On Thu, Jun 27, 2024 at 11:02:46AM +0800, zhouquan@iscas.ac.cn wrote:

From: Quan Zhou zhouquan@iscas.ac.cn

Expose orig_a0 to userspace to ensure that users can modify the actual value of `a0` in the traced process through the ptrace(PTRACE_SETREGSET, ...) path.

The addition of orig_a0 also requires the following adjustments:

1. Adjust the position of orig_a0 in pt_regs to ensure correct copying.
2. MAX_REG_OFFSET should match the new bottom of pt_regs.

Suggested-by: Charlie Jenkins charlie@rivosinc.com Signed-off-by: Quan Zhou zhouquan@iscas.ac.cn

---

arch/riscv/include/asm/ptrace.h | 7 ++++--- arch/riscv/include/uapi/asm/ptrace.h | 2 ++ 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/riscv/include/asm/ptrace.h b/arch/riscv/include/asm/ptrace.h index b5b0adcc85c1..380cf54c1f3d 100644 --- a/arch/riscv/include/asm/ptrace.h +++ b/arch/riscv/include/asm/ptrace.h @@ -12,6 +12,7 @@ #ifndef __ASSEMBLY__ +/* MAX_REG_OFFSET should match the bottom of pt_regs */ struct pt_regs { unsigned long epc; unsigned long ra; @@ -45,12 +46,12 @@ struct pt_regs { unsigned long t4; unsigned long t5; unsigned long t6;

• /* a0 value before the syscall */
• unsigned long orig_a0; /* Supervisor/Machine CSRs */ unsigned long status; unsigned long badaddr; unsigned long cause;

• /* a0 value before the syscall */
• unsigned long orig_a0;

}; #define PTRACE_SYSEMU 0x1f @@ -64,7 +65,7 @@ struct pt_regs { #define user_mode(regs) (((regs)->status & SR_PP) == 0) -#define MAX_REG_OFFSET offsetof(struct pt_regs, orig_a0) +#define MAX_REG_OFFSET offsetof(struct pt_regs, cause) /* Helpers for working with the instruction pointer */ static inline unsigned long instruction_pointer(struct pt_regs *regs) diff --git a/arch/riscv/include/uapi/asm/ptrace.h b/arch/riscv/include/uapi/asm/ptrace.h index a38268b19c3d..3e37f80cb3e8 100644 --- a/arch/riscv/include/uapi/asm/ptrace.h +++ b/arch/riscv/include/uapi/asm/ptrace.h @@ -54,6 +54,8 @@ struct user_regs_struct { unsigned long t4; unsigned long t5; unsigned long t6;

• /* a0 value before the syscall */
• unsigned long orig_a0;

}; struct __riscv_f_ext_state { -- 2.34.1

Thank you!

Reviewed-by: Charlie Jenkins charlie@rivosinc.com

On Thu, Jun 27, 2024 at 11:02:54AM +0800, zhouquan@iscas.ac.cn wrote:

From: Quan Zhou zhouquan@iscas.ac.cn

This test checks that orig_a0 allows a syscall argument to be modified, and that changing a0 does not change the syscall argument.

Suggested-by: Charlie Jenkins charlie@rivosinc.com Signed-off-by: Quan Zhou zhouquan@iscas.ac.cn

---

tools/testing/selftests/riscv/Makefile | 2 +- tools/testing/selftests/riscv/abi/.gitignore | 1 + tools/testing/selftests/riscv/abi/Makefile | 12 ++ tools/testing/selftests/riscv/abi/ptrace.c | 124 +++++++++++++++++++ 4 files changed, 138 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.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..d61c51358965 --- /dev/null +++ b/tools/testing/selftests/riscv/abi/.gitignore @@ -0,0 +1 @@ +ptrace diff --git a/tools/testing/selftests/riscv/abi/Makefile b/tools/testing/selftests/riscv/abi/Makefile new file mode 100644 index 000000000000..808d48a91ad7 --- /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

+include ../../lib.mk

+$(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 000000000000..f85f927cd685 --- /dev/null +++ b/tools/testing/selftests/riscv/abi/ptrace.c @@ -0,0 +1,124 @@ +// 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_MODIFY 0x01 +#define A0_MODIFY 0x02 +#define A0_OLD 0x03 +#define A0_NEW 0x04

+#define perr_and_exit(fmt, ...) \

• ({ \

• 	char buf[256];						\
  

Apologies, I missed this in the last review. In the above line there is a space in the middle of the tabs before `char buf[256];`.

• snprintf(buf, sizeof(buf), "%s:%d: " fmt ": %m\n",	\
  

• 	__func__, __LINE__, ##__VA_ARGS__);		\
  

• perror(buf);						\
  

• exit(-1);						\
  

• })

+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\n", pid);
  

• if (waitpid(pid, &status, 0) != pid)

• perr_and_exit("failed to wait for the tracee %d\n", pid);
  

+}

+static void ptrace_test(int opt, int *result) +{

• int status;
• pid_t pid;
• struct user_regs_struct regs;
• struct iovec iov = {

• .iov_base = &regs,
  

• .iov_len = sizeof(regs),
  

• };
• pid = fork();
• if (pid == 0) {

• /* Mark oneself being traced */
  

• long val = ptrace(PTRACE_TRACEME, 0, 0, 0);
  

• if (val)
  

• 	perr_and_exit("failed to request for tracer to trace me: %ld\n", val);
  

• kill(getpid(), SIGSTOP);
  

• /* Perform exit syscall that will be intercepted */
  

• exit(A0_OLD);
  

• }
• if (pid < 0)

• exit(1);
  

• if (waitpid(pid, &status, 0) != pid)

• perr_and_exit("failed to wait for the tracee %d\n", pid);
  

• /* Stop at the entry point of the syscall */
• resume_and_wait_tracee(pid, PTRACE_SYSCALL);
• /* Check tracee orig_a0 before the syscall */
• if (ptrace(PTRACE_GETREGSET, pid, NT_PRSTATUS, &iov))

• perr_and_exit("failed to get tracee registers\n");
  

• if (regs.orig_a0 != A0_OLD)

• perr_and_exit("unexpected orig_a0: 0x%lx\n", regs.orig_a0);
  

• /* Modify a0/orig_a0 for the syscall */
• switch (opt) {
• case A0_MODIFY:

• regs.a0 = A0_NEW;
  

• break;
  

• case ORIG_A0_MODIFY:

• regs.orig_a0 = A0_NEW;
  

• break;
  

• }
• if (ptrace(PTRACE_SETREGSET, pid, NT_PRSTATUS, &iov))

• perr_and_exit("failed to set tracee registers\n");
  

• /* Resume the tracee */
• ptrace(PTRACE_CONT, pid, 0, 0);
• if (waitpid(pid, &status, 0) != pid)

• perr_and_exit("failed to wait for the tracee\n");
  

• *result = WEXITSTATUS(status);

+}

+TEST(ptrace_modify_a0) +{

• int result;
• ptrace_test(A0_MODIFY, &result);
• /* The modification of a0 cannot affect the first argument of the syscall */
• EXPECT_EQ(A0_OLD, result);

+}

+TEST(ptrace_modify_orig_a0) +{

• int result;
• ptrace_test(ORIG_A0_MODIFY, &result);
• /* Only modify orig_a0 to change the first argument of the syscall */
• EXPECT_EQ(A0_NEW, result);

+}

+TEST_HARNESS_MAIN

2.34.1

Reviewed-by: Charlie Jenkins charlie@rivosinc.com