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Date: Wed, 19 Jun 2024 10:01:47 +0800
From: zhouquan@...as.ac.cn
To: linux-riscv@...ts.infradead.org,
linux-kernel@...r.kernel.org,
linux-kselftest@...r.kernel.org
Cc: oleg@...hat.com,
paul.walmsley@...ive.com,
palmer@...belt.com,
aou@...s.berkeley.edu,
andy.chiu@...ive.com,
shuah@...nel.org,
charlie@...osinc.com,
zhouquan@...as.ac.cn
Subject: [RFC PATCH 2/2] riscv: selftests: Add a ptrace test to check a0 of restarted syscall
From: Quan Zhou <zhouquan@...as.ac.cn>
This test creates two processes: a tracer and a tracee. The tracer actively
sends a SIGUSR1 signal in user mode to interrupt the read syscall being
executed by the tracee. We will reset a0/orig_a0 and then observe the value
of a0 held by the restarted read syscall.
Compared to the test program, a more common scenario is the use of the
exece syscall, which sends a signal in the kernel path to restart
the syscall.
Signed-off-by: Quan Zhou <zhouquan@...as.ac.cn>
---
tools/testing/selftests/riscv/Makefile | 2 +-
tools/testing/selftests/riscv/abi/.gitignore | 1 +
tools/testing/selftests/riscv/abi/Makefile | 12 ++
.../riscv/abi/ptrace_restart_syscall.c | 148 ++++++++++++++++++
4 files changed, 162 insertions(+), 1 deletion(-)
create mode 100644 tools/testing/selftests/riscv/abi/.gitignore
create mode 100644 tools/testing/selftests/riscv/abi/Makefile
create mode 100644 tools/testing/selftests/riscv/abi/ptrace_restart_syscall.c
diff --git a/tools/testing/selftests/riscv/Makefile b/tools/testing/selftests/riscv/Makefile
index 7ce03d832b64..98541dc2f164 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 $(ARCH),riscv))
-RISCV_SUBTARGETS ?= hwprobe vector mm sigreturn
+RISCV_SUBTARGETS ?= hwprobe vector mm sigreturn abi
else
RISCV_SUBTARGETS :=
endif
diff --git a/tools/testing/selftests/riscv/abi/.gitignore b/tools/testing/selftests/riscv/abi/.gitignore
new file mode 100644
index 000000000000..e1e00ffb9db9
--- /dev/null
+++ b/tools/testing/selftests/riscv/abi/.gitignore
@@ -0,0 +1 @@
+abi
diff --git a/tools/testing/selftests/riscv/abi/Makefile b/tools/testing/selftests/riscv/abi/Makefile
new file mode 100644
index 000000000000..634fa7de74e6
--- /dev/null
+++ b/tools/testing/selftests/riscv/abi/Makefile
@@ -0,0 +1,12 @@
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (C) 2021 ARM Limited
+# Originally tools/testing/arm64/abi/Makefile
+
+CFLAGS += -I$(top_srcdir)/tools/include
+
+TEST_GEN_PROGS := ptrace_restart_syscall
+
+include ../../lib.mk
+
+$(OUTPUT)/ptrace_restart_syscall: ptrace_restart_syscall.c
+ $(CC) -static -o$@ $(CFLAGS) $(LDFLAGS) $^
diff --git a/tools/testing/selftests/riscv/abi/ptrace_restart_syscall.c b/tools/testing/selftests/riscv/abi/ptrace_restart_syscall.c
new file mode 100644
index 000000000000..3e25548cb95e
--- /dev/null
+++ b/tools/testing/selftests/riscv/abi/ptrace_restart_syscall.c
@@ -0,0 +1,148 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <signal.h>
+#include <errno.h>
+#include <sys/types.h>
+#include <sys/ptrace.h>
+#include <sys/stat.h>
+#include <sys/user.h>
+#include <sys/wait.h>
+#include <sys/uio.h>
+#include <linux/elf.h>
+#include <linux/unistd.h>
+#include <asm/ptrace.h>
+
+#include "../../kselftest_harness.h"
+
+#define ORIG_A0_AFTER_MODIFIED 0x5
+#define MODIFY_A0 0x01
+#define MODIFY_ORIG_A0 0x02
+
+#define perr_and_exit(fmt, ...) do { \
+ char buf[256]; \
+ snprintf(buf, sizeof(buf), "%s:%d: " fmt ": %m\n", \
+ __func__, __LINE__, ##__VA_ARGS__); \
+ perror(buf); \
+ exit(-1); \
+} while (0)
+
+static inline void resume_and_wait_tracee(pid_t pid, int flag)
+{
+ int status;
+
+ if (ptrace(flag, pid, 0, 0))
+ perr_and_exit("failed to resume the tracee %d", pid);
+
+ if (waitpid(pid, &status, 0) != pid)
+ perr_and_exit("failed to wait for the tracee %d", pid);
+}
+
+static void ptrace_restart_syscall(int opt, int *result)
+{
+ int status;
+ int p[2], fd_zero;
+ pid_t pid;
+
+ struct user_regs_struct regs;
+ struct iovec iov = {
+ .iov_base = ®s,
+ .iov_len = sizeof(regs),
+ };
+
+ if (pipe(p))
+ perr_and_exit("failed to create a pipe");
+
+ fd_zero = open("/dev/zero", O_RDONLY);
+ if (fd_zero < 0)
+ perr_and_exit("failed to open /dev/zero");
+
+ pid = fork();
+ if (pid == 0) {
+ char c;
+
+ /* Mark oneself being traced */
+ if (ptrace(PTRACE_TRACEME, 0, 0, 0))
+ perr_and_exit("failed to request for tracer to trace me");
+
+ kill(getpid(), SIGSTOP);
+
+ if (read(p[0], &c, 1) != 1)
+ exit(1);
+
+ exit(0);
+ } else if (pid < 0)
+ exit(1);
+
+ if (waitpid(pid, &status, 0) != pid)
+ perr_and_exit("failed to wait for the tracee %d\n", pid);
+
+ /* Resume the tracee until the next syscall */
+ resume_and_wait_tracee(pid, PTRACE_SYSCALL);
+
+ /* Deliver a signal to interrupt the syscall */
+ kill(pid, SIGUSR1);
+
+ /* The tracee stops at syscall exit */
+ resume_and_wait_tracee(pid, PTRACE_SYSCALL);
+
+ /* Check tracee orig_a0 before syscall restart */
+ if (ptrace(PTRACE_GETREGSET, pid, NT_PRSTATUS, &iov))
+ perr_and_exit("failed to get tracee registers");
+ if (regs.orig_a0 != p[0])
+ perr_and_exit("unexpected a0");
+
+ /* Modify a0/orig_a0 for the restarted syscall */
+ switch (opt) {
+ case MODIFY_A0:
+ regs.a0 = fd_zero;
+ break;
+ case MODIFY_ORIG_A0:
+ regs.orig_a0 = fd_zero;
+ break;
+ }
+
+ if (ptrace(PTRACE_SETREGSET, pid, NT_PRSTATUS, &iov))
+ perr_and_exit("failed to set tracee registers");
+
+ /* Ignore SIGUSR1 signal */
+ resume_and_wait_tracee(pid, PTRACE_SYSCALL);
+
+ /* Stop at the entry point of the restarted syscall */
+ resume_and_wait_tracee(pid, PTRACE_SYSCALL);
+
+ /* Now, check regs.a0 of the restarted syscall */
+ if (ptrace(PTRACE_GETREGSET, pid, NT_PRSTATUS, &iov))
+ perr_and_exit("failed to get tracee registers");
+ *result = regs.a0;
+
+ /* Resume the tracee */
+ ptrace(PTRACE_CONT, pid, 0, 0);
+ if (waitpid(pid, &status, 0) != pid)
+ perr_and_exit("failed to wait for the tracee");
+}
+
+TEST(ptrace_modify_a0)
+{
+ int result;
+
+ ptrace_restart_syscall(MODIFY_A0, &result);
+
+ /* The tracer's modification of a0 cannot affect the restarted tracee */
+ EXPECT_NE(ORIG_A0_AFTER_MODIFIED, result);
+}
+
+TEST(ptrace_modify_orig_a0)
+{
+ int result;
+
+ ptrace_restart_syscall(MODIFY_ORIG_A0, &result);
+
+ /* The tracer must modify orig_a0 to actually change the tracee's a0 */
+ EXPECT_EQ(ORIG_A0_AFTER_MODIFIED, result);
+}
+
+TEST_HARNESS_MAIN
--
2.34.1
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