mmap: Remove support for MAP_ALIGNED_CHERI

Kernel reservation managment code takes care of alignment (and size)
rounding for CheriABI binaries.  Hybrid binaries that need CHERI
alignment can, and for length must, do their own rounding in code that
will already be CHERI-aware.

bin/cheribsdtest/cheribsdtest_vm.c

@@ -893,13 +893,6 @@ CHERIBSDTEST(vm_reservation_align,
 	    "mmap failed to align representable region with requested "
 	    "alignment %lx for %p", align_shift + 1, map);
 
-	/* Explicit cheri alignment */
-	map = CHERIBSDTEST_CHECK_SYSCALL(mmap(NULL, len,
-	    PROT_READ | PROT_WRITE, MAP_ANON | MAP_ALIGNED_CHERI, -1, 0));
-	CHERIBSDTEST_VERIFY2(((ptraddr_t)(map) & align_mask) == 0,
-	    "mmap failed to align representable region with requested "
-	    "cheri alignment for %p", map);
-
 	cheribsdtest_success();
 }
 

lib/libsys/mmap.2

@@ -198,23 +198,6 @@ will fail.
 The
 .Fa n
 argument specifies the binary logarithm of the desired alignment.
-.It Dv MAP_ALIGNED_CHERI
-Align the region as required to allow a CHERI capability to be created.
-If a suitable region cannot be found or the address of
-.Fa addr
-or the length in
-.Fa len
-is not representable as a precise capability,
-.Fn mmap
-will fail.
-The
-.Dv MAP_ALIGNED_CHERI
-flag is assumed for CheriABI programs when address space is being
-reserved.
-On architectures without CHERI support or where all capabilities are
-precise,
-.Dv MAP_ALIGNED_CHERI
-has no effect.
 .It Dv MAP_ALIGNED_SUPER
 Align the region to maximize the potential use of large
 .Pq Dq super
@@ -593,14 +576,6 @@ was specified, but
 .Dv MAP_FIXED
 was not.
 .It Bq Er EINVAL
-.Dv MAP_ALIGNED_CHERI
-(implied on CheriABI)
-was specified and
-.Fa addr
-or
-.Fa size
-was not sufficently aligned for the current architecture.
-.It Bq Er EINVAL
 .Dv MAP_GUARD
 was specified, but the
 .Fa offset

sys/sys/mman.h

@@ -120,14 +120,6 @@
 #define	MAP_ALIGNMENT_MASK	MAP_ALIGNED(0xff)
 #define	MAP_ALIGNED_SUPER	MAP_ALIGNED(1) /* align on a superpage */
 
-/*
- * CHERI specific flags and alignment constraints.
- *
- * MAP_ALIGNED_CHERI returns memory aligned appropriately for the requested
- * length or fails.  Passing an under-rounded length fails.
- */
-#define	MAP_ALIGNED_CHERI	MAP_ALIGNED(2)	/* align for CHERI data */
-
 /*
  * Flags provided to shm_rename
  */

sys/vm/vm_mmap.c

@@ -390,33 +390,6 @@ sys_mmap(struct thread *td, struct mmap_args *uap)
 		return (EPROT);
 	}
 
-	if ((flags & MAP_ALIGNMENT_MASK) == MAP_ALIGNED_SUPER) {
-#if VM_NRESERVLEVEL > 0
-		/*
-		 * pmap_align_superpage() is a no-op for allocations
-		 * less than a super page so request data alignment
-		 * in that case.
-		 *
-		 * In practice this is a no-op as super-pages are
-		 * precisely representable.
-		 */
-		if (uap->len < (1UL << (VM_LEVEL_0_ORDER + PAGE_SHIFT)) &&
-		    CHERI_REPRESENTABLE_ALIGNMENT(uap->len) > (1UL << PAGE_SHIFT)) {
-			flags &= ~MAP_ALIGNMENT_MASK;
-			flags |= MAP_ALIGNED_CHERI;
-		}
-#endif
-	}
-	else if ((flags & MAP_ALIGNMENT_MASK) != MAP_ALIGNED(0) &&
-	    (flags & MAP_ALIGNMENT_MASK) != MAP_ALIGNED(3) && /* MAP_ALIGNED_CHERI_SEAL */
-	    (flags & MAP_ALIGNMENT_MASK) != MAP_ALIGNED_CHERI) {
-		/* Reject nonsensical sub-page alignment requests */
-		if ((flags >> MAP_ALIGNMENT_SHIFT) < PAGE_SHIFT) {
-			SYSERRCAUSE("subpage alignment request");
-			return (EINVAL);
-		}
-	}
-
 	/*
 	 * NOTE: If this architecture requires an alignment constraint, it is
 	 * set at this point.  A simple assert is not easy to contruct...
@@ -626,37 +599,8 @@ kern_mmap(struct thread *td, const struct mmap_req *mrp)
 	if (len > size)
 		return (ENOMEM);
 
-	align = flags & MAP_ALIGNMENT_MASK;
-#if !__has_feature(capabilities)
-	/* In the non-CHERI case, remove the alignment request. */
-	if (align == MAP_ALIGNED_CHERI) {
-		flags &= ~MAP_ALIGNMENT_MASK;
-		align = 0;
-	}
-#else /* __has_feature(capabilities) */
-	/*
-	 * Convert MAP_ALIGNED_CHERI into explicit alignment
-	 * requests and pad lengths.  The combination of alignment (via
-	 * the updated, explicit alignment flags) and padding is required
-	 * for any request that would otherwise be unrepresentable due
-	 * to compressed capability bounds.
-	 */
-	if (align == MAP_ALIGNED_CHERI) {
-		flags &= ~MAP_ALIGNMENT_MASK;
-		if (CHERI_REPRESENTABLE_ALIGNMENT(size) > PAGE_SIZE) {
-			flags |= MAP_ALIGNED(CHERI_ALIGN_SHIFT(size));
-
-			if (size != CHERI_REPRESENTABLE_LENGTH(size))
-				size = CHERI_REPRESENTABLE_LENGTH(size);
-
-			if (CHERI_ALIGN_MASK(size) != 0)
-				addr_mask = CHERI_ALIGN_MASK(size);
-		}
-		align = flags & MAP_ALIGNMENT_MASK;
-	}
-#endif
-
 	/* Ensure alignment is at least a page and fits in a pointer. */
+	align = flags & MAP_ALIGNMENT_MASK;
 	if (align != 0 && align != MAP_ALIGNED_SUPER &&
 	    (align >> MAP_ALIGNMENT_SHIFT >= sizeof(void *) * NBBY ||
 	    align >> MAP_ALIGNMENT_SHIFT < PAGE_SHIFT)) {