malloc command

Synopsis

malloc info
malloc dump
malloc log [start|stop]

Description

The malloc command shows information about the malloc heap.

info

Shows memory-allocation statistics, including the total heap size, the amount currently in use, and call counts for malloc(), free(), and realloc().

dump

Walks the heap and prints each chunk’s address, size (in hex), and status. In-use chunks show no status label, while free chunks show <free>. Special entries show (chunk header), top, or end. This is useful for debugging memory allocation issues. When CONFIG_MCHECK_HEAP_PROTECTION is enabled, the caller string is also shown if available.

log

Controls the malloc traffic log. With no argument, dumps the recorded log entries. Use start to begin recording malloc/free/realloc calls, and stop to stop recording. Each entry shows the operation type, pointer address, size, and caller backtrace. This is useful for tracking down memory leaks or understanding allocation patterns.

The total heap size is set by CONFIG_SYS_MALLOC_LEN.

Example

=> malloc info
total bytes   = 96 MiB
in use bytes  = 700.9 KiB
malloc count  = 1234
free count    = 567
realloc count = 89

=> malloc dump
Heap dump: 19a0e000 - 1fa10000
     Address        Size  Status
----------------------------------
    19a0e000          10  (chunk header)
    19a0e010          a0
    19a0e0b0        6070
    19adfc30          60  <free>
    19adff90     5f3f030  top
    1fa10000              end
----------------------------------
Used: c2ef0 bytes in 931 chunks
Free: 5f3f0c0 bytes in 2 chunks + top

With CONFIG_MCHECK_HEAP_PROTECTION enabled, the caller backtrace is shown:

=> malloc dump
Heap dump: 18a1d000 - 1ea1f000
     Address        Size  Status
----------------------------------
    18a1d000          10  (chunk header)
    18a1d010          90  used  log_init:453 <-board_init_r:774
    18a1d0a0        6060  used  membuf_new:420 <-console_record
    18a3b840          90  used  of_alias_scan:911 <-board_init_
    ...

With CONFIG_CMD_MALLOC_LOG enabled, the log subcommand is available:

=> malloc log start
Malloc logging started
=> ... do some operations ...
=> malloc log stop
Malloc logging stopped
=> malloc log
Malloc log: 5 entries (max 524288, total 5)
 Seq  Type                   Ptr      Size  Caller
----  --------  ----------------  --------  ------
   0  alloc             16a01b90        20  hush_file_init:3277
              <-parse_file_outer:3295 <-run_pipe_real:1986
   1  alloc             16a01bc0       100  xmalloc:107 <-xzalloc:117
              <-new_pipe:1498 <-run_list_real:1702
   2  free              16a01bc0         0  free_pipe_list:2001
              <-parse_stream_outer:3208 <-parse_file_outer:3300
   ...

Configuration

The malloc command is enabled by CONFIG_CMD_MALLOC which depends on CONFIG_MALLOC_DEBUG. The log subcommand is enabled by CONFIG_CMD_MALLOC_LOG which additionally requires CONFIG_MCHECK_LOG.

Return value

The return value $? is 0 (true) on success, 1 (false) on failure.