| Message ID | 20240516133009.20224-5-lhruska@suse.cz (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | livepatch: klp-convert tool - Minimal version | expand |
On Thu 2024-05-16 15:30:07, Lukas Hruska 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_RELOC_SYMBOL macro. > > 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". > > Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> > Signed-off-by: Lukas Hruska <lhruska@suse.cz> > Reviewed-by: Petr Mladek <pmladek@suse.com> > --- > samples/livepatch/Makefile | 1 + > samples/livepatch/livepatch-extern-symbol.c | 84 +++++++++++++++++++++ > 2 files changed, 85 insertions(+) > create mode 100644 samples/livepatch/livepatch-extern-symbol.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-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-annotated-sample.o It seems that the sample has been renamed without updating the Makefile rule. There should be: +obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-extern-symbol.o Otherwise, I get: make[4]: *** No rule to make target 'samples/livepatch/livepatch-annotated-sample.o', needed by 'samples/livepatch/'. Stop. make[3]: *** [scripts/Makefile.build:485: samples/livepatch] Error 2 make[2]: *** [scripts/Makefile.build:485: samples] Error 2 make[1]: *** [/prace/kernel/linux/Makefile:1921: .] Error 2 make: *** [Makefile:240: __sub-make] Error 2 > diff --git a/samples/livepatch/livepatch-extern-symbol.c b/samples/livepatch/livepatch-extern-symbol.c > new file mode 100644 > index 000000000000..276a43d157b4 > --- /dev/null > +++ b/samples/livepatch/livepatch-extern-symbol.c > @@ -0,0 +1,84 @@ The test module works as expected after fixing the Makefile. Best Regards, Petr
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-extern-symbol.c b/samples/livepatch/livepatch-extern-symbol.c new file mode 100644 index 000000000000..276a43d157b4 --- /dev/null +++ b/samples/livepatch/livepatch-extern-symbol.c @@ -0,0 +1,84 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com> + */ + +/* + * livepatch-extern-symbol.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_RELOC_SYMBOL macros. + * These annotations are used by klp-convert to infer that the symbol + * saved_command_line is in the object vmlinux. + * + * 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 \ + KLP_RELOC_SYMBOL(vmlinux, vmlinux, 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; +} + +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");