Re: [ptrace] please review follow fork/exec changes

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The patch I sent earlier works for me. Just wanted to let you know to illustrate what I would like to see from the kernel.

I'm trying to see if there's way not to add flags with semantics similar to TDB_EXEC. I think the problem with TDB_EXEC is that is serves a trigger for a stop as well as an indicator to return PL_FLAG_EXEC. And in my case I still want to see all the stops but I only want to see the PL_FLAG_EXEC when PT_FOLLOW_EXEC is specified.

Do you think the attached patch will do what I'd like without compromising existing functionality?


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Index: sys/proc.h
===================================================================

--- sys/proc.h	(revision 231228)
+++ sys/proc.h	(working copy)
@@ -384,6 +384,7 @@ do {									\
 				      process */
 #define	TDB_STOPATFORK	0x00000080 /* Stop at the return from fork (child
 				      only) */
+#define	TDB_CHILD	0x00000100 /* New child indicator for ptrace() */
 
 /*
  * "Private" flags kept in td_pflags:
@@ -613,6 +614,7 @@ struct proc {
 #define	P_HWPMC		0x800000 /* Process is using HWPMCs */
 
 #define	P_JAILED	0x1000000 /* Process is in jail. */
+#define	P_FOLLOWEXEC	0x2000000 /* Report execs with ptrace. */
 #define	P_INEXEC	0x4000000 /* Process is in execve(). */
 #define	P_STATCHILD	0x8000000 /* Child process stopped or exited. */
 #define	P_INMEM		0x10000000 /* Loaded into memory. */
Index: sys/ptrace.h
===================================================================
--- sys/ptrace.h	(revision 231228)
+++ sys/ptrace.h	(working copy)
@@ -64,6 +64,7 @@
 #define	PT_SYSCALL	22
 
 #define	PT_FOLLOW_FORK	23
+#define	PT_FOLLOW_EXEC	24
 
 #define PT_GETREGS      33	/* get general-purpose registers */
 #define PT_SETREGS      34	/* set general-purpose registers */
@@ -106,7 +107,8 @@ struct ptrace_lwpinfo {
 #define	PL_FLAG_SCX	0x08	/* syscall leave point */
 #define	PL_FLAG_EXEC	0x10	/* exec(2) succeeded */
 #define	PL_FLAG_SI	0x20	/* siginfo is valid */
-#define	PL_FLAG_FORKED	0x40	/* new child */
+#define	PL_FLAG_FORKED	0x40	/* child born */
+#define	PL_FLAG_CHILD	0x80	/* I am from child */
 	sigset_t	pl_sigmask;	/* LWP signal mask */
 	sigset_t	pl_siglist;	/* LWP pending signal */
 	struct __siginfo pl_siginfo;	/* siginfo for signal */
Index: kern/kern_exec.c
===================================================================
--- kern/kern_exec.c	(revision 231228)
+++ kern/kern_exec.c	(working copy)
@@ -56,6 +56,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/proc.h>
 #include <sys/pioctl.h>
 #include <sys/namei.h>
+#include <sys/ptrace.h>
 #include <sys/resourcevar.h>
 #include <sys/sdt.h>
 #include <sys/sf_buf.h>
Index: kern/kern_fork.c
===================================================================
--- kern/kern_fork.c	(revision 231228)
+++ kern/kern_fork.c	(working copy)
@@ -1035,7 +1035,9 @@ fork_return(struct thread *td, struct trapframe *f
 			p->p_oppid = p->p_pptr->p_pid;
 			proc_reparent(p, dbg);
 			sx_xunlock(&proctree_lock);
+			td->td_dbgflags |= TDB_CHILD;
 			ptracestop(td, SIGSTOP);
+			td->td_dbgflags &= ~TDB_CHILD;
 		} else {
 			/*
 			 * ... otherwise clear the request.
Index: kern/sys_process.c
===================================================================
--- kern/sys_process.c	(revision 231228)
+++ kern/sys_process.c	(working copy)
@@ -660,6 +660,7 @@ kern_ptrace(struct thread *td, int req, pid_t pid,
 	case PT_TO_SCX:
 	case PT_SYSCALL:
 	case PT_FOLLOW_FORK:
+	case PT_FOLLOW_EXEC:
 	case PT_DETACH:
 		sx_xlock(&proctree_lock);
 		proctree_locked = 1;
@@ -873,6 +874,12 @@ kern_ptrace(struct thread *td, int req, pid_t pid,
 		else
 			p->p_flag &= ~P_FOLLOWFORK;
 		break;
+	case PT_FOLLOW_EXEC:
+		if (data)
+			p->p_flag |= P_FOLLOWEXEC;
+		else
+			p->p_flag &= ~P_FOLLOWEXEC;
+		break;
 
 	case PT_STEP:
 	case PT_CONTINUE:
@@ -936,7 +943,8 @@ kern_ptrace(struct thread *td, int req, pid_t pid,
 					p->p_sigparent = SIGCHLD;
 			}
 			p->p_oppid = 0;
-			p->p_flag &= ~(P_TRACED | P_WAITED | P_FOLLOWFORK);
+			p->p_flag &= ~(P_TRACED | P_WAITED | P_FOLLOWFORK |
+			    P_FOLLOWEXEC);
 
 			/* should we send SIGCHLD? */
 			/* childproc_continued(p); */
@@ -1139,12 +1147,15 @@ kern_ptrace(struct thread *td, int req, pid_t pid,
 			pl->pl_flags |= PL_FLAG_SCE;
 		else if (td2->td_dbgflags & TDB_SCX)
 			pl->pl_flags |= PL_FLAG_SCX;
-		if (td2->td_dbgflags & TDB_EXEC)
+		if (td2->td_dbgflags & TDB_EXEC &&
+		    (p->p_stops & S_PT_SCX || p->p_flag & P_FOLLOWEXEC))
 			pl->pl_flags |= PL_FLAG_EXEC;
 		if (td2->td_dbgflags & TDB_FORK) {
 			pl->pl_flags |= PL_FLAG_FORKED;
 			pl->pl_child_pid = td2->td_dbg_forked;
 		}
+		if (td2->td_dbgflags & TDB_CHILD)
+			pl->pl_flags |= PL_FLAG_CHILD;
 		pl->pl_sigmask = td2->td_sigmask;
 		pl->pl_siglist = td2->td_siglist;
 		strcpy(pl->pl_tdname, td2->td_name);

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