1) Add PtraceConnection which serves as the base class for specific
types of connections Crashpad uses to trace processes.
2) Add DirectPtraceConnection which is used when the handler process
has `ptrace` capabilities for the target process.
3) Move `ptrace` logic into Ptracer. This class isolates `ptrace` call
logic for use by various PtraceConnection implementations.
Bug: crashpad:30
Change-Id: I98083134a9f7d9f085e4cc816d2b85ffd6d73162
Reviewed-on: https://chromium-review.googlesource.com/671659
Commit-Queue: Joshua Peraza <jperaza@chromium.org>
Reviewed-by: Mark Mentovai <mark@chromium.org>
Reviewed-by: Leonard Mosescu <mosescu@chromium.org>
Linux supports TLS on x86 by allocating slots in the GDT, accessible
via the system calls get/set_thread_area. This allows segment
registers (%gs on x86) to be used to quickly access the TLS.
Previously, we used PTRACE_GETREGSET with the NT_386_TLS regset. This
"register set" provides access to the subarray of the GDT used for TLS.
However, there are multiple slots provided and we don't know which one
is being used by the threading library for the current thread's TLS.
Previously, we were just using the first one, which worked for x86 on
64-bit kernels, but not 32-bit kernels. On 32-bit kernels, the first
slot ended up pointing to the TLS of the main thread.
The authoritative index of the current thread's TLS in the GDT is
given by bits 3-15 of %gs. However, this index cannot be used with
PTRACE_GETREGSET+NT386_TLS because we don't know the location of the
TLS slots in the GDT. PTRACE_GET_THREAD_AREA, however, accepts an
index from the start of the GDT similarly to get/set_thread_area.
Bug: crashpad:30
Change-Id: Ie6dfbdd088c6816fad409812a1a97037d4b38fd7
Reviewed-on: https://chromium-review.googlesource.com/575318
Reviewed-by: Mark Mentovai <mark@chromium.org>
ThreadInfo provides a uniform interface to collect register sets or
the thread-local storage address across bitness for x86 and ARM family
architectures. Additionally, ThreadInfo.h defines context structs which
mirror those provided in sys/user.h. This allows tracing across bitness
as the structs in sys/user.h are only provided for a single target
architecture.
Bug: crashpad:30
Change-Id: I91d0d788927bdac5fb630a6ad3c6ea6d3645ef8a
Reviewed-on: https://chromium-review.googlesource.com/494075
Commit-Queue: Joshua Peraza <jperaza@chromium.org>
Reviewed-by: Mark Mentovai <mark@chromium.org>
