On 18/05/2023 17:06, Andrew Jones wrote:
On Mon, May 15, 2023 at 11:15:17PM +0100, Nikos Nikoleris wrote:
This changes allows a test to define and override the declared symbols,
taking control of the whole vector_table or a vector_stub.
Hi Nikos,
Can you add some motivation for this change to the commit message or
submit it along with some test that needs it?
Hi Drew,
Thanks for reviewing this.
What do you think about adding the following to the commit message?
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
> { > [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 ;
| 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 disturb the test.
[1]: https://diy.inria.fr/doc/litmus.html
If you think this is sufficient, I will update the patch. If not I could
look into adding a test in KUT but generally the code of these tests are
generated by a tool and the coding style (if one can call it a style) is
very different.
Thanks,
Nikos
Thanks,
drew
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
