Implement shmat(2) flag SHM_REMAP.
Based on the description in Linux man page. Reviewed by: markj, ngie (previous version) Sponsored by: Mellanox Technologies MFC after: 1 week Differential revision: https://reviews.freebsd.org/D18837
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@ -47,6 +47,7 @@
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#include <unistd.h>
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#include <sys/ipc.h>
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#include <sys/mman.h>
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#include <sys/msg.h>
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#include <sys/param.h>
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#include <sys/sem.h>
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@ -772,17 +773,25 @@ ATF_TC_BODY(shm, tc)
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atf_tc_fail("sender: received unexpected signal");
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}
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ATF_TC_CLEANUP(shm, tc)
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static void
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shmid_cleanup(const char *name)
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{
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int sender_shmid;
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int shmid;
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/*
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* Remove the shared memory area if it exists.
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*/
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sender_shmid = read_int("sender_shmid");
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if (sender_shmid != -1)
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if (shmctl(sender_shmid, IPC_RMID, NULL) == -1)
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shmid = read_int(name);
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if (shmid != -1) {
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if (shmctl(shmid, IPC_RMID, NULL) == -1)
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err(1, "shmctl IPC_RMID");
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}
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}
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ATF_TC_CLEANUP(shm, tc)
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{
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shmid_cleanup("sender_shmid");
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}
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void
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@ -837,12 +846,53 @@ sharer(void)
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exit(0);
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}
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#ifdef SHM_REMAP
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ATF_TC_WITH_CLEANUP(shm_remap);
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ATF_TC_HEAD(shm_remap, tc)
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{
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atf_tc_set_md_var(tc, "descr", "Checks SHM_REMAP");
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}
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ATF_TC_BODY(shm_remap, tc)
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{
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char *shm_buf;
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int shmid_remap;
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pgsize = sysconf(_SC_PAGESIZE);
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shmkey = get_ftok(4160);
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ATF_REQUIRE_MSG(shmkey != (key_t)-1, "get_ftok failed");
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ATF_REQUIRE_MSG((shmid_remap = shmget(shmkey, pgsize,
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IPC_CREAT | 0640)) != -1, "shmget: %d", errno);
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write_int("shmid_remap", shmid_remap);
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ATF_REQUIRE_MSG((shm_buf = mmap(NULL, pgsize, PROT_READ | PROT_WRITE,
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MAP_ANON | MAP_PRIVATE, -1, 0)) != MAP_FAILED, "mmap: %d", errno);
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ATF_REQUIRE_MSG(shmat(shmid_remap, shm_buf, 0) == (void *)-1,
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"shmat without MAP_REMAP succeeded");
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ATF_REQUIRE_MSG(shmat(shmid_remap, shm_buf, SHM_REMAP) == shm_buf,
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"shmat(SHM_REMAP): %d", errno);
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}
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ATF_TC_CLEANUP(shm_remap, tc)
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{
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shmid_cleanup("shmid_remap");
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}
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#endif /* SHM_REMAP */
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ATF_TP_ADD_TCS(tp)
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{
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ATF_TP_ADD_TC(tp, msg);
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ATF_TP_ADD_TC(tp, sem);
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ATF_TP_ADD_TC(tp, shm);
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#ifdef SHM_REMAP
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ATF_TP_ADD_TC(tp, shm_remap);
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#endif
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return atf_no_error();
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}
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@ -25,7 +25,7 @@
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.\"
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.\" $FreeBSD$
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.\"
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.Dd January 25, 2018
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.Dd January 14, 2019
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.Dt SHMAT 2
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.Os
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.Sh NAME
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@ -64,17 +64,38 @@ kernel.
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.It
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If
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.Fa addr
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is nonzero and SHM_RND is not specified in
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is nonzero and
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.Va SHM_RND
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is not specified in
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.Fa flag ,
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the segment is attached the specified address.
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.It
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If
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.Fa addr
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is specified and SHM_RND is specified,
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is specified and
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.Va SHM_RND
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is specified,
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.Fa addr
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is rounded down to the nearest multiple of SHMLBA.
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.El
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.Pp
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If the
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.Va SHM_REMAP
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flag is specified and the passed
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.Fa addr
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is not
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.Dv NULL ,
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any existing mappings in the virtual addresses range are
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cleared before the segment is attached.
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If the flag is not specified,
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.Fa addr
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is not
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.Dv NULL ,
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and the virtual address range contains
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some pre-existing mappings, the
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.Fn shmat
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call fails.
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.Pp
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The
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.Fn shmdt
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system call
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@ -104,6 +125,14 @@ The
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.Fa addr
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argument
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was not an acceptable address.
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.It Bq Er ENOMEM
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The specified
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.Fa addr
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cannot be used for mapping, for instance due to the amount of available
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space being smaller than the segment size,
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or because pre-existing mappings are in the range and no
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.Va SHM_REMAP
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flag was provided.
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.It Bq Er EMFILE
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Failed to attach the shared memory segment because the per-process
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.Va kern.ipc.shmseg
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@ -388,7 +388,7 @@ kern_shmat_locked(struct thread *td, int shmid, const void *shmaddr,
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vm_offset_t attach_va;
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vm_prot_t prot;
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vm_size_t size;
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int error, i, rv;
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int cow, error, find_space, i, rv;
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AUDIT_ARG_SVIPC_ID(shmid);
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AUDIT_ARG_VALUE(shmflg);
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@ -427,6 +427,7 @@ kern_shmat_locked(struct thread *td, int shmid, const void *shmaddr,
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return (EMFILE);
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size = round_page(shmseg->u.shm_segsz);
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prot = VM_PROT_READ;
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cow = MAP_INHERIT_SHARE | MAP_PREFAULT_PARTIAL;
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if ((shmflg & SHM_RDONLY) == 0)
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prot |= VM_PROT_WRITE;
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if (shmaddr != NULL) {
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@ -436,6 +437,9 @@ kern_shmat_locked(struct thread *td, int shmid, const void *shmaddr,
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attach_va = (vm_offset_t)shmaddr;
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else
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return (EINVAL);
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if ((shmflg & SHM_REMAP) != 0)
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cow |= MAP_REMAP;
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find_space = VMFS_NO_SPACE;
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} else {
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/*
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* This is just a hint to vm_map_find() about where to
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@ -443,12 +447,12 @@ kern_shmat_locked(struct thread *td, int shmid, const void *shmaddr,
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*/
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attach_va = round_page((vm_offset_t)p->p_vmspace->vm_daddr +
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lim_max(td, RLIMIT_DATA));
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find_space = VMFS_OPTIMAL_SPACE;
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}
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vm_object_reference(shmseg->object);
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rv = vm_map_find(&p->p_vmspace->vm_map, shmseg->object, 0, &attach_va,
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size, 0, shmaddr != NULL ? VMFS_NO_SPACE : VMFS_OPTIMAL_SPACE,
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prot, prot, MAP_INHERIT_SHARE | MAP_PREFAULT_PARTIAL);
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size, 0, find_space, prot, prot, cow);
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if (rv != KERN_SUCCESS) {
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vm_object_deallocate(shmseg->object);
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return (ENOMEM);
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@ -52,6 +52,7 @@
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#define SHM_RDONLY 010000 /* Attach read-only (else read-write) */
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#define SHM_RND 020000 /* Round attach address to SHMLBA */
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#define SHM_REMAP 030000 /* Unmap before mapping */
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#define SHMLBA PAGE_SIZE /* Segment low boundary address multiple */
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/* "official" access mode definitions; somewhat braindead since you have
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@ -1565,6 +1565,8 @@ vm_map_find(vm_map_t map, vm_object_t object, vm_ooffset_t offset,
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KASSERT((cow & (MAP_STACK_GROWS_DOWN | MAP_STACK_GROWS_UP)) == 0 ||
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object == NULL,
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("vm_map_find: non-NULL backing object for stack"));
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MPASS((cow & MAP_REMAP) == 0 || (find_space == VMFS_NO_SPACE &&
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(cow & (MAP_STACK_GROWS_DOWN | MAP_STACK_GROWS_UP)) == 0));
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if (find_space == VMFS_OPTIMAL_SPACE && (object == NULL ||
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(object->flags & OBJ_COLORED) == 0))
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find_space = VMFS_ANY_SPACE;
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@ -1595,6 +1597,14 @@ again:
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}
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goto done;
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}
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} else if ((cow & MAP_REMAP) != 0) {
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if (*addr < vm_map_min(map) ||
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*addr + length > vm_map_max(map) ||
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*addr + length <= length) {
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rv = KERN_INVALID_ADDRESS;
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goto done;
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}
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vm_map_delete(map, *addr, *addr + length);
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}
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if ((cow & (MAP_STACK_GROWS_DOWN | MAP_STACK_GROWS_UP)) != 0) {
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rv = vm_map_stack_locked(map, *addr, length, sgrowsiz, prot,
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@ -342,6 +342,7 @@ long vmspace_resident_count(struct vmspace *vmspace);
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#define MAP_DISABLE_COREDUMP 0x0100
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#define MAP_PREFAULT_MADVISE 0x0200 /* from (user) madvise request */
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#define MAP_VN_WRITECOUNT 0x0400
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#define MAP_REMAP 0x0800
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#define MAP_STACK_GROWS_DOWN 0x1000
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#define MAP_STACK_GROWS_UP 0x2000
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#define MAP_ACC_CHARGED 0x4000
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