[PATCH v6 3/3] riscv: selftests: Add a ptrace test to verify a0 and orig_a0 access

[Celeste Liu <uwu@coelacanthus.name>]

This test checks that orig_a0 and a0 can be modified and accessed
independently.

Co-developed-by: Quan Zhou <zhouquan@iscas.ac.cn>
Signed-off-by: Quan Zhou <zhouquan@iscas.ac.cn>
Co-developed-by: Charlie Jenkins <charlie@rivosinc.com>
Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
Reviewed-by: Björn Töpel <bjorn@rivosinc.com>
Signed-off-by: Celeste Liu <uwu@coelacanthus.name>
---
 tools/testing/selftests/riscv/abi/.gitignore |   1 +
 tools/testing/selftests/riscv/abi/Makefile   |   6 +-
 tools/testing/selftests/riscv/abi/ptrace.c   | 193 +++++++++++++++++++++++++++
 3 files changed, 199 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/riscv/abi/.gitignore b/tools/testing/selftests/riscv/abi/.gitignore
index b38358f91c4d2240ae64892871d9ca98bda1ae58..378c605919a3b3d58eec2701eb7af430cfe315d6 100644
--- a/tools/testing/selftests/riscv/abi/.gitignore
+++ b/tools/testing/selftests/riscv/abi/.gitignore
@@ -1 +1,2 @@
 pointer_masking
+ptrace
diff --git a/tools/testing/selftests/riscv/abi/Makefile b/tools/testing/selftests/riscv/abi/Makefile
index ed82ff9c664e7eb3f760cbab81fb957ff72579c5..359a082c88a401883fb3776b35e4dacf69beaaaa 100644
--- a/tools/testing/selftests/riscv/abi/Makefile
+++ b/tools/testing/selftests/riscv/abi/Makefile
@@ -1,10 +1,14 @@
 # SPDX-License-Identifier: GPL-2.0
 
 CFLAGS += -I$(top_srcdir)/tools/include
+CFLAGS += $(KHDR_INCLUDES)
 
-TEST_GEN_PROGS := pointer_masking
+TEST_GEN_PROGS := pointer_masking ptrace
 
 include ../../lib.mk
 
 $(OUTPUT)/pointer_masking: pointer_masking.c
 	$(CC) -static -o$@ $(CFLAGS) $(LDFLAGS) $^
+
+$(OUTPUT)/ptrace: ptrace.c
+	$(CC) -static -o$@ $(CFLAGS) $(LDFLAGS) $^
diff --git a/tools/testing/selftests/riscv/abi/ptrace.c b/tools/testing/selftests/riscv/abi/ptrace.c
new file mode 100644
index 0000000000000000000000000000000000000000..cbd60462021165ca2bcc38be24b8423c96047b93
--- /dev/null
+++ b/tools/testing/selftests/riscv/abi/ptrace.c
@@ -0,0 +1,193 @@
+// 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 <linux/ptrace.h>
+#include <linux/stddef.h>
+#include <asm/ptrace.h>
+
+#include "../../kselftest_harness.h"
+
+#define ORIG_A0_MODIFY      0x01
+#define A0_MODIFY           0x02
+#define A0_OLD              0xbadbeefbeeff
+#define A0_NEW              0xffeebfeebdab
+
+
+struct a0_regs {
+	__s64 orig_a0;
+	__u64 a0;
+};
+
+#define perr_and_exit(fmt, ...)						\
+	({								\
+		char buf[256];						\
+		snprintf(buf, sizeof(buf), "%s:%d:" fmt ": %m\n",	\
+			__func__, __LINE__, ##__VA_ARGS__);		\
+		ksft_exit_fail_perror(buf);				\
+	})
+
+static void ptrace_test(int opt, struct a0_regs result[])
+{
+	int status;
+	long rc;
+	pid_t pid;
+	struct user_regs_struct regs;
+	struct iovec iov = {
+		.iov_base = &regs,
+		.iov_len = sizeof(regs),
+	};
+
+	unsigned long orig_a0;
+	struct iovec a0_iov = {
+		.iov_base = &orig_a0,
+		.iov_len = sizeof(orig_a0),
+	};
+	struct ptrace_syscall_info syscall_info = {
+		.op = 0xff,
+	};
+	const unsigned int expected_sci_entry_size =
+		offsetofend(struct ptrace_syscall_info, entry.args);
+	const unsigned int expected_sci_exit_size =
+		offsetofend(struct ptrace_syscall_info, exit.is_error);
+
+	pid = fork();
+	if (pid == 0) {
+		/* Mark oneself being traced */
+		long val = ptrace(PTRACE_TRACEME, 0, 0, 0);
+
+		if (val < 0)
+			perr_and_exit("failed to request for tracer to trace me: %ld", val);
+
+		kill(getpid(), SIGSTOP);
+
+		/* Perform chdir syscall that will be intercepted */
+		syscall(__NR_chdir, A0_OLD);
+
+		exit(0);
+	}
+
+	if (pid < 0)
+		ksft_exit_fail_perror("failed to fork");
+
+	for (int i = 0; i < 3; i++) {
+		if (waitpid(pid, &status, 0) != pid)
+			perr_and_exit("failed to wait for the tracee %d", pid);
+		if (WIFSTOPPED(status)) {
+			switch (WSTOPSIG(status)) {
+			case SIGSTOP:
+				if (ptrace(PTRACE_SETOPTIONS, pid, 0, PTRACE_O_TRACESYSGOOD) < 0)
+					perr_and_exit("failed to set PTRACE_O_TRACESYSGOOD");
+				break;
+			case SIGTRAP|0x80:
+				/* Modify twice so GET_SYSCALL_INFO get modified a0 and orig_a0 */
+				if (ptrace(PTRACE_GETREGSET, pid, NT_PRSTATUS, &iov))
+					perr_and_exit("failed to get tracee registers");
+				if (ptrace(PTRACE_GETREGSET, pid, NT_RISCV_ORIG_A0, &a0_iov))
+					perr_and_exit("failed to get tracee registers");
+
+				/* Modify a0/orig_a0 for the syscall */
+				switch (opt) {
+				case A0_MODIFY:
+					regs.a0 = A0_NEW;
+					break;
+				case ORIG_A0_MODIFY:
+					orig_a0 = A0_NEW;
+					break;
+				}
+
+				if (ptrace(PTRACE_SETREGSET, pid, NT_PRSTATUS, &iov))
+					perr_and_exit("failed to set tracee registers");
+				if (ptrace(PTRACE_SETREGSET, pid, NT_RISCV_ORIG_A0, &a0_iov))
+					perr_and_exit("failed to set tracee registers");
+				switch (i) {
+				case 1:
+					/* Stop at the beginning of syscall */
+					rc = ptrace(PTRACE_GET_SYSCALL_INFO, pid,
+						sizeof(syscall_info), &syscall_info);
+					if (rc < 0)
+						perr_and_exit("failed to get syscall info of entry");
+					if (rc < expected_sci_entry_size
+						|| syscall_info.op != PTRACE_SYSCALL_INFO_ENTRY)
+						perr_and_exit("stop position of entry mismatched");
+					result[0].orig_a0 = syscall_info.entry.args[0];
+					break;
+
+				case 2:
+					/* Stop at the end of syscall */
+					rc = ptrace(PTRACE_GET_SYSCALL_INFO, pid,
+						sizeof(syscall_info), &syscall_info);
+					if (rc < 0)
+						perr_and_exit("failed to get syscall info of entry");
+					if (rc < expected_sci_exit_size
+						|| syscall_info.op != PTRACE_SYSCALL_INFO_EXIT)
+						perr_and_exit("stop position of exit mismatched");
+					result[0].a0 = syscall_info.exit.rval;
+
+					if (ptrace(PTRACE_GETREGSET, pid, NT_PRSTATUS, &iov))
+						perr_and_exit("failed to get tracee registers");
+					result[1].a0 = regs.a0;
+					if (ptrace(PTRACE_GETREGSET, pid, NT_RISCV_ORIG_A0,
+						   &a0_iov))
+						perr_and_exit("failed to get tracee registers");
+					result[1].orig_a0 = orig_a0;
+				}
+			}
+			if (ptrace(PTRACE_SYSCALL, pid, 0, 0) < 0)
+				perr_and_exit("failed to resume tracee");
+		}
+	}
+
+	/* 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_access_a0)
+{
+	struct a0_regs result[2];
+
+	ptrace_test(A0_MODIFY, result);
+
+	/* Verify PTRACE_SETREGSET */
+	/* The modification of a0 cannot affect the first argument of the syscall */
+	EXPECT_EQ(A0_OLD, result[0].orig_a0);
+	EXPECT_EQ(A0_NEW, result[0].a0);
+
+	/* Verify PTRACE_GETREGSET */
+	EXPECT_EQ(result[1].orig_a0, result[0].orig_a0);
+	EXPECT_EQ(result[1].a0, result[0].a0);
+}
+
+TEST(ptrace_access_orig_a0)
+{
+	struct a0_regs result[2];
+
+	ptrace_test(ORIG_A0_MODIFY, result);
+
+	/* Verify PTRACE_SETREGSET */
+	/* Only modify orig_a0 to change the first argument of the syscall */
+	EXPECT_EQ(A0_NEW, result[0].orig_a0);
+	/* a0 will not be affected */
+	EXPECT_NE(A0_NEW, result[0].a0);
+
+	/* Verify PTRACE_GETREGSET */
+	EXPECT_EQ(result[1].orig_a0, result[0].orig_a0);
+	EXPECT_EQ(result[1].a0, result[0].a0);
+}
+
+TEST_HARNESS_MAIN

-- 
2.48.0