Add RISC-V TEE support

Hi?Anup
I edit it in
https://github.com/riscv-non-isa/riscv-sbi-doc/blob/master/riscv-sbi.a
doc. I tried to push a document edit commit
[https://github.com/riscv-non-isa/riscv-sbi-doc/pull/106]. Please check. Am I doing what you expect me to do

Thanks
Liushiwei
-----????-----
???: Anup Patel [mailto:anup at brainfault.org]
????: 2023?1?13? 20:00
???: liushiwei <[email protected]>
??: Himanshu Chauhan <[email protected]>; opensbi at lists.infradead.org; chenchaokai at eswincomputing.com ??: Re: ??: [PATCH 1/1] Add RISC-V TEE support

Quoted 104 lines · liushiwei

Hi, Himanshu , These are my description:

In my design, The entire linux space is called REE (Rich Execution Environment), and TEE OS includes its user state called TEE (Trusted execution environment). adding TEE functionality to opensbi requires two configuration items.
For example:
add CONFIG_SBI_ECALL_TEE=y in platform/generic/configs/defconfig file.
add CONFIG_TEE_LOAD_ADDR=0x27C000000 platform/generic/objects.mk.
The value of CONFIG_TEE_LOAD_ADDR depends on the actual memory layout, It's a physical address.

When TEE is configured, opensbi adds the following functionality:
1. Boot TEE OS.
If TEE is enabled, tee_os_init() is called before entering sbi_hart_switch_mode(). tee_os_init saves the current context,
sets a new trap stack address, and runs to CONFIG_TEE_LOAD_ADDR as configured to complete TEE OS initialization. TEE OS returns via ecall, Go to opensbi sbi_ecall_tee_handler and use the characteristic value RETURN_ENTRY_DONE
to indicate the return after the TEE OS completes booting. Check whether the TEE OS boot successfully according to the parameter. If fails,
the system enters wfi and terminates the startup process of opensbi. If successful, it returns REE to switch into TEE's vector. then trap stack memory is restored, the context is restored, the tee_os_init call is returned,
and the rest of the process is performed.
2. REE switches to TEE.
When the TEE OS boot successfully, it returns an entry vector for REE into the TEE. It represents various entry points into TEE OS and is stored in opensbi's global variables. It is the optee_vectors_t structure, which contains nine entry cases:
1. yield_smc_entry;
2. fast_smc_entry;
3. cpu_on_entry;
4. cpu_off_entry;
5. cpu_resume_entry;
6. cpu_suspend_entry;
7. fiq_entry;
8. system_off_entry;
9. system_reset_entry;
yield_smc_entry means that this function entry TEE will start the thread function and enter the user state of TEE. It may also switch back to REE with RPC function, and then return to TEE after REE completes the corresponding function.
For the REE process that sent you this call, it may cause sleep.

fast_smc_entry indicates that this is a quick function that returns after the TEE OS does something, and that it does not cause the caller to sleep.

yield_smc_entry and fast_smc_entry return opensbi use eigenvalue RETURN_CALL_DONE. for yield_smc_entry, whether the call returns or the RPC returns is decided by linux.

cpu_on_entry/cpu_off_entry/cpu_resume_entry/cpu_suspend_entry and fiq_entry/system_off_entry/system_reset_entry they are not implemented currently.

3. TEE switches to REE.
opensbi needs to save the context when REE enters the TEE, and restore the context when it returns from the TEE.

4. TEE/REE Request a special function.
We have some specific functions, like get hartid from TEE, it need save and restore the TEE context.

Data structure.
opensbi adds the sbi_save_context declaration

   struct sbi_save_context {
      struct sbi_trap_regs regs;
      unsigned long sepc;
      unsigned long satp;
      unsigned long sstatus;
      unsigned long sie;
      unsigned long stvec;
      unsigned long sscratch;
      unsigned long scounteren;
      unsigned long scause;
      unsigned long stval;
      unsigned long sip;

};
sbi_save_context include sbi_trap_regs and S mode csr. Used to
hold the context of TEE or REE

   typedef struct optee_vectors {
      optee_vector_isn_t yield_smc_entry;
      optee_vector_isn_t fast_smc_entry;
      optee_vector_isn_t cpu_on_entry;
      optee_vector_isn_t cpu_off_entry;
      optee_vector_isn_t cpu_resume_entry;
      optee_vector_isn_t cpu_suspend_entry;
      optee_vector_isn_t fiq_entry;
      optee_vector_isn_t system_off_entry;
      optee_vector_isn_t system_reset_entry;
   } optee_vectors_t;
   optee_vectors represent the various entry points into TEE OS.

Variables defined by opensbi

   optee_vectors_t *optee_vector_table;
   struct sbi_save_context nsec_cpu_context[OPTEED_CORE_COUNT];
   struct sbi_save_context sec_cpu_context[OPTEED_CORE_COUNT];
   struct sbi_trap_regs cpu_start_context[OPTEED_CORE_COUNT];
   typedef ulong tee_tmp_trap_stack[1024];
   static tee_tmp_trap_stack tmp_stack[OPTEED_CORE_COUNT];

   optee_vector_table value is assigned after the TEE OS boot succeeds.
   nsec_cpu_context and sec_cpu_context is to save the context of TEE and REE,
   cpu_start_context save the context of opensbi before tee_os_init enter TEE OS,
   tee_tmp_stack is the trap stack when TEE OS return tee_os_init.

Quoted 3 lines

Under the current design, REE does not enable interrupts when
entering TEE, and the entire TEE, including opensbi, is the process context of linux. TEE processing must be brief and quick.

Looks like you do have some write-up for your proof-of-concept implementation which is good but we can look at your patches only after we have discussed your SBI OPTEE proposal.

I suggest you should create a textual/adoc description as if you are writing a chapter for
https://github.com/riscv-non-isa/riscv-sbi-doc/blob/master/riscv-sbi.a
doc

After you have this textual/adoc writeup for SBI OPTEE, we can discuss this in the Platform runtime services (PRS) or Trusted computing SIG meeting.

Your patches can be reviewed only after there is enough agreement on your SBI OPTEE proposal.

Regards,
Anup

Quoted 72 lines

Regards,
liushiwei
-----????-----
???: Himanshu Chauhan [mailto:hchauhan at ventanamicro.com] ????: 2023?1?11? 23:39
???: liushiwei <[email protected]>
??: opensbi at lists.infradead.org; chenchaokai at eswincomputing.com ??: Re: ??: [PATCH 1/1] Add RISC-V TEE support

Quoted 8 lines · liushiwei

Do you mean hardware? Our hardware design referred to arm's
trustzone technology. optee os is a software solution using arm
trustzone hardware, which mainly includes REE(linux), TEE(optee
os), ATF(ARM Trusted firmware), and then our software also
developed these three parts. opensbi is similar to ATF. whether if this is what you want? The current committed code is not hardware-dependent, but just
continues the idea of this workaround, and we may commit hardware-dependent code later.

No, I meant the software specification.

Quoted 36 lines

-----????-----
???: hchauhan at ventanamicro.com [mailto:hchauhan at ventanamicro.com] ????: 2023?1?11? 20:03
???: 'liushiwei' <[email protected]>; opensbi at lists.infradead. org
??: chenchaokai at eswincomputing.com
??: RE: [PATCH 1/1] Add RISC-V TEE support

-----Original Message-----

Quoted 5 lines

From: opensbi <[email protected]> On Behalf Of liushiwei
Sent: 11 January 2023 07:32
To: opensbi at lists.infradead.org
Cc: chenchaokai at eswincomputing.com; liushiwei

<[email protected]>

Quoted 4 lines

Subject: [PATCH 1/1] Add RISC-V TEE support

RISC-V Trusted Executable Environment security software includes linux,

opensbi, and OP-TEE OS. linux is the non-secure domain, and OP-TEE
OS is the secure domain. At boot time, opensbi boots OP->TEE OS and then starts linux. At runtime, opensbi acts as a secure monitor, responsible for
context saving and restoring when switching between linux and OP-TEE OS.

Quoted 2 lines

TEE function is off by default, when using configuration is added in the

config and objects file, such as platform/generic/configs/defconfig
add CONFIG_SBI_ECALL_TEE = y, In the >platform/generic/objects.mk add CONFIG_TEE_LOAD_ADDR = 0x27c000000, CONFIG_TEE_LOAD_ADDR is the starting address of the OP-TEE OS.

Hi Liushiwei,

Was there any formal specification or draft for this? Could you please point me to the draft or specification?

Quoted 8 lines

Regards
Himanshu

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