Ilias Apalodimas <ilias.apalodi...@linaro.org> writes: > Hi Jon, > > On Fri, 17 Jan 2025 at 00:02, Jon Humphreys <j-humphr...@ti.com> wrote: >> >> Sughosh Ganu <sughosh.g...@linaro.org> writes: >> >> > On Thu, 16 Jan 2025 at 14:07, Mattijs Korpershoek >> > <mkorpersh...@baylibre.com> wrote: >> >> >> >> Hi Jon, >> >> >> >> Sorry for the (very) late reply. I had some long holidays in between and >> >> since this is a difficult topic for me, I kept pushing this to the end >> >> of my backlog. >> >> >> >> On mer., déc. 18, 2024 at 17:09, Jon Humphreys <j-humphr...@ti.com> wrote: >> >> >> >> > Mattijs Korpershoek <mkorpersh...@baylibre.com> writes: >> >> > >> >> >> Hi Jonathan, >> >> >> >> >> >> Thank you for the patch. >> >> >> >> >> >> On mar., déc. 17, 2024 at 14:48, Jonathan Humphreys >> >> >> <j-humphr...@ti.com> wrote: >> >> >> >> >> >>> If CONFIG_SET_DFU_ALT_INFO is enabled, the dfu_alt_info environment >> >> >>> variable is dynamically set when initializing the DFU entities, which >> >> >>> is >> >> >>> done as part of normal flow of a DFU operation. >> >> >>> >> >> >>> The USB DFU boot support will set it's own specific value for >> >> >>> dfu_alt_info >> >> >>> before performing the DFU operation. This means that if >> >> >>> CONFIG_SET_DFU_ALT_INFO is enabled, the dfu_alt_info environment >> >> >>> variable >> >> >>> that the USB DFU boot path had set is overwritten, causing USB DFU >> >> >>> boot to >> >> >>> fail. >> >> >>> >> >> >>> Likewise, if the user sets their own value for dfu_alt_info, say at >> >> >>> the >> >> >>> U-Boot prompt, it get's overwritten if CONFIG_SET_DFU_ALT_INFO is >> >> >>> enabled. >> >> >>> >> >> >>> This patch will first check that dfu_alt_info isn't already set before >> >> >>> calling set_dfu_alt_info(), when CONFIG_SET_DFU_ALT_INFO is enabled. >> >> >> >> >> >> To me, this is a policy change: before we could override the >> >> >> environment >> >> >> via set_dfu_alt_info(). Now we cannot anymore (if "dfu_alt_info" is >> >> >> already >> >> >> set in the environment). >> >> >> >> >> >> Also, it seems that this change goes against the uefi doc which states: >> >> >> >> >> >> """ >> >> >> A string is defined which is to be used for populating the >> >> >> dfu_alt_info variable. This string is used by the function >> >> >> set_dfu_alt_info. Instead of taking the variable from the environment, >> >> >> the capsule update feature requires that the variable be set through >> >> >> the function, since that is more robust. Allowing the user to change >> >> >> the location of the firmware updates is not a very secure >> >> >> practice. Getting this information from the firmware itself is more >> >> >> secure, assuming the firmware has been verified by a previous stage >> >> >> boot loader. >> >> >> """ >> >> >> >> >> >> See: >> >> >> https://docs.u-boot.org/en/latest/develop/uefi/uefi.html#performing-the-update >> >> >> >> >> >> Moreover, looking at various boards that implement >> >> >> set_dfu_alt_info(), we can see different behaviours: >> >> >> >> >> >> Boards examples that won't override "dfu_alt_info" via >> >> >> set_dfu_alt_info() if "dfu_alt_info" is already set via environment >> >> >> >> >> >> * board/xilinx/zynq/board.c >> >> >> * board/emulation/common/qemu_dfu.c >> >> >> >> >> >> Boards examplesthat will always override the "dfu_alt_info" via >> >> >> set_dfu_alt_info(): >> >> >> >> >> >> * board/libre-computer/aml-a311d-cc/aml-a311d-cc.c >> >> >> * board/ti/am62px/evm.c >> >> >> >> >> >> Since set_dfu_alt_info() is a board specific callback, why can't this >> >> >> logic be implemented for boards that want this behaviour change? >> >> > >> >> > Because I would then need to duplicate the same logic for every board >> >> > that >> >> > wanted both USB DFU boot and EFI capsules to work. And the paramters >> >> > passed in do not allow the function to know the use case (am I DFU >> >> > booting >> >> > or updating EFI capsules?). See more below. >> >> >> >> I understand that duplicating logic for every board you maintain is not >> >> optimal, however, it gives each vendor the freedom of implementing their >> >> policy. >> >> >> >> I've added a couple of folks who I think could help giving their opinion >> >> on EFI capsules/policy. >> >> >> >> Heinrich, Ilias, Sugosh, do you have any opinion on this patch? >> >> >> >> > >> >> >> >> >> >> Regards, >> >> >> >> >> >> Mattijs >> >> >> >> >> >>> >> >> >>> Signed-off-by: Jonathan Humphreys <j-humphr...@ti.com> >> >> >>> --- >> >> >>> drivers/dfu/dfu.c | 7 +++++-- >> >> >>> 1 file changed, 5 insertions(+), 2 deletions(-) >> >> >>> >> >> >>> diff --git a/drivers/dfu/dfu.c b/drivers/dfu/dfu.c >> >> >>> index 756569217bb..ab8abae1d89 100644 >> >> >>> --- a/drivers/dfu/dfu.c >> >> >>> +++ b/drivers/dfu/dfu.c >> >> >>> @@ -169,10 +169,13 @@ int dfu_init_env_entities(char *interface, char >> >> >>> *devstr) >> >> >>> dfu_reinit_needed = false; >> >> >>> dfu_alt_info_changed = false; >> >> >>> >> >> >>> + str_env = env_get("dfu_alt_info"); >> >> >>> #ifdef CONFIG_SET_DFU_ALT_INFO >> >> >>> - set_dfu_alt_info(interface, devstr); >> >> >>> + if (!str_env) { >> >> >>> + set_dfu_alt_info(interface, devstr); >> >> >>> + str_env = env_get("dfu_alt_info"); >> >> >>> + } >> >> >>> #endif >> >> >>> - str_env = env_get("dfu_alt_info"); >> >> >>> if (!str_env) { >> >> >>> pr_err("\"dfu_alt_info\" env variable not defined!\n"); >> >> >>> return -EINVAL; >> >> >>> -- >> >> >>> 2.34.1 >> >> > >> >> > Mattijs, thanks for the thorough reply. I did wrestle a lot with how >> >> > wide >> >> > of a fix to propose for this problem, and in the end, decided on the >> >> > narrow >> >> > fix of simply preventing the overwriting of the variable. >> >> > >> >> > Yes it is a policy change, but the policy is already unclear, >> >> > inconsistent, >> >> > and confusing, IMO. >> >> > >> >> > For example: >> >> > 1) EFI capsule update wants to very strictly control the dfu alt values >> >> > by setting it in set_dfu_alt_info(), but then any other DFU use >> >> > case breaks. USB DFU boot is now broken. >> >> > 2) The behavior the user sees wrt the dfu_alt_info env variable is very >> >> > confusing and non-intuitive. Take this example: >> >> > >> >> > => env set dfu_alt_info "sf 0:0=exe1.bin raw 0 88000;exe2.bin raw 88000 >> >> > 100000" >> >> > => env print dfu_alt_info >> >> > dfu_alt_info=sf 0:0=exe1.bin raw 0 88000;exe2.bin raw 88000 100000 >> >> > => dfu 0 list >> >> > DFU alt settings list: >> >> > dev: SF alt: 0 name: tiboot3.bin layout: RAW_ADDR >> >> > dev: SF alt: 1 name: tispl.bin layout: RAW_ADDR >> >> > dev: SF alt: 2 name: u-boot.img layout: RAW_ADDR >> >> > => env print dfu_alt_info >> >> > dfu_alt_info=sf 0:0=tiboot3.bin raw 0 80000;tispl.bin raw 80000 >> >> > 200000;u-boot.img raw 280000 400000 >> >> > => >> >> > >> >> > As you can see, the user set's the dfu_alt_info variable according to >> >> > their >> >> > specific use case, then simply tries to list the DFU alt settings, and >> >> > because this code goes through the dfu_init_env_entities() path, it gets >> >> > changed to the EFI capsule settings. >> >> > >> >> > I was hoping to get a simpler fix in now so we can get USB DFU boot >> >> > working >> >> > again, and we can visit the overall policy design next. As you >> >> > suggest, I >> >> > could also push the testing of overwriting into the board specific >> >> > set_dfu_alt_info() function, but then I need to duplicate the code in 8 >> >> > different places for the TI boards, and other vendors may still have the >> >> > problem. >> >> >> >> I agree that the above behaviour is confusing and I'm reconsidering to >> >> take up this patch. I'd like some buy-in from either Heinrich, Ilias or >> >> Sughosh on this since I'm not 100% confortable with the "policy change" >> > >> > A little context here. The DFU driver already had this policy in place >> > where, if the CONFIG_SET_DFU_ALT_INFO was set, the dfu_alt_info string >> > would be set by U-Boot, instead of taking the user provided string. It >> > was decided to use this for EFI capsule updates, as getting the string >> > which determines the location of writing the update images from within >> > U-Boot is more resilient than taking some user provided string. >> > >> > >> >> >> >> > >> >> > Looking to the longer term solution, here are my thoughts. >> >> > 1) We need to decouple CONFIG_SET_DFU_ALT_INFO from EFI capsules. The >> >> > only >> >> > reason TI boards are now setting CONFIG_SET_DFU_ALT_INFO is because >> >> > EFI >> >> > capsule update is enabled. Outside of a few legacy uses (I think - >> >> > it >> >> > appears they were introduced prior to supporting multi-interface dfu >> >> > alt >> >> > strings), I think this is true for other vendor's boards as well. >> >> > 2) Have EFI capsule support do as USB DFU boot does today, and set the >> >> > dfu alt string it wants used *before* initiating the DFU operation. >> >> > With >> >> > CONFIG_SET_DFU_ALT_INFO no longer enabled, the value it set will not >> >> > get >> >> > overridden. >> >> > 3) Have the actual value of the dfu alt string used in the DFU >> >> > operation be >> >> > passed in, rather than read from the dfu_alt_info environment >> >> > variable. >> >> > The USB DFU and EFI capsule use case will pass in the dfu alt string >> >> > they want. The standard 'dfu' command can pass in the value of the >> >> > dfu_alt_info env variable. Note that this effectively decouples the >> >> > dfu >> >> > command from the alt settings that USB DFU boot and EFI capsules use, >> >> > but I think this is what we want. >> > >> > I think either of 2) or 3) above can be looked at. Although not sure >> > if 2) will be breaking the current DFU policy. >> > >> > -sughosh >> > >> >> Thanks for the comments. I have looked into this a bit further and see 2 >> options we can take for the EFI capsule update use case: >> >> 1) stick with the more traditional approach and do as DFU BOOT does by >> setting the value of the dfu_alt_info env variable just before >> initiating the DFU operation. As Ilias sugggested, we could also add a >> save/restore so this is transparent to other DFU users. >> >> 2) move to a model where we explicitly pass in to the DFU operation the >> value of dfu_alt_info that we want used. In the normal/legacy DFU use >> cases, this would involve calling env_get() for the dfu_alt_info env >> variable and pass that value. I like this approach because it is >> cleaner and more explicit. However, there are many layers of function >> calls between the driver of the DFU operation (the one that would decide >> what dfu_alt_info value to use) and dfu_init_env_entities() where it is >> used, and passing this info across the function interfaces would >> involved lots of function interface updates. >> >> I'm curious if there is apetite for 2) or should we go with the more >> traditional approach in 1). >> >> The above assumes we decouple CONFIG_SET_DFU_ALT_INFO from EFI capsules. >> For platforms still setting CONFIG_SET_DFU_ALT_INFO, the presumption is that >> if they override the dfu_alt_info env variable, they know what they are >> doing. > > Decoupling that should be pretty easy. I personally like 2) more since > it's much more scalable and doesn't involve saving.restoring values. > But I am not sure how big of a task it is >
I went with option 1 above. I started working on option 2 however the changes are quite invasive, touching all of the DFU interfaces, and I do not have the understanding of the different DFU use cases nor access to the different hardware using those use cases to test. I also think that this change should be part of a broader DFU cleanup to use only the latest dfu_alt_info string format allowing multiple devices, so that we no longer need to pass around the interface and devstr parameters. Please take a look at the patch series titled "EFI Capsule update explicitly sets dfu_alt_info" that I will post shortly. thanks Jon > Cheers > /Ilias >> >> Thanks >> Jon >> >> >> > >> >> > This then allows both USB DFU boot and EFI capsule use cases to work as >> >> > intended and allows the dfu command to operate on the user defined >> >> > dfu_alt_info value. >> >> > >> >> > I welcome comments from those that have the history and intended >> >> > behavior >> >> > background of the DFU support :). >> >> >> >> I do as well. I have taken over maintaince on this subsystem a year ago >> >> and have not had much patches/work done on the subsystem. Therefore I'm >> >> not as knowledgeable as I would have liked to be. I'm sorry about that. >> >> >> >> > >> >> > I also welcome comments on how to proceed for 2025.01. Should we live >> >> > with >> >> > USB DFU boot broken until we get the long term fix in, or ok with the >> >> > patch >> >> > posted here. The patch posted here does allow for a user to change EFI >> >> > capsule's dfu alt settings, as Mattijs says, but especially given >> >> > capsules >> >> > can be authenticated, I'm not sure how this would be exploited, and if >> >> > that >> >> > risk is worse that broken DFU boot. >> >> > >> >> > thank >> >> > Jon
