'.' function names exist only in ELFv1. ELFv2 does away with function
descriptors, and look more like they do on powerpc(32) and most other
platforms, as direct function pointers. Stop blacklisting regular function
names in ELFv2.
Submitted by: Brandon Bergren
Differential Revision: https://reviews.freebsd.org/D20346
The FBT fuction boundary prober was setting one return probe marker value,
but the dtrace handler was expecting another. This causes a hang when
tracing return probes.
With GNU ifuncs, multiple FBT probes may correspond to the same
instruction. fbt_invop() assumed that this could not happen and
would return after the first probe found in the global FBT hash
table, which might not be the one that's enabled. Fix the problem
on x86 by linking probes that share a tracepoint and having each
linked probe fire when the tracepoint is hit.
PR: 230846
Approved by: re (gjb)
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D16921
r314370 changed EXC_DTRACE to a different instruction, but neglected to
make the same change to fbt, so dtrace didn't actually pick it up,
resulting in entering KDB instead of trapping for dtrace.
MFC after: 1 week
This restriction was inherited from upstream but is not relevant on FreeBSD.
Furthermore, it hindered the tracing of locking primitive subroutines.
MFC after: 1 week
Currently this argument is a pointer into the stack which is used by FBT
to fetch the first five probe arguments. On all non-x86 architectures it's
simply the trapframe address, so this change has no functional impact. On
amd64 it's a pointer into the trapframe such that stack[1 .. 5] gives the
first five argument registers, which are deliberately grouped together in
the amd64 trapframe definition.
A trapframe argument simplifies the invop handlers on !x86 and makes the
x86 FBT invop handler easier to understand. Moreover, it allows for invop
handlers that may want to modify the register set of the interrupted thread.
* Use a constant to define the number of stack frames in a probe exception.
* Only allow function symbols in powerpc64 ('.' prefixed)
* Set the fbtp_roffset for return probes, so the correct dtrace_probe call is
made.
MFC after: 1 week
Summary:
Fix the stack tracing for dtrace/powerpc by using the trapexit/asttrapexit
return address sentinels instead of checking within the kernel address space.
As part of this, I had to add new inline functions. FBT traces the kernel, so
we have to have special case handling for this, since a trap will create a full
new trap frame, and there's no way to pass around the 'real' stack. I handle
this by special-casing 'aframes == 0' with the trap frame. If aframes counts
out to the trap frame, then assume we're looking for the full kernel trap frame,
so switch to the real stack pointer.
Test Plan: Tested on powerpc64
Reviewers: rpaulo, markj, nwhitehorn
Reviewed By: markj, nwhitehorn
Differential Revision: https://reviews.freebsd.org/D788
MFC after: 3 week
Relnotes: Yes
duplicating the entire implementation for both x86 and powerpc. This makes
it easier to add support for other architectures and has no functional
impact.
Phabric: D613
Reviewed by: gnn, jhibbits, rpaulo
Tested by: jhibbits (powerpc)
MFC after: 2 weeks
