MIME-Version: 1.0
From:   jim.cromie@gmail.com
Date:   Sun, 19 Mar 2023 23:05:52 -0600
Message-ID: <CAJfuBxyeKz3bsc=WfjJZDKgAHScC80_irQvmsecxPukjM-J8gw@mail.gmail.com>
Subject: RFC - KBUILD_MODNAME is misleading in builtins, as seen in /proc/dynamic_debug/control
To:     LKML <linux-kernel@vger.kernel.org>, linux-kbuild@vger.kernel.org
Cc:     Greg KH <gregkh@linuxfoundation.org>,
        Jason Baron <jbaron@akamai.com>,
        Luis Chamberlain <mcgrof@kernel.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

dynamic-debug METADATA uses KBUILD_MODNAME as:

#define DEFINE_DYNAMIC_DEBUG_METADATA_CLS(name, cls, fmt)       \
        static struct _ddebug  __aligned(8)                     \
        __section("__dyndbg") name = {                          \
                .modname = KBUILD_MODNAME,                      \

This is going amiss for some builtins, ie those enabled here, by:

    echo module main +pmf > /proc/dynamic_debug_control
    grep =pmf /proc/dynamic_debug/control

init/main.c:1187 [main]initcall_blacklist =pmf "blacklisting initcall %s\n"
init/main.c:1226 [main]initcall_blacklisted =pmf "initcall %s blacklisted\n"
init/main.c:1432 [main]run_init_process =pmf "  with arguments:\n"
init/main.c:1434 [main]run_init_process =pmf "    %s\n"
init/main.c:1435 [main]run_init_process =pmf "  with environment:\n"
init/main.c:1437 [main]run_init_process =pmf "    %s\n"
kernel/module/main.c:336 [main]find_symbol =pmf "Failed to find symbol %s\n"
kernel/module/main.c:567 [main]already_uses =pmf "%s uses %s!\n"
kernel/module/main.c:571 [main]already_uses =pmf "%s does not use %s!\n"
kernel/module/main.c:586 [main]add_module_usage =pmf "Allocating new
usage for %s.\n"
kernel/module/main.c:627 [main]module_unload_free =pmf "%s unusing %s\n"
kernel/module/main.c:733 [main]__do_sys_delete_module =pmf "%s already dying\n"
kernel/module/main.c:1345 [main]simplify_symbols =pmf "Common symbol: %s\n"
kernel/module/main.c:1353 [main]simplify_symbols =pmf "Absolute
symbol: 0x%08lx\n"
kernel/module/main.c:1508 [main]__layout_sections =pmf "\t%s\n"
kernel/module/main.c:1526 [main]layout_sections =pmf "Core section
allocation order:\n"
kernel/module/main.c:1529 [main]layout_sections =pmf "Init section
allocation order:\n"
kernel/module/main.c:2168 [main]move_module =pmf "final section addresses:\n"
kernel/module/main.c:2183 [main]move_module =pmf "\t0x%lx %s\n"
kernel/module/main.c:2921 [main]__do_sys_init_module =pmf
"init_module: umod=%p, len=%lu, uargs=%p\n"
kernel/module/main.c:2942 [main]__do_sys_finit_module =pmf
"finit_module: fd=%d, uargs=%p, flags=%i\n"
drivers/base/power/main.c:135 [main]device_pm_add =pmf "Adding info for %s:%s\n"
drivers/base/power/main.c:156 [main]device_pm_remove =pmf "Removing
info for %s:%s\n"
drivers/base/power/main.c:175 [main]device_pm_move_before =pmf "Moving
%s:%s before %s:%s\n"
drivers/base/power/main.c:189 [main]device_pm_move_after =pmf "Moving
%s:%s after %s:%s\n"
drivers/base/power/main.c:202 [main]device_pm_move_last =pmf "Moving
%s:%s to end of list\n"
drivers/base/power/main.c:441 [main]pm_dev_dbg =pmf "PM: %s%s%s driver
flags: %x\n"
drivers/base/power/main.c:467 [main]dpm_show_time =pmf "%s%s%s of
devices %s after %ld.%03ld msecs\n"
bash-5.2#

Basically, KBUILD_MODNAME appears to get basename,
not something specific, set in some config (such as pm, or module)
or cleverly picked out of the path (power is possible)

this compromises the clarity of  dyndbg's module keyword

is some heuristic possible to improve this,
with a manual setting to fix when heuristic fails ?