On Fri 2021-04-09 18:52:51, Stephen Boyd wrote: > Add the running kernel's build ID[1] to the stacktrace information > header. This makes it simpler for developers to locate the vmlinux with > full debuginfo for a particular kernel stacktrace. Combined with > scripts/decode_stracktrace.sh, a developer can download the correct > vmlinux from a debuginfod[2] server and find the exact file and line > number for the functions plus offsets in a stacktrace. > > This is especially useful for pstore crash debugging where the kernel > crashes are recorded in the pstore logs and the recovery kernel is > different or the debuginfo doesn't exist on the device due to space > concerns (the data can be large and a security concern). The stacktrace > can be analyzed after the crash by using the build ID to find the > matching vmlinux and understand where in the function something went > wrong. > > Example stacktrace from lkdtm: > > WARNING: CPU: 4 PID: 3255 at drivers/misc/lkdtm/bugs.c:83 > lkdtm_WARNING+0x28/0x30 [lkdtm] > Modules linked in: lkdtm rfcomm algif_hash algif_skcipher af_alg xt_cgroup > uinput xt_MASQUERADE > CPU: 4 PID: 3255 Comm: bash Not tainted 5.11 #3 > aa23f7a1231c229de205662d5a9e0d4c580f19a1 > Hardware name: Google Lazor (rev3+) with KB Backlight (DT) > pstate: 00400009 (nzcv daif +PAN -UAO -TCO BTYPE=--) > pc : lkdtm_WARNING+0x28/0x30 [lkdtm] > > The hex string aa23f7a1231c229de205662d5a9e0d4c580f19a1 is the build ID, > following the kernel version number. Put it all behind a config option, > STACKTRACE_BUILD_ID, so that kernel developers can remove this > information if they decide it is too much. > > Cc: Jiri Olsa <jo...@kernel.org> > Cc: Alexei Starovoitov <a...@kernel.org> > Cc: Jessica Yu <j...@kernel.org> > Cc: Evan Green <evgr...@chromium.org> > Cc: Hsin-Yi Wang <hsi...@chromium.org> > Cc: Petr Mladek <pmla...@suse.com> > Cc: Steven Rostedt <rost...@goodmis.org> > Cc: Andy Shevchenko <andriy.shevche...@linux.intel.com> > Cc: Matthew Wilcox <wi...@infradead.org> > Link: https://fedoraproject.org/wiki/Releases/FeatureBuildId [1] > Link: https://sourceware.org/elfutils/Debuginfod.html [2] > Signed-off-by: Stephen Boyd <swb...@chromium.org>
Reviewed-by: Petr Mladek <pmla...@suse.com> Tested-by: Petr Mladek <pmla...@suse.com> One comment below. > --- > lib/Kconfig.debug | 11 +++++++++++ > lib/dump_stack.c | 13 +++++++++++-- > 2 files changed, 22 insertions(+), 2 deletions(-) > > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > index 2779c29d9981..5f883e50f406 100644 > --- a/lib/Kconfig.debug > +++ b/lib/Kconfig.debug > @@ -35,6 +35,17 @@ config PRINTK_CALLER > no option to enable/disable at the kernel command line parameter or > sysfs interface. > > +config STACKTRACE_BUILD_ID > + bool "Show build ID information in stacktraces" > + depends on PRINTK > + help > + Selecting this option adds build ID information for symbols in > + stacktraces printed with the printk format '%p[SR]b'. > + > + This option is intended for distros where debuginfo is not easily > + accessible but can be downloaded given the build ID of the vmlinux or > + kernel module where the function is located. > + > config CONSOLE_LOGLEVEL_DEFAULT > int "Default console loglevel (1-15)" > range 1 15 > diff --git a/lib/dump_stack.c b/lib/dump_stack.c > index f5a33b6f773f..d685331b065f 100644 > --- a/lib/dump_stack.c > +++ b/lib/dump_stack.c > @@ -5,6 +5,7 @@ > */ > > #include <linux/kernel.h> > +#include <linux/buildid.h> > #include <linux/export.h> > #include <linux/sched.h> > #include <linux/sched/debug.h> > @@ -36,6 +37,14 @@ void __init dump_stack_set_arch_desc(const char *fmt, ...) > va_end(args); > } > > +#if IS_ENABLED(CONFIG_STACKTRACE_BUILD_ID) > +#define BUILD_ID_FMT " %20phN" > +#define BUILD_ID_VAL vmlinux_build_id > +#else > +#define BUILD_ID_FMT "%s" > +#define BUILD_ID_VAL "" > +#endif 3rd patch always defines and initializes vmlinux_build_id. But it is used only when CONFIG_STACKTRACE_BUILD_ID is enabled. Is it intentional, please? It is not a big deal for vmlinux_build_id. But it is more questionable for the per-module id. I am going to open this question for 5th patch as well. Best Regards, Petr
