This can be used to allow automatically handling structures that require
special behavior for one member but are automatically repackable otherwise.
The feature is enabled using the new custom_repack annotation and requires
additional repacking functions to be defined in the host file for each
customized member.
This behaves exactly like pidof but only searches for FEX applications.
This fixes a long standing annoyance of mine that pidof doesn't work for
FEX. This behaves exactly like pidof but knows how to decode the command
line options to pull out the program data.
If the Linux kernel ever accepts the patches for binfmt_misc to change
how the interpreter is handled then this will become redundant, but
until that happens here is a utility that I want.
cmpxchg handles rax specially, so cmpxchg with dest=rax is a special case. test
also the general case.
Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
To avoid performance traps, several conditions must hold for exit repacking
to apply:
* Argument must be a pointer
* The pointee type must have differing data layout between guest and host
* The pointee type must be non-const
Arguments that don't meet the first two conditions are safe *not* to repack
on exit, since they're either passed by copy or have consistent data layout.
The third condition is a heuristic: In principle, an API function could modify
data through nested pointers even if the argument pointer is const. However,
automatic repacking is not supported for such types anyway, so this is a safe
heuristic to use.
Primary goal for this is to ensure that the delinker doesn't need to
allocate any memory. This delinker can end up getting hit heavily with
JIT code so we don't want it to be allocating memory.
Currently all uses of the forward label calls in to jemalloc to allocate
memory. This allows a forward label that doesn't require any memory
allocation, which is the common case in FEX.
The delinker step of the JIT was using std::function with capture
lambdas that required memory allocation when unnecessary.
Because the compiler can't see through our std::function usage it could
never decompose these by itself.
By passing the Thread's frame and record to the function as arguments
then we can have the signature be a raw function pointer.
This fixes an area of concern from:
https://github.com/FEX-Emu/FEX/blob/main/docs/ProgrammingConcerns.md#stdfunction-and-lambdas
If the Dst register is allocated as VectorIndices or VectorTable,
using Dst as an operand to perform the tbx operation will result in an error.
For example:
%131(FPR0) i128 = LoadNamedVectorIndexedConstant u8:Tmp:RegisterSize, #0x6, #0xaa0
%132(FPR0) i128 = VTBX1 u8:Tmp:RegisterSize, %129(FPRFixed6) i32v4, %126(FPRFixed10) i16v8, %131(FPR0) i128
Since the tbx instruction's destination register is also the original operand,
this is consistent with the semantics of VTBX1. Therefore,
directly using VectorSrcDst as the destination operand for the tbx instruction is safe.
While locking a shared_lock and doing an empty table lookup is fairly
fast, just remove them from the hot path entirely if no custom IR
handlers are installed.
This is only used for our IRLoader, which is losing its importance
significantly and should probably be removed anyway.
Pointer types inherently cause data layout compatibility issues, so they're
worth special-casing here. The wrappers will type-pun pointers to 32-bit or
64-bit integers (matching the guest architecture) to avoid direct host-side
use of guest pointers without consideration.
The guest_layout wrapper provides an architecture-agnostic representation of
the guest data layout of each struct used in a thunked library. A constructor
is added to host_layout to allow conversion of the data to the host layout.
For types that are already fully compatible, both layout wrappers are simple
type aliases to minimize overhead.
