* Use the right incantation to get the next stack pointer. Since powerpc uses
special frames for traps, dereferencing the stack pointer straight up won't
get us the next stack pointer in every case.
* Clear EE using the correct instruction sequence. The PowerISA states that
'andi.' ANDs the register with 0||<imm>, instead of sign extending or filling
out the unavailable bits with 1. Even if it did sign extend, PSL_EE is
0x8000, so ~PSL_EE is 0x7fff, and the upper bits would be cleared. Use rlwinm
in the 32-bit case, and a two-rotate sequence in the 64-bit case, the latter
chosen to follow the output generated by gcc.
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
much of which is not necessary for PowerPC.
The FBT module can likely be factored into 3 separate files: common,
intel, and powerpc, rather than duplicating most of the code between
the x86 and PowerPC flavors.
All DTrace modules for PowerPC will be MFC'd together once Fasttrap is
completed.
There is one known issue: Some probes will display an error message along the
lines of: "Invalid address (0)"
I tested this with both a simple dtrace probe and dtruss on a few different
binaries on 32-bit. I only compiled 64-bit, did not run it, but I don't expect
problems without the modules loaded. Volunteers are welcome.
MFC after: 1 month
