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Date: Wed, 22 May 2024 09:40:31 -0700 (PDT)
Subject:     Re: [PATCH] riscv: selftests: Add signal handling vector tests
In-Reply-To: <20240403-vector_sigreturn_tests-v1-1-2e68b7a3b8d7@rivosinc.com>
CC: shuah@kernel.org, Paul Walmsley <paul.walmsley@sifive.com>,
  aou@eecs.berkeley.edu, andy.chiu@sifive.com, bjorn@kernel.org, Vineet Gupta <vineetg@rivosinc.com>,
  linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-riscv@lists.infradead.org,
  Charlie Jenkins <charlie@rivosinc.com>
From: Palmer Dabbelt <palmer@dabbelt.com>
To: Charlie Jenkins <charlie@rivosinc.com>
Message-ID: <mhng-50849ea8-b103-43af-aef4-073aff99ae61@palmer-ri-x1c9>
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On Wed, 03 Apr 2024 16:50:29 PDT (-0700), 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.
>
> Signed-off-by: Charlie Jenkins <charlie@rivosinc.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.

Thaks.  I'm just staging this, I have a testcase too that I keep 
forgetting to post because I haven't gotten in into the selftests sanely 
yet...

    #include "../../kselftest.h"
    #include <signal.h>
    #include <stdlib.h>
    #include <asm/ptrace.h>
    #include <stdint.h>
    
    #define ITERATIONS     (1 << 24)
    #define RISCV_V_MAGIC  0x53465457
    
    struct __riscv_ctx_hdr {
            __u32 magic;
            __u32 size;
    };
    
    struct __riscv_extra_ext_header {
            __u32 __padding[129] __attribute__((aligned(16)));
            /*
             * Reserved for expansion of sigcontext structure.  Currently zeroed
             * upon signal, and must be zero upon sigreturn.
             */
            __u32 reserved;
            struct __riscv_ctx_hdr hdr;
    };
    
    
    struct __riscv_v_ext_state {
            unsigned long vstart;
            unsigned long vl;
            unsigned long vtype;
            unsigned long vcsr;
            unsigned long vlenb;
            void *datap;
            /*
             * In signal handler, datap will be set a correct user stack offset
             * and vector registers will be copied to the address of datap
             * pointer.
             */
    };
    
    /* The beginning of the actual state. */
    int count;
    
    void handler(int, siginfo_t *si, void *ucontext_void)
    {
    	ucontext_t *ucontext = ucontext_void;
    
    	/* Skip over the SEGV by just jumping to a0. */
    	ucontext->uc_mcontext.__gregs[REG_PC] = ucontext->uc_mcontext.__gregs[REG_A0];
    
    	/* Increment the first element of v0. */
    	{
    		struct __riscv_extra_ext_header *ext;
    		struct __riscv_v_ext_state *v_ext_state;
    		uint32_t val;
    
    		/* Find the vector context. */
    		ext = (void *)(&ucontext->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));
    
    		/* Actually do the increment. */
    		memcpy(&val, v_ext_state->datap, sizeof(val));
    		val++;
    		memcpy(v_ext_state->datap, &val, sizeof(val));
    	}
    
    	/* Count the delivered signal, to make sure we don't miss any. */
    	count++;
    }
    
    void sigill(int, siginfo_t *si, void *ucontext_void)
    {
    	fprintf(stderr, "SIGILL after %d iterations\n", count);
    	abort();
    }
    
    void check_signal(void)
    {
    	int check = rand();
    	int out;
    
    	__asm__ volatile (
    		"vsetvli a0, %2, e32, ta, ma\n\t"
    		"vmv.s.x v0, %1\n\t"
    		"la a0, 1f\n\t"
    		"lw t0, 0(x0)\n\t"
    		"1:\n\t"
    		"vmv.x.s %0, v0"
    		: "=&r"(out)
    		: "r"(check-1), "r"(1)
    		: "a0"
    #ifdef __riscv_vector
    		  , "v0"
    #endif
    	);
    
    	if (out != check) {
    		fprintf(stderr, "out: %d\ncheck: %d\n", out, check);
    		abort();
    	}
    }
    
    int main(void)
    {
    	struct sigaction sa_segv, sa_ill;
    
    	memset(&sa_segv, 0, sizeof(sa_segv));
    	sa_segv.sa_sigaction = &handler;
    	sa_segv.sa_flags     = SA_SIGINFO;
    	sigaction(SIGSEGV, &sa_segv, NULL);
    
    	memset(&sa_ill, 0, sizeof(sa_ill));
    	sa_ill.sa_sigaction = &sigill;
    	sa_ill.sa_flags     = SA_SIGINFO;
    	sigaction(SIGILL, &sa_ill, NULL);
    
    	count = 0;
    	for (int i = 0; i < ITERATIONS; ++i)
    		check_signal();
    
    	if (count != ITERATIONS) {
    		fprintf(stderr, "count: %d\n", count);
    		abort();
    	}
    
    	return 0;
    }

> ---
>  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