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The exception table for CMOs comes from CTSRD-CHERI/cheri-specification#65.
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@sorear
sorear committed Feb 2, 2024
1 parent 296c904 commit 3d77127
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3 changes: 2 additions & 1 deletion src/insns/cgetlen_32bit.adoc
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Expand Up @@ -19,7 +19,8 @@ Calculate the length of `cs1` 's bounds and write the result in `rd`. The length
is defined as the difference between the decoded bounds' top and base addresses
i.e. `top - base`. It is not required that the input capability `cs1` has its
tag set to 1. <<CGETLEN>> outputs 0 if `cs1` 's bounds are malformed (see
xref:section_cap_malformed[xrefstyle=short]).
xref:section_cap_malformed[xrefstyle=short]), and 2^XLENMAX^-1 if the length of
`cs1` is 2^XLENMAX^.
Prerequisites::
{cheri_base_ext_name}
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5 changes: 3 additions & 2 deletions src/insns/cjalr_jalr_32bit.adoc
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Expand Up @@ -32,8 +32,9 @@ include::wavedrom/ct-unconditional-2.adoc[]

Capability Mode Description::
CJALR allows unconditional, indirect jumps to a target capability. The
target capability is obtained by unsealing `cs1` and incrementing its address by the
sign-extended 12-bit immediate, and then setting the least-significant bit of the
target capability is obtained by unsealing `cs1` if the immediate is zero and
incrementing its address by the sign-extended 12-bit immediate otherwise,
and then setting the least-significant bit of the
result to zero. The target capability may have
xref:section_invalid_addr_conv[xrefstyle=short]
performed and is then installed in <<pcc>>. The <<pcc>>
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52 changes: 31 additions & 21 deletions src/riscv-integration.adoc
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Expand Up @@ -86,7 +86,7 @@ tag is set and 0 otherwise
permission fields of the input capability
* <<CGETBASE>>: outputs the expanded base address of the input capability
* <<CGETLEN>>: outputs the length of the input capability. Length is defined as
`top - base`. The output is 2^XLEN^-1 when the capability's length is
`top - base`. The output is 2^XLENMAX^-1 when the capability's length is
2^XLENMAX^
* <<CRAM>>: outputs the nearest bounds alignment that a valid capability can
represent
Expand Down Expand Up @@ -243,16 +243,18 @@ The capability jump and link register (<<CJALR>>) instruction replaces the jump
and link register (<<JALR>>) instruction at the same encoding. This instruction
allows unconditional jumps to a target capability. The target capability is
obtained by incrementing the capability in the *c* register operand by the
sign-extended 12-bit immediate, then setting the least significant bit of the
result to zero. The capability with the address of the instruction following
the jump (<<pcc>> + 4) is written to a *c* register.
sign-extended 12-bit immediate if the immediate is not zero, then setting the
least significant bit of the result to zero, then unsealing. The capability
with the address of the instruction following the jump (<<pcc>> + 4) is sealed
and written to a *c* register.

All jumps cause CHERI exceptions when a minimum sized instruction
at the target address is not within the bounds of the <<pcc>>.

<<CJALR>> causes a CHERI exception when:

* The target capability's tag is zero
* The target capability is sealed and the immediate is not zero
* A minimum sized instruction at the target capability's address is not
within bounds
* The target capability does not grant execute permission
Expand Down Expand Up @@ -1020,7 +1022,7 @@ xref:mtval-cheri-causes[xrefstyle=short] respectively.
=== Unprivileged CSRs

Unlike machine and supervisor level CSRs, {cheri_base_ext_name} does not require
<<pcc>> to grant <<asr_perm>> to access privileged CSRs.
<<pcc>> to grant <<asr_perm>> to access unprivileged CSRs.

[#pcc,reftext="pcc"]
==== Program Counter Capability (pcc)
Expand Down Expand Up @@ -1057,32 +1059,39 @@ NOTE: `auth_cap` is <<ddc>> for Legacy mode and `cs1` for Capability Mode
6+| *CSR/Xret additional exception check*
| CSR*, <<MRET>>, <<SRET>> | {cheri_excep_mcause} | {cheri_excep_type_pcc} | {cheri_excep_cause_perm} | <<pcc>> permission | not(<<pcc>>.<<asr_perm>>) when required for CSR access or execution of <<MRET>>/<<SRET>>
6+| *direct jumps additional exception check*
| <<CJAL>>, <<JAL>>, <<insns-conbr-32bit>> | {cheri_excep_mcause} | {cheri_excep_type_jump} | {cheri_excep_cause_length} | <<pcc>> length | any byte of 16-bit instruction at target out of <<pcc>> bounds
6+| *indirect jumps and conditional branches additional exception checks*
| indirect jumps and conditional branches | {cheri_excep_mcause} | {cheri_excep_type_jump} | {cheri_excep_cause_tag} |`cs1` tag | not(`cs1.tag`)
| indirect jumps and conditional branches | {cheri_excep_mcause} | {cheri_excep_type_jump} | {cheri_excep_cause_seal} |`cs1` seal | isCapSealed(`cs1`)
| indirect jumps and conditional branches | {cheri_excep_mcause} | {cheri_excep_type_jump} | {cheri_excep_cause_perm} |`cs1` permission| not(`cs1`.<<x_perm>>)
| indirect jumps and conditional branches | {cheri_excep_mcause} | {cheri_excep_type_jump} | {cheri_excep_cause_length} |`cs1` length | any byte of 16-bit instruction at target out of `cs1` bounds
| <<CJAL>>, <<JAL>>, <<insns-conbr-32bit>> | {cheri_excep_mcause} | {cheri_excep_type_jump} | {cheri_excep_cause_length} | <<pcc>> length | any byte of minimum length instruction at target out of <<pcc>> bounds
6+| *indirect jumps additional exception checks*
| indirect jumps | {cheri_excep_mcause} | {cheri_excep_type_jump} | {cheri_excep_cause_tag} |`cs1` tag | not(`cs1.tag`)
| indirect jumps | {cheri_excep_mcause} | {cheri_excep_type_jump} | {cheri_excep_cause_seal} |`cs1` seal | isCapSealed(`cs1`) and imm12 != 0
| indirect jumps | {cheri_excep_mcause} | {cheri_excep_type_jump} | {cheri_excep_cause_perm} |`cs1` permission| not(`cs1`.<<x_perm>>)
| indirect jumps | {cheri_excep_mcause} | {cheri_excep_type_jump} | {cheri_excep_cause_length} |`cs1` length | any byte of minimum length instruction at target out of `cs1` bounds
6+| *Load additional exception checks*
| all loads | {cheri_excep_mcause} | {cheri_excep_type_data} | {cheri_excep_cause_tag} | `auth_cap` tag | not(`auth_cap.tag`)
| all loads | {cheri_excep_mcause} | {cheri_excep_type_data} | {cheri_excep_cause_seal} | `auth_cap` seal | isCapSealed(`auth_cap`)
| all loads | {cheri_excep_mcause} | {cheri_excep_type_data} | {cheri_excep_cause_perm} | `auth_cap` permission | not(`auth_cap`.<<r_perm>>)
| all loads | {cheri_excep_mcause} | {cheri_excep_type_data} | {cheri_excep_cause_length} | `auth_cap` length | Any byte of load access out of `auth_cap` bounds
| capability loads | 4 | N/A | N/A | load address misaligned | Misaligned capability load
6+| *Store/atomic/cache-block-operation additional exception checks*
| all stores, all atomics, all cbos | {cheri_excep_mcause} | {cheri_excep_type_data} | {cheri_excep_cause_tag} |`auth_cap` tag | not(`auth_cap.tag`)
| all stores, all atomics, all cbos | {cheri_excep_mcause} | {cheri_excep_type_data} | {cheri_excep_cause_seal} |`auth_cap` seal | isCapSealed(`auth_cap`)
| all atomics, all cbos | {cheri_excep_mcause} | {cheri_excep_type_data} | {cheri_excep_cause_perm} |`auth_cap` permission | AMO only: not(`auth_cap`.<<r_perm>>)
| all stores, all atomics, all cbos | {cheri_excep_mcause} | {cheri_excep_type_data} | {cheri_excep_cause_perm} |`auth_cap` permission | not(auto_cap.<<w_perm>>)
| all stores, all atomics | {cheri_excep_mcause} | {cheri_excep_type_data} | {cheri_excep_cause_length} |`auth_cap` length | any byte of access^1^ out of `auth_cap` bounds
| capability stores, all atomics |6 | N/A | N/A |Misaligned store/AMO| Misaligned capability store or AMO
| all stores, all atomics, all cbos | {cheri_excep_mcause} | {cheri_excep_type_data} | {cheri_excep_cause_tag} |`auth_cap` tag | not(`auth_cap.tag`)
| all stores, all atomics, all cbos | {cheri_excep_mcause} | {cheri_excep_type_data} | {cheri_excep_cause_seal} |`auth_cap` seal | isCapSealed(`auth_cap`)
| all atomics, CBO.INVAL* | {cheri_excep_mcause} | {cheri_excep_type_data} | {cheri_excep_cause_perm} |`auth_cap` permission | not(`auth_cap`.<<r_perm>>)
| all stores, all atomics, CBO.INVAL*, CBO.ZERO* | {cheri_excep_mcause} | {cheri_excep_type_data} | {cheri_excep_cause_perm} |`auth_cap` permission | not(`auth_cap`.<<w_perm>>)
| CBO.CLEAN*, CBO.FLUSH* | {cheri_excep_mcause} | {cheri_excep_type_data} | {cheri_excep_cause_perm} |`auth_cap` permission | not(`auth_cap`.<<r_perm>>) and not(`auth_cap`.<<w_perm>>)
| all stores, all atomics | {cheri_excep_mcause} | {cheri_excep_type_data} | {cheri_excep_cause_length} |`auth_cap` length | any byte of access out of `auth_cap` bounds
| CBO.ZERO*, CBO.INVAL* | {cheri_excep_mcause} | {cheri_excep_type_data} | {cheri_excep_cause_length} |`auth_cap` length | any byte of cache block out of `auth_cap` bounds
| CBO.CLEAN*, CBO.FLUSH* | {cheri_excep_mcause} | {cheri_excep_type_data} | {cheri_excep_cause_length} |`auth_cap` length | all bytes of cache block out of `auth_cap` bounds
| CBO.INVAL* | {cheri_excep_mcause} | {cheri_excep_type_pcc} | {cheri_excep_cause_perm} |<<pcc>> permission | not(<<pcc>>.<<asr_perm>>)
| capability stores | 6 | N/A | N/A |capability alignment | Misaligned capability store
|=========================================================================================

NOTE: Indirect branches are <<CJALR>>, <<JALR>>, <<JALR.PCC>>, <<JALR.CAP>>, conditional branches are <<insns-conbr-32bit>>.

NOTE: <<CBO.ZERO.CAP>>, <<CBO.ZERO>> issues as a cache line wide store

NOTE: ^1^Other CBOs (<<CBO.FLUSH.CAP>>, <<CBO.FLUSH>>, <<CBO.CLEAN.CAP>>, <<CBO.CLEAN>>, <<CBO.INVAL.CAP>>, <<CBO.INVAL>>) require at least one byte of the access to be in `auth_cap` bounds
NOTE: <<CBO.ZERO.CAP>>, <<CBO.ZERO>> issues as a cache block wide store. All
CMOs operate on the cache block which contains the address. Prefetches check
that the capability is tagged, not sealed, has the permission (<<r_perm>>,
<<w_perm>>, <<x_perm>>) corresponding to the instruction, and has bounds which
include at least one byte of the cache block; if any check fails, the prefetch
is not performed but no exception is generated.

[#CHERI_SPEC,reftext="CHERI Exceptions and speculative execution"]
=== CHERI Exceptions and speculative execution
Expand All @@ -1098,7 +1107,8 @@ is desirable that harts supporting {cheri_base_ext_name} extend PMAs with a
_taggable_ attribute indicating whether a memory region allows storing tagged
data.

When the hart attempts to store or load data with the tag set to memory regions
Data loaded from memory regions that are not taggable will always have the tag
cleared. When the hart attempts to store data with the tag set to memory regions
that are not taggable, the implementation may:

* Cause an access fault exception
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