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Message-ID: <76e57304-3a03-462e-bb82-61d0a0385dda@coelacanthus.name>
Date: Thu, 26 Dec 2024 18:58:29 +0800
From: Celeste Liu <uwu@...lacanthus.name>
To: Oleg Nesterov <oleg@...hat.com>, Paul Walmsley
<paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>,
Eric Biederman <ebiederm@...ssion.com>, Kees Cook <kees@...nel.org>,
Shuah Khan <shuah@...nel.org>, Albert Ou <aou@...s.berkeley.edu>
Cc: Alexandre Ghiti <alex@...ti.fr>, "Dmitry V. Levin" <ldv@...ace.io>,
Andrea Bolognani <abologna@...hat.com>, Björn Töpel
<bjorn@...nel.org>, Thomas Gleixner <tglx@...utronix.de>,
Ron Economos <re@...z.net>, Charlie Jenkins <charlie@...osinc.com>,
Andrew Jones <ajones@...tanamicro.com>, Quan Zhou <zhouquan@...as.ac.cn>,
Felix Yan <felixonmars@...hlinux.org>, Ruizhe Pan <c141028@...il.com>,
Guo Ren <guoren@...nel.org>, Yao Zi <ziyao@...root.org>,
linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
linux-mm@...ck.org, linux-kselftest@...r.kernel.org,
Björn Töpel <bjorn@...osinc.com>
Subject: Re: [PATCH v3 2/2] riscv: selftests: Add a ptrace test to verify
syscall parameter modification
On 2024-12-26 18:45, Celeste Liu wrote:
> This test checks that orig_a0 allows a syscall argument to be modified,
> and that changing a0 does not change the syscall argument.
>
> Co-developed-by: Quan Zhou <zhouquan@...as.ac.cn>
> Signed-off-by: Quan Zhou <zhouquan@...as.ac.cn>
> Co-developed-by: Charlie Jenkins <charlie@...osinc.com>
> Signed-off-by: Charlie Jenkins <charlie@...osinc.com>
> Reviewed-by: Björn Töpel <bjorn@...osinc.com>
> Signed-off-by: Celeste Liu <uwu@...lacanthus.name>
> ---
> tools/testing/selftests/riscv/abi/.gitignore | 1 +
> tools/testing/selftests/riscv/abi/Makefile | 5 +-
> tools/testing/selftests/riscv/abi/ptrace.c | 151 +++++++++++++++++++++++++++
> 3 files changed, 156 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..3f74d059dfdcbce4d45d8ff618781ccea1419061 100644
> --- a/tools/testing/selftests/riscv/abi/Makefile
> +++ b/tools/testing/selftests/riscv/abi/Makefile
> @@ -2,9 +2,12 @@
>
> CFLAGS += -I$(top_srcdir)/tools/include
>
> -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..c89343cb4abc7da57f83879ecce619f503c438bb
> --- /dev/null
> +++ b/tools/testing/selftests/riscv/abi/ptrace.c
> @@ -0,0 +1,151 @@
> +// 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 <asm/ptrace.h>
> +
> +#include "../../kselftest_harness.h"
> +
> +#define ORIG_A0_MODIFY 0x01
> +#define A0_MODIFY 0x02
> +#define A0_OLD 0x03
> +#define A0_NEW 0x04
> +
> +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 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, struct a0_regs *result)
> +{
> + int status;
> + pid_t pid;
> + struct user_regs_struct regs;
> + struct iovec iov = {
> + .iov_base = ®s,
> + .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_entry, syscall_info_exit;
> +
> + 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)
> + ksft_exit_fail_perror("failed to fork");
> +
> + 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 regs before the syscall */
> + if (ptrace(PTRACE_GETREGSET, pid, NT_PRSTATUS, &iov))
> + perr_and_exit("failed to get tracee registers\n");
> + if (ptrace(PTRACE_GETREGSET, pid, NT_RISCV_ORIG_A0, &a0_iov))
> + perr_and_exit("failed to get tracee registers\n");
> + if (orig_a0 != A0_OLD)
> + perr_and_exit("unexpected orig_a0: 0x%lx\n", orig_a0);
> +
> + /* 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, &a0_iov))
> + perr_and_exit("failed to set tracee registers\n");
v4 has been sent because I found a uncommited fix for this...
> + if (ptrace(PTRACE_SETREGSET, pid, NT_RISCV_ORIG_A0, &a0_iov))
> + perr_and_exit("failed to set tracee registers\n");
> +
> + if (ptrace(PTRACE_GET_SYSCALL_INFO, pid, PTRACE_SYSCALL_INFO_ENTRY, &syscall_info_entry))
> + perr_and_exit("failed to get syscall info of entry\n");
> + result->orig_a0 = syscall_info_entry->entry.args[0];
> + if (ptrace(PTRACE_GET_SYSCALL_INFO, pid, PTRACE_SYSCALL_INFO_EXIT, &syscall_info_exit))
> + perr_and_exit("failed to get syscall info of exit\n");
> + result->a0 = syscall_info_exit->exit.rval;
> +
> + /* 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");
> +
> +}
> +
> +TEST(ptrace_modify_a0)
> +{
> + struct a0_regs result;
> +
> + ptrace_test(A0_MODIFY, &result);
> +
> + /* The modification of a0 cannot affect the first argument of the syscall */
> + EXPECT_EQ(A0_OLD, result.orig_a0);
> + EXPECT_EQ(A0_NEW, result.a0);
> +}
> +
> +TEST(ptrace_modify_orig_a0)
> +{
> + struct a0_regs result;
> +
> + ptrace_test(ORIG_A0_MODIFY, &result);
> +
> + /* Only modify orig_a0 to change the first argument of the syscall */
> + EXPECT_EQ(A0_NEW, result.orig_a0);
> + /* a0 will keep default value, orig_a0 or -ENOSYS, depends on internal. */
> + EXPECT_NE(A0_NEW, result.a0);
> +}
> +
> +TEST_HARNESS_MAIN
>
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