cred: distribute reference count per thread
This avoids dirtying creds in the common case, see the comment in kern_prot.c for details. Reviewed by: kib Differential Revision: https://reviews.freebsd.org/D24007
This commit is contained in:
Mateusz Guzik
parent
b4a7ce0690
commit
1724c563e6
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=361993
@ -541,7 +541,10 @@ proc0_init(void *dummy __unused)
|
||||
/* End hack. creds get properly set later with thread_cow_get_proc */
|
||||
curthread->td_ucred = NULL;
|
||||
newcred->cr_prison = &prison0;
|
||||
newcred->cr_users++; /* avoid assertion failure */
|
||||
proc_set_cred_init(p, newcred);
|
||||
newcred->cr_users--;
|
||||
crfree(newcred);
|
||||
#ifdef AUDIT
|
||||
audit_cred_kproc0(newcred);
|
||||
#endif
|
||||
@ -810,8 +813,9 @@ create_init(const void *udata __unused)
|
||||
#endif
|
||||
proc_set_cred(initproc, newcred);
|
||||
td = FIRST_THREAD_IN_PROC(initproc);
|
||||
crfree(td->td_ucred);
|
||||
td->td_ucred = crhold(initproc->p_ucred);
|
||||
crcowfree(td);
|
||||
td->td_realucred = crcowget(initproc->p_ucred);
|
||||
td->td_ucred = td->td_realucred;
|
||||
PROC_UNLOCK(initproc);
|
||||
sx_xunlock(&proctree_lock);
|
||||
crfree(oldcred);
|
||||
|
||||
@ -961,7 +961,7 @@ fork1(struct thread *td, struct fork_req *fr)
|
||||
* XXX: This is ugly; when we copy resource usage, we need to bump
|
||||
* per-cred resource counters.
|
||||
*/
|
||||
proc_set_cred_init(newproc, crhold(td->td_ucred));
|
||||
proc_set_cred_init(newproc, td->td_ucred);
|
||||
|
||||
/*
|
||||
* Initialize resource accounting for the child process.
|
||||
@ -998,8 +998,7 @@ fork1(struct thread *td, struct fork_req *fr)
|
||||
#endif
|
||||
racct_proc_exit(newproc);
|
||||
fail1:
|
||||
crfree(newproc->p_ucred);
|
||||
newproc->p_ucred = NULL;
|
||||
proc_unset_cred(newproc);
|
||||
fail2:
|
||||
if (vm2 != NULL)
|
||||
vmspace_free(vm2);
|
||||
|
||||
@ -1840,6 +1840,98 @@ p_canwait(struct thread *td, struct proc *p)
|
||||
return (0);
|
||||
}
|
||||
|
||||
/*
|
||||
* Credential management.
|
||||
*
|
||||
* struct ucred objects are rarely allocated but gain and lose references all
|
||||
* the time (e.g., on struct file alloc/dealloc) turning refcount updates into
|
||||
* a significant source of cache-line ping ponging. Common cases are worked
|
||||
* around by modifying thread-local counter instead if the cred to operate on
|
||||
* matches td_realucred.
|
||||
*
|
||||
* The counter is split into 2 parts:
|
||||
* - cr_users -- total count of all struct proc and struct thread objects
|
||||
* which have given cred in p_ucred and td_ucred respectively
|
||||
* - cr_ref -- the actual ref count, only valid if cr_users == 0
|
||||
*
|
||||
* If users == 0 then cr_ref behaves similarly to refcount(9), in particular if
|
||||
* the count reaches 0 the object is freeable.
|
||||
* If users > 0 and curthread->td_realucred == cred, then updates are performed
|
||||
* against td_ucredref.
|
||||
* In other cases updates are performed against cr_ref.
|
||||
*
|
||||
* Changing td_realucred into something else decrements cr_users and transfers
|
||||
* accumulated updates.
|
||||
*/
|
||||
struct ucred *
|
||||
crcowget(struct ucred *cr)
|
||||
{
|
||||
|
||||
mtx_lock(&cr->cr_mtx);
|
||||
KASSERT(cr->cr_users > 0, ("%s: users %d not > 0 on cred %p",
|
||||
__func__, cr->cr_users, cr));
|
||||
cr->cr_users++;
|
||||
cr->cr_ref++;
|
||||
mtx_unlock(&cr->cr_mtx);
|
||||
return (cr);
|
||||
}
|
||||
|
||||
static struct ucred *
|
||||
crunuse(struct thread *td)
|
||||
{
|
||||
struct ucred *cr, *crold;
|
||||
|
||||
cr = td->td_ucred;
|
||||
mtx_lock(&cr->cr_mtx);
|
||||
cr->cr_ref += td->td_ucredref;
|
||||
td->td_ucredref = 0;
|
||||
KASSERT(cr->cr_users > 0, ("%s: users %d not > 0 on cred %p",
|
||||
__func__, cr->cr_users, cr));
|
||||
cr->cr_users--;
|
||||
if (cr->cr_users == 0) {
|
||||
KASSERT(cr->cr_ref > 0, ("%s: ref %d not > 0 on cred %p",
|
||||
__func__, cr->cr_ref, cr));
|
||||
crold = cr;
|
||||
} else {
|
||||
cr->cr_ref--;
|
||||
crold = NULL;
|
||||
}
|
||||
mtx_unlock(&cr->cr_mtx);
|
||||
return (crold);
|
||||
}
|
||||
|
||||
void
|
||||
crcowfree(struct thread *td)
|
||||
{
|
||||
struct ucred *cr;
|
||||
|
||||
cr = crunuse(td);
|
||||
if (cr != NULL)
|
||||
crfree(cr);
|
||||
}
|
||||
|
||||
struct ucred *
|
||||
crcowsync(void)
|
||||
{
|
||||
struct thread *td;
|
||||
struct proc *p;
|
||||
struct ucred *crnew, *crold;
|
||||
|
||||
td = curthread;
|
||||
p = td->td_proc;
|
||||
PROC_LOCK_ASSERT(p, MA_OWNED);
|
||||
|
||||
MPASS(td->td_realucred == td->td_ucred);
|
||||
if (td->td_realucred == p->p_ucred)
|
||||
return (NULL);
|
||||
|
||||
crnew = crcowget(p->p_ucred);
|
||||
crold = crunuse(td);
|
||||
td->td_realucred = crnew;
|
||||
td->td_ucred = td->td_realucred;
|
||||
return (crold);
|
||||
}
|
||||
|
||||
/*
|
||||
* Allocate a zeroed cred structure.
|
||||
*/
|
||||
@ -1849,7 +1941,8 @@ crget(void)
|
||||
struct ucred *cr;
|
||||
|
||||
cr = malloc(sizeof(*cr), M_CRED, M_WAITOK | M_ZERO);
|
||||
refcount_init(&cr->cr_ref, 1);
|
||||
mtx_init(&cr->cr_mtx, "cred", NULL, MTX_DEF);
|
||||
cr->cr_ref = 1;
|
||||
#ifdef AUDIT
|
||||
audit_cred_init(cr);
|
||||
#endif
|
||||
@ -1868,8 +1961,18 @@ crget(void)
|
||||
struct ucred *
|
||||
crhold(struct ucred *cr)
|
||||
{
|
||||
struct thread *td;
|
||||
|
||||
refcount_acquire(&cr->cr_ref);
|
||||
td = curthread;
|
||||
if (__predict_true(td->td_realucred == cr)) {
|
||||
KASSERT(cr->cr_users > 0, ("%s: users %d not > 0 on cred %p",
|
||||
__func__, cr->cr_users, cr));
|
||||
td->td_ucredref++;
|
||||
return (cr);
|
||||
}
|
||||
mtx_lock(&cr->cr_mtx);
|
||||
cr->cr_ref++;
|
||||
mtx_unlock(&cr->cr_mtx);
|
||||
return (cr);
|
||||
}
|
||||
|
||||
@ -1879,36 +1982,51 @@ crhold(struct ucred *cr)
|
||||
void
|
||||
crfree(struct ucred *cr)
|
||||
{
|
||||
struct thread *td;
|
||||
|
||||
KASSERT(cr->cr_ref > 0, ("bad ucred refcount: %d", cr->cr_ref));
|
||||
KASSERT(cr->cr_ref != 0xdeadc0de, ("dangling reference to ucred"));
|
||||
if (refcount_release(&cr->cr_ref)) {
|
||||
/*
|
||||
* Some callers of crget(), such as nfs_statfs(),
|
||||
* allocate a temporary credential, but don't
|
||||
* allocate a uidinfo structure.
|
||||
*/
|
||||
if (cr->cr_uidinfo != NULL)
|
||||
uifree(cr->cr_uidinfo);
|
||||
if (cr->cr_ruidinfo != NULL)
|
||||
uifree(cr->cr_ruidinfo);
|
||||
/*
|
||||
* Free a prison, if any.
|
||||
*/
|
||||
if (cr->cr_prison != NULL)
|
||||
prison_free(cr->cr_prison);
|
||||
if (cr->cr_loginclass != NULL)
|
||||
loginclass_free(cr->cr_loginclass);
|
||||
td = curthread;
|
||||
if (td->td_realucred == cr) {
|
||||
KASSERT(cr->cr_users > 0, ("%s: users %d not > 0 on cred %p",
|
||||
__func__, cr->cr_users, cr));
|
||||
td->td_ucredref--;
|
||||
return;
|
||||
}
|
||||
mtx_lock(&cr->cr_mtx);
|
||||
KASSERT(cr->cr_users >= 0, ("%s: users %d not >= 0 on cred %p",
|
||||
__func__, cr->cr_users, cr));
|
||||
cr->cr_ref--;
|
||||
if (cr->cr_users > 0) {
|
||||
mtx_unlock(&cr->cr_mtx);
|
||||
return;
|
||||
}
|
||||
KASSERT(cr->cr_ref >= 0, ("%s: ref %d not >= 0 on cred %p",
|
||||
__func__, cr->cr_ref, cr));
|
||||
if (cr->cr_ref > 0) {
|
||||
mtx_unlock(&cr->cr_mtx);
|
||||
return;
|
||||
}
|
||||
/*
|
||||
* Some callers of crget(), such as nfs_statfs(), allocate a temporary
|
||||
* credential, but don't allocate a uidinfo structure.
|
||||
*/
|
||||
if (cr->cr_uidinfo != NULL)
|
||||
uifree(cr->cr_uidinfo);
|
||||
if (cr->cr_ruidinfo != NULL)
|
||||
uifree(cr->cr_ruidinfo);
|
||||
if (cr->cr_prison != NULL)
|
||||
prison_free(cr->cr_prison);
|
||||
if (cr->cr_loginclass != NULL)
|
||||
loginclass_free(cr->cr_loginclass);
|
||||
#ifdef AUDIT
|
||||
audit_cred_destroy(cr);
|
||||
audit_cred_destroy(cr);
|
||||
#endif
|
||||
#ifdef MAC
|
||||
mac_cred_destroy(cr);
|
||||
mac_cred_destroy(cr);
|
||||
#endif
|
||||
if (cr->cr_groups != cr->cr_smallgroups)
|
||||
free(cr->cr_groups, M_CRED);
|
||||
free(cr, M_CRED);
|
||||
}
|
||||
mtx_destroy(&cr->cr_mtx);
|
||||
if (cr->cr_groups != cr->cr_smallgroups)
|
||||
free(cr->cr_groups, M_CRED);
|
||||
free(cr, M_CRED);
|
||||
}
|
||||
|
||||
/*
|
||||
@ -1982,7 +2100,7 @@ void
|
||||
proc_set_cred_init(struct proc *p, struct ucred *newcred)
|
||||
{
|
||||
|
||||
p->p_ucred = newcred;
|
||||
p->p_ucred = crcowget(newcred);
|
||||
}
|
||||
|
||||
/*
|
||||
@ -1998,10 +2116,20 @@ proc_set_cred_init(struct proc *p, struct ucred *newcred)
|
||||
void
|
||||
proc_set_cred(struct proc *p, struct ucred *newcred)
|
||||
{
|
||||
struct ucred *cr;
|
||||
|
||||
MPASS(p->p_ucred != NULL);
|
||||
cr = p->p_ucred;
|
||||
MPASS(cr != NULL);
|
||||
PROC_LOCK_ASSERT(p, MA_OWNED);
|
||||
KASSERT(newcred->cr_users == 0, ("%s: users %d not 0 on cred %p",
|
||||
__func__, newcred->cr_users, newcred));
|
||||
mtx_lock(&cr->cr_mtx);
|
||||
KASSERT(cr->cr_users > 0, ("%s: users %d not > 0 on cred %p",
|
||||
__func__, cr->cr_users, cr));
|
||||
cr->cr_users--;
|
||||
mtx_unlock(&cr->cr_mtx);
|
||||
p->p_ucred = newcred;
|
||||
newcred->cr_users = 1;
|
||||
PROC_UPDATE_COW(p);
|
||||
}
|
||||
|
||||
@ -2010,9 +2138,17 @@ proc_unset_cred(struct proc *p)
|
||||
{
|
||||
struct ucred *cr;
|
||||
|
||||
MPASS(p->p_state == PRS_ZOMBIE);
|
||||
MPASS(p->p_state == PRS_ZOMBIE || p->p_state == PRS_NEW);
|
||||
cr = p->p_ucred;
|
||||
p->p_ucred = NULL;
|
||||
KASSERT(cr->cr_users > 0, ("%s: users %d not > 0 on cred %p",
|
||||
__func__, cr->cr_users, cr));
|
||||
mtx_lock(&cr->cr_mtx);
|
||||
cr->cr_users--;
|
||||
if (cr->cr_users == 0)
|
||||
KASSERT(cr->cr_ref > 0, ("%s: ref %d not > 0 on cred %p",
|
||||
__func__, cr->cr_ref, cr));
|
||||
mtx_unlock(&cr->cr_mtx);
|
||||
crfree(cr);
|
||||
}
|
||||
|
||||
|
||||
@ -82,9 +82,9 @@ _Static_assert(offsetof(struct thread, td_flags) == 0xfc,
|
||||
"struct thread KBI td_flags");
|
||||
_Static_assert(offsetof(struct thread, td_pflags) == 0x104,
|
||||
"struct thread KBI td_pflags");
|
||||
_Static_assert(offsetof(struct thread, td_frame) == 0x498,
|
||||
_Static_assert(offsetof(struct thread, td_frame) == 0x4a8,
|
||||
"struct thread KBI td_frame");
|
||||
_Static_assert(offsetof(struct thread, td_emuldata) == 0x6a0,
|
||||
_Static_assert(offsetof(struct thread, td_emuldata) == 0x6b0,
|
||||
"struct thread KBI td_emuldata");
|
||||
_Static_assert(offsetof(struct proc, p_flag) == 0xb0,
|
||||
"struct proc KBI p_flag");
|
||||
@ -102,9 +102,9 @@ _Static_assert(offsetof(struct thread, td_flags) == 0x98,
|
||||
"struct thread KBI td_flags");
|
||||
_Static_assert(offsetof(struct thread, td_pflags) == 0xa0,
|
||||
"struct thread KBI td_pflags");
|
||||
_Static_assert(offsetof(struct thread, td_frame) == 0x2fc,
|
||||
_Static_assert(offsetof(struct thread, td_frame) == 0x304,
|
||||
"struct thread KBI td_frame");
|
||||
_Static_assert(offsetof(struct thread, td_emuldata) == 0x340,
|
||||
_Static_assert(offsetof(struct thread, td_emuldata) == 0x348,
|
||||
"struct thread KBI td_emuldata");
|
||||
_Static_assert(offsetof(struct proc, p_flag) == 0x68,
|
||||
"struct proc KBI p_flag");
|
||||
@ -463,7 +463,8 @@ thread_cow_get_proc(struct thread *newtd, struct proc *p)
|
||||
{
|
||||
|
||||
PROC_LOCK_ASSERT(p, MA_OWNED);
|
||||
newtd->td_ucred = crhold(p->p_ucred);
|
||||
newtd->td_realucred = crcowget(p->p_ucred);
|
||||
newtd->td_ucred = newtd->td_realucred;
|
||||
newtd->td_limit = lim_hold(p->p_limit);
|
||||
newtd->td_cowgen = p->p_cowgen;
|
||||
}
|
||||
@ -472,7 +473,9 @@ void
|
||||
thread_cow_get(struct thread *newtd, struct thread *td)
|
||||
{
|
||||
|
||||
newtd->td_ucred = crhold(td->td_ucred);
|
||||
MPASS(td->td_realucred == td->td_ucred);
|
||||
newtd->td_realucred = crcowget(td->td_realucred);
|
||||
newtd->td_ucred = newtd->td_realucred;
|
||||
newtd->td_limit = lim_hold(td->td_limit);
|
||||
newtd->td_cowgen = td->td_cowgen;
|
||||
}
|
||||
@ -481,8 +484,8 @@ void
|
||||
thread_cow_free(struct thread *td)
|
||||
{
|
||||
|
||||
if (td->td_ucred != NULL)
|
||||
crfree(td->td_ucred);
|
||||
if (td->td_realucred != NULL)
|
||||
crcowfree(td);
|
||||
if (td->td_limit != NULL)
|
||||
lim_free(td->td_limit);
|
||||
}
|
||||
@ -495,13 +498,9 @@ thread_cow_update(struct thread *td)
|
||||
struct plimit *oldlimit;
|
||||
|
||||
p = td->td_proc;
|
||||
oldcred = NULL;
|
||||
oldlimit = NULL;
|
||||
PROC_LOCK(p);
|
||||
if (td->td_ucred != p->p_ucred) {
|
||||
oldcred = td->td_ucred;
|
||||
td->td_ucred = crhold(p->p_ucred);
|
||||
}
|
||||
oldcred = crcowsync();
|
||||
if (td->td_limit != p->p_limit) {
|
||||
oldlimit = td->td_limit;
|
||||
td->td_limit = lim_hold(p->p_limit);
|
||||
|
||||
@ -267,7 +267,8 @@ struct thread {
|
||||
struct lock_list_entry *td_sleeplocks; /* (k) Held sleep locks. */
|
||||
int td_intr_nesting_level; /* (k) Interrupt recursion. */
|
||||
int td_pinned; /* (k) Temporary cpu pin count. */
|
||||
struct ucred *td_ucred; /* (k) Reference to credentials. */
|
||||
struct ucred *td_realucred; /* (k) Reference to credentials. */
|
||||
struct ucred *td_ucred; /* (k) Used credentials, temporarily switchable. */
|
||||
struct plimit *td_limit; /* (k) Resource limits. */
|
||||
int td_slptick; /* (t) Time at sleep. */
|
||||
int td_blktick; /* (t) Time spent blocked. */
|
||||
@ -305,6 +306,7 @@ struct thread {
|
||||
int td_errno; /* (k) Error from last syscall. */
|
||||
size_t td_vslock_sz; /* (k) amount of vslock-ed space */
|
||||
struct kcov_info *td_kcov_info; /* (*) Kernel code coverage data */
|
||||
u_int td_ucredref; /* (k) references on td_realucred */
|
||||
#define td_endzero td_sigmask
|
||||
|
||||
/* Copied during fork1() or create_thread(). */
|
||||
|
||||
@ -35,6 +35,10 @@
|
||||
#ifndef _SYS_UCRED_H_
|
||||
#define _SYS_UCRED_H_
|
||||
|
||||
#if defined(_KERNEL) || defined(_WANT_UCRED)
|
||||
#include <sys/_lock.h>
|
||||
#include <sys/_mutex.h>
|
||||
#endif
|
||||
#include <bsm/audit.h>
|
||||
|
||||
struct loginclass;
|
||||
@ -46,10 +50,19 @@ struct loginclass;
|
||||
*
|
||||
* Please do not inspect cr_uid directly to determine superuserness. The
|
||||
* priv(9) interface should be used to check for privilege.
|
||||
*
|
||||
* Lock reference:
|
||||
* c - cr_mtx
|
||||
*
|
||||
* Unmarked fields are constant after creation.
|
||||
*
|
||||
* See "Credential management" comment in kern_prot.c for more information.
|
||||
*/
|
||||
#if defined(_KERNEL) || defined(_WANT_UCRED)
|
||||
struct ucred {
|
||||
u_int cr_ref; /* reference count */
|
||||
struct mtx cr_mtx;
|
||||
u_int cr_ref; /* (c) reference count */
|
||||
u_int cr_users; /* (c) proc + thread using this cred */
|
||||
#define cr_startcopy cr_uid
|
||||
uid_t cr_uid; /* effective user id */
|
||||
uid_t cr_ruid; /* real user id */
|
||||
@ -115,8 +128,11 @@ void proc_set_cred_init(struct proc *p, struct ucred *cr);
|
||||
void proc_set_cred(struct proc *p, struct ucred *cr);
|
||||
void proc_unset_cred(struct proc *p);
|
||||
void crfree(struct ucred *cr);
|
||||
struct ucred *crcowsync(void);
|
||||
struct ucred *crget(void);
|
||||
struct ucred *crhold(struct ucred *cr);
|
||||
struct ucred *crcowget(struct ucred *cr);
|
||||
void crcowfree(struct thread *td);
|
||||
void cru2x(struct ucred *cr, struct xucred *xcr);
|
||||
void cru2xt(struct thread *td, struct xucred *xcr);
|
||||
void crsetgroups(struct ucred *cr, int n, gid_t *groups);
|
||||
|
||||
Loading…
Reference in New Issue
Block a user