfds, sizeof(fd_set))) != OK)
SELF, D, (vir_bytes) &selecttab[s].readfds, fd_setsize)) != OK)
return r;
if (selecttab[s].vir_writefds
&& (r=sys_vircopy(who_e, D, (vir_bytes) m_in.SEL_WRITEFDS,
SELF, D, (vir_bytes) &selecttab[s].writefds, sizeof(fd_set))) != OK)
SELF, D, (vir_bytes) &selecttab[s].writefds, fd_setsize)) != OK)
return r;
if (selecttab[s].vir_errorfds
&& (r=sys_vircopy(who_e, D, (vir_bytes) m_in.SEL_ERRORFDS,
SELF, D, (vir_bytes) &selecttab[s].errorfds, sizeof(fd_set))) != OK)
SELF, D, (vir_bytes) &selecttab[s].errorfds, fd_setsize)) != OK)
return r;
if (!m_in.SEL_TIMEOUT)