Enabled erase=noop in test_rbyd, changed read* to error on leb128 overflow

Now that reproducibility issues with erase_value=-1 (erase=noop) are
fixed, this much more useful to test than erase_value=0x1b. Especially
since erase=noop is filled with so many sharp corners.

These tests already found that we were being too confident with our
leb128/lleb128/tag parsing. Since we need to partially parse unfinished/
old commits, lfsr_dir_read* can easily encounter invalid leb128s during
normal operation. If this happens we should not assert.

Doing things correctly has a bit of a cost:

           code          stack
  before: 33928           2824
  after:  33976 (+0.1%)   2824 (+0.0%)

At least we haven't seen any issues with our valid bit invalidating
logic yet.

lfs.c

@@ -1075,7 +1075,9 @@ static lfs_ssize_t lfsr_bd_readtag_(lfs_t *lfs,
         return d_;
     }
     // weights should be limited to 31-bits
-    LFS_ASSERT(weight <= 0x7fffffff);
+    if (weight > 0x7fffffff) {
+        return LFS_ERR_CORRUPT;
+    }
     d += d_;
 
     lfs_size_t size;
@@ -1084,7 +1086,9 @@ static lfs_ssize_t lfsr_bd_readtag_(lfs_t *lfs,
         return d_;
     }
     // sizes should be limited to 28-bits
-    LFS_ASSERT(size <= 0x0fffffff);
+    if (size > 0x0fffffff) {
+        return LFS_ERR_CORRUPT;
+    }
     d += d_;
 
     // optional checksum
@@ -1405,7 +1409,9 @@ static int lfsr_data_readleb128(lfs_t *lfs, lfsr_data_t *data,
         return d;
     }
     // all leb128s in our system reserve the sign bit
-    LFS_ASSERT(*word_ <= 0x7fffffff);
+    if (*word_ > 0x7fffffff) {
+        return LFS_ERR_CORRUPT;
+    }
 
     *data = lfsr_data_slice(*data, d, -1);
     return 0;
@@ -1422,9 +1428,11 @@ static inline int lfsr_data_readlleb128(lfs_t *lfs, lfsr_data_t *data,
     if (err) {
         return err;
     }
-
     // little-leb128s should be limited to 28-bits
-    LFS_ASSERT(*word_ <= 0x0fffffff);
+    if (*word_ > 0x0fffffff) {
+        return LFS_ERR_CORRUPT;
+    }
+
     return 0;
 }
 

tests/test_rbyd.toml

@@ -2,7 +2,7 @@
 after = 'test_bd'
 
 # test with a number of different erase values
-defines.ERASE_VALUE = [0xff, 0x00, 0x1b]
+defines.ERASE_VALUE = [0xff, 0x00, -1]
 
 # set block_size to the full size of disk so we can test arbitrarily
 # large rbyd trees, we don't really care about block sizes at this