tree ac3ac3e0e62e7df44d232b91a7e95ced2c8248d6
parent c949b5f8e83df73166dd8c9eb5edffba93e02992
author Daniele Di Proietto <ddiproietto@google.com> 1638458237 +0000
committer Daniele Di Proietto <ddiproietto@google.com> 1638784435 +0000

Accept non zero-terminated strings in ftrace fields

ReadIntoString() fails if strings are not null terminated.

There are three cases in which ReadIntoString() is called:

1. For fixed fields declared as:

  ```
          field:char newcomm[16]; offset:28;      size:16;        signed:1;
  ```
  the max length of the string is bounded by the fixed size.

2. For variable length fields declared at the end of an event:

  ```
          field:char buf[];       offset:16;      size:0; signed:1;
  ```
  the max length of the buffer is bounded by the event size.

3. For __data_loc fields:

  ```
          field:__data_loc char[] name;   offset:16;      size:4; signed:1;
  ```
  each field has an offset and a size. The max length of the string is
  bounded by the fixed size.

In some rare cases, e.g., if this kernel commit is missing:

`f0a515780393("tracing: Don't make assumptions about length of string on task rename")`

the kernel can output a buffer that's not zero-terminated (e.g. for case
1)

In all cases, the string size is limited explicitly. The code should
still stop copying when it finds the '\0' terminator, but, if it doesn't
find that, it could still copy what's there. There's no risk of going
out of bounds, so this commit stops complaining (and eventually hitting
a PERFETTO_CHECK), if strings are not null terminated.

Bug: 205763418
Change-Id: I2159ecbc4dd42d31f54613efa5e77c9d7eca09fb