To allow direct modification of the elfcorehdr by the kernel, in
response to CPU and memory hot un/plug and/or online/offline events,
the buffer containing the:
- elfcorehdr must be excluded from the purgatory checksum/digest
(see "crashdump: exclude elfcorehdr segment from digest for
hotplug")
- the elfcorehdr segment must be large enough, and
- the kernel must be permitted to modify the elfcorehdr
For hotplug, the size of the elfcorehdr segment is obtained from the
kernel, or from the command line option.
The KEXEC_UPDATE_ELFCOREHDR flag indicates to the kernel that it can
make direct modifications to the elfcorehdr.
Signed-off-by: Eric DeVolder <eric.devolder@xxxxxxxxxx>
---
kexec/kexec.c | 22 ++++++++++++++++++++++
1 file changed, 22 insertions(+)
diff --git a/kexec/kexec.c b/kexec/kexec.c
index 4a64e53..c59e795 100644
--- a/kexec/kexec.c
+++ b/kexec/kexec.c
@@ -1626,6 +1626,28 @@ int main(int argc, char *argv[])
die("--load-live-update can only be used with xen\n");
}
+ /* NOTE: Xen KEXEC_LIVE_UPDATE and KEXEC_UPDATE_ELFCOREHDR collide */
+ if (do_hotplug) {
+ const char *ces = "/sys/kernel/crash_elfcorehdr_size";
+ if (!elfcorehdrsz) {
+ unsigned long ul;
+ char *buf;
+ off_t nread = 0;
+ buf = slurp_file_len(ces, sizeof(buf)-1, &nread);
+ if (buf) {
+ ul = strtoul(buf, NULL, 0);
+ elfcorehdrsz = ul;
+ }
+ }
+ if (!elfcorehdrsz) {
+ die("If path %s does not exist, must specify the\n"
+ "--elfcorehdrsz= option\n", ces);
+ }
+ dbgprintf("ELFCOREHDR_SIZE %lu\n", elfcorehdrsz);
+ /* Indicate to the kernel it is ok to modify the elfcorehdr */
+ kexec_flags |= KEXEC_UPDATE_ELFCOREHDR;
+ }
+
fileind = optind;
/* Reset getopt for the next pass; called in other source modules */
opterr = 1;
--
2.31.1
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