The branch main has been updated by dchagin: URL: https://cgit.FreeBSD.org/src/commit/?id=3d2fec7db856c67e1a94a87a846d8ffe6f48b61f
commit 3d2fec7db856c67e1a94a87a846d8ffe6f48b61f Author: Dmitry Chagin <[email protected]> AuthorDate: 2023-05-29 08:15:28 +0000 Commit: Dmitry Chagin <[email protected]> CommitDate: 2023-05-29 08:15:28 +0000 namei: Add the abilty for the ABI to specify an alternate root path For now a non-native ABI (i.e., Linux) uses the kern_alternate_path() facility to dynamically reroot lookups. First, an attempt is made to lookup the file in /compat/linux/original-path. If that fails, the lookup is done in /original-path. Thats requires a bit of code in every ABI syscall implementation where path name translation is needed. Also our kern_alternate_path() does not properly lookups absolute symlinks in second attempt, i.e., does not append /compat/linux part to the resolved link. The change is intended to avoid this by specifiyng the ABI root directory for namei(), using one call to pwd_altroot() during exec-time into the ABI. In that case namei() will dynamically reroot lookups as mentioned above. PR: 72920 Reviewed by: kib Differential revision: https://reviews.freebsd.org/D38933 MFC after: 2 month --- sys/kern/kern_descrip.c | 61 +++++++++++++++++++++++++++++++++++++++++++++++-- sys/kern/vfs_cache.c | 4 ++-- sys/kern/vfs_lookup.c | 30 +++++++++++++++++++++--- sys/sys/filedesc.h | 4 ++++ sys/sys/namei.h | 11 +++++++-- 5 files changed, 101 insertions(+), 9 deletions(-) diff --git a/sys/kern/kern_descrip.c b/sys/kern/kern_descrip.c index 0be59e930dd4..908c3352514b 100644 --- a/sys/kern/kern_descrip.c +++ b/sys/kern/kern_descrip.c @@ -3839,6 +3839,11 @@ pwd_fill(struct pwd *oldpwd, struct pwd *newpwd) vrefact(oldpwd->pwd_jdir); newpwd->pwd_jdir = oldpwd->pwd_jdir; } + + if (newpwd->pwd_adir == NULL && oldpwd->pwd_adir != NULL) { + vrefact(oldpwd->pwd_adir); + newpwd->pwd_adir = oldpwd->pwd_adir; + } } struct pwd * @@ -3930,6 +3935,8 @@ pwd_drop(struct pwd *pwd) vrele(pwd->pwd_rdir); if (pwd->pwd_jdir != NULL) vrele(pwd->pwd_jdir); + if (pwd->pwd_adir != NULL) + vrele(pwd->pwd_adir); uma_zfree_smr(pwd_zone, pwd); } @@ -3967,6 +3974,8 @@ pwd_chroot(struct thread *td, struct vnode *vp) vrefact(vp); newpwd->pwd_rdir = vp; + vrefact(vp); + newpwd->pwd_adir = vp; if (oldpwd->pwd_jdir == NULL) { vrefact(vp); newpwd->pwd_jdir = vp; @@ -3997,6 +4006,40 @@ pwd_chdir(struct thread *td, struct vnode *vp) pwd_drop(oldpwd); } +/* + * Process is transitioning to/from a non-native ABI. + */ +void +pwd_altroot(struct thread *td, struct vnode *altroot_vp) +{ + struct pwddesc *pdp; + struct pwd *newpwd, *oldpwd; + + newpwd = pwd_alloc(); + pdp = td->td_proc->p_pd; + PWDDESC_XLOCK(pdp); + oldpwd = PWDDESC_XLOCKED_LOAD_PWD(pdp); + if (altroot_vp != NULL) { + /* + * Native process to a non-native ABI. + */ + + vrefact(altroot_vp); + newpwd->pwd_adir = altroot_vp; + } else { + /* + * Non-native process to the native ABI. + */ + + vrefact(oldpwd->pwd_rdir); + newpwd->pwd_adir = oldpwd->pwd_rdir; + } + pwd_fill(oldpwd, newpwd); + pwd_set(pdp, newpwd); + PWDDESC_XUNLOCK(pdp); + pwd_drop(oldpwd); +} + /* * jail_attach(2) changes both root and working directories. */ @@ -4030,6 +4073,8 @@ pwd_chroot_chdir(struct thread *td, struct vnode *vp) vrefact(vp); newpwd->pwd_jdir = vp; } + vrefact(vp); + newpwd->pwd_adir = vp; pwd_fill(oldpwd, newpwd); pwd_set(pdp, newpwd); PWDDESC_XUNLOCK(pdp); @@ -4046,7 +4091,8 @@ pwd_ensure_dirs(void) pdp = curproc->p_pd; PWDDESC_XLOCK(pdp); oldpwd = PWDDESC_XLOCKED_LOAD_PWD(pdp); - if (oldpwd->pwd_cdir != NULL && oldpwd->pwd_rdir != NULL) { + if (oldpwd->pwd_cdir != NULL && oldpwd->pwd_rdir != NULL && + oldpwd->pwd_adir != NULL) { PWDDESC_XUNLOCK(pdp); return; } @@ -4064,6 +4110,10 @@ pwd_ensure_dirs(void) vrefact(rootvnode); newpwd->pwd_rdir = rootvnode; } + if (newpwd->pwd_adir == NULL) { + vrefact(rootvnode); + newpwd->pwd_adir = rootvnode; + } pwd_set(pdp, newpwd); PWDDESC_XUNLOCK(pdp); pwd_drop(oldpwd); @@ -4084,6 +4134,8 @@ pwd_set_rootvnode(void) newpwd->pwd_cdir = rootvnode; vrefact(rootvnode); newpwd->pwd_rdir = rootvnode; + vrefact(rootvnode); + newpwd->pwd_adir = rootvnode; pwd_fill(oldpwd, newpwd); pwd_set(pdp, newpwd); PWDDESC_XUNLOCK(pdp); @@ -4119,7 +4171,8 @@ mountcheckdirs(struct vnode *olddp, struct vnode *newdp) if (oldpwd == NULL || (oldpwd->pwd_cdir != olddp && oldpwd->pwd_rdir != olddp && - oldpwd->pwd_jdir != olddp)) { + oldpwd->pwd_jdir != olddp && + oldpwd->pwd_adir != olddp)) { PWDDESC_XUNLOCK(pdp); pddrop(pdp); continue; @@ -4136,6 +4189,10 @@ mountcheckdirs(struct vnode *olddp, struct vnode *newdp) vrefact(newdp); newpwd->pwd_jdir = newdp; } + if (oldpwd->pwd_adir == olddp) { + vrefact(newdp); + newpwd->pwd_adir = newdp; + } pwd_fill(oldpwd, newpwd); pwd_set(pdp, newpwd); PWDDESC_XUNLOCK(pdp); diff --git a/sys/kern/vfs_cache.c b/sys/kern/vfs_cache.c index e4977392349f..8daaf5bc53ad 100644 --- a/sys/kern/vfs_cache.c +++ b/sys/kern/vfs_cache.c @@ -4349,7 +4349,7 @@ cache_fpl_terminated(struct cache_fpl *fpl) (NC_NOMAKEENTRY | NC_KEEPPOSENTRY | LOCKLEAF | LOCKPARENT | WANTPARENT | \ FAILIFEXISTS | FOLLOW | EMPTYPATH | LOCKSHARED | WILLBEDIR | \ ISOPEN | NOMACCHECK | AUDITVNODE1 | AUDITVNODE2 | NOCAPCHECK | OPENREAD | \ - OPENWRITE | WANTIOCTLCAPS) + OPENWRITE | WANTIOCTLCAPS | ISRESTARTED) #define CACHE_FPL_INTERNAL_CN_FLAGS \ (ISDOTDOT | MAKEENTRY | ISLASTCN) @@ -6238,7 +6238,7 @@ cache_fplookup(struct nameidata *ndp, enum cache_fpl_status *status, fpl.pwd = pwdp; pwd = pwd_get_smr(); *(fpl.pwd) = pwd; - ndp->ni_rootdir = pwd->pwd_rdir; + namei_setup_rootdir(ndp, cnp, pwd); ndp->ni_topdir = pwd->pwd_jdir; if (cnp->cn_pnbuf[0] == '/') { diff --git a/sys/kern/vfs_lookup.c b/sys/kern/vfs_lookup.c index a75ea4ca16d6..593e1e487c6f 100644 --- a/sys/kern/vfs_lookup.c +++ b/sys/kern/vfs_lookup.c @@ -81,6 +81,13 @@ static void NDVALIDATE_impl(struct nameidata *, int); #define NDVALIDATE(ndp) #endif +#define NDRESTART(ndp) do { \ + NDREINIT_DBG(ndp); \ + ndp->ni_resflags = 0; \ + ndp->ni_cnd.cn_flags &= ~NAMEI_INTERNAL_FLAGS; \ + ndp->ni_cnd.cn_flags |= ISRESTARTED; \ +} while (0) + SDT_PROVIDER_DEFINE(vfs); SDT_PROBE_DEFINE4(vfs, namei, lookup, entry, "struct vnode *", "char *", "unsigned long", "bool"); @@ -334,7 +341,7 @@ namei_setup(struct nameidata *ndp, struct vnode **dpp, struct pwd **pwdp) * The reference on ni_rootdir is acquired in the block below to avoid * back-to-back atomics for absolute lookups. */ - ndp->ni_rootdir = pwd->pwd_rdir; + namei_setup_rootdir(ndp, cnp, pwd); ndp->ni_topdir = pwd->pwd_jdir; if (cnp->cn_pnbuf[0] == '/') { @@ -594,6 +601,7 @@ namei(struct nameidata *ndp) MPASS(ndp->ni_startdir == NULL || ndp->ni_startdir->v_type == VDIR || ndp->ni_startdir->v_type == VBAD); +restart: ndp->ni_lcf = 0; ndp->ni_loopcnt = 0; ndp->ni_vp = NULL; @@ -628,6 +636,12 @@ namei(struct nameidata *ndp) case CACHE_FPL_STATUS_HANDLED: if (error == 0) NDVALIDATE(ndp); + else if (__predict_false(pwd->pwd_adir != pwd->pwd_rdir && + (cnp->cn_flags & ISRESTARTED) == 0)) { + namei_cleanup_cnp(cnp); + NDRESTART(ndp); + goto restart; + } return (error); case CACHE_FPL_STATUS_PARTIAL: TAILQ_INIT(&ndp->ni_cap_tracker); @@ -668,8 +682,18 @@ namei(struct nameidata *ndp) for (;;) { ndp->ni_startdir = dp; error = vfs_lookup(ndp); - if (error != 0) - goto out; + if (error != 0) { + if (__predict_false(pwd->pwd_adir != pwd->pwd_rdir && + error == ENOENT && + (cnp->cn_flags & ISRESTARTED) == 0)) { + nameicap_cleanup(ndp); + pwd_drop(pwd); + namei_cleanup_cnp(cnp); + NDRESTART(ndp); + goto restart; + } else + goto out; + } /* * If not a symbolic link, we're done. diff --git a/sys/sys/filedesc.h b/sys/sys/filedesc.h index 578b84696663..bba12d08287c 100644 --- a/sys/sys/filedesc.h +++ b/sys/sys/filedesc.h @@ -89,6 +89,8 @@ struct fdescenttbl { /* * This struct is copy-on-write and allocated from an SMR zone. * All fields are constant after initialization apart from the reference count. + * The ABI root directory is initialized as the root directory and changed + * during process transiting to or from non-native ABI. * * Check pwd_* routines for usage. */ @@ -97,6 +99,7 @@ struct pwd { struct vnode *pwd_cdir; /* current directory */ struct vnode *pwd_rdir; /* root directory */ struct vnode *pwd_jdir; /* jail root directory */ + struct vnode *pwd_adir; /* abi root directory */ }; typedef SMR_POINTER(struct pwd *) smrpwd_t; @@ -342,6 +345,7 @@ struct pwddesc *pdinit(struct pwddesc *pdp, bool keeplock); struct pwddesc *pdshare(struct pwddesc *pdp); void pdunshare(struct thread *td); +void pwd_altroot(struct thread *td, struct vnode *altroot_vp); void pwd_chdir(struct thread *td, struct vnode *vp); int pwd_chroot(struct thread *td, struct vnode *vp); int pwd_chroot_chdir(struct thread *td, struct vnode *vp); diff --git a/sys/sys/namei.h b/sys/sys/namei.h index e12d79b19c6e..88ddb0f13458 100644 --- a/sys/sys/namei.h +++ b/sys/sys/namei.h @@ -159,7 +159,7 @@ int cache_fplookup(struct nameidata *ndp, enum cache_fpl_status *status, * Namei parameter descriptors. */ #define RDONLY 0x00000200 /* lookup with read-only semantics */ -/* UNUSED 0x00000400 */ +#define ISRESTARTED 0x00000400 /* restarted namei */ /* UNUSED 0x00000800 */ #define ISWHITEOUT 0x00001000 /* found whiteout */ #define DOWHITEOUT 0x00002000 /* do whiteouts */ @@ -187,7 +187,7 @@ int cache_fplookup(struct nameidata *ndp, enum cache_fpl_status *status, */ #define NAMEI_INTERNAL_FLAGS \ (NOEXECCHECK | MAKEENTRY | ISSYMLINK | ISLASTCN | ISDOTDOT | \ - TRAILINGSLASH) + TRAILINGSLASH | ISRESTARTED) /* * Namei results flags @@ -293,6 +293,13 @@ int namei(struct nameidata *ndp); int vfs_lookup(struct nameidata *ndp); int vfs_relookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp, bool refstart); + +#define namei_setup_rootdir(ndp, cnp, pwd) do { \ + if (__predict_true((cnp->cn_flags & ISRESTARTED) == 0)) \ + ndp->ni_rootdir = pwd->pwd_adir; \ + else \ + ndp->ni_rootdir = pwd->pwd_rdir; \ +} while (0) #endif /*
