From 49418ad0e534a759c63d20fe00ccdd4983ccd321 Mon Sep 17 00:00:00 2001
From: Ben Grande <ben@invisiblethingslab.com>
Date: Thu, 25 Jun 2026 17:11:42 +0200
Subject: [PATCH] Report swapinfo

Allows distinguishing how much memory the qube is using from what is
assigned by using "meminfo - swapinfo".

For: https://github.com/QubesOS/qubes-core-admin/pull/827
---
 qmemman/meminfo-writer.c | 40 +++++++++++++++++++++++++++-------------
 1 file changed, 27 insertions(+), 13 deletions(-)

diff --git a/qmemman/meminfo-writer.c b/qmemman/meminfo-writer.c
index c9615182..179f174b 100644
--- a/qmemman/meminfo-writer.c
+++ b/qmemman/meminfo-writer.c
@@ -16,10 +16,16 @@ int used_mem_change_threshold;
 int delay;
 int usr1_received;
 
-const char *parse(const char *meminfo_buf, const char* dom_current_buf)
+typedef struct {
+    char *mem;
+    char *swap;
+} UsedMem;
+
+UsedMem parse(const char *meminfo_buf, const char* dom_current_buf)
 {
 	const char *ptr = meminfo_buf;
-	static char outbuf[4096];
+	static char used_mem_buf[4096];
+	static char used_swap_buf[4096];
 	long long val;
 	int len;
 	int ret;
@@ -27,6 +33,7 @@ const char *parse(const char *meminfo_buf, const char* dom_current_buf)
 	    0, SwapFree = 0;
 	unsigned long long key;
 	long long used_mem, used_mem_diff;
+	long long used_swap;
 	int nitems = 0;
 
 	while (nitems != (1<<6)-1 || !*ptr) {
@@ -68,7 +75,8 @@ const char *parse(const char *meminfo_buf, const char* dom_current_buf)
 	used_mem =
 	    MemTotal - Buffers - Cached - MemFree + SwapTotal - SwapFree;
 	if (used_mem < 0)
-		return NULL;
+		return (UsedMem){ .mem = NULL, .swap = NULL };
+	used_swap = SwapTotal - SwapFree;
 
 	used_mem_diff = used_mem - prev_used_mem;
 	if (used_mem_diff < 0)
@@ -78,10 +86,13 @@ const char *parse(const char *meminfo_buf, const char* dom_current_buf)
 	    || (used_mem > prev_used_mem && used_mem / 10 > (MemTotal+12) / 13
 		&& used_mem_diff > used_mem_change_threshold/2)) {
 		prev_used_mem = used_mem;
-		sprintf(outbuf, "%lld", used_mem);
-		return outbuf;
+		sprintf(used_mem_buf, "%lld", used_mem);
+		sprintf(used_swap_buf, "%lld", used_swap);
+		snprintf(used_mem_buf, sizeof used_mem_buf, "%lld", used_mem);
+		snprintf(used_swap_buf, sizeof used_swap_buf, "%lld", used_swap);
+		return (UsedMem){ .mem = used_mem_buf, .swap = used_swap_buf };
 	}
-	return NULL;
+	return (UsedMem){ .mem = NULL, .swap = NULL };
 }
 
 void usage(void)
@@ -94,10 +105,14 @@ void usage(void)
 	exit(1);
 }
 
-void send_to_qmemman(struct xs_handle *xs, const char *data)
+void send_to_qmemman(struct xs_handle *xs, const char *mem, const char *swap)
 {
-	if (!xs_write(xs, XBT_NULL, "memory/meminfo", data, strlen(data))) {
-		syslog(LOG_DAEMON | LOG_ERR, "error writing xenstore ?");
+	if (!xs_write(xs, XBT_NULL, "memory/meminfo", mem, strlen(mem))) {
+		syslog(LOG_DAEMON | LOG_ERR, "error writing meminfo to xenstore ?");
+		exit(1);
+	}
+	if (!xs_write(xs, XBT_NULL, "memory/swapinfo", swap, strlen(swap))) {
+		syslog(LOG_DAEMON | LOG_ERR, "error writing swapinfo to xenstore ?");
 		exit(1);
 	}
 }
@@ -121,7 +136,6 @@ static void update(struct xs_handle *xs, int meminfo_fd, int dom_current_fd)
 	char dom_current_buf[32];
 	char dom_current_buf2[32];
 	char meminfo_buf[4096];
-	const char *meminfo_data;
 
 	pread0_string(dom_current_fd, dom_current_buf, sizeof(dom_current_buf));
 
@@ -140,9 +154,9 @@ static void update(struct xs_handle *xs, int meminfo_fd, int dom_current_fd)
 			break;
 	}
 
-	meminfo_data = parse(meminfo_buf, dom_current_buf);
-	if (meminfo_data)
-		send_to_qmemman(xs, meminfo_data);
+	UsedMem meminfo_data = parse(meminfo_buf, dom_current_buf);
+	if (meminfo_data.mem && meminfo_data.mem[0])
+		send_to_qmemman(xs, meminfo_data.mem, meminfo_data.swap);
 }
 
 int main(int argc, char **argv)