Add doc page on sysvar accounts (#13237)

* Add doc page on sysvar accounts

* Update with suggestions

docs/sidebars.js

@@ -70,6 +70,7 @@ module.exports = {
       "apps/jsonrpc-api",
       "apps/javascript-api",
       "apps/builtins",
+      "apps/sysvars",
     ],
     "Integrating": ["integrations/exchange"],
     "Validating": [

docs/src/apps/sysvars.md

@@ -0,0 +1,90 @@
+---
+title: Sysvar Cluster Data
+---
+
+Solana exposes a variety of cluster state data to programs via
+[`sysvar`](terminology.md#sysvar) accounts. These accounts are populated at
+known addresses published along with the account layouts in the
+[`solana-sdk`](https://docs.rs/solana-sdk/VERSION_FOR_DOCS_RS/solana_sdk/sysvar/index.html),
+and outlined below.
+
+To include sysvar data in program operations, pass the sysvar account address in
+the list of accounts in a transaction. The account can be read in your
+instruction processor like any other account. Access to sysvars is always
+*readonly*.
+
+## Clock
+
+The Clock sysvar contains data on cluster time, including the current slot,
+epoch, and estimated wall-clock Unix timestamp. It is updated every slot.
+
+- Address: `SysvarC1ock11111111111111111111111111111111`
+- Layout: [Clock](https://docs.rs/solana-sdk/VERSION_FOR_DOCS_RS/solana_sdk/sysvar/clock/struct.Clock.html)
+
+## EpochSchedule
+
+The EpochSchedule sysvar contains epoch scheduling constants that are set in
+genesis, and enables calculating the number of slots in a given epoch, the epoch
+for a given slot, etc. (Note: the epoch schedule is distinct from the
+[`leader schedule`](terminology.md#leader-schedule))
+
+- Address: `SysvarEpochSchedu1e111111111111111111111111`
+- Layout: [EpochSchedule](https://docs.rs/solana-sdk/VERSION_FOR_DOCS_RS/solana_sdk/sysvar/epoch_schedule/struct.EpochSchedule.html)
+
+## Fees
+
+The Fees sysvar contains the fee calculator for the current slot. It is updated
+every slot, based on the fee-rate governor.
+
+- Address: `SysvarFees111111111111111111111111111111111`
+- Layout: [Fees](https://docs.rs/solana-sdk/VERSION_FOR_DOCS_RS/solana_sdk/sysvar/fees/struct.Fees.html)
+
+## Instructions
+
+The Instructions sysvar contains the serialized instructions in a Message while
+that Message is being processed. This allows program instructions to reference
+other instructions in the same transaction. Read more information on
+[instruction introspection](implemented-proposals/instruction_introspection.md).
+
+- Address: `Sysvar1nstructions1111111111111111111111111`
+- Layout: [Instructions](https://docs.rs/solana-sdk/VERSION_FOR_DOCS_RS/solana_sdk/sysvar/instructions/type.Instructions.html)
+
+## RecentBlockhashes
+
+The RecentBlockhashes sysvar contains the active recent blockhashes as well as
+their associated fee calculators. It is updated every slot.
+
+- Address: `SysvarRecentB1ockHashes11111111111111111111`
+- Layout: [RecentBlockhashes](https://docs.rs/solana-sdk/VERSION_FOR_DOCS_RS/solana_sdk/sysvar/recent_blockhashes/struct.RecentBlockhashes.html)
+
+## Rent
+
+The Rent sysvar contains the rental rate. Currently, the rate is static and set
+in genesis. The Rent burn percentage is modified by manual feature activation.
+
+- Address: `SysvarRent111111111111111111111111111111111`
+- Layout: [Rent](https://docs.rs/solana-sdk/VERSION_FOR_DOCS_RS/solana_sdk/sysvar/rent/struct.Rent.html)
+
+## SlotHashes
+
+The SlotHashes sysvar contains the most recent hashes of the slot's parent
+banks. It is updated every slot.
+
+- Address: `SysvarS1otHashes111111111111111111111111111`
+- Layout: [SlotHashes](https://docs.rs/solana-sdk/VERSION_FOR_DOCS_RS/solana_sdk/sysvar/slot_hashes/struct.SlotHashes.html)
+
+## SlotHistory
+
+The SlotHistory sysvar contains a bitvector of slots present over the last
+epoch. It is updated every slot.
+
+- Address: `SysvarS1otHistory11111111111111111111111111`
+- Layout: [SlotHistory](https://docs.rs/solana-sdk/VERSION_FOR_DOCS_RS/solana_sdk/sysvar/slot_history/struct.SlotHistory.html)
+
+## StakeHistory
+
+The StakeHistory sysvar contains the history of cluster-wide stake activations
+and de-activations per epoch. It is updated at the start of every epoch.
+
+- Address: `SysvarStakeHistory1111111111111111111111111`
+- Layout: [StakeHistory](https://docs.rs/solana-sdk/VERSION_FOR_DOCS_RS/solana_sdk/sysvar/stake_history/struct.StakeHistory.html)