Re: [PATCH 0/6] kexec: A new system call to allow in kernel loading

From: Vivek Goyal
Date: Thu Nov 21 2013 - 14:47:00 EST

On Thu, Nov 21, 2013 at 02:07:29PM -0500, Vivek Goyal wrote:

[..]
> > Very good stuff, thanks for working on this. How have you been testing
> > this on the userspace side? Are there patches to kexec, or are you just
> > using a small test program with the new syscall?
>
> I wrote a patch for kexec-tools. One can choose to use new system call
> by passing command line option --use-kexec2-syscall. I will post
> that patch soon in this mail thread.

I have been using following kexec-tools patch to test this code.

Thanks
Vivek


kexec-tools: Provide an option to make use of new system call

This patch provides and option --use-kexec2-syscall, to force use of
new system call for kexec. Default is to continue to use old syscall.

Signed-off-by: Vivek Goyal <vgoyal@xxxxxxxxxx>
---
kexec/arch/x86_64/kexec-bzImage64.c | 86 ++++++++++++++++++++++++++
kexec/kexec-syscall.h | 24 +++++++
kexec/kexec.c | 118 +++++++++++++++++++++++++++++++++++-
kexec/kexec.h | 9 ++
4 files changed, 234 insertions(+), 3 deletions(-)

Index: kexec-tools/kexec/kexec.c
===================================================================
--- kexec-tools.orig/kexec/kexec.c 2013-11-20 10:28:26.652380051 -0500
+++ kexec-tools/kexec/kexec.c 2013-11-20 11:31:44.906046486 -0500
@@ -51,6 +51,7 @@
unsigned long long mem_min = 0;
unsigned long long mem_max = ULONG_MAX;
static unsigned long kexec_flags = 0;
+static unsigned long kexec2_flags = 0;
int kexec_debug = 0;

void die(const char *fmt, ...)
@@ -781,6 +782,19 @@ static int my_load(const char *type, int
return result;
}

+static int kexec2_unload(unsigned long kexec2_flags)
+{
+ int ret = 0;
+
+ ret = kexec_file_load(-1, -1, NULL, 0, kexec2_flags);
+ if (ret != 0) {
+ /* The unload failed, print some debugging information */
+ fprintf(stderr, "kexec_file_load(unload) failed\n: %s\n",
+ strerror(errno));
+ }
+ return ret;
+}
+
static int k_unload (unsigned long kexec_flags)
{
int result;
@@ -919,6 +933,7 @@ void usage(void)
" (0 means it's not jump back or\n"
" preserve context)\n"
" to original kernel.\n"
+ " -s --use-kexec2-syscall Use new syscall for kexec operation\n"
" -d, --debug Enable debugging to help spot a failure.\n"
"\n"
"Supported kernel file types and options: \n");
@@ -1066,6 +1081,70 @@ char *concat_cmdline(const char *base, c
return cmdline;
}

+/* New file based kexec system call related code */
+static int kexec2_load(int fileind, int argc, char **argv,
+ unsigned long flags) {
+
+ char *kernel;
+ int kernel_fd, i;
+ struct kexec_info info;
+ int ret = 0;
+ char *kernel_buf;
+ off_t kernel_size;
+
+ memset(&info, 0, sizeof(info));
+ info.segment = NULL;
+ info.nr_segments = 0;
+ info.entry = NULL;
+ info.backup_start = 0;
+ info.kexec_flags = flags;
+
+ info.file_mode = 1;
+ info.initrd_fd = -1;
+
+ if (argc - fileind <= 0) {
+ fprintf(stderr, "No kernel specified\n");
+ usage();
+ return -1;
+ }
+
+ kernel = argv[fileind];
+
+ kernel_fd = open(kernel, O_RDONLY);
+ if (kernel_fd == -1) {
+ fprintf(stderr, "Failed to open file %s:%s\n", kernel,
+ strerror(errno));
+ return -1;
+ }
+
+ /* slurp in the input kernel */
+ kernel_buf = slurp_decompress_file(kernel, &kernel_size);
+
+ for (i = 0; i < file_types; i++) {
+ if (file_type[i].probe(kernel_buf, kernel_size) >= 0)
+ break;
+ }
+
+ if (i == file_types) {
+ fprintf(stderr, "Cannot determine the file type " "of %s\n",
+ kernel);
+ return -1;
+ }
+
+ ret = file_type[i].load(argc, argv, kernel_buf, kernel_size, &info);
+ if (ret < 0) {
+ fprintf(stderr, "Cannot load %s\n", kernel);
+ return ret;
+ }
+
+ ret = kexec_file_load(kernel_fd, info.initrd_fd, info.command_line,
+ info.command_line_len, info.kexec_flags);
+ if (ret != 0)
+ fprintf(stderr, "kexec_file_load failed: %s\n",
+ strerror(errno));
+ return ret;
+}
+

int main(int argc, char *argv[])
{
@@ -1077,6 +1156,7 @@ int main(int argc, char *argv[])
int do_ifdown = 0;
int do_unload = 0;
int do_reuse_initrd = 0;
+ int do_use_kexec2_syscall = 0;
void *entry = 0;
char *type = 0;
char *endptr;
@@ -1089,6 +1169,23 @@ int main(int argc, char *argv[])
};
static const char short_options[] = KEXEC_ALL_OPT_STR;

+ /*
+ * First check if --use-kexec2-syscall is set. That changes lot of
+ * things
+ */
+ while ((opt = getopt_long(argc, argv, short_options,
+ options, 0)) != -1) {
+ switch(opt) {
+ case OPT_USE_KEXEC2_SYSCALL:
+ do_use_kexec2_syscall = 1;
+ break;
+ }
+ }
+
+ /* Reset getopt for the next pass. */
+ opterr = 1;
+ optind = 1;
+
while ((opt = getopt_long(argc, argv, short_options,
options, 0)) != -1) {
switch(opt) {
@@ -1121,6 +1218,8 @@ int main(int argc, char *argv[])
do_shutdown = 0;
do_sync = 0;
do_unload = 1;
+ if (do_use_kexec2_syscall)
+ kexec2_flags |= KEXEC_FILE_UNLOAD;
break;
case OPT_EXEC:
do_load = 0;
@@ -1163,7 +1262,10 @@ int main(int argc, char *argv[])
do_exec = 0;
do_shutdown = 0;
do_sync = 0;
- kexec_flags = KEXEC_ON_CRASH;
+ if (do_use_kexec2_syscall)
+ kexec2_flags |= KEXEC_FILE_ON_CRASH;
+ else
+ kexec_flags = KEXEC_ON_CRASH;
break;
case OPT_MEM_MIN:
mem_min = strtoul(optarg, &endptr, 0);
@@ -1188,6 +1290,9 @@ int main(int argc, char *argv[])
case OPT_REUSE_INITRD:
do_reuse_initrd = 1;
break;
+ case OPT_USE_KEXEC2_SYSCALL:
+ /* We already parsed it. Nothing to do. */
+ break;
default:
break;
}
@@ -1232,10 +1337,17 @@ int main(int argc, char *argv[])
}

if (do_unload) {
- result = k_unload(kexec_flags);
+ if (do_use_kexec2_syscall)
+ result = kexec2_unload(kexec2_flags);
+ else
+ result = k_unload(kexec_flags);
}
if (do_load && (result == 0)) {
- result = my_load(type, fileind, argc, argv, kexec_flags, entry);
+ if (do_use_kexec2_syscall)
+ result = kexec2_load(fileind, argc, argv, kexec2_flags);
+ else
+ result = my_load(type, fileind, argc, argv,
+ kexec_flags, entry);
}
/* Don't shutdown unless there is something to reboot to! */
if ((result == 0) && (do_shutdown || do_exec) && !kexec_loaded()) {
Index: kexec-tools/kexec/kexec.h
===================================================================
--- kexec-tools.orig/kexec/kexec.h 2013-11-20 10:28:26.652380051 -0500
+++ kexec-tools/kexec/kexec.h 2013-11-20 10:28:47.806336565 -0500
@@ -154,6 +154,13 @@ struct kexec_info {
unsigned long kexec_flags;
unsigned long backup_src_start;
unsigned long backup_src_size;
+ /* Set to 1 if we are using kexec2 syscall */
+ unsigned long file_mode :1;
+
+ /* Filled by kernel image processing code */
+ int initrd_fd;
+ char *command_line;
+ int command_line_len;
};

struct arch_map_entry {
@@ -205,6 +212,7 @@ extern int file_types;
#define OPT_UNLOAD 'u'
#define OPT_TYPE 't'
#define OPT_PANIC 'p'
+#define OPT_USE_KEXEC2_SYSCALL 's'
#define OPT_MEM_MIN 256
#define OPT_MEM_MAX 257
#define OPT_REUSE_INITRD 258
@@ -228,6 +236,7 @@ extern int file_types;
{ "mem-min", 1, 0, OPT_MEM_MIN }, \
{ "mem-max", 1, 0, OPT_MEM_MAX }, \
{ "reuseinitrd", 0, 0, OPT_REUSE_INITRD }, \
+ { "use-kexec2-syscall", 0, 0, OPT_USE_KEXEC2_SYSCALL }, \
{ "debug", 0, 0, OPT_DEBUG }, \

#define KEXEC_OPT_STR "h?vdfxluet:p"
Index: kexec-tools/kexec/arch/x86_64/kexec-bzImage64.c
===================================================================
--- kexec-tools.orig/kexec/arch/x86_64/kexec-bzImage64.c 2013-11-20 10:28:26.652380051 -0500
+++ kexec-tools/kexec/arch/x86_64/kexec-bzImage64.c 2013-11-20 10:28:47.807336610 -0500
@@ -229,6 +229,89 @@ static int do_bzImage64_load(struct kexe
return 0;
}

+/* This assumes file is being loaded using file based kexec2 syscall */
+int bzImage64_load_file(int argc, char **argv, struct kexec_info *info)
+{
+ int ret = 0;
+ char *command_line = NULL, *tmp_cmdline = NULL;
+ const char *ramdisk = NULL, *append = NULL;
+ int entry_16bit = 0, entry_32bit = 0;
+ int opt;
+ int command_line_len;
+
+ /* See options.h -- add any more there, too. */
+ static const struct option options[] = {
+ KEXEC_ARCH_OPTIONS
+ { "command-line", 1, 0, OPT_APPEND },
+ { "append", 1, 0, OPT_APPEND },
+ { "reuse-cmdline", 0, 0, OPT_REUSE_CMDLINE },
+ { "initrd", 1, 0, OPT_RAMDISK },
+ { "ramdisk", 1, 0, OPT_RAMDISK },
+ { "real-mode", 0, 0, OPT_REAL_MODE },
+ { "entry-32bit", 0, 0, OPT_ENTRY_32BIT },
+ { 0, 0, 0, 0 },
+ };
+ static const char short_options[] = KEXEC_ARCH_OPT_STR "d";
+
+ while ((opt = getopt_long(argc, argv, short_options, options, 0)) != -1) {
+ switch (opt) {
+ default:
+ /* Ignore core options */
+ if (opt < OPT_ARCH_MAX)
+ break;
+ case OPT_APPEND:
+ append = optarg;
+ break;
+ case OPT_REUSE_CMDLINE:
+ tmp_cmdline = get_command_line();
+ break;
+ case OPT_RAMDISK:
+ ramdisk = optarg;
+ break;
+ case OPT_REAL_MODE:
+ entry_16bit = 1;
+ break;
+ case OPT_ENTRY_32BIT:
+ entry_32bit = 1;
+ break;
+ }
+ }
+ command_line = concat_cmdline(tmp_cmdline, append);
+ if (tmp_cmdline)
+ free(tmp_cmdline);
+ command_line_len = 0;
+ if (command_line) {
+ command_line_len = strlen(command_line) + 1;
+ } else {
+ command_line = strdup("\0");
+ command_line_len = 1;
+ }
+
+ if (entry_16bit || entry_32bit) {
+ fprintf(stderr, "Kexec2 syscall does not support 16bit"
+ " or 32bit entry yet\n");
+ ret = -1;
+ goto out;
+ }
+
+ if (ramdisk) {
+ info->initrd_fd = open(ramdisk, O_RDONLY);
+ if (info->initrd_fd == -1) {
+ fprintf(stderr, "Could not open initrd file %s:%s\n",
+ ramdisk, strerror(errno));
+ ret = -1;
+ goto out;
+ }
+ }
+
+ info->command_line = command_line;
+ info->command_line_len = command_line_len;
+ return ret;
+out:
+ free(command_line);
+ return ret;
+}
+
int bzImage64_load(int argc, char **argv, const char *buf, off_t len,
struct kexec_info *info)
{
@@ -241,6 +324,9 @@ int bzImage64_load(int argc, char **argv
int opt;
int result;

+ if (info->file_mode)
+ return bzImage64_load_file(argc, argv, info);
+
/* See options.h -- add any more there, too. */
static const struct option options[] = {
KEXEC_ARCH_OPTIONS
Index: kexec-tools/kexec/kexec-syscall.h
===================================================================
--- kexec-tools.orig/kexec/kexec-syscall.h 2013-11-20 10:28:26.652380051 -0500
+++ kexec-tools/kexec/kexec-syscall.h 2013-11-20 10:28:47.808336655 -0500
@@ -50,6 +50,18 @@
#endif
#endif /*ifndef __NR_kexec_load*/

+#ifndef __NR_kexec_file_load
+
+#ifdef __x86_64__
+#define __NR_kexec_file_load 314
+#endif
+
+#ifndef __NR_kexec_file_load
+#error Unknown processor architecture. Needs a kexec_load syscall number.
+#endif
+
+#endif /*ifndef __NR_kexec_file_load*/
+
struct kexec_segment;

static inline long kexec_load(void *entry, unsigned long nr_segments,
@@ -58,10 +70,22 @@ static inline long kexec_load(void *entr
return (long) syscall(__NR_kexec_load, entry, nr_segments, segments, flags);
}

+static inline long kexec_file_load(int kernel_fd, int initrd_fd,
+ const char *cmdline_ptr, unsigned long cmdline_len,
+ unsigned long flags)
+{
+ return (long) syscall(__NR_kexec_file_load, kernel_fd, initrd_fd,
+ cmdline_ptr, cmdline_len, flags);
+}
+
#define KEXEC_ON_CRASH 0x00000001
#define KEXEC_PRESERVE_CONTEXT 0x00000002
#define KEXEC_ARCH_MASK 0xffff0000

+/* Flags for kexec file based system call */
+#define KEXEC_FILE_UNLOAD 0x00000001
+#define KEXEC_FILE_ON_CRASH 0x00000002
+
/* These values match the ELF architecture values.
* Unless there is a good reason that should continue to be the case.
*/
--
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