CHERI RISC-V Cheatsheet
The following is a Cheatsheet designed to ease development with CHERI RISC-V.
The Cheatsheet is best-effort and may be incomplete. If you notice a mistake or think a piece of information is missing, open a merge request with your proposal!
Registers
Register |
ABI Name |
Description |
Purecap Saver |
|---|---|---|---|
c0 |
cnull |
NULL Pointer |
|
c1 |
cra |
Return address |
Caller |
c2 |
csp |
Stack Pointer |
Callee |
c3 |
cgp |
Global Pointer |
|
c4 |
ctp |
Thread Pointer |
|
c5 |
ct0 |
Temporary/alternate link resgister |
Caller |
c6-7 |
ct1-2 |
Temporaries |
Caller |
c8 |
cs0/cfp |
Saved regsister/frame pointer |
Callee |
c9 |
cs1 |
Saved register |
Callee |
c110-11 |
ca0-1 |
Function arguments/return values |
Caller |
c12-17 |
ca2-7 |
Function arguments |
Caller |
c18-27 |
cs2-11 |
Saved Registers |
Callee |
c28-31 |
ct3-6 |
Temporaries |
Caller |
Capability Instructions
Capability length in imm: 16
(Pseudo) Instruction |
Semantics |
Comment |
|---|---|---|
auipcc cd, imm |
cd <= PCC with PCC.addr + (imm << 12) |
If imm is %[captab_]pcrel_hi(sym), equivalent to load high 20 bits of abs addr sym to cd |
cincoffset cd, cs1, rs2/imm |
cd <= cs1 with addr += rs2/imm |
|
cllc cd, sym |
cd <= PCC with addr to sym |
1: auipcc cd, %pcrel_hi(sym)<br>cincoffset cd, cd, %pcrel_lo(1b) |
clc cd, imm(cs1) |
cd <= Mem[cs1.addr + imm] |
Exception if cs1 sealed, no Permit_Load, cd invalidated without exception if cs1 no Permit_Load_Capability |
clgc cd, sym |
cd <= CapTable[sym] |
1: auipcc cd, %captab_pcrel_hi(sym)<br>clc cd, %pcrel_lo(1b)(cd) |
csc cs2, imm(cs1) |
Mem[cs1.addr + imm] <= cs2 |
Exception if cs1 unseal or no Permit_Store((_Local)_Capability) |
csetaddr cd, cs1, cs2 |
cd <= cs1 with cs2.addr |
Exception if cs1 is sealed |
csetbounds cd, cs1, rs2 |
cd <= cs1.addr as base and rs2 as length |
Exception if cs1 is sealed or has smaller length |
cjalr [cd,] cs1 |
cd <= next inst, PCC <= cs1 |
cd is cra if omitted, cd auto sealed, cs1 auto unsealed |
cret |
cjalr cnull, cra |
|
cseal cd, cs1, cs2 |
cd <= seal cs1 with cs2.addr |
|
cmove cd, cs1 |
cd <= cs1 |
Capability-Extended Data Instructions
(Pseudo) Instruction |
Semantics |
Comment |
|---|---|---|
cl{bhwd} rd, offset(cs) |
rd <- Mem[cs + offset] as signed |
|
cl{bhwd}u rd, offset(cs) |
rd <- Mem[cs + offset] as unsigned |
|
cs{bhwd} rs, offset(cds) |
Mem[cd + offset] <- rs |