git: fc36cd43fd7f - stable/13 - linux: implement PTRACE_EVENT_EXEC

The branch stable/13 has been updated by trasz:

URL: https://cgit.FreeBSD.org/src/commit/?id=fc36cd43fd7f03261d608ceaa69e8c46ef3e0c38

commit fc36cd43fd7f03261d608ceaa69e8c46ef3e0c38
Author:     Edward Tomasz Napierala <trasz@FreeBSD.org>
AuthorDate: 2021-10-23 18:13:14 +0000
Commit:     Edward Tomasz Napierala <trasz@FreeBSD.org>
CommitDate: 2022-02-21 13:35:51 +0000

    linux: implement PTRACE_EVENT_EXEC
    
    This fixes strace(1) from Ubuntu Focal.
    
    Reviewed By:    jhb
    Sponsored By:   EPSRC
    Differential Revision:  https://reviews.freebsd.org/D32367
    
    (cherry picked from commit 6e66030c4c05331f9b0adf87c31f2f233dd3ae1f)
---
 sys/amd64/linux/linux_ptrace.c |  9 +++++++--
 sys/kern/subr_syscall.c        | 12 ++++++++++++
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/sys/amd64/linux/linux_ptrace.c b/sys/amd64/linux/linux_ptrace.c
index e87e0a63f5b4..7abb9c5ee933 100644
--- a/sys/amd64/linux/linux_ptrace.c
+++ b/sys/amd64/linux/linux_ptrace.c
@@ -72,6 +72,7 @@ __FBSDID("$FreeBSD$");
 #define	LINUX_PTRACE_SEIZE		0x4206
 #define	LINUX_PTRACE_GET_SYSCALL_INFO	0x420e
 
+#define	LINUX_PTRACE_EVENT_EXEC		4
 #define	LINUX_PTRACE_EVENT_EXIT		6
 
 #define	LINUX_PTRACE_O_TRACESYSGOOD	1
@@ -152,8 +153,12 @@ linux_ptrace_status(struct thread *td, pid_t pid, int status)
 	    lwpinfo.pl_flags & PL_FLAG_SCE)
 		status |= (LINUX_SIGTRAP | 0x80) << 8;
 	if ((pem->ptrace_flags & LINUX_PTRACE_O_TRACESYSGOOD) &&
-	    lwpinfo.pl_flags & PL_FLAG_SCX)
-		status |= (LINUX_SIGTRAP | 0x80) << 8;
+	    lwpinfo.pl_flags & PL_FLAG_SCX) {
+		if (lwpinfo.pl_flags & PL_FLAG_EXEC)
+			status |= (LINUX_SIGTRAP | LINUX_PTRACE_EVENT_EXEC << 8) << 8;
+		else
+			status |= (LINUX_SIGTRAP | 0x80) << 8;
+	}
 	if ((pem->ptrace_flags & LINUX_PTRACE_O_TRACEEXIT) &&
 	    lwpinfo.pl_flags & PL_FLAG_EXITED)
 		status |= (LINUX_SIGTRAP | LINUX_PTRACE_EVENT_EXIT << 8) << 8;
diff --git a/sys/kern/subr_syscall.c b/sys/kern/subr_syscall.c
index 85a0814a2125..dee81ba0fa48 100644
--- a/sys/kern/subr_syscall.c
+++ b/sys/kern/subr_syscall.c
@@ -255,6 +255,18 @@ syscallret(struct thread *td)
 	if (__predict_false(traced ||
 	    (td->td_dbgflags & (TDB_EXEC | TDB_FORK)) != 0)) {
 		PROC_LOCK(p);
+		/*
+		 * Linux debuggers expect an additional stop for exec,
+		 * between the usual syscall entry and exit.  Raise
+		 * the exec event now and then clear TDB_EXEC so that
+		 * the next stop is reported as a syscall exit by
+		 * linux_ptrace_status().
+		 */
+		if ((td->td_dbgflags & TDB_EXEC) != 0 &&
+		    SV_PROC_ABI(td->td_proc) == SV_ABI_LINUX) {
+			ptracestop(td, SIGTRAP, NULL);
+			td->td_dbgflags &= ~TDB_EXEC;
+		}
 		/*
 		 * If tracing the execed process, trap to the debugger
 		 * so that breakpoints can be set before the program