From: Lennart Poettering <lennart@poettering.net>
Date: Tue, 8 Feb 2022 10:23:19 +0000 (+0100)
Subject: sd-boot: add overflow check to TSC reads
X-Git-Tag: v251-rc1~326^2~4
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=476c0e969a704387c24bd4f125e4c7c53013c876;p=thirdparty%2Fsystemd.git

sd-boot: add overflow check to TSC reads

On some archs the counter is 32bit, and in case of virtualization it
might actually overflow, who knows.
---

diff --git a/src/boot/efi/ticks.c b/src/boot/efi/ticks.c
index 68b2d5806ce..fd0e2b23484 100644
--- a/src/boot/efi/ticks.c
+++ b/src/boot/efi/ticks.c
@@ -45,6 +45,10 @@ UINT64 ticks_freq(void) {
         BS->Stall(1000);
         ticks_end = ticks_read();
 
+        if (ticks_end < ticks_start) /* Check for an overflow (which is not that unlikely, given on some
+                                      * archs the value is 32bit) */
+                return 0;
+
         return (ticks_end - ticks_start) * 1000UL;
 }
 #endif