| Message ID | 20220216163940.228309-7-joe.lawrence@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | livepatch: klp-convert tool | expand |
On Wed, Feb 16, 2022 at 11:39:34AM -0500, Joe Lawrence wrote: > From: Josh Poimboeuf <jpoimboe@redhat.com> > > Add a new livepatch sample in samples/livepatch/ to make use of symbols > that must be post-processed to enable load-time relocation resolution. > As the new sample is to be used as an example, it is annotated with > KLP_MODULE_RELOC and with KLP_SYMPOS macros. > > The livepatch sample updates the function cmdline_proc_show to print the > string referenced by the symbol saved_command_line appended by the > string "livepatch=1". > > Update livepatch-sample.c to remove livepatch MODULE_INFO statement. LGTM. Reviewed-by: Marcos Paulo de Souza <mpdesouza@suse.com> > > Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> > Signed-off-by: Joao Moreira <jmoreira@suse.de> > Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com> > --- > samples/livepatch/Makefile | 1 + > .../livepatch/livepatch-annotated-sample.c | 93 +++++++++++++++++++ > 2 files changed, 94 insertions(+) > create mode 100644 samples/livepatch/livepatch-annotated-sample.c > > diff --git a/samples/livepatch/Makefile b/samples/livepatch/Makefile > index 9f853eeb6140..f2b41f4d6c16 100644 > --- a/samples/livepatch/Makefile > +++ b/samples/livepatch/Makefile > @@ -6,3 +6,4 @@ obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-shadow-fix2.o > obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-callbacks-demo.o > obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-callbacks-mod.o > obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-callbacks-busymod.o > +obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-annotated-sample.o > diff --git a/samples/livepatch/livepatch-annotated-sample.c b/samples/livepatch/livepatch-annotated-sample.c > new file mode 100644 > index 000000000000..4fe0e16423c7 > --- /dev/null > +++ b/samples/livepatch/livepatch-annotated-sample.c > @@ -0,0 +1,93 @@ > +// SPDX-License-Identifier: GPL-2.0-or-later > +/* > + * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com> > + */ > + > +/* > + * livepatch-annotated-sample.c - Kernel Live Patching Sample Module > + */ > + > +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt > + > +#include <linux/module.h> > +#include <linux/kernel.h> > +#include <linux/livepatch.h> > + > +/* > + * This (dumb) live patch overrides the function that prints the > + * kernel boot cmdline when /proc/cmdline is read. > + * > + * This livepatch uses the symbol saved_command_line whose relocation > + * must be resolved during load time. To enable that, this module > + * must be post-processed by a tool called klp-convert, which embeds > + * information to be used by the loader to solve the relocation. > + * > + * The module is annotated with KLP_MODULE_RELOC/KLP_SYMPOS macros. > + * These annotations are used by klp-convert to infer that the symbol > + * saved_command_line is in the object vmlinux. > + * > + * As saved_command_line has no other homonimous symbol across > + * kernel objects, this annotation is not a requirement, and can be > + * suppressed with no harm to klp-convert. Yet, it is kept here as an > + * example on how to annotate livepatch modules that contain symbols > + * whose names are used in more than one kernel object. > + * > + * Example: > + * > + * $ cat /proc/cmdline > + * <your cmdline> > + * > + * $ insmod livepatch-sample.ko > + * $ cat /proc/cmdline > + * <your cmdline> livepatch=1 > + * > + * $ echo 0 > /sys/kernel/livepatch/livepatch_sample/enabled > + * $ cat /proc/cmdline > + * <your cmdline> > + */ > + > +extern char *saved_command_line; > + > +#include <linux/seq_file.h> > +static int livepatch_cmdline_proc_show(struct seq_file *m, void *v) > +{ > + seq_printf(m, "%s livepatch=1\n", saved_command_line); > + return 0; > +} > + > +KLP_MODULE_RELOC(vmlinux) vmlinux_relocs[] = { > + KLP_SYMPOS(saved_command_line, 0) > +}; > + > +static struct klp_func funcs[] = { > + { > + .old_name = "cmdline_proc_show", > + .new_func = livepatch_cmdline_proc_show, > + }, { } > +}; > + > +static struct klp_object objs[] = { > + { > + /* name being NULL means vmlinux */ > + .funcs = funcs, > + }, { } > +}; > + > +static struct klp_patch patch = { > + .mod = THIS_MODULE, > + .objs = objs, > +}; > + > +static int livepatch_init(void) > +{ > + return klp_enable_patch(&patch); > +} > + > +static void livepatch_exit(void) > +{ > +} > + > +module_init(livepatch_init); > +module_exit(livepatch_exit); > +MODULE_LICENSE("GPL"); > +MODULE_INFO(livepatch, "Y"); > -- > 2.26.3 >
diff --git a/samples/livepatch/Makefile b/samples/livepatch/Makefile index 9f853eeb6140..f2b41f4d6c16 100644 --- a/samples/livepatch/Makefile +++ b/samples/livepatch/Makefile @@ -6,3 +6,4 @@ obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-shadow-fix2.o obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-callbacks-demo.o obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-callbacks-mod.o obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-callbacks-busymod.o +obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-annotated-sample.o diff --git a/samples/livepatch/livepatch-annotated-sample.c b/samples/livepatch/livepatch-annotated-sample.c new file mode 100644 index 000000000000..4fe0e16423c7 --- /dev/null +++ b/samples/livepatch/livepatch-annotated-sample.c @@ -0,0 +1,93 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com> + */ + +/* + * livepatch-annotated-sample.c - Kernel Live Patching Sample Module + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include <linux/module.h> +#include <linux/kernel.h> +#include <linux/livepatch.h> + +/* + * This (dumb) live patch overrides the function that prints the + * kernel boot cmdline when /proc/cmdline is read. + * + * This livepatch uses the symbol saved_command_line whose relocation + * must be resolved during load time. To enable that, this module + * must be post-processed by a tool called klp-convert, which embeds + * information to be used by the loader to solve the relocation. + * + * The module is annotated with KLP_MODULE_RELOC/KLP_SYMPOS macros. + * These annotations are used by klp-convert to infer that the symbol + * saved_command_line is in the object vmlinux. + * + * As saved_command_line has no other homonimous symbol across + * kernel objects, this annotation is not a requirement, and can be + * suppressed with no harm to klp-convert. Yet, it is kept here as an + * example on how to annotate livepatch modules that contain symbols + * whose names are used in more than one kernel object. + * + * Example: + * + * $ cat /proc/cmdline + * <your cmdline> + * + * $ insmod livepatch-sample.ko + * $ cat /proc/cmdline + * <your cmdline> livepatch=1 + * + * $ echo 0 > /sys/kernel/livepatch/livepatch_sample/enabled + * $ cat /proc/cmdline + * <your cmdline> + */ + +extern char *saved_command_line; + +#include <linux/seq_file.h> +static int livepatch_cmdline_proc_show(struct seq_file *m, void *v) +{ + seq_printf(m, "%s livepatch=1\n", saved_command_line); + return 0; +} + +KLP_MODULE_RELOC(vmlinux) vmlinux_relocs[] = { + KLP_SYMPOS(saved_command_line, 0) +}; + +static struct klp_func funcs[] = { + { + .old_name = "cmdline_proc_show", + .new_func = livepatch_cmdline_proc_show, + }, { } +}; + +static struct klp_object objs[] = { + { + /* name being NULL means vmlinux */ + .funcs = funcs, + }, { } +}; + +static struct klp_patch patch = { + .mod = THIS_MODULE, + .objs = objs, +}; + +static int livepatch_init(void) +{ + return klp_enable_patch(&patch); +} + +static void livepatch_exit(void) +{ +} + +module_init(livepatch_init); +module_exit(livepatch_exit); +MODULE_LICENSE("GPL"); +MODULE_INFO(livepatch, "Y");