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Date: Wed, 3 Apr 2024 17:27:23 -0700
From: Vineet Gupta <vineetg@...osinc.com>
To: Charlie Jenkins <charlie@...osinc.com>, Shuah Khan <shuah@...nel.org>,
Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt
<palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
Andy Chiu <andy.chiu@...ive.com>, Björn Töpel
<bjorn@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
linux-riscv@...ts.infradead.org
Subject: Re: [PATCH] riscv: selftests: Add signal handling vector tests
On 4/3/24 16:50, Charlie Jenkins wrote:
> Add two tests to check vector save/restore when a signal is received
> during a vector routine. One test ensures that a value is not clobbered
> during signal handling. The other verifies that vector registers
> modified in the signal handler are properly reflected when the signal
> handling is complete.
Hmm, isn't this testing two contradictory things ?
We do want V regs to be not clobbered across a handled signal, o/w V
enabled code would just not work at all.
That implies that anything done by signal handler should just be
discarded - no ?
Am I missing something.
-Vineet
>
> Signed-off-by: Charlie Jenkins <charlie@...osinc.com>
> ---
> These tests came about to highlight the bug fixed in
> https://lore.kernel.org/lkml/20240403072638.567446-1-bjorn@kernel.org/
> and will only pass with that fix applied.
> ---
> tools/testing/selftests/riscv/Makefile | 2 +-
> tools/testing/selftests/riscv/sigreturn/.gitignore | 1 +
> tools/testing/selftests/riscv/sigreturn/Makefile | 12 ++++
> .../testing/selftests/riscv/sigreturn/sigreturn.c | 82 ++++++++++++++++++++++
> 4 files changed, 96 insertions(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/riscv/Makefile b/tools/testing/selftests/riscv/Makefile
> index 4a9ff515a3a0..7ce03d832b64 100644
> --- a/tools/testing/selftests/riscv/Makefile
> +++ b/tools/testing/selftests/riscv/Makefile
> @@ -5,7 +5,7 @@
> ARCH ?= $(shell uname -m 2>/dev/null || echo not)
>
> ifneq (,$(filter $(ARCH),riscv))
> -RISCV_SUBTARGETS ?= hwprobe vector mm
> +RISCV_SUBTARGETS ?= hwprobe vector mm sigreturn
> else
> RISCV_SUBTARGETS :=
> endif
> diff --git a/tools/testing/selftests/riscv/sigreturn/.gitignore b/tools/testing/selftests/riscv/sigreturn/.gitignore
> new file mode 100644
> index 000000000000..35002b8ae780
> --- /dev/null
> +++ b/tools/testing/selftests/riscv/sigreturn/.gitignore
> @@ -0,0 +1 @@
> +sigreturn
> diff --git a/tools/testing/selftests/riscv/sigreturn/Makefile b/tools/testing/selftests/riscv/sigreturn/Makefile
> new file mode 100644
> index 000000000000..eb8bac9279a8
> --- /dev/null
> +++ b/tools/testing/selftests/riscv/sigreturn/Makefile
> @@ -0,0 +1,12 @@
> +# SPDX-License-Identifier: GPL-2.0
> +# Copyright (C) 2021 ARM Limited
> +# Originally tools/testing/arm64/abi/Makefile
> +
> +CFLAGS += -I$(top_srcdir)/tools/include
> +
> +TEST_GEN_PROGS := sigreturn
> +
> +include ../../lib.mk
> +
> +$(OUTPUT)/sigreturn: sigreturn.c
> + $(CC) -static -o$@ $(CFLAGS) $(LDFLAGS) $^
> diff --git a/tools/testing/selftests/riscv/sigreturn/sigreturn.c b/tools/testing/selftests/riscv/sigreturn/sigreturn.c
> new file mode 100644
> index 000000000000..62397d5934f1
> --- /dev/null
> +++ b/tools/testing/selftests/riscv/sigreturn/sigreturn.c
> @@ -0,0 +1,82 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +#include <signal.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <ucontext.h>
> +#include <linux/ptrace.h>
> +#include "../../kselftest_harness.h"
> +
> +#define RISCV_V_MAGIC 0x53465457
> +#define DEFAULT_VALUE 2
> +#define SIGNAL_HANDLER_OVERRIDE 3
> +
> +static void simple_handle(int sig_no, siginfo_t *info, void *vcontext)
> +{
> + ucontext_t *context = vcontext;
> +
> + context->uc_mcontext.__gregs[REG_PC] = context->uc_mcontext.__gregs[REG_PC] + 4;
> +}
> +
> +static void vector_override(int sig_no, siginfo_t *info, void *vcontext)
> +{
> + ucontext_t *context = vcontext;
> +
> + // vector state
> + struct __riscv_extra_ext_header *ext;
> + struct __riscv_v_ext_state *v_ext_state;
> +
> + /* Find the vector context. */
> + ext = (void *)(&context->uc_mcontext.__fpregs);
> + if (ext->hdr.magic != RISCV_V_MAGIC) {
> + fprintf(stderr, "bad vector magic: %x\n", ext->hdr.magic);
> + abort();
> + }
> +
> + v_ext_state = (void *)((char *)(ext) + sizeof(*ext));
> +
> + *(int *)v_ext_state->datap = SIGNAL_HANDLER_OVERRIDE;
> +
> + context->uc_mcontext.__gregs[REG_PC] = context->uc_mcontext.__gregs[REG_PC] + 4;
> +}
> +
> +static int vector_sigreturn(int data, void (*handler)(int, siginfo_t *, void *))
> +{
> + int after_sigreturn;
> + struct sigaction sig_action = {
> + .sa_sigaction = handler,
> + .sa_flags = SA_SIGINFO
> + };
> +
> + sigaction(SIGSEGV, &sig_action, 0);
> +
> + asm(".option push \n\
> + .option arch, +v \n\
> + vsetivli x0, 1, e32, ta, ma \n\
> + vmv.s.x v0, %1 \n\
> + # Generate SIGSEGV \n\
> + lw a0, 0(x0) \n\
> + vmv.x.s %0, v0 \n\
> + .option pop" : "=r" (after_sigreturn) : "r" (data));
> +
> + return after_sigreturn;
> +}
> +
> +TEST(vector_restore)
> +{
> + int result;
> +
> + result = vector_sigreturn(DEFAULT_VALUE, &simple_handle);
> +
> + EXPECT_EQ(DEFAULT_VALUE, result);
> +}
> +
> +TEST(vector_restore_signal_handler_override)
> +{
> + int result;
> +
> + result = vector_sigreturn(DEFAULT_VALUE, &vector_override);
> +
> + EXPECT_EQ(SIGNAL_HANDLER_OVERRIDE, result);
> +}
> +
> +TEST_HARNESS_MAIN
>
> ---
> base-commit: 4cece764965020c22cff7665b18a012006359095
> change-id: 20240403-vector_sigreturn_tests-8118f0ac54fa
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