Re: [PATCH 17/23] arm64: ptrace: handle ptrace_request differently for aarch32 and ilp32

[zhouchengming <zhouchengming1@huawei.com>]

On 2016/5/24 8:04, Yury Norov wrote:
> Here new aarch32 ptrace syscall handler is introsuced to avoid run-time
> detection of the task type.
>
> Signed-off-by: Yury Norov<ynorov@caviumnetworks.com>
> ---
>   arch/arm64/include/asm/unistd32.h |  2 +-
>   arch/arm64/kernel/ptrace.c        | 50 ++++++++++++++++++++++++++++++++++++++-
>   arch/arm64/kernel/sys32.c         |  1 +
>   include/linux/ptrace.h            |  6 +++++
>   kernel/ptrace.c                   | 10 ++++----
>   5 files changed, 62 insertions(+), 7 deletions(-)
>
> diff --git a/arch/arm64/include/asm/unistd32.h b/arch/arm64/include/asm/unistd32.h
> index 5b925b7..f57bbe3 100644
> --- a/arch/arm64/include/asm/unistd32.h
> +++ b/arch/arm64/include/asm/unistd32.h
> @@ -74,7 +74,7 @@ __SYSCALL(__NR_getuid, sys_getuid16)
>   			/* 25 was sys_stime */
>   __SYSCALL(25, sys_ni_syscall)
>   #define __NR_ptrace 26
> -__SYSCALL(__NR_ptrace, compat_sys_ptrace)
> +__SYSCALL(__NR_ptrace, compat_sys_aarch32_ptrace)
>   			/* 27 was sys_alarm */
>   __SYSCALL(27, sys_ni_syscall)
>   			/* 28 was sys_fstat */
> diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
> index 38a09338..a861105 100644
> --- a/arch/arm64/kernel/ptrace.c
> +++ b/arch/arm64/kernel/ptrace.c
> @@ -29,6 +29,7 @@
>   #include<linux/user.h>
>   #include<linux/seccomp.h>
>   #include<linux/security.h>
> +#include<linux/syscalls.h>
>   #include<linux/init.h>
>   #include<linux/signal.h>
>   #include<linux/uaccess.h>
> @@ -1114,7 +1115,7 @@ static int compat_ptrace_sethbpregs(struct task_struct *tsk, compat_long_t num,
>   }
>   #endif	/* CONFIG_HAVE_HW_BREAKPOINT */
>
> -long compat_arch_ptrace(struct task_struct *child, compat_long_t request,
> +static long compat_a32_ptrace(struct task_struct *child, compat_long_t request,
>   			compat_ulong_t caddr, compat_ulong_t cdata)
>   {
>   	unsigned long addr = caddr;
> @@ -1191,8 +1192,55 @@ long compat_arch_ptrace(struct task_struct *child, compat_long_t request,
>
>   	return ret;
>   }
> +
> +COMPAT_SYSCALL_DEFINE4(aarch32_ptrace, compat_long_t, request, compat_long_t, pid,
> +		       compat_long_t, addr, compat_long_t, data)
> +{
> +	struct task_struct *child;
> +	long ret;
> +
> +	if (request == PTRACE_TRACEME) {
> +		ret = ptrace_traceme();
> +		goto out;
> +	}
> +
> +	child = ptrace_get_task_struct(pid);
> +	if (IS_ERR(child)) {
> +		ret = PTR_ERR(child);
> +		goto out;
> +	}
> +
> +	if (request == PTRACE_ATTACH || request == PTRACE_SEIZE) {
> +		ret = ptrace_attach(child, request, addr, data);
> +		goto out_put_task_struct;
> +	}
> +
> +	ret = ptrace_check_attach(child, request == PTRACE_KILL ||
> +				  request == PTRACE_INTERRUPT);
> +	if (!ret) {
> +		ret = compat_a32_ptrace(child, request, addr, data);
> +		if (ret || request != PTRACE_DETACH)
> +			ptrace_unfreeze_traced(child);
> +	}
> +
> + out_put_task_struct:
> +	put_task_struct(child);
> + out:
> +	return ret;
> +}
> +
>   #endif /* CONFIG_AARCH32_EL0 */
>
> +#ifdef CONFIG_COMPAT
> +
> +long compat_arch_ptrace(struct task_struct *child, compat_long_t request,
> +			compat_ulong_t caddr, compat_ulong_t cdata)
> +{
> +	return compat_ptrace_request(child, request, caddr, cdata);
> +}
> +
> +#endif /* CONFIG_COMPAT */
> +
>   const struct user_regset_view *task_user_regset_view(struct task_struct *task)
>   {
>   #ifdef CONFIG_AARCH32_EL0
> diff --git a/arch/arm64/kernel/sys32.c b/arch/arm64/kernel/sys32.c
> index a40b134..3752443 100644
> --- a/arch/arm64/kernel/sys32.c
> +++ b/arch/arm64/kernel/sys32.c
> @@ -38,6 +38,7 @@ asmlinkage long compat_sys_fadvise64_64_wrapper(void);
>   asmlinkage long compat_sys_sync_file_range2_wrapper(void);
>   asmlinkage long compat_sys_fallocate_wrapper(void);
>   asmlinkage long compat_sys_mmap2_wrapper(void);
> +asmlinkage long compat_sys_aarch32_ptrace(void);
>
>   #undef __SYSCALL
>   #define __SYSCALL(nr, sym)	[nr] = sym,
> diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
> index 504c98a..75887a0 100644
> --- a/include/linux/ptrace.h
> +++ b/include/linux/ptrace.h
> @@ -97,6 +97,12 @@ int generic_ptrace_peekdata(struct task_struct *tsk, unsigned long addr,
>   			    unsigned long data);
>   int generic_ptrace_pokedata(struct task_struct *tsk, unsigned long addr,
>   			    unsigned long data);
> +int ptrace_traceme(void);
> +struct task_struct *ptrace_get_task_struct(pid_t pid);
> +int ptrace_attach(struct task_struct *task, long request,
> +			 unsigned long addr, unsigned long flags);
> +int ptrace_check_attach(struct task_struct *child, bool ignore_state);
> +void ptrace_unfreeze_traced(struct task_struct *task);
>
>   /**
>    * ptrace_parent - return the task that is tracing the given task
> diff --git a/kernel/ptrace.c b/kernel/ptrace.c
> index d49bfa1..cadf24c 100644
> --- a/kernel/ptrace.c
> +++ b/kernel/ptrace.c
> @@ -136,7 +136,7 @@ static bool ptrace_freeze_traced(struct task_struct *task)
>   	return ret;
>   }
>
> -static void ptrace_unfreeze_traced(struct task_struct *task)
> +void ptrace_unfreeze_traced(struct task_struct *task)
>   {
>   	if (task->state != __TASK_TRACED)
>   		return;
> @@ -168,7 +168,7 @@ static void ptrace_unfreeze_traced(struct task_struct *task)
>    * RETURNS:
>    * 0 on success, -ESRCH if %child is not ready.
>    */
> -static int ptrace_check_attach(struct task_struct *child, bool ignore_state)
> +int ptrace_check_attach(struct task_struct *child, bool ignore_state)
>   {
>   	int ret = -ESRCH;
>
> @@ -292,7 +292,7 @@ bool ptrace_may_access(struct task_struct *task, unsigned int mode)
>   	return !err;
>   }
>
> -static int ptrace_attach(struct task_struct *task, long request,
> +int ptrace_attach(struct task_struct *task, long request,
>   			 unsigned long addr,
>   			 unsigned long flags)
>   {
> @@ -406,7 +406,7 @@ out:
>    * Performs checks and sets PT_PTRACED.
>    * Should be used by all ptrace implementations for PTRACE_TRACEME.
>    */
> -static int ptrace_traceme(void)
> + int ptrace_traceme(void)
>   {
>   	int ret = -EPERM;
>
> @@ -1056,7 +1056,7 @@ int ptrace_request(struct task_struct *child, long request,
>   	return ret;
>   }
>
> -static struct task_struct *ptrace_get_task_struct(pid_t pid)
> +struct task_struct *ptrace_get_task_struct(pid_t pid)
>   {
>   	struct task_struct *child;
>

Hello, I found ilp32 will use sys_ptrace, not compat_sys_ptrace. So I 
write a little patch to see if can solve the problem correctly.

Thanks.

 From f6156236df578bb05c4a17e7f9776ceaf8f7afe6 Mon Sep 17 00:00:00 2001
From: Zhou Chengming <zhouchengming1@huawei.com>
Date: Wed, 8 Jun 2016 09:46:23 +0800
Subject: [PATCH] ilp32: use compat_sys_ptrace instead of sys_ptrace

When we analyze a testcase of ptrace that failed on ilp32, we found
the syscall that the ilp32 uses is sys_ptrace, not compat_sys_ptrace.
Because in include/uapi/asm-generic/unistd.h it's defined like:
__SYSCALL(__NR_ptrace, sys_ptrace)
So we change it to __SC_COMP(__NR_ptrace, sys_ptrace, compat_sys_ptrace),
let compat tasks use the compat_sys_ptrace.

Signed-off-by: Zhou Chengming <zhouchengming1@huawei.com>
---
  include/uapi/asm-generic/unistd.h |    2 +-
  1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/include/uapi/asm-generic/unistd.h 
b/include/uapi/asm-generic/unistd.h
index 2862d2e..50ee770 100644
--- a/include/uapi/asm-generic/unistd.h
+++ b/include/uapi/asm-generic/unistd.h
@@ -364,7 +364,7 @@ __SC_WRAP(__NR_syslog, sys_syslog)

  /* kernel/ptrace.c */
  #define __NR_ptrace 117
-__SYSCALL(__NR_ptrace, sys_ptrace)
+__SC_COMP(__NR_ptrace, sys_ptrace, compat_sys_ptrace)

  /* kernel/sched/core.c */
  #define __NR_sched_setparam 118
-- 
1.7.7