[PATCH v2] kexec-tools/s390: add --reuseinitrd support

[Joseph Cathcart <josephc@linux.ibm.com>]

Currently, the --reuseinitrd param is not supported on s390. This
prevents testing kexec in environments such as virtme-ng, which by
default does not store the initrd on disk.

When --reuseinitrd is specified, fetch retained initrd memory range
from /proc/iomem and fill new kernel parmarea directly with retained
initrd base and size, rather than memory range of a new ramdisk.

Add die() cases for when user uses --reuseinitrd:
        - in addition to --ramdisk or --initrd
        - while booting a crash kernel.
        - with kexec-file-load syscall (default syscall)
        - and no initrd entry is found in /proc/iomem

Signed-off-by: Joseph Cathcart <josephc@linux.ibm.com>
---
 kexec/arch/s390/Makefile      |  2 ++
 kexec/arch/s390/kexec-image.c | 15 ++++++++++++++-
 kexec/arch/s390/kexec-s390.c  | 14 ++++++++++++++
 kexec/arch/s390/kexec-s390.h  |  2 ++
 4 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/kexec/arch/s390/Makefile b/kexec/arch/s390/Makefile
index fab3e68..17f9dc8 100644
--- a/kexec/arch/s390/Makefile
+++ b/kexec/arch/s390/Makefile
@@ -6,6 +6,8 @@ s390_KEXEC_SRCS += kexec/arch/s390/kexec-image.c
 s390_KEXEC_SRCS += kexec/arch/s390/kexec-elf-rel-s390.c
 s390_KEXEC_SRCS += kexec/arch/s390/crashdump-s390.c
 
+s390_ARCH_REUSE_INITRD =
+
 dist += kexec/arch/s390/Makefile $(s390_KEXEC_SRCS)			\
 	kexec/arch/s390/kexec-s390.h					\
 	kexec/arch/s390/include/arch/options.h
diff --git a/kexec/arch/s390/kexec-image.c b/kexec/arch/s390/kexec-image.c
index 69aaf96..a9e5442 100644
--- a/kexec/arch/s390/kexec-image.c
+++ b/kexec/arch/s390/kexec-image.c
@@ -78,6 +78,10 @@ int image_s390_load_file(int argc, char **argv, struct kexec_info *info)
 		}
 	}
 
+	if (reuse_initrd)
+		die("--reuseinitrd not supported with --kexec-file-syscall. "
+			"Please use --kexec-syscall\n");
+
 	if (ramdisk) {
 		info->initrd_fd = open(ramdisk, O_RDONLY);
 		if (info->initrd_fd == -1) {
@@ -104,7 +108,7 @@ image_s390_load(int argc, char **argv, const char *kernel_buf,
 	char *rd_buffer;
 	const char *ramdisk;
 	off_t ramdisk_len;
-	unsigned int ramdisk_origin;
+	unsigned long long ramdisk_origin;
 	int opt, ret = -1;
 
 	if (info->file_mode)
@@ -137,6 +141,12 @@ image_s390_load(int argc, char **argv, const char *kernel_buf,
 		}
 	}
 
+	if (ramdisk && reuse_initrd)
+		die("Can't specify --ramdisk or --initrd with --reuseinitrd\n");
+
+	if (reuse_initrd && (info->kexec_flags & KEXEC_ON_CRASH))
+		die("Can't specify --reuseinitrd while booting a crash kernel\n");
+
 	if (info->kexec_flags & KEXEC_ON_CRASH) {
 		if (parse_iomem_single("Crash kernel\n", &crash_base,
 				       &crash_end))
@@ -165,6 +175,9 @@ image_s390_load(int argc, char **argv, const char *kernel_buf,
 		ramdisk_origin = _ALIGN_UP(ramdisk_origin, 0x100000);
 		add_segment_check(info, rd_buffer, ramdisk_len,
 				  ramdisk_origin, ramdisk_len);
+	} else if (reuse_initrd) {
+		ramdisk_origin = retained_initrd_base;
+		ramdisk_len = (off_t)retained_initrd_size;
 	}
 	if (info->kexec_flags & KEXEC_ON_CRASH) {
 		if (load_crashdump_segments(info, crash_base, crash_end))
diff --git a/kexec/arch/s390/kexec-s390.c b/kexec/arch/s390/kexec-s390.c
index 86c9fb8..fd0d87e 100644
--- a/kexec/arch/s390/kexec-s390.c
+++ b/kexec/arch/s390/kexec-s390.c
@@ -25,6 +25,20 @@
 #include <arch/options.h>
 
 static struct memory_range memory_range[MAX_MEMORY_RANGES];
+unsigned long long retained_initrd_base, retained_initrd_size;
+unsigned char reuse_initrd;
+
+void arch_reuse_initrd(void)
+{
+	uint64_t start, end;
+
+	if (parse_iomem_single("initrd\n", &start, &end))
+		die("Couldn't find initrd entry in /proc/iomem\n");
+
+	retained_initrd_base = (unsigned long long)start;
+	retained_initrd_size = (unsigned long long)end - retained_initrd_base + 1;
+	reuse_initrd = 1;
+}
 
 /*
  * Read string from file
diff --git a/kexec/arch/s390/kexec-s390.h b/kexec/arch/s390/kexec-s390.h
index 6a99518..7e85976 100644
--- a/kexec/arch/s390/kexec-s390.h
+++ b/kexec/arch/s390/kexec-s390.h
@@ -34,5 +34,7 @@ extern int load_crashdump_segments(struct kexec_info *info,
 extern int get_memory_ranges_s390(struct memory_range range[], int *ranges,
 				  int with_crashk);
 extern int command_line_add(struct kexec_info *info, const char *str);
+extern unsigned long long retained_initrd_base, retained_initrd_size;
+extern unsigned char reuse_initrd;
 
 #endif /* KEXEC_S390_H */
-- 
2.55.0

base commit: 29898e149feb5c615b3ab6313260d58315bf1d8d