switcher: symbolic names of seal types

Co-authored-by: Robert Norton <[email protected]>

sdk/core/loader/boot.cc

@@ -11,7 +11,6 @@
 #include <string.h>
 
 #include "../switcher/tstack.h"
-#include "../switcher/misc-assembly.h"
 #include "constants.h"
 #include "debug.hh"
 #include "defines.h"
@@ -145,6 +144,14 @@ namespace
 		FirstDynamicSoftware = 0x1000000,
 	};
 
+	// The switcher assembly includes the types of import table entries and
+	// trusted stacks.  This enumeration and the assembly must be kept in sync.
+	// This will fail if the enumeration value changes.
+	static_assert(int(SealedImportTableEntries) == 9,
+	              "If this fails, update switcher/entry.S to the new value");
+	static_assert(int(SealedTrustedStacks) == 10,
+	              "If this fails, update switcher/entry.S to the new value");
+
 	// The allocator and static sealing types must be contiguous so that the
 	// token library can hold a permit-unseal capability for both.
 	static_assert(int(Allocator) + 1 == int(StaticToken),
@@ -163,6 +170,18 @@ namespace
 	static_assert(magic_enum::enum_count<SealingType>() <= 12,
 	              "Too many sealing types reserved for a 3-bit otype field");
 
+} // namespace
+
+/*
+ * Unusually late, include this where we have access to the above enum
+ * SealingType, but early enough that the constants defined herein are available
+ * to the rest of the code.
+ */
+#include "../switcher/misc-assembly.h"
+
+namespace
+{
+
 	constexpr auto StoreLPerm = Root::Permissions<Root::Type::RWStoreL>;
 	/// PCC permissions for the switcher.
 	constexpr auto SwitcherPccPermissions =

sdk/core/switcher/entry.S

@@ -257,7 +257,7 @@ __Z26compartment_switcher_entryz:
 
 	// Fetch the sealing key
 	LoadCapPCC         cs0, compartment_switcher_sealing_key
-	li                 gp, 9
+	li                 gp, SEAL_TYPE_SealedImportTableEntries
 	csetaddr           cs0, cs0, gp
 	// The target capability is in ct1. Unseal, check tag and load the entry point offset.
 	cunseal            ct1, ct1, cs0
@@ -535,7 +535,7 @@ exception_entry_asm:
 
 	// Switch onto the new thread's trusted stack
 	LoadCapPCC         ct0, compartment_switcher_sealing_key
-	li                 gp, 10
+	li                 gp, SEAL_TYPE_SealedTrustedStacks
 	csetaddr           ct0, ct0, gp
 	cunseal            csp, ca0, ct0
 	clw                t0, TrustedStack_offset_mcause(csp)
@@ -965,7 +965,7 @@ __Z25switcher_interrupt_threadPv:
 	// Load the unsealing key into a register that we will clobber two
 	// instructions later.
 	LoadCapPCC         ca1, compartment_switcher_sealing_key
-	li                 a2, 10
+	li                 a2, SEAL_TYPE_SealedTrustedStacks
 	csetaddr           ca1, ca1, a2
 	// The target capability is in ct1. Unseal, check tag and load the entry point offset.
 	cunseal            ca1, ca0, ca1
@@ -1024,7 +1024,7 @@ __Z25switcher_interrupt_threadPv:
 	.type __Z23switcher_current_threadv,@function
 __Z23switcher_current_threadv:
 	LoadCapPCC         ca0, compartment_switcher_sealing_key
-	li                 a1, 10
+	li                 a1, SEAL_TYPE_SealedTrustedStacks
 	csetaddr           ca0, ca0, a1
 	cspecialr          ca1, mtdc
 	cseal              ca0, ca1, ca0

sdk/core/switcher/misc-assembly.h

@@ -34,3 +34,10 @@ using namespace priv;
 EXPORT_ASSEMBLY_NAME(MCAUSE_THREAD_EXIT, 24)
 EXPORT_ASSEMBLY_NAME(MCAUSE_THREAD_INTERRUPT, 25)
 EXPORT_ASSEMBLY_NAME(MCAUSE_CHERI, 28)
+
+EXPORT_ASSEMBLY_EXPRESSION(SEAL_TYPE_SealedImportTableEntries,
+                           SealingType::SealedImportTableEntries,
+                           9)
+EXPORT_ASSEMBLY_EXPRESSION(SEAL_TYPE_SealedTrustedStacks,
+                           SealingType::SealedTrustedStacks,
+                           10)