um: Replace PT_DTRACE with TIF_SINGLESTEP

Eric W. Biederman Tue, 26 Apr 2022 15:53:07 -0700

User mode linux is the last user of the PT_DTRACE flag.  Using the flag to 
indicate
single stepping is a little confusing and worse changing tsk->ptrace without 
locking
could potentionally cause problems.


So use a thread info flag with a better name instead of flag in tsk->ptrace.

Remove the definition PT_DTRACE as uml is the last user.

Signed-off-by: "Eric W. Biederman" <ebied...@xmission.com>
---
 arch/um/include/asm/thread_info.h | 2 ++
 arch/um/kernel/exec.c             | 2 +-
 arch/um/kernel/process.c          | 2 +-
 arch/um/kernel/ptrace.c           | 8 ++++----
 arch/um/kernel/signal.c           | 4 ++--
 include/linux/ptrace.h            | 1 -
 6 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/arch/um/include/asm/thread_info.h 
b/arch/um/include/asm/thread_info.h
index 1395cbd7e340..c7b4b49826a2 100644
--- a/arch/um/include/asm/thread_info.h
+++ b/arch/um/include/asm/thread_info.h
@@ -60,6 +60,7 @@ static inline struct thread_info *current_thread_info(void)
 #define TIF_RESTORE_SIGMASK    7
 #define TIF_NOTIFY_RESUME      8
 #define TIF_SECCOMP            9       /* secure computing */
+#define TIF_SINGLESTEP         10      /* single stepping userspace */
 
 #define _TIF_SYSCALL_TRACE     (1 << TIF_SYSCALL_TRACE)
 #define _TIF_SIGPENDING                (1 << TIF_SIGPENDING)
@@ -68,5 +69,6 @@ static inline struct thread_info *current_thread_info(void)
 #define _TIF_MEMDIE            (1 << TIF_MEMDIE)
 #define _TIF_SYSCALL_AUDIT     (1 << TIF_SYSCALL_AUDIT)
 #define _TIF_SECCOMP           (1 << TIF_SECCOMP)
+#define _TIF_SINGLESTEP                (1 << TIF_SINGLESTEP)
 
 #endif
diff --git a/arch/um/kernel/exec.c b/arch/um/kernel/exec.c
index c85e40c72779..58938d75871a 100644
--- a/arch/um/kernel/exec.c
+++ b/arch/um/kernel/exec.c
@@ -43,7 +43,7 @@ void start_thread(struct pt_regs *regs, unsigned long eip, 
unsigned long esp)
 {
        PT_REGS_IP(regs) = eip;
        PT_REGS_SP(regs) = esp;
-       current->ptrace &= ~PT_DTRACE;
+       clear_thread_flag(TIF_SINGLESTEP);
 #ifdef SUBARCH_EXECVE1
        SUBARCH_EXECVE1(regs->regs);
 #endif
diff --git a/arch/um/kernel/process.c b/arch/um/kernel/process.c
index 80504680be08..88c5c7844281 100644
--- a/arch/um/kernel/process.c
+++ b/arch/um/kernel/process.c
@@ -335,7 +335,7 @@ int singlestepping(void * t)
 {
        struct task_struct *task = t ? t : current;
 
-       if (!(task->ptrace & PT_DTRACE))
+       if (!test_thread_flag(TIF_SINGLESTEP))
                return 0;
 
        if (task->thread.singlestep_syscall)
diff --git a/arch/um/kernel/ptrace.c b/arch/um/kernel/ptrace.c
index bfaf6ab1ac03..5154b27de580 100644
--- a/arch/um/kernel/ptrace.c
+++ b/arch/um/kernel/ptrace.c
@@ -11,7 +11,7 @@
 
 void user_enable_single_step(struct task_struct *child)
 {
-       child->ptrace |= PT_DTRACE;
+       set_tsk_thread_flag(child, TIF_SINGLESTEP);
        child->thread.singlestep_syscall = 0;
 
 #ifdef SUBARCH_SET_SINGLESTEPPING
@@ -21,7 +21,7 @@ void user_enable_single_step(struct task_struct *child)
 
 void user_disable_single_step(struct task_struct *child)
 {
-       child->ptrace &= ~PT_DTRACE;
+       clear_tsk_thread_flag(child, TIF_SINGLESTEP);
        child->thread.singlestep_syscall = 0;
 
 #ifdef SUBARCH_SET_SINGLESTEPPING
@@ -120,7 +120,7 @@ static void send_sigtrap(struct uml_pt_regs *regs, int 
error_code)
 }
 
 /*
- * XXX Check PT_DTRACE vs TIF_SINGLESTEP for singlestepping check and
+ * XXX Check TIF_SINGLESTEP for singlestepping check and
  * PT_PTRACED vs TIF_SYSCALL_TRACE for syscall tracing check
  */
 int syscall_trace_enter(struct pt_regs *regs)
@@ -144,7 +144,7 @@ void syscall_trace_leave(struct pt_regs *regs)
        audit_syscall_exit(regs);
 
        /* Fake a debug trap */
-       if (ptraced & PT_DTRACE)
+       if (test_thread_flag(TIF_SINGLESTEP))
                send_sigtrap(&regs->regs, 0);
 
        if (!test_thread_flag(TIF_SYSCALL_TRACE))
diff --git a/arch/um/kernel/signal.c b/arch/um/kernel/signal.c
index 88cd9b5c1b74..ae4658f576ab 100644
--- a/arch/um/kernel/signal.c
+++ b/arch/um/kernel/signal.c
@@ -53,7 +53,7 @@ static void handle_signal(struct ksignal *ksig, struct 
pt_regs *regs)
        unsigned long sp;
        int err;
 
-       if ((current->ptrace & PT_DTRACE) && (current->ptrace & PT_PTRACED))
+       if (test_thread_flag(TIF_SINGLESTEP) && (current->ptrace & PT_PTRACED))
                singlestep = 1;
 
        /* Did we come from a system call? */
@@ -128,7 +128,7 @@ void do_signal(struct pt_regs *regs)
         * on the host.  The tracing thread will check this flag and
         * PTRACE_SYSCALL if necessary.
         */
-       if (current->ptrace & PT_DTRACE)
+       if (test_thread_flag(TIF_SINGLESTEP))
                current->thread.singlestep_syscall =
                        is_syscall(PT_REGS_IP(&current->thread.regs));
 
diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index 15b3d176b6b4..4c06f9f8ef3f 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -30,7 +30,6 @@ extern int ptrace_access_vm(struct task_struct *tsk, unsigned 
long addr,
 
 #define PT_SEIZED      0x00010000      /* SEIZE used, enable new behavior */
 #define PT_PTRACED     0x00000001
-#define PT_DTRACE      0x00000002      /* delayed trace (used on m68k, i386) */
 
 #define PT_OPT_FLAG_SHIFT      3
 /* PT_TRACE_* event enable flags */
-- 
2.35.3


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[PATCH 3/9] ptrace/um: Replace PT_DTRACE with TIF_SINGLESTEP

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