June 2020 - Hafnium - lists.trustedfirmware.org

change.submitWholeTopic option for Gerrit

by Andrew Walbran

Hello, How would people feel about enabling the change.submitWholeTopic option ( https://gerrit-review.googlesource.com/Documentation/config-gerrit.html#cha…) for Gerrit? So far, we have relied on this to ensure that submodule changes get submitted along with the corresponding change to the main repository. Our usual workflow has been that whenever a change is made to one of the submodule repositories, both that change and the corresponding change to the main repository are tagged with the same topic. That way it is only possible to submit either once they have all been reviewed +2 and the main change has passed presubmit. This avoids submodules getting out of sync or changes to them being missed or not properly tested. However, it looks like this is a per-host configuration option rather than per-repository, so it would also affect the other Trusted Firmware projects using the same Gerrit host. Are there any other uses of topics there which would conflict with this config change? (If there are other people who might have an opinion on this please add them to the thread.)

4 years, 3 months

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New TrustedFirmware.org security incident process is now live

by Dan Handley

Hi all The new TrustedFirmware.org security incident process is now live. This process is described here: https://developer.trustedfirmware.org/w/collaboration/security_center/repor… Initially the process will be used for the following projects: TF-A, TF-M, OP-TEE and Mbed TLS. The security documentation for each project will be updated soon to reflect this change. If you are part of an organization that believes it should receive security vulnerability information before it is made public then please ask your relevant colleagues to register as Trusted Stakeholders as described here: https://developer.trustedfirmware.org/w/collaboration/security_center/trust… Note we prefer individuals in each organization to coordinate their registration requests with each other and to provide us with an email alias managed by your organization instead of us managing a long list of individual addresses. Best regards Dan. (on behalf of the TrustedFirmware.org security team)

4 years, 3 months

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Re: [Hafnium] Running hafnium in Secure-world

by Olivier Deprez

Hi Raghu, Here are a few more technical details. An SPM design doc is in progress here: https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/4637 The following WIP patches enable an early testing (spm-wip topic branch): https://review.trustedfirmware.org/q/topic:%22spm-wip%22+(status:open%20OR%… As Matteo said, those patches are not yet marked under review waiting for re-licensing to complete. See the build script below if you wish to reproduce. Currently only FVP is supported by enabling Armv8.4-SecEL2 model toggle. This is running the TF-A-tests framework, although a reasonable target is to also have secure world test cases within Hafnium CI/test scripts. Test payloads at S-EL1 are TF-A-tests Cactus bare metal partitions (https://git.trustedfirmware.org/TF-A/tf-a-tests.git/tree/spm/cactus/cactus_…) The test scenario is: TF-A boots and BL2 loads: Hafnium as BL32 in secure world, an SPMC manifest, two Cactus Secure Partition payloads. Hafnium is booted at S-EL2 in the secure world and returns to EL3. Normal world hands over to TFTF at NS-EL2. TFTF boots and initiates basic PSA FF-A direct messaging communication with one and the other Cactus SP. I can share more from the test logs if necessary. There is more to come related to booting a real TEE in place of Cactus. Regards, Olivier. #== Sample build script ========================================== <put bash shebang here> mkdir SPM; cd SPM # Build Hafnium git clone https://review.trustedfirmware.org/hafnium/hafnium && cd hafnium git submodule update --init git fetch "https://review.trustedfirmware.org/hafnium/hafnium" refs/changes/20/4720/1 && git checkout FETCH_HEAD git checkout -b spm cd project/reference git checkout -b spm git fetch "https://review.trustedfirmware.org/hafnium/project/reference" refs/changes/21/4721/1 && git cherry-pick FETCH_HEAD cd ../.. make PROJECT=reference cd .. # Build TF-A-tests git clone https://review.trustedfirmware.org/TF-A/tf-a-tests && cd tf-a-tests make CROSS_COMPILE=aarch64-none-elf- PLAT=fvp DEBUG=1 TESTS=spm cd .. # Build TF-A git clone https://review.trustedfirmware.org/TF-A/trusted-firmware-a && cd trusted-firmware-a make \ CROSS_COMPILE=aarch64-none-elf- \ SPD=spmd \ CTX_INCLUDE_EL2_REGS=1 \ ARM_ARCH_MINOR=4 \ PLAT=fvp \ DEBUG=1 \ BL33=../tf-a-tests/build/fvp/debug/tftf.bin \ BL32=../hafnium/out/reference/secure_aem_v8a_fvp_clang/hafnium.bin \ SP_LAYOUT_FILE=../tf-a-tests/build/fvp/debug/sp_layout.json \ all fip #===================================================== ________________________________________ From: Hafnium <hafnium-bounces(a)lists.trustedfirmware.org> on behalf of Matteo Carlini via Hafnium <hafnium(a)lists.trustedfirmware.org> Sent: 19 June 2020 10:47 To: raghu.ncstate(a)icloud.com Cc: hafnium(a)lists.trustedfirmware.org Subject: Re: [Hafnium] Running hafnium in Secure-world Hi Raghu, Hafnium is going to be precisely the reference Secure EL2 SPM, collaboratively developed and hosted here by Trusted Firmware.org. The project is finalising its migration as we speak (look at the relicensing commit here https://review.trustedfirmware.org/c/hafnium/hafnium/+/4616) and we'll soon create a blogpost to celebrate the final migration and its new life under Trusted Firmware. The development teams are already working internally to achieve the above S-EL2 goal and they'll be posting the initial enablement patches and proto-branches as soon as the relicensing is complete, so to continue the development completely in the open and welcome partners' comments and help. They can certainly chime in here and provide their current status from a technical perspective. The Normal world instance of Hafnium remains for now just as test payload for the PSA FF-A (SPCI) interface to help developing the Secure-EL2 SPM side of it, nothing more than that. You can always refer to my Linaro presentation back in March that described the overall goal and direction for this enablement: https://connect.linaro.org/resources/ltd20/ltd20-200k/ Please note there will also be a TF-A Tech Forum session entirely focused on the Secure EL2 / Hafnium development topic quite soon (2nd July tentative), watch this space: https://www.trustedfirmware.org/meetings/tf-a-technical-forum/ So I'd strongly encourage to participate to it, to discuss live all the latest news. Thanks Matteo > From: Hafnium <hafnium-bounces(a)lists.trustedfirmware.org> on behalf of > Raghu K via Hafnium <hafnium(a)lists.trustedfirmware.org> > Sent: 18 June 2020 22:59 > To: hafnium(a)lists.trustedfirmware.org > Subject: [Hafnium] Running hafnium in Secure-world > > All, > > Is it possible to run hafnium in SEL2? From looking at the code, it seems like > hafnium currently only supports running in NS world. Is my understanding > correct? I was wondering if/when there is a plan for secure world support in > hafnium and if anybody is working on it. > > Thanks > Raghu -- Hafnium mailing list Hafnium(a)lists.trustedfirmware.org https://lists.trustedfirmware.org/mailman/listinfo/hafnium

4 years, 3 months

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Re: [Hafnium] Running hafnium in Secure-world

by Matteo Carlini

Hi Raghu, Hafnium is going to be precisely the reference Secure EL2 SPM, collaboratively developed and hosted here by Trusted Firmware.org. The project is finalising its migration as we speak (look at the relicensing commit here https://review.trustedfirmware.org/c/hafnium/hafnium/+/4616) and we'll soon create a blogpost to celebrate the final migration and its new life under Trusted Firmware. The development teams are already working internally to achieve the above S-EL2 goal and they'll be posting the initial enablement patches and proto-branches as soon as the relicensing is complete, so to continue the development completely in the open and welcome partners' comments and help. They can certainly chime in here and provide their current status from a technical perspective. The Normal world instance of Hafnium remains for now just as test payload for the PSA FF-A (SPCI) interface to help developing the Secure-EL2 SPM side of it, nothing more than that. You can always refer to my Linaro presentation back in March that described the overall goal and direction for this enablement: https://connect.linaro.org/resources/ltd20/ltd20-200k/ Please note there will also be a TF-A Tech Forum session entirely focused on the Secure EL2 / Hafnium development topic quite soon (2nd July tentative), watch this space: https://www.trustedfirmware.org/meetings/tf-a-technical-forum/ So I'd strongly encourage to participate to it, to discuss live all the latest news. Thanks Matteo > From: Hafnium <hafnium-bounces(a)lists.trustedfirmware.org> on behalf of > Raghu K via Hafnium <hafnium(a)lists.trustedfirmware.org> > Sent: 18 June 2020 22:59 > To: hafnium(a)lists.trustedfirmware.org > Subject: [Hafnium] Running hafnium in Secure-world > > All, > > Is it possible to run hafnium in SEL2? From looking at the code, it seems like > hafnium currently only supports running in NS world. Is my understanding > correct? I was wondering if/when there is a plan for secure world support in > hafnium and if anybody is working on it. > > Thanks > Raghu

4 years, 3 months

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Running hafnium in Secure-world

by Raghu K

All, Is it possible to run hafnium in SEL2? From looking at the code, it seems like hafnium currently only supports running in NS world. Is my understanding correct? I was wondering if/when there is a plan for secure world support in hafnium and if anybody is working on it. Thanks Raghu

4 years, 3 months

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Re: [Hafnium] Determine security state of a memory region

by Olivier Deprez

Thinking a bit further, this does not prevents a compromised SP to later change the region security state. So I guess if using AT instruction, this check has to be done at least in any FFA memory sharing operation transiting through the SPM. Though this might have to be complemented with a security state field in memory region tracking logic? Also related to VTCR_EL2 NSA/NSW this is related to Stage-2 IPA to PA translation. So I suspect this might have to be set always, whichever using one or two sets of page tables because an NS IPA from Stage-1 shall be routed as an NS PA to TZ controller (?) ________________________________________ From: Hafnium <hafnium-bounces(a)lists.trustedfirmware.org> on behalf of Olivier Deprez via Hafnium <hafnium(a)lists.trustedfirmware.org> Sent: 09 June 2020 14:55 To: Raghu Krishnamurthy; Andrew Walbran; Achin Gupta Cc: hafnium(a)lists.trustedfirmware.org Subject: Re: [Hafnium] Determine security state of a memory region Hi, I think the subtlety resides in PAR_EL1.NS (bit 9). When a secure hypervisor performs AT S1E1R, then the resulting translation output is the SEL1 IPA (including the NS bit state). I did the following trials with SPM executing AT S1E1R for a known region mapped by an SP: -the SP does not map the region =>PAR_EL1.F=1 -the SP maps the regions secure =>PAR_EL1.NS=0 -the SP maps the region non-secure =>PAR_EL1.NS=1 This permits checking the SP region security state without trusting the SP. On a related topic I also noticed VTCR_EL2.NSA and VTCR_EL2.NSW (and VSTCR_EL2.SA/SW=0). With default values of 0, this means Stage-1 translations always result to Secure IPA space (also in the case S-EL1 MMU is disabled). Hence I think PTWs always go through VSTTBR. I guess the two VTCR_EL2 bits shall be set if we adopt a model where: -any NS shared mapping resolves to VTTBR -remaining SP mappings resolve to VSTTBR Regards, Olivier. ________________________________________ From: Hafnium <hafnium-bounces(a)lists.trustedfirmware.org> on behalf of Raghu Krishnamurthy via Hafnium <hafnium(a)lists.trustedfirmware.org> Sent: 08 June 2020 17:11 To: hafnium(a)lists.trustedfirmware.org Subject: Re: [Hafnium] Determine security state of a memory region Never mind question 2 below. Educated myself that there is no NS bit in the stage 2 tables which i had assumed. I think Andrew's suggestion should work too, however it does have the issue that the SP may see incoherent data if there is an NS attribute mismatch. With option 4 i suggested, you would get a fault when incorrect attributes are used. No strong preference though. -Raghu On 6/8/20 7:10 AM, Raghu Krishnamurthy via Hafnium wrote: > Hi Achin, > > Thanks for the explanation. Agree that this is a problem. > > 1) Pasting Andrew's question for continuity: Is it possible that the > SPMC could map it in both the secure and non-secure stage 2 page > tables, so the SP can decide which security state to map it in at stage > 1? Or am I misunderstanding how this works? > > 2) Perhaps i'm missing something, but I'm surprised by the assumption > that a given SP(which runs only in secure world) will have multiple S2 > tables. How would the SPMC decide whether to point VSTTBR_EL2 to the > secure or non-secure S2 tables when entering an SP? Unless the way this > works architecturally is that the stage 1 walk's NS attribute is used to > select VSTTBR_EL2 or VTTBR_EL2. That seems backward. > > 3) Have you considered option 4, where an FFA_MEM_SHARE between 2 SP's > shall always share only pages mapped as secure and between SP and a VM > share only pages mapped as non-secure? Or is this not an option? This > will make the SPMC design simpler and puts the onus on lower privileged > SP's to know if they are communicating with secure world or NS world > components. This obviously incurs overhead from the SP's point of view > but if the more important goal is to keep S-EL2 simpler, this might be a > good option. > > Thanks > Raghu > > On 6/8/20 2:37 AM, Andrew Walbran wrote: >> On Sun, 7 Jun 2020 at 16:46, Achin Gupta via Hafnium >> <hafnium(a)lists.trustedfirmware.org >> <mailto:hafnium@lists.trustedfirmware.org>> wrote: >> >> Hi Raghu, >> >> Howdy! CIL… >> >> > On 4 Jun 2020, at 16:21, Raghu K via Hafnium >> <hafnium(a)lists.trustedfirmware.org >> <mailto:hafnium@lists.trustedfirmware.org>> wrote: >> > >> > Hi Achin, >> > >> > Would you mind elaborating more on why the SPM needs to determine >> the security state and why it is important to do this without >> trusting the SP? When you say SPM, it sounds like you are talking >> about the SPMD running in EL3 for ex., that is not a part of the >> SPMC which perhaps runs as S-EL2 and the SPMD may need to know this >> to figure out how to map a particular physical page. Is that the use >> case you are thinking about? >> >> So this is in the context of PSA FF-A Memory management ABIs. Also, >> I have the S-EL2 SPMC case in mind. SPMD in EL3 does not participate >> in memory management in this case when it comes to managing any >> architectural state i.e. translation tables, control regs etc >> >> Say, a SP0 invokes FFA_MEM_SHARE to share a single page A with SP1. >> The SPMC would need to map page A in SP’s stage 2 tables. To do >> this, it would need to determine whether the IPA of page A belongs >> to the Secure or Non-secure IPA space. This is under the assumption >> that some memory ranges in SP0’s IPA space will be Non-secure. >> >> IMO, this information can be determined in one of the following ways: >> >> 1. Perform PTW in SW to determine whether IPA is mapped in the >> tables referenced by VSTTBR_EL2 or VTTBR_EL2. I am assuming the SPMC >> maintains separate S2 translations for the Secure and NS address >> spaces. >> >> 2. Through an internal data structure which tracks the attributes of >> a memory region assigned to a guest. >> >> 3. SP0 specifies the security state of page A in FFA_MEM_SHARE. The >> spec does not cover this currently. However, the SPMC cannot trust >> that the SP0 is providing the right security state and must verify >> this independently anyways. >> >> 1 seems clunky. 2 is not done in upstream Hf. 3 does not really help. >> >> I think I had misunderstood that a AT* instruction could be used. >> There do not seem to be any in the Arm ARM that only perform a IPA >> to PA i.e. a S2 translation. >> >> So I am wondering what can be done to solve this problem assuming we >> agree that this is a problem in the first place. >> >> >> Is it possible that the SPMC could map it in both the secure and >> non-secure stage 2 page tables, so the SP can decide which security >> state to map it in at stage 1? Or am I misunderstanding how this works? >> >> >> Hth, >> >> Cheers, >> Achin >> >> > >> > Thanks >> > Raghu >> > >> > On 6/4/20 3:07 AM, Achin Gupta via Hafnium wrote: >> >> Hi All, >> >> >> >> I am thinking of a scenario where a SP shares Non-secure memory >> with one or more SPs or VMs. The NS memory region could have been >> donated to the SP by a VM earlier (far fetched but possible). >> >> >> >> The question is how does the SPM determine the security state of >> the memory region being shared by the SP. >> >> >> >> It is especially important that the SPM does this without >> trusting the SP. >> >> >> >> I don't think it should rely on the AT* instructions. The SP >> could change the security state of the region in S1. AFAIK, there >> are no AT* instructions that only do S2 walks with a IPA as an input. >> >> >> >> So is the only option to perform a walk in both the Secure and >> Non-secure S2 tables to determine where is the address mapped. >> >> >> >> This seems a bit clunky. So wondering if I am missing anything >> and there is an easier way to do this. >> >> >> >> What do you reckon? >> >> >> >> cheers, >> >> Achin >> > >> > -- >> > Hafnium mailing list >> > Hafnium(a)lists.trustedfirmware.org >> <mailto:Hafnium@lists.trustedfirmware.org> >> > https://lists.trustedfirmware.org/mailman/listinfo/hafnium >> >> -- Hafnium mailing list >> Hafnium(a)lists.trustedfirmware.org >> <mailto:Hafnium@lists.trustedfirmware.org> >> https://lists.trustedfirmware.org/mailman/listinfo/hafnium >> -- Hafnium mailing list Hafnium(a)lists.trustedfirmware.org https://lists.trustedfirmware.org/mailman/listinfo/hafnium -- Hafnium mailing list Hafnium(a)lists.trustedfirmware.org https://lists.trustedfirmware.org/mailman/listinfo/hafnium

4 years, 3 months

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Re: [Hafnium] CPTR_EL2 configuration

by Serban Constantinescu

+Andrew Scull <ascull(a)google.com> who kindly answered this offline. On Fri, May 22, 2020 at 9:38 AM Olivier Deprez via Hafnium < hafnium(a)lists.trustedfirmware.org> wrote: > Hi, > > Hafnium sets CPTR_EL2.TTA (bit 28), which traps accesses to trace system > registers to EL2. > > https://git.trustedfirmware.org/hafnium/hafnium.git/tree/src/arch/aarch64/s… > > However CPTR_EL2 register has a different bit field definition depending > on HCR_EL2.E2H state. > When HCR_EL2.E2H=0 (Hafnium case) CPTR_EL2.TTA bit position is 20. > > Is this a slight issue needing fix? > It sounds like this was copied badly from the spec and should be fixed. We don't enable VHE and we should do as the spec says. HTH, Serban > > Regards, > Olivier. > IMPORTANT NOTICE: The contents of this email and any attachments are > confidential and may also be privileged. If you are not the intended > recipient, please notify the sender immediately and do not disclose the > contents to any other person, use it for any purpose, or store or copy the > information in any medium. Thank you. > -- > Hafnium mailing list > Hafnium(a)lists.trustedfirmware.org > https://lists.trustedfirmware.org/mailman/listinfo/hafnium >

4 years, 3 months

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Re: [Hafnium] Determine security state of a memory region

by Olivier Deprez

Hi, I think the subtlety resides in PAR_EL1.NS (bit 9). When a secure hypervisor performs AT S1E1R, then the resulting translation output is the SEL1 IPA (including the NS bit state). I did the following trials with SPM executing AT S1E1R for a known region mapped by an SP: -the SP does not map the region =>PAR_EL1.F=1 -the SP maps the regions secure =>PAR_EL1.NS=0 -the SP maps the region non-secure =>PAR_EL1.NS=1 This permits checking the SP region security state without trusting the SP. On a related topic I also noticed VTCR_EL2.NSA and VTCR_EL2.NSW (and VSTCR_EL2.SA/SW=0). With default values of 0, this means Stage-1 translations always result to Secure IPA space (also in the case S-EL1 MMU is disabled). Hence I think PTWs always go through VSTTBR. I guess the two VTCR_EL2 bits shall be set if we adopt a model where: -any NS shared mapping resolves to VTTBR -remaining SP mappings resolve to VSTTBR Regards, Olivier. ________________________________________ From: Hafnium <hafnium-bounces(a)lists.trustedfirmware.org> on behalf of Raghu Krishnamurthy via Hafnium <hafnium(a)lists.trustedfirmware.org> Sent: 08 June 2020 17:11 To: hafnium(a)lists.trustedfirmware.org Subject: Re: [Hafnium] Determine security state of a memory region Never mind question 2 below. Educated myself that there is no NS bit in the stage 2 tables which i had assumed. I think Andrew's suggestion should work too, however it does have the issue that the SP may see incoherent data if there is an NS attribute mismatch. With option 4 i suggested, you would get a fault when incorrect attributes are used. No strong preference though. -Raghu On 6/8/20 7:10 AM, Raghu Krishnamurthy via Hafnium wrote: > Hi Achin, > > Thanks for the explanation. Agree that this is a problem. > > 1) Pasting Andrew's question for continuity: Is it possible that the > SPMC could map it in both the secure and non-secure stage 2 page > tables, so the SP can decide which security state to map it in at stage > 1? Or am I misunderstanding how this works? > > 2) Perhaps i'm missing something, but I'm surprised by the assumption > that a given SP(which runs only in secure world) will have multiple S2 > tables. How would the SPMC decide whether to point VSTTBR_EL2 to the > secure or non-secure S2 tables when entering an SP? Unless the way this > works architecturally is that the stage 1 walk's NS attribute is used to > select VSTTBR_EL2 or VTTBR_EL2. That seems backward. > > 3) Have you considered option 4, where an FFA_MEM_SHARE between 2 SP's > shall always share only pages mapped as secure and between SP and a VM > share only pages mapped as non-secure? Or is this not an option? This > will make the SPMC design simpler and puts the onus on lower privileged > SP's to know if they are communicating with secure world or NS world > components. This obviously incurs overhead from the SP's point of view > but if the more important goal is to keep S-EL2 simpler, this might be a > good option. > > Thanks > Raghu > > On 6/8/20 2:37 AM, Andrew Walbran wrote: >> On Sun, 7 Jun 2020 at 16:46, Achin Gupta via Hafnium >> <hafnium(a)lists.trustedfirmware.org >> <mailto:hafnium@lists.trustedfirmware.org>> wrote: >> >> Hi Raghu, >> >> Howdy! CIL… >> >> > On 4 Jun 2020, at 16:21, Raghu K via Hafnium >> <hafnium(a)lists.trustedfirmware.org >> <mailto:hafnium@lists.trustedfirmware.org>> wrote: >> > >> > Hi Achin, >> > >> > Would you mind elaborating more on why the SPM needs to determine >> the security state and why it is important to do this without >> trusting the SP? When you say SPM, it sounds like you are talking >> about the SPMD running in EL3 for ex., that is not a part of the >> SPMC which perhaps runs as S-EL2 and the SPMD may need to know this >> to figure out how to map a particular physical page. Is that the use >> case you are thinking about? >> >> So this is in the context of PSA FF-A Memory management ABIs. Also, >> I have the S-EL2 SPMC case in mind. SPMD in EL3 does not participate >> in memory management in this case when it comes to managing any >> architectural state i.e. translation tables, control regs etc >> >> Say, a SP0 invokes FFA_MEM_SHARE to share a single page A with SP1. >> The SPMC would need to map page A in SP’s stage 2 tables. To do >> this, it would need to determine whether the IPA of page A belongs >> to the Secure or Non-secure IPA space. This is under the assumption >> that some memory ranges in SP0’s IPA space will be Non-secure. >> >> IMO, this information can be determined in one of the following ways: >> >> 1. Perform PTW in SW to determine whether IPA is mapped in the >> tables referenced by VSTTBR_EL2 or VTTBR_EL2. I am assuming the SPMC >> maintains separate S2 translations for the Secure and NS address >> spaces. >> >> 2. Through an internal data structure which tracks the attributes of >> a memory region assigned to a guest. >> >> 3. SP0 specifies the security state of page A in FFA_MEM_SHARE. The >> spec does not cover this currently. However, the SPMC cannot trust >> that the SP0 is providing the right security state and must verify >> this independently anyways. >> >> 1 seems clunky. 2 is not done in upstream Hf. 3 does not really help. >> >> I think I had misunderstood that a AT* instruction could be used. >> There do not seem to be any in the Arm ARM that only perform a IPA >> to PA i.e. a S2 translation. >> >> So I am wondering what can be done to solve this problem assuming we >> agree that this is a problem in the first place. >> >> >> Is it possible that the SPMC could map it in both the secure and >> non-secure stage 2 page tables, so the SP can decide which security >> state to map it in at stage 1? Or am I misunderstanding how this works? >> >> >> Hth, >> >> Cheers, >> Achin >> >> > >> > Thanks >> > Raghu >> > >> > On 6/4/20 3:07 AM, Achin Gupta via Hafnium wrote: >> >> Hi All, >> >> >> >> I am thinking of a scenario where a SP shares Non-secure memory >> with one or more SPs or VMs. The NS memory region could have been >> donated to the SP by a VM earlier (far fetched but possible). >> >> >> >> The question is how does the SPM determine the security state of >> the memory region being shared by the SP. >> >> >> >> It is especially important that the SPM does this without >> trusting the SP. >> >> >> >> I don't think it should rely on the AT* instructions. The SP >> could change the security state of the region in S1. AFAIK, there >> are no AT* instructions that only do S2 walks with a IPA as an input. >> >> >> >> So is the only option to perform a walk in both the Secure and >> Non-secure S2 tables to determine where is the address mapped. >> >> >> >> This seems a bit clunky. So wondering if I am missing anything >> and there is an easier way to do this. >> >> >> >> What do you reckon? >> >> >> >> cheers, >> >> Achin >> > >> > -- >> > Hafnium mailing list >> > Hafnium(a)lists.trustedfirmware.org >> <mailto:Hafnium@lists.trustedfirmware.org> >> > https://lists.trustedfirmware.org/mailman/listinfo/hafnium >> >> -- Hafnium mailing list >> Hafnium(a)lists.trustedfirmware.org >> <mailto:Hafnium@lists.trustedfirmware.org> >> https://lists.trustedfirmware.org/mailman/listinfo/hafnium >> -- Hafnium mailing list Hafnium(a)lists.trustedfirmware.org https://lists.trustedfirmware.org/mailman/listinfo/hafnium

4 years, 3 months

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Re: [Hafnium] Mismatched memory attributes in Hf?

by Andrew Walbran

I don't understand the cache specification well enough to comment, but perhaps Andrew or Wedson can help or give some background? On Mon, 8 Jun 2020 at 11:11, Achin Gupta via Hafnium < hafnium(a)lists.trustedfirmware.org> wrote: > Hi All, > > In Arm, we are experimenting with running OP-TEE under Hafnium as the SPMC > in S-EL2. We have been debugging this Stage 2 fault that OP-TEE runs into a > during a test to share memory (xtest 1003). It seems this is due to a bug > in Hafnium but want to be sure before posting a fix. Some thoughts below to > this end. Apologies for the verbosity but I hope you will appreciate it is > required. > > The fault occurs when OP-TEE tries to access a memory region that was > shared with it by the OP-TEE driver in Linux i.e. the driver has called > FFA_MEM_SHARE to share the memory, OP-TEE has called FFA_MEM_RETRIEVE_REQ > to map it in its S2 and Hf has called FFA_MEM_RETRIVE_RESP to describe the > IPA range to OP-TEE. So, the S2 tables are created correctly before OP-TEE > tries to use them. > > The S2 fault is a L3 Translation fault. The L3 descriptor in S2 tables is > NULL when the fault occurs. So this makes sense. This also implies that the > translation is not cached in the TLBs. > > The key thing is that the fault only occurs when cache state modelling is > turned on in the FVP_Base_RevC-2xAEMv8A model we are using for development. > The fault occurs both when the S2 tables are created and accessed on the > same PE as well as different PEs. It does not matter whether the PEs are in > the same or different clusters. The fault occurs both with and without a > Hypervisor (Hf) in the Normal world. So presence of Hf in EL2 is not a > factor. > > We noticed that Hf marks its internal memory as outer-shareable. See [1] > and [2]. It uses inner-shareable for S2 PTWs though. See [3]. This is a > mismatch of memory attributes as per Page 2563 in ARM DDI 0487F.b. The > start of the text is quoted below. > > "The rules about mismatched attributes given in Mismatched memory > attributes…” > > And indeed, the fault is not seen if we mark Hf’s internal memory as inner > shareable to match the PTWs. The DSBs after creating the S2 tables in [4] > are for inner-shareable access types. It seems that the inner-shareable PTW > is unable to observe the outer shareable page table write. Using the inner > shareable attributes for the internal memory makes the write observable. > > Alternatively, if we change shareability of PTWs in VTCR_EL2 to outer > shareable then the fault is no longer observed. It is not clear how the > PTWs and page table writes are synchronised in this case without a DSB OSH. > This is not a violation of the architecture afaiu. > > It seems that it would be worth aligning these attributes. > > The next bit is why Hf uses the outer shareable attribute for internal > memory in the first place. The recommendation seems to be to use > inner-shareable. See [5] and [6]. > > So we are wondering if this should be fixed too. Please let me know if we > have misunderstood anything so far. Happy to post a patch if not or provide > more information. > > Cheers, > Achin > > [1] > https://hafnium.googlesource.com/hafnium/+/refs/heads/master/src/arch/aarch… > [2] > https://hafnium.googlesource.com/hafnium/+/refs/heads/master/src/mm.c#1043 > [3] > https://hafnium.googlesource.com/hafnium/+/refs/heads/master/src/arch/aarch… > [4] > https://hafnium.googlesource.com/hafnium/+/refs/heads/master/src/arch/aarch… > [5] "Shareable Normal memory” in Pg. 154 in ARM DDI 0487F.b > [6] > https://linux-arm-kernel.infradead.narkive.com/RZHvk1cT/question-how-can-we… > > > -- > Hafnium mailing list > Hafnium(a)lists.trustedfirmware.org > https://lists.trustedfirmware.org/mailman/listinfo/hafnium >

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Re: [Hafnium] Determine security state of a memory region

by Raghu Krishnamurthy

Never mind question 2 below. Educated myself that there is no NS bit in the stage 2 tables which i had assumed. I think Andrew's suggestion should work too, however it does have the issue that the SP may see incoherent data if there is an NS attribute mismatch. With option 4 i suggested, you would get a fault when incorrect attributes are used. No strong preference though. -Raghu On 6/8/20 7:10 AM, Raghu Krishnamurthy via Hafnium wrote: > Hi Achin, > > Thanks for the explanation. Agree that this is a problem. > > 1) Pasting Andrew's question for continuity: Is it possible that the > SPMC could map it in both the secure and non-secure stage 2 page > tables, so the SP can decide which security state to map it in at stage > 1? Or am I misunderstanding how this works? > > 2) Perhaps i'm missing something, but I'm surprised by the assumption > that a given SP(which runs only in secure world) will have multiple S2 > tables. How would the SPMC decide whether to point VSTTBR_EL2 to the > secure or non-secure S2 tables when entering an SP? Unless the way this > works architecturally is that the stage 1 walk's NS attribute is used to > select VSTTBR_EL2 or VTTBR_EL2. That seems backward. > > 3) Have you considered option 4, where an FFA_MEM_SHARE between 2 SP's > shall always share only pages mapped as secure and between SP and a VM > share only pages mapped as non-secure? Or is this not an option? This > will make the SPMC design simpler and puts the onus on lower privileged > SP's to know if they are communicating with secure world or NS world > components. This obviously incurs overhead from the SP's point of view > but if the more important goal is to keep S-EL2 simpler, this might be a > good option. > > Thanks > Raghu > > On 6/8/20 2:37 AM, Andrew Walbran wrote: >> On Sun, 7 Jun 2020 at 16:46, Achin Gupta via Hafnium >> <hafnium(a)lists.trustedfirmware.org >> <mailto:hafnium@lists.trustedfirmware.org>> wrote: >> >> Hi Raghu, >> >> Howdy! CIL… >> >> > On 4 Jun 2020, at 16:21, Raghu K via Hafnium >> <hafnium(a)lists.trustedfirmware.org >> <mailto:hafnium@lists.trustedfirmware.org>> wrote: >> > >> > Hi Achin, >> > >> > Would you mind elaborating more on why the SPM needs to determine >> the security state and why it is important to do this without >> trusting the SP? When you say SPM, it sounds like you are talking >> about the SPMD running in EL3 for ex., that is not a part of the >> SPMC which perhaps runs as S-EL2 and the SPMD may need to know this >> to figure out how to map a particular physical page. Is that the use >> case you are thinking about? >> >> So this is in the context of PSA FF-A Memory management ABIs. Also, >> I have the S-EL2 SPMC case in mind. SPMD in EL3 does not participate >> in memory management in this case when it comes to managing any >> architectural state i.e. translation tables, control regs etc >> >> Say, a SP0 invokes FFA_MEM_SHARE to share a single page A with SP1. >> The SPMC would need to map page A in SP’s stage 2 tables. To do >> this, it would need to determine whether the IPA of page A belongs >> to the Secure or Non-secure IPA space. This is under the assumption >> that some memory ranges in SP0’s IPA space will be Non-secure. >> >> IMO, this information can be determined in one of the following ways: >> >> 1. Perform PTW in SW to determine whether IPA is mapped in the >> tables referenced by VSTTBR_EL2 or VTTBR_EL2. I am assuming the SPMC >> maintains separate S2 translations for the Secure and NS address >> spaces. >> >> 2. Through an internal data structure which tracks the attributes of >> a memory region assigned to a guest. >> >> 3. SP0 specifies the security state of page A in FFA_MEM_SHARE. The >> spec does not cover this currently. However, the SPMC cannot trust >> that the SP0 is providing the right security state and must verify >> this independently anyways. >> >> 1 seems clunky. 2 is not done in upstream Hf. 3 does not really help. >> >> I think I had misunderstood that a AT* instruction could be used. >> There do not seem to be any in the Arm ARM that only perform a IPA >> to PA i.e. a S2 translation. >> >> So I am wondering what can be done to solve this problem assuming we >> agree that this is a problem in the first place. >> >> >> Is it possible that the SPMC could map it in both the secure and >> non-secure stage 2 page tables, so the SP can decide which security >> state to map it in at stage 1? Or am I misunderstanding how this works? >> >> >> Hth, >> >> Cheers, >> Achin >> >> > >> > Thanks >> > Raghu >> > >> > On 6/4/20 3:07 AM, Achin Gupta via Hafnium wrote: >> >> Hi All, >> >> >> >> I am thinking of a scenario where a SP shares Non-secure memory >> with one or more SPs or VMs. The NS memory region could have been >> donated to the SP by a VM earlier (far fetched but possible). >> >> >> >> The question is how does the SPM determine the security state of >> the memory region being shared by the SP. >> >> >> >> It is especially important that the SPM does this without >> trusting the SP. >> >> >> >> I don't think it should rely on the AT* instructions. The SP >> could change the security state of the region in S1. AFAIK, there >> are no AT* instructions that only do S2 walks with a IPA as an input. >> >> >> >> So is the only option to perform a walk in both the Secure and >> Non-secure S2 tables to determine where is the address mapped. >> >> >> >> This seems a bit clunky. So wondering if I am missing anything >> and there is an easier way to do this. >> >> >> >> What do you reckon? >> >> >> >> cheers, >> >> Achin >> > >> > -- >> > Hafnium mailing list >> > Hafnium(a)lists.trustedfirmware.org >> <mailto:Hafnium@lists.trustedfirmware.org> >> > https://lists.trustedfirmware.org/mailman/listinfo/hafnium >> >> -- Hafnium mailing list >> Hafnium(a)lists.trustedfirmware.org >> <mailto:Hafnium@lists.trustedfirmware.org> >> https://lists.trustedfirmware.org/mailman/listinfo/hafnium >>

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Hafnium June 2020