Re: [PATCH v5 2/3] riscv: Add breakpoint and watchpoint test for riscv

[Jesse Taube]

On Thu, Jul 23, 2026 at 4:50 AM Himanshu Chauhan
<himanshu.chauhan@xxxxxxxxxxxxxxxx> wrote:
>
> Add self test for riscv architecture. It uses ptrace to ptrace framework

This uses the perf framework
i sent patches to add support for breakpoints using the ptrace framework here
https://lore.kernel.org/all/20250822174715.1269138-7-jesse@xxxxxxxxxxxx/
https://lore.kernel.org/all/20250822174715.1269138-8-jesse@xxxxxxxxxxxx/
And the test here
https://lore.kernel.org/all/20250822174715.1269138-9-jesse@xxxxxxxxxxxx/

> to set/unset break/watchpoint and uses signals to check triggers.
>
> Signed-off-by: Himanshu Chauhan <himanshu.chauhan@xxxxxxxxxxxxxxxx>
> ---
>  tools/testing/selftests/breakpoints/Makefile  |   5 +
>  .../breakpoints/breakpoint_test_riscv.c       | 219 ++++++++++++++++++
>  2 files changed, 224 insertions(+)
>  create mode 100644 tools/testing/selftests/breakpoints/breakpoint_test_riscv.c
>
> diff --git a/tools/testing/selftests/breakpoints/Makefile b/tools/testing/selftests/breakpoints/Makefile
> index 0b8f5acf7c78..c16782460b49 100644
> --- a/tools/testing/selftests/breakpoints/Makefile
> +++ b/tools/testing/selftests/breakpoints/Makefile
> @@ -12,5 +12,10 @@ ifneq (,$(filter $(ARCH),aarch64 arm64))
>  TEST_GEN_PROGS += breakpoint_test_arm64
>  endif
>
> +ifneq (,$(filter $(ARCH),riscv))
> +CFLAGS += -static
> +TEST_GEN_PROGS += breakpoint_test_riscv
> +endif
> +
>  include ../lib.mk
>
> diff --git a/tools/testing/selftests/breakpoints/breakpoint_test_riscv.c b/tools/testing/selftests/breakpoints/breakpoint_test_riscv.c
> new file mode 100644
> index 000000000000..0649940b709e
> --- /dev/null
> +++ b/tools/testing/selftests/breakpoints/breakpoint_test_riscv.c
> @@ -0,0 +1,219 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2026 Qualcomm Technologies, Inc.
> + *
> + * Author: Himanshu Chauhan <himanshu.chauhan@xxxxxxxxxxxxxxxx>
> + */
> +
> +#define _GNU_SOURCE
> +#include <linux/perf_event.h>    /* Definition of PERF_* constants */
> +#include <linux/hw_breakpoint.h> /* Definition of HW_* constants */
> +#include <sys/syscall.h>         /* Definition of SYS_* constants */
> +#include <unistd.h>
> +#include <stdbool.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <sys/ioctl.h>
> +#include <time.h>
> +#include <fcntl.h>
> +#include <signal.h>
> +#include <sys/mman.h>
> +#include <string.h>
> +#include <semaphore.h>
> +#include <errno.h>
> +
> +#ifndef noinline
> +#define noinline __attribute__((noinline))
> +#endif
> +
> +static int gfd;
> +sem_t ib_mtx, wp_mtx;
> +static int bp_triggered, wp_triggered;
> +static int test_func_sink;
> +static const int wait_timeout_sec = 5;
> +
> +int setup_bp(bool is_x, void *addr, int sig)
> +{
> +       struct perf_event_attr pe;
> +       int fd;
> +
> +       memset(&pe, 0, sizeof(struct perf_event_attr));
> +       pe.type = PERF_TYPE_BREAKPOINT;
> +       pe.size = sizeof(struct perf_event_attr);
> +
> +       pe.config = 0;
> +       pe.bp_type = is_x ? HW_BREAKPOINT_X : HW_BREAKPOINT_W;
> +       pe.bp_addr = (unsigned long)addr;
> +       pe.bp_len = sizeof(long);
> +
> +       pe.sample_period = 1;
> +       pe.sample_type = PERF_SAMPLE_IP;
> +       pe.wakeup_events = 1;
> +
> +       pe.disabled = 1;
> +       pe.exclude_kernel = 1;
> +       pe.exclude_hv = 1;
> +
> +       fd = syscall(SYS_perf_event_open, &pe, 0, -1, -1, 0);
> +       if (fd < 0) {
> +               printf("Failed to open event: %llx\n", pe.config);
> +               return -1;
> +       }
> +
> +       fcntl(fd, F_SETFL, O_RDWR | O_NONBLOCK | O_ASYNC);
> +       fcntl(fd, F_SETSIG, sig);
> +       fcntl(fd, F_SETOWN, getpid());
> +
> +       ioctl(fd, PERF_EVENT_IOC_RESET, 0);
> +
> +       return fd;
> +}
> +
> +static void sig_handler_bp(int signum, siginfo_t *oh, void *uc)
> +{
> +       int ret;
> +
> +       bp_triggered++;
> +
> +       printf("Breakpoint triggered!\n");
> +       ioctl(gfd, PERF_EVENT_IOC_DISABLE, 0);
> +       ret = sem_post(&ib_mtx);
> +       if (ret) {
> +               printf("Failed to report BP success\n");
> +               return;
> +       }
> +}
> +
> +static void sig_handler_wp(int signum, siginfo_t *oh, void *uc)
> +{
> +       int ret;
> +
> +       printf("Watchpoint triggered!\n");
> +       ioctl(gfd, PERF_EVENT_IOC_DISABLE, 0);
> +       wp_triggered++;
> +
> +       ret = sem_post(&wp_mtx);
> +
> +       if (ret) {
> +               printf("Failed to report WP success\n");
> +               return;
> +       }
> +}
> +
> +/*
> + * Keep a real instruction address for HW execute breakpoints: prevent inlining
> + * and force a visible side effect so the function can't be optimized away.
> + */
> +static noinline void test_func(void)
> +{
> +       test_func_sink++;
> +       __asm__ __volatile__("" : : "g" (test_func_sink));
> +}
> +
> +static int trigger_bp(void)
> +{
> +       struct sigaction sa;
> +
> +       memset(&sa, 0, sizeof(struct sigaction));
> +       sa.sa_sigaction = (void *)sig_handler_bp;
> +       sa.sa_flags = SA_SIGINFO;
> +
> +       if (sigaction(SIGIO, &sa, NULL) < 0) {
> +               printf("Failed to setup signal handler\n");
> +               return -1;
> +       }
> +
> +       gfd = setup_bp(1, test_func, SIGIO);
> +
> +       if (gfd < 0) {
> +               printf("Failed to setup breakpoint.\n");
> +               return -1;
> +       }
> +
> +       ioctl(gfd, PERF_EVENT_IOC_ENABLE, 0);
> +
> +       test_func();
> +
> +       ioctl(gfd, PERF_EVENT_IOC_DISABLE, 0);
> +
> +       close(gfd);
> +
> +       return 0;
> +}
> +
> +static int trigger_wp(void)
> +{
> +       struct sigaction sa;
> +       unsigned long test_data;
> +
> +       memset(&sa, 0, sizeof(struct sigaction));
> +       sa.sa_sigaction = (void *)sig_handler_wp;
> +       sa.sa_flags = SA_SIGINFO;
> +
> +       if (sigaction(SIGUSR1, &sa, NULL) < 0) {
> +               printf("Failed to setup signal handler\n");
> +               return -1;
> +       }
> +
> +       gfd = setup_bp(0, &test_data, SIGUSR1);
> +
> +       if (gfd < 0) {
> +               printf("Failed to setup watchpoint\n");
> +               return -1;
> +       }
> +
> +       ioctl(gfd, PERF_EVENT_IOC_ENABLE, 0);
> +       test_data = 0xdeadbeef;
> +       ioctl(gfd, PERF_EVENT_IOC_DISABLE, 0);
> +
> +       return 0;
> +}
> +
> +static int wait_event(sem_t *sem, const char *name)
> +{
> +       struct timespec ts;
> +
> +       if (clock_gettime(CLOCK_REALTIME, &ts)) {
> +               printf("%s: Failed to get current time\n", name);
> +               return -1;
> +       }
> +
> +       /*
> +        * Deadlock fix: avoid blocking forever on sem_wait() if the breakpoint/
> +        * watchpoint signal never arrives. Use a bounded wait and fail the test
> +        * on timeout instead.
> +        */
> +       ts.tv_sec += wait_timeout_sec;
> +       if (!sem_timedwait(sem, &ts))
> +               return 0;
> +
> +       if (errno == ETIMEDOUT)
> +               printf("%s: Timed out waiting for event\n", name);
> +       else
> +               printf("%s: sem_timedwait() failed with %d\n", name, errno);
> +
> +       return -1;
> +}
> +
> +int main(int argc, char *argv[])
> +{
> +       sem_init(&ib_mtx, 0, 0);
> +       if (trigger_bp() < 0)
> +               return -1;
> +       if (wait_event(&ib_mtx, "Breakpoint") < 0)
> +               return -1;
> +
> +       if (bp_triggered)
> +               printf("Breakpoint test passed!\n");
> +
> +       sem_init(&wp_mtx, 0, 0);
> +       if (trigger_wp() < 0)
> +               return -1;
> +       if (wait_event(&wp_mtx, "Watchpoint") < 0)
> +               return -1;
> +
> +       if (wp_triggered)
> +               printf("Watchpoint test passed!\n");
> +
> +       return 0;
> +}
> --
> 2.43.0
>
>
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