[sui-system] minimum staking threshold of 1 SUI (#9961)

## Description 

Took over the work @dmitri-perelman started (and almost finished) in
#9825 because I can't push to his fork of the repo.

## Test Plan 

Added some tests.

---
If your changes are not user-facing and not a breaking change, you can
skip the following section. Otherwise, please indicate what changed, and
then add to the Release Notes section as highlighted during the release
process.

### Type of Change (Check all that apply)

- [x] user-visible impact
- [ ] breaking change for a client SDKs
- [ ] breaking change for FNs (FN binary must upgrade)
- [ ] breaking change for validators or node operators (must upgrade
binaries)
- [ ] breaking change for on-chain data layout
- [ ] necessitate either a data wipe or data migration

### Release notes

---------

Co-authored-by: Dmitri Perelman <[email protected]>

Author: emmazzz

crates/sui-config/tests/snapshots/snapshot_tests__populated_genesis_snapshot_matches-2.snap

@@ -240,56 +240,56 @@ validators:
         next_epoch_worker_address: ~
         extra_fields:
           id:
-            id: "0xf64a2f2782984f7b7a36a99c9d77a83b3b6b5ebecf6ee0eaf118a37d74925c00"
+            id: "0x5e311ba6292362f225da9c71cf52097ca86b95fe6f4863a88c8e34a262a01193"
           size: 0
       voting_power: 10000
-      operation_cap_id: "0x62a99cd4412cb992da5a1035d6021db91e041704625a4010af68d1b0100a3177"
+      operation_cap_id: "0x669f5c0b0ca9066ace330aba5135ea3d5bbfdd4da5733574d0c596c8787d92de"
       gas_price: 1
       staking_pool:
-        id: "0xa110faecebe16b6d167929f7ee40acb2c8c1341eb80c5a24e92fe8dc1cd85015"
+        id: "0x2a6e996bd69665ad4b2e880c60ec497fb38ca17cc282264222f5ba00ea5d25c8"
         activation_epoch: 0
         deactivation_epoch: ~
         sui_balance: 20000000000000000
         rewards_pool:
           value: 0
         pool_token_balance: 20000000000000000
         exchange_rates:
-          id: "0x77dbaaae503d2664c5e6dfdd01d0bc46b1edf85fc927be9ece5cfd5f0c7a48ef"
+          id: "0x34c71362a7bfbbd2f2e1ddc116e22834185f8e84635dd819e5432b35bca560aa"
           size: 1
         pending_stake: 0
         pending_total_sui_withdraw: 0
         pending_pool_token_withdraw: 0
         extra_fields:
           id:
-            id: "0x4898c94bc523d09495c8f9f0947785a3d27e6fbc904c7aa13f48bd90b3032ac7"
+            id: "0x9540bb52b6eb64682154ab9f190069b2f65408326ca1cde6879bcd22f41ea436"
           size: 0
       commission_rate: 0
       next_epoch_stake: 20000000000000000
       next_epoch_gas_price: 1
       next_epoch_commission_rate: 0
       extra_fields:
         id:
-          id: "0x6daf7eb399ff05a5c2567b7bbb125c9451433af8b425904ab54debbdd28b38df"
+          id: "0x32da93ecef6352085e4a98e8fdc6ef53f58a87867735e5963e2862da4ca7ebf4"
         size: 0
   pending_active_validators:
     contents:
-      id: "0x66748b0af8b5eb3e9414d0fd7b424031ec634dc036b8a7a16d17b59e48c514f4"
+      id: "0x2c9d0fce0e485143215ddf9b3bad49a90faaa08abbe603d6268064e0fa11de63"
       size: 0
   pending_removals: []
   staking_pool_mappings:
-    id: "0x8091ccc40b81fafe63c18b385bef35ca34f86dc8ce03b14a5c5bd2ecc764dfcc"
+    id: "0x0e8b457d90c99717d5deafde80d2e6c2c930ededf359d0dde79488fae9d2c70d"
     size: 1
   inactive_validators:
-    id: "0xd2427484e7572464744d5ac7805d36e083ab262fef2f8c8cb16e4bf80eeba28e"
+    id: "0xe5e4e20e15059e13633058858aa474a3d50e647ba500b6ab2eab85a1ffd31ac2"
     size: 0
   validator_candidates:
-    id: "0x575efc4d1aa2dac9276de776fe85bab09f1dcde06481d19309094b460d4666d5"
+    id: "0xc7bb461afa1ee2ca919443255525031ccf3dfafd6aabca790053afffaef11258"
     size: 0
   at_risk_validators:
     contents: []
   extra_fields:
     id:
-      id: "0x341985f35823807fb3acf0a34c0b8bf152b355c3638dca24a3222701324eafe7"
+      id: "0x89b6475302daabe7d012b2f70b706551cbe84e6c4f23ae4713e472af36bcb239"
     size: 0
 storage_fund:
   total_object_storage_rebates:
@@ -306,7 +306,7 @@ parameters:
   validator_low_stake_grace_period: 7
   extra_fields:
     id:
-      id: "0xfcfc2dd968cefbf2e4d4679d06ac311ad5eb58fc4ea7d2e988eec89b8e1ec85f"
+      id: "0xa95d9ca79ae9361d0fa0086c09d61818a4c95926d4ff8873af54fa7c3d033288"
     size: 0
 reference_gas_price: 1
 validator_report_records:
@@ -320,7 +320,7 @@ stake_subsidy:
   stake_subsidy_decrease_rate: 10000
   extra_fields:
     id:
-      id: "0x08d8bb5dcbae6e7e0cff0ba0aa23ec8998794cb8e465dd0db6c45cf84752b25b"
+      id: "0x7590e21a4280f3e5b567da3338e491df195f724b7f908e6cf543717dbbaf3040"
     size: 0
 safe_mode: false
 safe_mode_storage_rewards:
@@ -332,6 +332,6 @@ safe_mode_non_refundable_storage_fee: 0
 epoch_start_timestamp_ms: 10
 extra_fields:
   id:
-    id: "0x1f79bdc6d1399738cc06184895e2bc41c76b3c06ddb3d3ece4549f45bf0de724"
+    id: "0x139f148cc3a7ad72f792389ed8d63875c594fbd59bd7c65a6c4bb01c1a28be49"
   size: 0
 

crates/sui-framework/docs/staking_pool.md

@@ -343,6 +343,15 @@ A self-custodial object holding the staked SUI tokens.
 
 
 
+<a name="0x3_staking_pool_EStakedSuiBelowThreshold"></a>
+
+
+
+<pre><code><b>const</b> <a href="staking_pool.md#0x3_staking_pool_EStakedSuiBelowThreshold">EStakedSuiBelowThreshold</a>: u64 = 18;
+</code></pre>
+
+
+
 <a name="0x3_staking_pool_ETokenBalancesDoNotMatchExchangeRate"></a>
 
 
@@ -397,6 +406,16 @@ A self-custodial object holding the staked SUI tokens.
 
 
 
+<a name="0x3_staking_pool_MIN_STAKING_THRESHOLD"></a>
+
+StakedSui objects cannot be split to below this amount.
+
+
+<pre><code><b>const</b> <a href="staking_pool.md#0x3_staking_pool_MIN_STAKING_THRESHOLD">MIN_STAKING_THRESHOLD</a>: u64 = 1000000000;
+</code></pre>
+
+
+
 <a name="0x3_staking_pool_new"></a>
 
 ## Function `new`
@@ -1049,7 +1068,7 @@ Split the given StakedSui to the two parts, one with principal <code>split_amoun
 transfer the newly split part to the sender address.
 
 
-<pre><code><b>public</b> entry <b>fun</b> <a href="staking_pool.md#0x3_staking_pool_split_staked_sui">split_staked_sui</a>(c: &<b>mut</b> <a href="staking_pool.md#0x3_staking_pool_StakedSui">staking_pool::StakedSui</a>, split_amount: u64, ctx: &<b>mut</b> <a href="_TxContext">tx_context::TxContext</a>)
+<pre><code><b>public</b> entry <b>fun</b> <a href="staking_pool.md#0x3_staking_pool_split_staked_sui">split_staked_sui</a>(stake: &<b>mut</b> <a href="staking_pool.md#0x3_staking_pool_StakedSui">staking_pool::StakedSui</a>, split_amount: u64, ctx: &<b>mut</b> <a href="_TxContext">tx_context::TxContext</a>)
 </code></pre>
 
 
@@ -1058,8 +1077,14 @@ transfer the newly split part to the sender address.
 <summary>Implementation</summary>
 
 
-<pre><code><b>public</b> entry <b>fun</b> <a href="staking_pool.md#0x3_staking_pool_split_staked_sui">split_staked_sui</a>(c: &<b>mut</b> <a href="staking_pool.md#0x3_staking_pool_StakedSui">StakedSui</a>, split_amount: u64, ctx: &<b>mut</b> TxContext) {
-    <a href="_transfer">transfer::transfer</a>(<a href="staking_pool.md#0x3_staking_pool_split">split</a>(c, split_amount, ctx), <a href="_sender">tx_context::sender</a>(ctx));
+<pre><code><b>public</b> entry <b>fun</b> <a href="staking_pool.md#0x3_staking_pool_split_staked_sui">split_staked_sui</a>(stake: &<b>mut</b> <a href="staking_pool.md#0x3_staking_pool_StakedSui">StakedSui</a>, split_amount: u64, ctx: &<b>mut</b> TxContext) {
+    <b>let</b> original_amount = <a href="_value">balance::value</a>(&stake.principal);
+    <b>assert</b>!(split_amount &lt;= original_amount, <a href="staking_pool.md#0x3_staking_pool_EInsufficientSuiTokenBalance">EInsufficientSuiTokenBalance</a>);
+    <b>let</b> remaining_amount = original_amount - split_amount;
+    // Both resulting parts should have at least <a href="staking_pool.md#0x3_staking_pool_MIN_STAKING_THRESHOLD">MIN_STAKING_THRESHOLD</a>.
+    <b>assert</b>!(remaining_amount &gt;= <a href="staking_pool.md#0x3_staking_pool_MIN_STAKING_THRESHOLD">MIN_STAKING_THRESHOLD</a>, <a href="staking_pool.md#0x3_staking_pool_EStakedSuiBelowThreshold">EStakedSuiBelowThreshold</a>);
+    <b>assert</b>!(split_amount &gt;= <a href="staking_pool.md#0x3_staking_pool_MIN_STAKING_THRESHOLD">MIN_STAKING_THRESHOLD</a>, <a href="staking_pool.md#0x3_staking_pool_EStakedSuiBelowThreshold">EStakedSuiBelowThreshold</a>);
+    <a href="_transfer">transfer::transfer</a>(<a href="staking_pool.md#0x3_staking_pool_split">split</a>(stake, split_amount, ctx), <a href="_sender">tx_context::sender</a>(ctx));
 }
 </code></pre>
 

crates/sui-framework/docs/validator_set.md

@@ -351,6 +351,15 @@ The epoch value corresponds to the first epoch this change takes place.
 ## Constants
 
 
+<a name="0x3_validator_set_MIN_STAKING_THRESHOLD"></a>
+
+
+
+<pre><code><b>const</b> <a href="validator_set.md#0x3_validator_set_MIN_STAKING_THRESHOLD">MIN_STAKING_THRESHOLD</a>: u64 = 1000000000;
+</code></pre>
+
+
+
 <a name="0x3_validator_set_EInvalidCap"></a>
 
 
@@ -477,6 +486,15 @@ The epoch value corresponds to the first epoch this change takes place.
 
 
 
+<a name="0x3_validator_set_EStakingBelowThreshold"></a>
+
+
+
+<pre><code><b>const</b> <a href="validator_set.md#0x3_validator_set_EStakingBelowThreshold">EStakingBelowThreshold</a>: u64 = 10;
+</code></pre>
+
+
+
 <a name="0x3_validator_set_EValidatorNotCandidate"></a>
 
 
@@ -743,6 +761,7 @@ Only an active validator can request to be removed.
 Called by <code><a href="sui_system.md#0x3_sui_system">sui_system</a></code>, to add a new stake to the validator.
 This request is added to the validator's staking pool's pending stake entries, processed at the end
 of the epoch.
+Aborts in case the staking amount is smaller than MIN_STAKING_THRESHOLD
 
 
 <pre><code><b>public</b>(<b>friend</b>) <b>fun</b> <a href="validator_set.md#0x3_validator_set_request_add_stake">request_add_stake</a>(self: &<b>mut</b> <a href="validator_set.md#0x3_validator_set_ValidatorSet">validator_set::ValidatorSet</a>, validator_address: <b>address</b>, stake: <a href="_Balance">balance::Balance</a>&lt;<a href="_SUI">sui::SUI</a>&gt;, ctx: &<b>mut</b> <a href="_TxContext">tx_context::TxContext</a>)
@@ -760,6 +779,8 @@ of the epoch.
     stake: Balance&lt;SUI&gt;,
     ctx: &<b>mut</b> TxContext,
 ) {
+    <b>let</b> sui_amount = <a href="_value">balance::value</a>(&stake);
+    <b>assert</b>!(sui_amount &gt;= <a href="validator_set.md#0x3_validator_set_MIN_STAKING_THRESHOLD">MIN_STAKING_THRESHOLD</a>, <a href="validator_set.md#0x3_validator_set_EStakingBelowThreshold">EStakingBelowThreshold</a>);
     <b>let</b> <a href="validator.md#0x3_validator">validator</a> = <a href="validator_set.md#0x3_validator_set_get_candidate_or_active_validator_mut">get_candidate_or_active_validator_mut</a>(self, validator_address);
     <a href="validator.md#0x3_validator_request_add_stake">validator::request_add_stake</a>(<a href="validator.md#0x3_validator">validator</a>, stake, <a href="_sender">tx_context::sender</a>(ctx), ctx);
 }

crates/sui-framework/packages/sui-system/sources/staking_pool.move

@@ -17,6 +17,9 @@ module sui_system::staking_pool {
     friend sui_system::validator;
     friend sui_system::validator_set;
 
+    /// StakedSui objects cannot be split to below this amount.
+    const MIN_STAKING_THRESHOLD: u64 = 1_000_000_000; // 1 SUI
+
     const EInsufficientPoolTokenBalance: u64 = 0;
     const EWrongPool: u64 = 1;
     const EWithdrawAmountCannotBeZero: u64 = 2;
@@ -35,6 +38,7 @@ module sui_system::staking_pool {
     const EPoolNotPreactive: u64 = 15;
     const EActivationOfInactivePool: u64 = 16;
     const EDelegationOfZeroSui: u64 = 17;
+    const EStakedSuiBelowThreshold: u64 = 18;
 
     /// A staking pool embedded in each validator struct in the system state object.
     struct StakingPool has key, store {
@@ -342,8 +346,14 @@ module sui_system::staking_pool {
 
     /// Split the given StakedSui to the two parts, one with principal `split_amount`,
     /// transfer the newly split part to the sender address.
-    public entry fun split_staked_sui(c: &mut StakedSui, split_amount: u64, ctx: &mut TxContext) {
-        transfer::transfer(split(c, split_amount, ctx), tx_context::sender(ctx));
+    public entry fun split_staked_sui(stake: &mut StakedSui, split_amount: u64, ctx: &mut TxContext) {
+        let original_amount = balance::value(&stake.principal);
+        assert!(split_amount <= original_amount, EInsufficientSuiTokenBalance);
+        let remaining_amount = original_amount - split_amount;
+        // Both resulting parts should have at least MIN_STAKING_THRESHOLD.
+        assert!(remaining_amount >= MIN_STAKING_THRESHOLD, EStakedSuiBelowThreshold);
+        assert!(split_amount >= MIN_STAKING_THRESHOLD, EStakedSuiBelowThreshold);
+        transfer::transfer(split(stake, split_amount, ctx), tx_context::sender(ctx));
     }
 
     /// Consume the staked sui `other` and add its value to `self`.

crates/sui-framework/packages/sui-system/sources/validator_set.move

@@ -108,6 +108,7 @@ module sui_system::validator_set {
     const ANY_VALIDATOR: u8 = 3;
 
     const BASIS_POINT_DENOMINATOR: u128 = 10000;
+    const MIN_STAKING_THRESHOLD: u64 = 1_000_000_000; // 1 SUI
 
     // Errors
     const ENonValidatorInReportRecords: u64 = 0;
@@ -120,7 +121,7 @@ module sui_system::validator_set {
     const EValidatorNotCandidate: u64 = 7;
     const ENotValidatorCandidate: u64 = 8;
     const ENotActiveOrPendingValidator: u64 = 9;
-
+    const EStakingBelowThreshold: u64 = 10;
     const EInvalidCap: u64 = 101;
 
 
@@ -265,12 +266,15 @@ module sui_system::validator_set {
     /// Called by `sui_system`, to add a new stake to the validator.
     /// This request is added to the validator's staking pool's pending stake entries, processed at the end
     /// of the epoch.
+    /// Aborts in case the staking amount is smaller than MIN_STAKING_THRESHOLD
     public(friend) fun request_add_stake(
         self: &mut ValidatorSet,
         validator_address: address,
         stake: Balance<SUI>,
         ctx: &mut TxContext,
     ) {
+        let sui_amount = balance::value(&stake);
+        assert!(sui_amount >= MIN_STAKING_THRESHOLD, EStakingBelowThreshold);
         let validator = get_candidate_or_active_validator_mut(self, validator_address);
         validator::request_add_stake(validator, stake, tx_context::sender(ctx), ctx);
     }