[PATCH v4 3/6] bootm: Append bootargs value when bootmeth_android provide cmdline
george chan
gchan9527 at gmail.com
Thu Oct 9 17:26:47 CEST 2025
Hi Simon and Mattijs,
在 2025年10月9日週四 20:46，Mattijs Korpershoek <mkorpershoek at kernel.org> 寫道：
> Hi George,
>
> On Wed, Oct 08, 2025 at 00:03, george chan <gchan9527 at gmail.com> wrote:
>
> > Hi Simon,
> >
> > Thx for feedback.
> >
> >
> > 在 2025年10月7日週二 04:38，Simon Glass <sjg at chromium.org> 寫道：
> >
> >> Hi George,
> >>
> >> On Sun, 5 Oct 2025 at 09:41, george chan <gchan9527 at gmail.com> wrote:
> >> >
> >> >
> >> >
> >> > 在 2025年10月5日週日 00:35，george chan <gchan9527 at gmail.com> 寫道：
> >> >>
> >> >> Hi Simon and Mattijs,
> >> >>
> >> >> Thx for feedback. Just in case the discussion drift to other
> direction,
> >> do let me have a chance to put some background info here.
> >> >>
> >> >> there are ways for pre-set env variable and its value. Firstly
> external
> >> env file and loaded by uboot, like, runtime handling; and another type
> is
> >> build time embed env file into uboot body.
> >> >>
> >> >> maybe in chromeos case first stage boot loader will pass along
> bootinfo
> >> struct to uboot and treat as preset defaults.
> >> >>
> >> >> so in either case uboot can have right to choose the preset from (by
> >> disable external env file, secured/trusted boot?), and then either
> follow
> >> the bootinfo struct preset value and/or concat and/or overrite with
> uboot’s
> >> own embedded env value at boot time, and then runtime modify.
> >> >>
> >> >> This behavior maybe enable or disable by kconfig. but in secured boot
> >> context point of view, env file kind of thing, might have potential
> design
> >> wise conflict. And this is not within my scope.
> >> >>
> >> >> in some other use case like simulation of vendor bootloader behavior
> to
> >> have a build time preset default value, this is within my scope. and
> thats
> >> why i decided to put those preset into env file and embeded.
> >> >>
> >> >> let me reply below inline.
> >> >>
> >> >> 在 2025年10月2日週四 00:22，Simon Glass <sjg at chromium.org> 寫道：
> >> >>>
> >> >>> Hi Mattijs, George,
> >> >>>
> >> >>> On Tue, 30 Sept 2025 at 01:29, Mattijs Korpershoek
> >> >>> <mkorpershoek at kernel.org> wrote:
> >> >>> >
> >> >>> > Hi Simon,
> >> >>> >
> >> >>> > Now that you are back, could you please have a look at ...
> >> >>> >
> >> >>> > On Fri, Jul 18, 2025 at 14:03, Mattijs Korpershoek <
> >> mkorpershoek at kernel.org> wrote:
> >> >>> >
> >> >>> > > Hi George,
> >> >>> > >
> >> >>> > > On Wed, Jul 16, 2025 at 19:55, george chan <gchan9527 at gmail.com
> >
> >> wrote:
> >> >>> > >
> >> >>> > >> Hi Mattijs,
> >> >>> > >>
> >> >>> > >> Thx for reply.
> >> >>> > >>
> >> >>> > >> 在 2025年7月16日週三 17:05，Mattijs Korpershoek <
> mkorpershoek at kernel.org>
> >> 寫道：
> >> >>> > >>
> >> >>> > >>> Hi George,
> >> >>> > >>>
> >> >>> > >>> Thank you for the patch.
> >> >>> > >>>
> >> >>> > >> ...
> >> >>> > >>
> >> >>> > >>>
> >> >>> > >>> > - ret = env_set("bootargs", cmdline);
> >> >>> > >>> > + ret = android_image_modify_bootargs_env(cmdline,
> NULL);
> >> >>> > >>>
> >> >>> > >>> I don't think it can be done this way. bootm_boot_start() is
> >> used in the
> >> >>> > >>> ChromeOS bootmethod as well (boot/bootmeth_cros.c)
> >> >>> > >>>
> >> >>> > >>
> >> >>> > >> I got your point. I have 3 ideas come out.
> >> >>> > >>
> >> >>> > >> (1) The logic purposely empty the env bootargs, either
> developer
> >> don't use
> >> >>> > >> env bootargs or those use cases touched bootargs in some early
> >> step. And
> >> >>> > >> then wanna disregard previous u-boot bootmeth operation, and
> >> empty bootargs
> >> >>> > >> for that ongoing bootmeth stage...well that's not congruent
> >> behavior; I
> >> >>> > >> have a gut feeling this is a bug or band-aid anyway, it closed
> >> the door for
> >> >>> > >
> >> >>> > > Simon, is it *intentional* that override the bootargs variable
> in
> >> >>> > > commit daffb0be2c83 ("bootstd: cros: Add ARM support") ?
> >> >>> > >
> >> >>> > > Shouldn't we get the bootargs from the environment, and append
> >> cmdline
> >> >>> > > to the existing bootargs instead ?
> >> >>>
> >> >>> The way U-Boot operates today, bootargs defines the entire cmdline,
> >> >>> not just part of it. So if you use 'env set bootargs ..' you are
> >> >>> changing the entire cmdline passed to Linux, etc.
> >> >>
> >> >>
> >> >> This is runtime change. My test case in fastboot path, it get
> bootargs
> >> wiped and filling in with something from boot img. That might share same
> >> procedure with other boot method like chromeos do. Wipe env default each
> >> time in fastboot (when fail) might be a secure-wise handling.
> >> >>
> >> >> And I feel it is a critical entry point logic like a central hub, and
> >> looking good to decide uboot behavior here. By kconfig whatever? Again,
> out
> >> of my scope.
> >> >>
> >> >>>
> >> >>> With ChromeOS, after 'bootflow read', the cmdline can be edited
> using
> >> >>> 'bootflow cmdline set' etc., which also changes bootargs. But in
> >> >>> general ChromeOS provides the whole Linux cmdline to U-Boot.
> >> >>
> >> >>
> >> >> this is also runtime change. And as a side note, if by doing bootflow
> >> select, should env bootargs gets overrided or appended? This is a bigger
> >> arch-wise question worth at least a public paper. and I might not go
> into
> >> this depth.
> >> >>
> >> >>>
> >> >>> If you are wanting to append, I suggest writing a new function, or
> >> >>
> >> >>
> >> >> yeah agreed. I do more appreciate and feel it really lower project
> >> management/test cost.
> >> >>
> >> >>> perhaps adding a 'bool append' arg to bootm_boot_start(), if all the
> >> >>> other code is useful for Android.
> >> >>
> >> >>
> >> >> A more simpler method is to create
> bootm_boot_start_ex(kernel_cmd_line,
> >> vendor_cmd_line) as
> >> >> I proposed to complement with
> >> >> bootm_boot_start(cmdline) or even add one layer of abstract, called
> >> from bootm_boot_start(), make vendor_cmd_line param as null. As can
> >> preserve the old logic and behavior.
> >> >>
> >> >> So build time env preset value, and runtime value override decision
> can
> >> live in this new function, or elsewhere; but is not within my scope.
> >> >
> >> >
> >> > Tr/Dr I wrote a proof of concept code here:
> >> >
> >> >
> >>
> https://github.com/99degree/u-boot/compare/before_tag...reboot-mode?expand=1
> >>
> >> This thread is a bit confusing now, but it seems you have written a
> >>
> >
> > I am sorry but I had to prove my patch is necessary and correctnessly and
> > also limit the scope of the patch. Thanks for your understand.
> >
> > new function and that is fine with me, as it won't affect ChromeOS.
> >>
> >
> > There is no new function at all. I am sorry to put more info here again
> to
> > let related code to be clear for every audience here.
> >
> > As you may notice function bootm_modify_bootargs_env() is a renamed and
> > move to bootm.c which is split/extracted from existing function
> > android_image_get_kernel()
> >
> > And bootm_boot_start_ex() is split from
> > bootm_boot_start() with your suggested enable param.
> >
> > I am afraid if you or other reviewer might wonder why move to bootm.c and
> > here is the reason.
> >
> > Supposed with below 2 code paths:
> >
> > Boot->bootflow->bootmeth_android->bootm
> > Boot->fastboot->do_bootm->bootm
> >
> > I believe android_image_get_kernel is living around within
> bootmeth_android
> > stage so first two patch has taken care of. But fastboot path is not.
> that
> > might be the reason above two path need separate special handling for.
> >
> > So as to code reuse with fastboot path then those code had to move to
> bootm
> > layer.
>
> Initially, I did not understand that you were wanting to support both
> "fastboot boot" and booting via bootmeth_android.
>
> Things make more sense now. Please send a new series so that Simon and I
> can review. Thanks again for your patience!
>
Thanks for feedback. if you have other detail wanted to share or have in
next round, please let me know. I planed to have next submission mid/end
next week. If you feel comfortable with GitHub code diff, please take a
closer look and I can make modification accordingly.
Regards,
George
>
>
> >
> > And my understanding each stage is isolated, and depends on env as a kind
> > of api to link up each stage. Then I believe the patch is now a clean
> > solution. Anyway welcome to jot a mail if there are suggestions, if any
> > doubt, please jot a mail too.
> >
> > Thanks,
> > George
> >
> >
> >>
> >> >
> >> >
> >> >>
> >> >> So I leave it as a open-end question here. Once you had decided then
> >> feel free to let me know and I can do one extra round patch. Thank again
> >> for feedback.
> >> >>
> >> >> George
> >> >>
> >> >>>
> >> >>> >
> >> >>> > ... this question ?
> >> >>> >
> >> >>> > We are wondering why bootm_boot_start() overrides the bootargs
> >> variable
> >> >>> > instead of appending cmdline to the existing bootargs instead.
> >> >>> >
> >> >>> > >
> >> >>> > >
> >> >>> > >> people (potentially abootimg) inject needed boot param between
> >> bootmeth
> >> >>> > >> stage. Perhaps, either clean up bootargs before bootmeth load
> >> stage, or add
> >> >>> > >> kconfig to check and enable this logic, a better
> representation.
> >> >>> > >>
> >> >>> > >> (2) One more thing, the vendor_boot cmdline is not handle
> neither
> >> in
> >> >>> > >> original logic nor in url from you provided. So I can say the
> url
> >> one is
> >> >>> > >> not capable for extended with Android boot img version > 2
> since
> >> >>> > >> vendor_boot cmdline not handled.
> >> >>> > >
> >> >>> > > What do you mean by the vendor_boot cmdline is not handled?
> >> >>> > >
> >> >>> > > When parsing the vendor_boot image, we go through
> >> >>> > > android_vendor_boot_image_v3_v4_parse_hdr()
> >> >>> > >
> >> >>> > > That function copies the vendor_boot cmdline with:
> >> >>> > >
> >> >>> > > data->kcmdline_extra = hdr->cmdline;
> >> >>> > >
> >> >>> > > (to the struct andr_image_data).
> >> >>> > >
> >> >>> > > Later on, in android_image_get_kernel(), this gets copied to the
> >> >>> > > bootargs:
> >> >>> > >
> >> >>> > > if (img_data.kcmdline_extra && *img_data.kcmdline_extra) {
> >> >>> > > if (*newbootargs) /* If there is something in
> >> newbootargs, a space is needed */
> >> >>> > > strcat(newbootargs, " ");
> >> >>> > > strcat(newbootargs, img_data.kcmdline_extra);
> >> >>> > > }
> >> >>> > >
> >> >>> > > env_set("bootargs", newbootargs);
> >> >>> > >
> >> >>> > >>
> >> >>> > >> (3) I don't think it is very much different between your
> >> mentioned url with
> >> >>> > >> my patch. There is nothing advanced, but just existing code
> logic
> >> reuse and
> >> >>> > >> that logic handled vendor_cmdline in other path. I prefer code
> >> logic reuse.
> >> >>> > >
> >> >>> > > The difference is that in the patch I've linked is that we only
> >> change
> >> >>> > > Android specific boot behaviour. So less risk to impact
> ChromeOS.
> >> >>> > >
> >> >>> > >>
> >> >>> > >> And I believe above are not the important thing....
> >> >>> > >>
> >> >>> > >>>
> >> >>> > >>> Changing this would potentially break ChromeOS boot behaviour
> so
> >> I'd
> >> >>> > >>> prefer to find another solution.
> >> >>> > >>>
> >> >>> > >>> I know that TI has a downstream patch that changes
> >> bootmeth_android.c
> >> >>> > >>> instead:
> >> >>> > >>>
> >> >>> > >>>
> >> >>> > >>>
> >>
> https://git.ti.com/cgit/ti-u-boot/ti-u-boot/commit/?h=ti-u-boot-2024.04-next&id=9d802d798ac143e06ffe545606aa657a6c32cc63
> >> >>> > >>
> >> >>> > >>
> >> >>> > >> ...
> >> >>> > >>
> >> >>> > >>
> >> >>> > >>> Would that work for you?
> >> >>> > >>>
> >> >>> > >>>
> >> >>> > >> Well, the one from url also fine with me.
> >> >>> > >>
> >> >>> > >> The important thing is here. So as to ease the change with
> >> "minimal impact"
> >> >>> > >> gets in. I can add one extra check to maintain original
> behavior
> >> in case
> >> >>> > >> people have concern of breakage. Code example as below:
> >> >>> > >>
> >> >>> > >> + If
> (IS_ENABLED(CONFIG_ANDROID_BOOT_IMAGE_PREPEND_ENV_BOOTARGS))
> >> >>> > >> + ret = android_image_modify_bootargs_env(cmdline, NULL);
> >> >>> > >> + else
> >> >>> > >> ret = env_set("bootargs", cmdline);
> >> >>> > >>
> >> >>> > >> This logic eliminated the concern, but it also limited those
> >> potential use
> >> >>> > >> cases for Android boot header version > 2, unless the newly
> >> introduced
> >> >>> > >> CONFIG_ANDROID_BOOT_IMAGE_PREPEND_ENV_BOOTARGS is defined.
> >> >>> > >
> >> >>> > > I'm not sure about why this is better, as from what I
> understand we
> >> >>> > > handle vendor_boot cmdline properly already.
> >> >>> > >
> >> >>> > > Can you provide me with a test case or some example commands
> that
> >> show
> >> >>> > > that vendor_boot cmdline is not handled properly?
> >> >>> > >
> >> >>> > >>
> >> >>> > >> Or this one with good extendible.
> >> >>> > >> + /* Clean up bootargs purposely */
> >> >>> > >> + if (IS_ENABLED(SOME_FLAG))
> >> >>> > >> + env_set("bootargs", "");
> >> >>> > >> + ret = android_image_modify_bootargs_env(cmdline, NULL);
> >> >>> > >>
> >> >>> > >> Either way. I prefer first one and can blindly apply without
> >> afford. I
> >> >>> > >> leave the idea above to people more concern with it. Please let
> >> me know
> >> >>> > >> your decision, I can provide one more revision later.
> >> >>> > >
> >> >>> > > I'm sorry there is so much back and forth on this series. I hope
> >> we can
> >> >>> > > come to a common agreement and get something merged.
> >>
> >> Regards,
> >> Simon
> >>
>
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