Add ISA test #29

rmn30 · 2023-03-10T17:41:49Z

This adds a test that attempts to trigger various ISA corner cases and increase test coverage.

tests/isa-test.cc

davidchisnall · 2023-03-13T16:34:58Z

tests/isa-test.cc

+	[[cheri::interrupt_state(disabled)]] void *get_interrupts_disabled_sentry()
+	{
+		void *returnCap;
+		asm volatile("cjal %0, 4" : "=C"(returnCap));


This is beautifully horrifying, can you add a comment explaining it?

It is just a jump and link to the next instruction, putting the link cap in returnCap. I guess might be better written with local label rather than hardcoded offset?

Probably "cjal %0, 1f;\n1:" is the right thing to do, but if you want to be extra horrifying, there's GCC's asm goto... :D

If we ever have a programming guide, we should point to this example as something really contra-indicated. Would you object to a comment here and on the similar method below that this is deliberately unsafe handling of a dangerous thing?

Or maybe even simplified to &get_interrupts_disabled_sentry given the way the ABI works.

tests/isa-test.cc

nwf-msr

Generally, this is really great. The combinator approach works out really nicely, even if C++ will never be as nice as Haskell. ;)

A small pile of nits, but nothing big.

tests/isa-test.cc

nwf-msr · 2023-03-13T17:28:19Z

tests/isa-test.cc

+	[[cheri::interrupt_state(disabled)]] void *get_interrupts_disabled_sentry()
+	{
+		void *returnCap;
+		asm volatile("cjal %0, 4" : "=C"(returnCap));


Probably "cjal %0, 1f;\n1:" is the right thing to do, but if you want to be extra horrifying, there's GCC's asm goto... :D

If we ever have a programming guide, we should point to this example as something really contra-indicated. Would you object to a comment here and on the similar method below that this is deliberately unsafe handling of a dangerous thing?

nwf-msr · 2023-03-13T18:10:06Z

tests/isa-test.cc

+	 * We call this with values we expect to fault and want to know the address
+	 * of the faulting instruction. Since it is so simple it will have no
+	 * prelude so we can use the address of the function as the address of the
+	 * store. Obviously we can't allow it to be inlined.


I'm not sure about the names; these are not intrinsically going to fault, they're just used that way ("He's not evil, he's just written that way")... maybe perform_store or something like that?

Perhaps this and faulting_load should be in assembler rather than relying on the (sensible, probably not going to change, but still not contractual) behavior of the compiler?

nwf-msr · 2023-03-13T18:10:58Z

tests/isa-test.cc

+	 * flexible ways before attempting tests.
+	 */
+	template<class T>
+	using CapabilityFilter = Capability<T> (*)(Capability<T>);


This really is Haskell in C++! 👍

nwf-msr · 2023-03-13T18:14:54Z

tests/isa-test.cc

+	 */
+	void do_load_test(CauseCode               expectedFault,
+	                  CapabilityFilter<int *> baseFilter,
+	                  size_t                  anExpectedMCause = MCauseCheri)


Very minor nit, but maybe the argument order should be baseFilter, expectedFault, anExpectedMCause, so that it's read as something like "I expect a load with this filter to cause this fault and this code"?

tests/isa-test.cc

nwf-msr · 2023-03-13T18:24:03Z

tests/isa-test.cc

+		// Storing untagged cap via data-only cap is allowed.
+		do_store_test(
+		  std::nullopt,
+		  permission_filter<PermissionSet{Permission::Load, Permission::Store}>,


Why not identity_filter?

nwf-msr · 2023-03-13T18:26:38Z

tests/isa-test.cc

+	 * nops so that we can test things like half of an instruction being in
+	 * bounds. Clang doesn't seem to emit a prelude for this function. If it
+	 * does (e.g. at -O0) our expected error PC calculations will be wrong due
+	 * to alignment.


Maybe these, too, should be in assembler?

This specifically aims to test features that are not likely to occur in normal operation, such as exceptions. Hits quite a few potential corner cases but some are best tested in bare metal assembly and can't be easily tested in an RTOS tests.

Co-authored-by: Nathaniel Filardo <[email protected]>

The static casts in the pointer DebugFormatArgumentAdapters prevented function pointers from being printed as the compiler does not permit static casts from function pointer to void*. Removing them seems to work fine so not sure what they were there for.

Still some TODOs to resolve.

… review. Also address a few other review comments.

nwf-msr · 2024-07-02T16:29:08Z

tests/isa-test.cc

+		// sentry {}", reinterpret_cast<void*>(interruptsDisabledSentry.get()));
+		// TEST(interruptsDisabledSentry.type() == 2,
+		//      "Expected type 2 but got {}",
+		//      interruptsDisabledSentry.type());


Is there no good way to get these?

I got the linker error in the comment. Suspect it might be a bug @davidchisnall ?

rmn30 force-pushed the isa_test branch 2 times, most recently from f11cf92 to 44b3b0b Compare March 10, 2023 18:10

saaramar reviewed Mar 12, 2023

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davidchisnall reviewed Mar 13, 2023

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rmn30 force-pushed the isa_test branch from 44b3b0b to b3f4829 Compare March 13, 2023 15:05

davidchisnall reviewed Mar 13, 2023

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nwf-msr reviewed Mar 13, 2023

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davidchisnall force-pushed the isa_test branch from c1c6ad6 to 3da6479 Compare October 7, 2023 08:42

rmn30 force-pushed the isa_test branch from 3da6479 to 3642b13 Compare July 1, 2024 15:21

rmn30 and others added 5 commits July 1, 2024 15:23

Add an invalidate method on Capability for clearing the tag.

4d3b18d

Add a test for some hardware features

6e188ec

This specifically aims to test features that are not likely to occur in normal operation, such as exceptions. Hits quite a few potential corner cases but some are best tested in bare metal assembly and can't be easily tested in an RTOS tests.

Update tests/isa-test.cc

1962414

Co-authored-by: Nathaniel Filardo <[email protected]>

Update ISA test for ISA changes.

c5108c1

Still some TODOs to resolve.

rmn30 force-pushed the isa_test branch from 3642b13 to c5108c1 Compare July 1, 2024 15:29

ronorton added 2 commits July 2, 2024 10:41

Move to_representable function into PermissionSet as suggested during…

d3a31b5

… review. Also address a few other review comments.

Clang format.

a9de887

nwf-msr reviewed Jul 2, 2024

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Add ISA test #29

Add ISA test #29

rmn30 commented Mar 10, 2023

davidchisnall Mar 13, 2023

rmn30 Mar 13, 2023

nwf-msr Mar 13, 2023

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rmn30 Jul 2, 2024

Add ISA test #29

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