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Support OP-TEE dynamic shared memory #714

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16 changes: 15 additions & 1 deletion litebox_common_optee/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2025,7 +2025,7 @@ impl From<&OpteeSmcArgsPage> for OpteeSmcArgs {
/// OP-TEE SMC call arguments.
#[derive(Clone, Copy, Default, FromBytes)]
pub struct OpteeSmcArgs {
args: [usize; Self::NUM_OPTEE_SMC_ARGS],
pub args: [usize; Self::NUM_OPTEE_SMC_ARGS],
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@sangho2 sangho2 Mar 12, 2026

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does it require pub?

}

impl OpteeSmcArgs {
Expand All @@ -2050,6 +2050,19 @@ impl OpteeSmcArgs {
}
}

/// Get the shared memory reference and offset for the physical address of `OpteeMsgArgs`.
pub fn optee_regd_shm_ref_and_offset(&self) -> Result<(u64, usize), OpteeSmcReturnCode> {
// args[1]:args[2] contains the shared memory reference (pointer)
// and args[3] contains the offset within that shared memory.
if self.args[1] & 0xffff_ffff_0000_0000 == 0 && self.args[2] & 0xffff_ffff_0000_0000 == 0 {
let shm_ref = (self.args[1] << 32) | self.args[2];
let offset = self.args[3];
Ok((shm_ref as u64, offset))
} else {
Err(OpteeSmcReturnCode::EBadAddr)
}
}

/// Set the return code of an OP-TEE SMC call
pub fn set_return_code(&mut self, code: OpteeSmcReturnCode) {
self.args[0] = code as usize;
Expand Down Expand Up @@ -2121,6 +2134,7 @@ pub enum OpteeSmcResult<'a> {
CallWithArg {
msg_args: Box<OpteeMsgArgs>,
rpc_args: Option<Box<OpteeRpcArgs>>,
msg_args_phys_addr: u64,
},
}

Expand Down
5 changes: 1 addition & 4 deletions litebox_runner_lvbs/src/lib.rs
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Expand Up @@ -417,17 +417,14 @@ fn optee_smc_handler(smc_args_addr: usize) -> OpteeSmcArgs {
let Ok(mut smc_args) = (unsafe { smc_args_ptr.read_at_offset(0) }) else {
return make_error_response(OpteeSmcReturnCode::EBadAddr);
};
let Ok(msg_args_phys_addr) = smc_args.optee_msg_args_phys_addr() else {
smc_args.set_return_code(OpteeSmcReturnCode::EBadAddr);
return *smc_args;
};
let Ok(smc_result) = handle_optee_smc_args(&mut smc_args) else {
smc_args.set_return_code(OpteeSmcReturnCode::EBadCmd);
return *smc_args;
};
if let OpteeSmcResult::CallWithArg {
msg_args,
rpc_args: _,
msg_args_phys_addr,
} = smc_result
{
let mut msg_args = *msg_args;
Expand Down
29 changes: 27 additions & 2 deletions litebox_shim_optee/src/msg_handler.rs
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Expand Up @@ -185,13 +185,38 @@ pub fn handle_optee_smc_args(
Ok(OpteeSmcResult::CallWithArg {
msg_args,
rpc_args: None,
msg_args_phys_addr: msg_args_addr as u64,
})
}
OpteeSmcFunction::CallWithRpcArg | OpteeSmcFunction::CallWithRegdArg => {
OpteeSmcFunction::CallWithRpcArg => {
let msg_args_addr = smc.optee_msg_args_phys_addr()?;
let msg_args_addr: usize = msg_args_addr.truncate();
let (msg_args, rpc_args) = read_optee_msg_args_from_phys(msg_args_addr, true)?;
Ok(OpteeSmcResult::CallWithArg { msg_args, rpc_args })
Ok(OpteeSmcResult::CallWithArg {
msg_args,
rpc_args,
msg_args_phys_addr: msg_args_addr as u64,
})
}
OpteeSmcFunction::CallWithRegdArg => {
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@praveen-pk praveen-pk Mar 12, 2026

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just curios, when is this method invoked?

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@athvu athvu Mar 12, 2026

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On the VTL0 side, the optee_smc_do_call_with_arg() function will pass OPTEE_SMC_CALL_WITH_REGD_ARG if the tee shared memory was dynamically allocated

// `OpteeMsgArgs` is located at the offset specified in args[3] within the shared memory region pointed by args[1]:args[2].
let (shm_ref, offset) = smc.optee_regd_shm_ref_and_offset()?;
let shm_info = shm_ref_map()
.get(shm_ref)
.ok_or(OpteeSmcReturnCode::EBadAddr)?;
let page_index = (shm_info.page_offset + offset) / PAGE_SIZE;
let offset_in_page = (shm_info.page_offset + offset) % PAGE_SIZE;
Comment on lines +207 to +208
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@sangho2 sangho2 Mar 12, 2026

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it might better to do shm_info.page_offset.checked_add(offset).ok_or(OpteeSmcReturnCode::EBadAddr)?; to deal with potential integer overflow attacks. Also, we don't have to compute this twice.

if page_index >= shm_info.page_addrs.len() {
return Err(OpteeSmcReturnCode::EBadAddr);
}
let msg_args_addr = shm_info.page_addrs[page_index].as_usize() + offset_in_page;

let (msg_args, rpc_args) = read_optee_msg_args_from_phys(msg_args_addr, true)?;
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@praveen-pk praveen-pk Mar 12, 2026

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LiteBox has read_data_from_shm which reads from offset 0. Could you add another method to read with an offset and use that method here?

Ok(OpteeSmcResult::CallWithArg {
msg_args,
rpc_args,
msg_args_phys_addr: msg_args_addr as u64,
})
}
OpteeSmcFunction::ExchangeCapabilities => {
// TODO: update the below when we support more features
Expand Down
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