From aa6108d70f2889bc35bc0a0b16526f907fbbaa81 Mon Sep 17 00:00:00 2001
From: Simon Bucher <ebners@google.com>
Date: Wed, 30 Sep 2026 07:29:37 +0000
Subject: [PATCH] kernel: handle EINTR and signal termination in run_command

When `run_command` reads subprocess output via `fgets` in a multi-threaded process, incoming signals can interrupt the underlying `read` syscall with `EINTR`. Previously, `while (fgets(...) != NULL)` exited the read loop immediately on `EINTR` and called `pclose`, closing the pipe early while the child was still running (or causing the child to die with `SIGPIPE`). Additionally, `run_command` returned `WEXITSTATUS(ret)` without checking `WIFEXITED(ret)`, which evaluates to `0` when a child terminates due to an unhandled signal.

Retry `fgets` after clearing the stream error state when `ferror(f) && errno == EINTR`, and return `-1` if `!WIFEXITED(ret)`.
---
 kernel/yosys.cc | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/kernel/yosys.cc b/kernel/yosys.cc
index 999c7a45b..ab073dd1c 100644
--- a/kernel/yosys.cc
+++ b/kernel/yosys.cc
@@ -192,10 +192,17 @@ int run_command(const std::string &command, std::function<void(const std::string
 
 	std::string line;
 	char logbuf[128];
-	while (fgets(logbuf, 128, f) != NULL) {
-		line += logbuf;
-		if (!line.empty() && line.back() == '\n')
-			process_line(line), line.clear();
+	while (true) {
+		if (fgets(logbuf, 128, f) != NULL) {
+			line += logbuf;
+			if (!line.empty() && line.back() == '\n')
+				process_line(line), line.clear();
+		} else if (ferror(f) && errno == EINTR) {
+			clearerr(f);
+			continue;
+		} else {
+			break;
+		}
 	}
 	if (!line.empty())
 		process_line(line);
@@ -206,6 +213,8 @@ int run_command(const std::string &command, std::function<void(const std::string
 #ifdef _WIN32
 	return ret;
 #else
+	if (!WIFEXITED(ret))
+		return -1;
 	return WEXITSTATUS(ret);
 #endif
 }