tree 5607e39182d7e8d94c7b1b232b9e2fa316b93b33
parent 957d6d513e543699afa0af6219968a59e4ac228f
author Lalit Maganti <lalitm@google.com> 1629989210 +0100
committer Lalit Maganti <lalitm@google.com> 1632936807 +0100

bionic: fix broken end atrace events

When calling write on an FD for trace_marker, it is expected that the
pointer passed will be paged into memory. If this isn't the case, the
kernel will ignore the string passed and instead write "<faulted>" to
the ring buffer.

For end events, we were passing a constant string which resides in
the rodata section of the ELF file. If this section is paged out, we
end up not closing atrace stacks correctly leading to very broken traces.

For even more context, see the associated bug.

Fix this issue by reading the constant string to the stack first
which should mean the string is always paged in.

Bug: 197620214
Change-Id: I6a444ac6fe83a6a9fb696c5621e392eca7e9437a