The following table lists the instantiation parameters of the CHERIoT memory subsystem.
Theory of Operation.
| Parameter | Default | Top Earlgrey | Description |
|---|
addr_t | logic [top_pkg::TL_AW-1:0] | logic [31:0] | TL-UL address type. |
MainSramBaseAddr | 0x1000_0000 | 0x1000_0000 | Base address of the main SRAM region, inclusive. |
MainSramTopAddr | 0x1003_0000 | 0x1003_0000 | Top address of the main SRAM region, exclusive. |
NvmBaseAddr | 0x3000_0000 | 0x3000_0000 | Base address of the NVM region, inclusive. |
NvmTopAddr | 0x3020_0000 | 0x3020_0000 | Top address of the NVM region, exclusive. |
MetaSramBaseAddr | 0x1100_0000 | 0x1100_0000 | Base address of the unified meta SRAM. |
Referring to the Comportable guideline for peripheral device functionality, the module cheriot_mem_sys has the following hardware interfaces defined
- Primary Clock:
clk_i
- Other Clocks: none
- Bus Device Interfaces (TL-UL):
regs_tl_d, revbm_tl_d
- Bus Host Interfaces (TL-UL):
cored_tl_h, tbre_tl_h
- Peripheral Pins for Chip IO: none
| Port Name | Package::Struct | Type | Act | Width | Description |
|---|
| cheriot_ena | prim_mubi_pkg::mubi4 | uni | rcv | 1 | CHERIoT mode enable. |
| cored_tl_d | tlul_pkg::tl | req_rsp | rsp | 1 | Data port from the core. |
| cored_tag_h2d | logic | uni | rcv | 1 | CHERIoT capability tag carried with the A-channel of cored_tl_h. |
| cored_tag_d2h | logic | uni | req | 1 | Capability tag returned on the D-channel of cored_tl_h. |
| corerevbm_tl | tlul_pkg::tl | req_rsp | rsp | 1 | TRVK (tag revocation) revocation bitmap port from the core. |
| meta_sram_tl | tlul_pkg::tl | req_rsp | req | 1 | Host TL-UL port to the external meta SRAM controller’s RAM interface. |
| cored_tl_h | tlul_pkg::tl | req_rsp | req | 1 | |
| tbre_tl_h | tlul_pkg::tl | req_rsp | req | 1 | |
| regs_tl_d | tlul_pkg::tl | req_rsp | rsp | 1 | |
| revbm_tl_d | tlul_pkg::tl | req_rsp | rsp | 1 | |
| Interrupt Name | Type | Description |
|---|
| tbre_done | Event | Raised when the revocation engine has resolved every capability of a sweep. |
| Alert Name | Description |
|---|
| fatal_fault | This fatal alert is triggered when an integrity fault is detected, when the meta SRAM path returns a device error, when the revocation engine reports a fault, when a capability store to the NVM is partial, or when a request breaks the core’s capability store sequence. |
| Countermeasure ID | Description |
|---|
| CHERIOT_MEM_SYS.BUS.INTEGRITY | End-to-end bus integrity between the Ibex lockstep and the storage cells. Relies on LOGIC.SHADOW, which is not implemented yet. |
| CHERIOT_MEM_SYS.LOGIC.SHADOW | The CHERIoT memory subsystem is instantiated in lockstep. Not implemented yet. This also covers the pointers of the subsystem’s FIFOs, which therefore are not redundantly encoded (CTR.REDUN). |
| CHERIOT_MEM_SYS.MEM.SW_NOACCESS | The capability tag store is not memory mapped. |
| CHERIOT_MEM_SYS.INTERSIG.MUBI | The CHERIoT mode enable is multi-bit encoded. |