svn commit: r357700 - in head/sys: kern sys

[Konstantin Belousov]

Author: kib
Date: Sun Feb  9 12:29:51 2020
New Revision: 357700
URL: https://svnweb.freebsd.org/changeset/base/357700

Log:
  Add sysctl kern.proc.sigfastblk for reporting sigfastblock word address.
  
  Tested by:	pho
  Disscussed with:	cem, emaste, jilles
  Sponsored by:	The FreeBSD Foundation
  Differential revision:	https://reviews.freebsd.org/D12773

Modified:
  head/sys/kern/kern_proc.c
  head/sys/sys/sysctl.h

Modified: head/sys/kern/kern_proc.c
==============================================================================
--- head/sys/kern/kern_proc.c	Sun Feb  9 12:29:13 2020	(r357699)
+++ head/sys/kern/kern_proc.c	Sun Feb  9 12:29:51 2020	(r357700)
@@ -2962,6 +2962,77 @@ sysctl_kern_proc_sigtramp(SYSCTL_HANDLER_ARGS)
 	return (error);
 }
 
+static int
+sysctl_kern_proc_sigfastblk(SYSCTL_HANDLER_ARGS)
+{
+	int *name = (int *)arg1;
+	u_int namelen = arg2;
+	pid_t pid;
+	struct proc *p;
+	struct thread *td1;
+	uintptr_t addr;
+#ifdef COMPAT_FREEBSD32
+	uint32_t addr32;
+#endif
+	int error;
+
+	if (namelen != 1 || req->newptr != NULL)
+		return (EINVAL);
+
+	pid = (pid_t)name[0];
+	error = pget(pid, PGET_HOLD | PGET_NOTWEXIT | PGET_CANDEBUG, &p);
+	if (error != 0)
+		return (error);
+
+	PROC_LOCK(p);
+#ifdef COMPAT_FREEBSD32
+	if (SV_CURPROC_FLAG(SV_ILP32)) {
+		if (!SV_PROC_FLAG(p, SV_ILP32)) {
+			error = EINVAL;
+			goto errlocked;
+		}
+	}
+#endif
+	if (pid <= PID_MAX) {
+		td1 = FIRST_THREAD_IN_PROC(p);
+	} else {
+		FOREACH_THREAD_IN_PROC(p, td1) {
+			if (td1->td_tid == pid)
+				break;
+		}
+	}
+	if (td1 == NULL) {
+		error = ESRCH;
+		goto errlocked;
+	}
+	/*
+	 * The access to the private thread flags.  It is fine as far
+	 * as no out-of-thin-air values are read from td_pflags, and
+	 * usermode read of the td_sigblock_ptr is racy inherently,
+	 * since target process might have already changed it
+	 * meantime.
+	 */
+	if ((td1->td_pflags & TDP_SIGFASTBLOCK) != 0)
+		addr = (uintptr_t)td1->td_sigblock_ptr;
+	else
+		error = ENOTTY;
+
+errlocked:
+	_PRELE(p);
+	PROC_UNLOCK(p);
+	if (error != 0)
+		return (error);
+
+#ifdef COMPAT_FREEBSD32
+	if (SV_CURPROC_FLAG(SV_ILP32)) {
+		addr32 = addr;
+		error = SYSCTL_OUT(req, &addr32, sizeof(addr32));
+	} else
+#endif
+		error = SYSCTL_OUT(req, &addr, sizeof(addr));
+	return (error);
+}
+
 SYSCTL_NODE(_kern, KERN_PROC, proc, CTLFLAG_RD,  0, "Process table");
 
 SYSCTL_PROC(_kern_proc, KERN_PROC_ALL, all, CTLFLAG_RD|CTLTYPE_STRUCT|
@@ -3074,6 +3145,10 @@ static SYSCTL_NODE(_kern_proc, KERN_PROC_OSREL, osrel,
 static SYSCTL_NODE(_kern_proc, KERN_PROC_SIGTRAMP, sigtramp, CTLFLAG_RD |
 	CTLFLAG_MPSAFE, sysctl_kern_proc_sigtramp,
 	"Process signal trampoline location");
+
+static SYSCTL_NODE(_kern_proc, KERN_PROC_SIGFASTBLK, sigfastblk, CTLFLAG_RD |
+	CTLFLAG_ANYBODY | CTLFLAG_MPSAFE, sysctl_kern_proc_sigfastblk,
+	"Thread sigfastblock address");
 
 int allproc_gen;
 

Modified: head/sys/sys/sysctl.h
==============================================================================
--- head/sys/sys/sysctl.h	Sun Feb  9 12:29:13 2020	(r357699)
+++ head/sys/sys/sysctl.h	Sun Feb  9 12:29:51 2020	(r357700)
@@ -1017,6 +1017,7 @@ TAILQ_HEAD(sysctl_ctx_list, sysctl_ctx_entry);
 #define	KERN_PROC_SIGTRAMP	41	/* signal trampoline location */
 #define	KERN_PROC_CWD		42	/* process current working directory */
 #define	KERN_PROC_NFDS		43	/* number of open file descriptors */
+#define	KERN_PROC_SIGFASTBLK	44	/* address of fastsigblk magic word */
 
 /*
  * KERN_IPC identifiers