On Tue, May 23, 2023 at 02:53:25PM +0100, Nikos Nikoleris wrote:
> This changes allows a test to define and override the declared symbols,
> taking control of all or some execptions.
>
> With the ability to override specific exception handlers, litmus7 [1] a
> tool used to generate c sources for a given memory model litmus test,
> can override the el1h_sync symbol to implement tests with explicit
> exception handlers. For example:
>
> AArch64 LDRv0+I2V-dsb.ishst-once
> {
> [PTE(x)]=(oa:PA(x),valid:0);
> x=1;
>
> 0:X1=x;
> 0:X3=PTE(x);
> 0:X2=(oa:PA(x),valid:1);
> }
> P0 | P0.F ;
> L0: | ADD X8,X8,#1 ;
> LDR W0,[X1] | STR X2,[X3] ;
> | DSB ISHST ;
> | ADR X9,L0 ;
> | MSR ELR_EL1,X9 ;
> | ERET ;
> exists(0:X0=0 \/ 0:X8!=1)
>
> In this test, a thread running in core P0 executes a load to a memory
> location x. The PTE of the virtual address x is initially invalid. The
> execution of the load causes a synchronous EL1 exception which is
> handled by the code in P0.F. P0.F increments a counter which is
> maintained in X8, updates the PTE of x and makes it valid, executes a
> DSB ISHST and calls ERET which is expected to return and retry the
> execution of the load in P0:L0.
>
> The postcondition checks if there is any execution where the load wasn't
> executed (X0 its destination register is not update), or that the P0.F
> handler was invoked more than once (the counter X8 is not 1).
>
> For this tests, litmus7 needs to control the el1h_sync. Calling
> install_exception_handler() would be suboptimal because the
> vector_stub would wrap around the code of P0.F and perturb the test.
>
> [1]: https://diy.inria.fr/doc/litmus.html
>
> Signed-off-by: Nikos Nikoleris <nikos.nikoleris@xxxxxxx>
> ---
> arm/cstart64.S | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/arm/cstart64.S b/arm/cstart64.S
> index e4ab7d06..eda0daa5 100644
> --- a/arm/cstart64.S
> +++ b/arm/cstart64.S
> @@ -275,8 +275,11 @@ exceptions_init:
> /*
> * Vector stubs
> * Adapted from arch/arm64/kernel/entry.S
> + * Declare as weak to allow external tests to redefine and override a
> + * vector_stub.
> */
> .macro vector_stub, name, vec
> +.weak \name
> \name:
> stp x0, x1, [sp, #-S_FRAME_SIZE]!
> stp x2, x3, [sp, #16]
> @@ -369,7 +372,13 @@ vector_stub el0_error_32, 15
> b \label
> .endm
>
> +
> +/*
> + * Declare as weak to allow external tests to redefine and override the
> + * default vector table.
> + */
> .align 11
> +.weak vector_table
> vector_table:
> ventry el1t_sync // Synchronous EL1t
> ventry el1t_irq // IRQ EL1t
> --
> 2.25.1
>
Applied to arm/queue. Thanks!
https://gitlab.com/jones-drew/kvm-unit-tests/-/commits/arm/queue
drew
