strace/0184-startup_tcb-add-a-comment.patch

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From 2048c136ba6edc4282dbc976c499e038d5b60c03 Mon Sep 17 00:00:00 2001
From: "Dmitry V. Levin" <ldv@strace.io>
Date: Mon, 28 Oct 2024 08:00:00 +0000
Subject: [PATCH 184/185] startup_tcb: add a comment
* src/strace.c (startup_tcb): Add a comment explaining why it is safe
to call get_scno().
---
src/strace.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/src/strace.c b/src/strace.c
index 45ab48c43..1a9d53bc8 100644
--- a/src/strace.c
+++ b/src/strace.c
@@ -3549,8 +3549,16 @@ startup_tcb(struct tcb *tcp)
}
}
- if ((tcp->flags & TCB_GRABBED) && (get_scno(tcp) == 1))
- tcp->s_prev_ent = tcp->s_ent;
+ if (tcp->flags & TCB_GRABBED) {
+ /*
+ * There is no guarantee the state of the tracee is such that
+ * would allow get_scno() to obtain meaningful information.
+ * However, if the tracee is not in a syscall, then the garbage
+ * obtained by get_scno() is not going to be used.
+ */
+ if (get_scno(tcp) == 1)
+ tcp->s_prev_ent = tcp->s_ent;
+ }
if (cflag) {
tcp->atime = tcp->stime;
--
2.13.6