RE: [PATCH v3] Hexagon: add PC alignment check and exception

[<ltaylorsimpson@gmail.com>]

> -----Original Message-----
> From: Matheus Tavares Bernardino <quic_mathbern@quicinc.com>
> Sent: Tuesday, April 30, 2024 9:25 AM
> To: qemu-devel@nongnu.org
> Cc: bcain@quicinc.com; sidneym@quicinc.com; ale@rev.ng; anjo@rev.ng;
> ltaylorsimpson@gmail.com; richard.henderson@linaro.org; Laurent Vivier
> <laurent@vivier.eu>
> Subject: [PATCH v3] Hexagon: add PC alignment check and exception
> 
> The Hexagon Programmer's Reference Manual says that the exception 0x1e
> should be raised upon an unaligned program counter. Let's implement that
> and also add some tests.
> 
> Signed-off-by: Matheus Tavares Bernardino <quic_mathbern@quicinc.com>
> ---
> v2: https://lore.kernel.org/qemu-
> devel/e559b521d1920f804df10244c8c07564431aeba5.1714419461.git.quic_ma
> thbern@quicinc.com/
> 
> Thanks for the comments, Richard and Taylor!
> 
> Changed in v3:
> - Removed now unnecessary pkt_raises_exception addition.
> - Added HEX_EXCP_PC_NOT_ALIGNED handling at
>   linux-user/hexagon/cpu_loop.c.
> - Merged all tests into a C file that uses signal handler to check
>   that the exception was raised.
> 
>  target/hexagon/cpu.h                       |  7 ++
>  target/hexagon/cpu_bits.h                  |  4 +
>  target/hexagon/macros.h                    |  3 -
>  linux-user/hexagon/cpu_loop.c              |  4 +
>  target/hexagon/op_helper.c                 |  9 +--
>  tests/tcg/hexagon/unaligned_pc.c           | 85 ++++++++++++++++++++++
>  tests/tcg/hexagon/Makefile.target          |  4 +
>  tests/tcg/hexagon/unaligned_pc_multi_cof.S |  5 ++
>  8 files changed, 113 insertions(+), 8 deletions(-)  create mode 100644
> tests/tcg/hexagon/unaligned_pc.c  create mode 100644
> tests/tcg/hexagon/unaligned_pc_multi_cof.S
> 



> a/tests/tcg/hexagon/unaligned_pc.c b/tests/tcg/hexagon/unaligned_pc.c
> new file mode 100644
> index 0000000000..1add2d0d99
> --- /dev/null
> +++ b/tests/tcg/hexagon/unaligned_pc.c
> @@ -0,0 +1,85 @@
> +#include <stdio.h>
> +#include <signal.h>
> +#include <setjmp.h>
> +#include <stdlib.h>
> +
> +/* will be changed in signal handler */ volatile sig_atomic_t
> +completed_tests; static jmp_buf after_test; static int nr_tests;
> +
> +void __attribute__((naked)) test_return(void) {
> +    asm volatile(
> +        "allocframe(#0x8)\n"
> +        "r0 = #0xffffffff\n"
> +        "framekey = r0\n"
> +        "dealloc_return\n"
> +        : : : "r0");

Add r29, r30, r31 to clobbers list.
Add framekey to clobbers list (assuming the compiler will take it).

> +}
> +
> +void test_endloop(void)
> +{
> +    asm volatile(
> +        "loop0(1f, #2)\n"
> +        "1: r0 = #0x3\n"
> +        "sa0 = r0\n"
> +        "{ nop }:endloop0\n"
> +        : : : "r0");
> +}

Add sa0, lc0, usr to the clobbers list.

> +
> +void test_multi_cof(void)
> +{
> +    asm volatile(
> +        "p0 = cmp.eq(r0, r0)\n"
> +        "{\n"
> +        "    if (p0) jump test_multi_cof_unaligned\n"
> +        "    jump 1f\n"
> +        "}\n"
> +        "1: nop\n"
> +        : : : "p0");
> +}
> +
> +void sigbus_handler(int signum)
> +{
> +    /* retore framekey after test_return */
> +    asm volatile(
> +        "r0 = #0\n"
> +        "framekey = r0\n"
> +        : : : "r0");

Add framekey to the clobbers list.

> +    printf("Test %d complete\n", completed_tests);
> +    completed_tests++;
> +    siglongjmp(after_test, 1);
> +}
> +
> +void test_done(void)
> +{
> +    int err = (completed_tests != nr_tests);
> +    puts(err ? "FAIL" : "PASS");
> +    exit(err);
> +}
> +
> +typedef void (*test_fn)(void);
> +
> +int main()
> +{
> +    test_fn tests[] = { test_return, test_endloop, test_multi_cof,
test_done
> };
> +    nr_tests = (sizeof(tests) / sizeof(tests[0])) - 1;
> +
> +    struct sigaction sa = {
> +        .sa_sigaction = sigbus_handler,
> +        .sa_flags = SA_SIGINFO
> +    };
> +
> +    if (sigaction(SIGBUS, &sa, NULL) < 0) {
> +        perror("sigaction");
> +        return EXIT_FAILURE;
> +    }
> +
> +    sigsetjmp(after_test, 1);
> +    tests[completed_tests]();
> +
> +    /* should never get here */
> +    puts("FAIL");
> +    return 1;
> +}
> diff --git a/tests/tcg/hexagon/Makefile.target
> b/tests/tcg/hexagon/Makefile.target
> index f839b2c0d5..75139e731c 100644
> --- a/tests/tcg/hexagon/Makefile.target
> +++ b/tests/tcg/hexagon/Makefile.target
> @@ -51,6 +51,7 @@ HEX_TESTS += scatter_gather  HEX_TESTS += hvx_misc
> HEX_TESTS += hvx_histogram  HEX_TESTS += invalid-slots
> +HEX_TESTS += unaligned_pc
> 
>  run-and-check-exception = $(call run-test,$2,$3 2>$2.stderr; \
>  	test $$? -eq 1 && grep -q "exception $(strip $1)" $2.stderr) @@ -
> 108,6 +109,9 @@ preg_alias: preg_alias.c hex_test.h
>  read_write_overlap: read_write_overlap.c hex_test.h
>  reg_mut: reg_mut.c hex_test.h
> 
> +unaligned_pc: unaligned_pc.c unaligned_pc_multi_cof.S
> +	$(CC) $(CFLAGS) $(CROSS_CC_GUEST_CFLAGS) -mv73 $^ -o $@
> $(LDFLAGS)
> +
>  # This test has to be compiled for the -mv67t target
>  usr: usr.c hex_test.h
>  	$(CC) $(CFLAGS) -mv67t -O2 -Wno-inline-asm -Wno-expansion-to-
> defined $< -o $@ $(LDFLAGS) diff --git
> a/tests/tcg/hexagon/unaligned_pc_multi_cof.S
> b/tests/tcg/hexagon/unaligned_pc_multi_cof.S
> new file mode 100644
> index 0000000000..10accd0057
> --- /dev/null
> +++ b/tests/tcg/hexagon/unaligned_pc_multi_cof.S
> @@ -0,0 +1,5 @@
> +.org 0x3
> +.global test_multi_cof_unaligned
> +test_multi_cof_unaligned:
> +	nop
> +	jumpr r31
> --
> 2.37.2