Revocation control test revocation happens.

The test now writes two capabilities to the end of SRAM, one with base
zero and one with base at the end of SRAM. After the sweep it checks
that the base zero capability's tag stays in tact while the one at the
end of SRAM is cleared. Note this is different from the CLC test because
the revocation tags are cleared before testing so the CLC will not clear
the tags if the hardware revocer hasn't already.

sw/cheri/checks/tag_test.S

@@ -140,8 +140,9 @@ revtags:
 
 // Test of hardware revoker
 hw_rev:
-  // Capability to revocation tags
-  li t0, 0x30000000
+  // Capability to end of revocation tags
+  li t0, 0x30000800
+  addi t0, t0, -4
   csetaddr ct0, ca0, t0
   // Zero revocation tags
   csw zero, 0(ct0)
@@ -150,14 +151,29 @@ hw_rev:
   csetaddr ct1, ca0, t1
   li t2, 0x00120000 // End of SRAM
   addi t2, t2, -8 // Point to last capability aligned region in SRAM
+  csetaddr ct2, ca0, t2
+  csc ct0, 0(ct2) // Write capability with base 0, which should not be cleared.
   csw t2, 4(ct1) // Set end of memory to sweep
   addi t2, t2, -8 // Second to last capability in SRAM.
+  csetaddr ca3, ca0, t2
+  csetboundsimm ca3, ca3, 1
+  csetaddr ct2, ca0, t2
+  csc ca3, 0(ct2) // Write capability with base 0x11FFE0, which should be cleared
+  // Revoke end of SRAM
+  li a3, 0xFFFFFFFF
+  csw a3, 0(ct0)
   csw t2, 0(ct1) // Set start of memory to sweep
   clw t2, 12(ct1) // Read current epoch
-  andi t2, t2, 1 // Get running bit
+  andi t2, t2, 1 // Get running bit, which should be 0
   bnez t2, fail
   li t2, 1
   csw t2, 8(ct1) // Start sweep
+  nop // Wait a few cycles to allow run to be set to 1
+  nop
+  nop
+  clw t2, 12(ct1) // Read current epoch
+  andi t2, t2, 1 // Get running bit, which should be 1
+  beqz t2, fail
   // Wait for some cycles while the sweep happens.
   li t2, 10
 wait_loop:
@@ -167,6 +183,21 @@ wait_loop:
   clw t2, 16(ct1)
   beqz t2, fail
   csw zero, 16(ct1) // Clear interrupt status
+  // Unrevoke end of SRAM to disable load capability barrier.
+  csw zero, 0(ct0)
+  li t2, 0x00120000 // End of SRAM
+  addi t2, t2, -8 // Point to last capability aligned region in SRAM
+  csetaddr ct2, ca0, t2
+  clc ca3, 0(ct2) // Read capability for which tag should stay 1.
+  cgettag a3, ca3
+  beqz a3, fail
+  addi t2, t2, -8 // Second to last capability in SRAM.
+  csetaddr ct2, ca0, t2
+  clc ca3, 0(ct2) // Read capability for which tag should be 0.
+  cgettag a3, ca3
+  bnez a3, fail
+
+hw_rev_intr:
   li t2, 1
   csw t2, 20(ct1) // Enable interrupts
   csw t2, 8(ct1) // Start sweep