From: Zbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl>
Date: Tue, 26 May 2020 19:08:10 +0000 (+0200)
Subject: shared/efi-loader: remove check that uses absolute tick value
X-Git-Tag: v246-rc1~268^2
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=refs%2Fpull%2F15934%2Fhead;p=thirdparty%2Fsystemd.git

shared/efi-loader: remove check that uses absolute tick value

sd-boot uses rdtsc to set those timestamps. There is no guarantee that the tsc
has any particular absolute value.

On my VM:
$ head /sys/firmware/efi/efivars/LoaderTime*
==> /sys/firmware/efi/efivars/LoaderTimeExecUSec-4a67b082-0a4c-41cf-b6c7-440b29bb8c4f <==
4397904074
==> /sys/firmware/efi/efivars/LoaderTimeInitUSec-4a67b082-0a4c-41cf-b6c7-440b29bb8c4f <==
4396386839
==> /sys/firmware/efi/efivars/LoaderTimeMenuUSec-4a67b082-0a4c-41cf-b6c7-440b29bb8c4f <==
4396392521

$ build/test-boot-timestamps
...
LoaderTimeExecUSec=4396386839 too large, refusing.
Failed to read EFI loader data: Input/output error
Assertion 'q >= 0' failed at src/test/test-boot-timestamps.c:84, function main(). Aborting.

(with patch)
$ build/test-boot-timestamps
...
EFI Loader: start=1h 13min 16.386s exit=1h 13min 17.904s duration=1.517s
Firmware began 1h 13min 17.904074s before kernel.
Loader began 1.517235s before kernel.
Firmware began Tue 2020-05-26 11:04:13 CEST.
Loader began Tue 2020-05-26 12:17:30 CEST.
Kernel began Tue 2020-05-26 12:17:31 CEST.
---

diff --git a/src/shared/efi-loader.c b/src/shared/efi-loader.c
index 34196537b78..c288176fd18 100644
--- a/src/shared/efi-loader.c
+++ b/src/shared/efi-loader.c
@@ -531,15 +531,11 @@ int efi_loader_get_boot_usec(usec_t *firmware, usec_t *loader) {
         if (r < 0)
                 return log_debug_errno(r, "Failed to read LoaderTimeExecUSec: %m");
 
-        if (y == 0 || y < x)
+        if (y == 0 || y < x || y - x > USEC_PER_HOUR)
                 return log_debug_errno(SYNTHETIC_ERRNO(EIO),
                                        "Bad LoaderTimeInitUSec=%"PRIu64", LoaderTimeExecUSec=%" PRIu64"; refusing.",
                                        x, y);
 
-        if (y > USEC_PER_HOUR)
-                return log_debug_errno(SYNTHETIC_ERRNO(EIO),
-                                       "LoaderTimeExecUSec=%"PRIu64" too large, refusing.", x);
-
         *firmware = x;
         *loader = y;