V8 port for platform where code is in execute-only memory
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martin dobrev
May 26, 2021, 9:43:01 AM5/26/21
to v8-users
Hi,
Recently i ported v8 for unix base platform (architecture is x64) where all executable memory is "execute only" => each instruction which try to read from executable memory result in access violation. The problem is that some of the code generated by `torque` needs to read from the code segments . For example Math.floor defined this constant `TNode<Float64T> two_52 = Float64Constant(4503599627370496.0E0);`
later used in couple places in function implementation. And `torque` generate following assebly which result in crash, because instuction on '00000000F34A0909' try to read from the code segment.
Is there a way to force `torque` to generate immediate/direct mov instead of relative one for constants or maybe i can move them in data segments somehow ?
Recently i ported v8 for unix base platform (architecture is x64) where all executable memory is "execute only" => each instruction which try to read from executable memory result in access violation. The problem is that some of the code generated by `torque` needs to read from the code segments . For example Math.floor defined this constant `TNode<Float64T> two_52 = Float64Constant(4503599627370496.0E0);`
later used in couple places in function implementation. And `torque` generate following assebly which result in crash, because instuction on '00000000F34A0909' try to read from the code segment.
Is there a way to force `torque` to generate immediate/direct mov instead of relative one for constants or maybe i can move them in data segments somehow ?
Jakob Gruber
May 31, 2021, 1:46:43 AM5/31/21
to v8-u...@googlegroups.com
Yes, running with a non-readable .text section should work. Pass --no-partial-constant-pool to disable the mechanism you mentioned above.
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martin dobrev
May 31, 2021, 11:46:03 AM5/31/21
to v8-users
Looks like this do the job.
Thank you for the fast response.
Thank you for the fast response.
Clemens Backes
Jun 1, 2021, 8:11:49 AM6/1/21
to v8-u...@googlegroups.com
Note that WebAssembly far jump tables also read the target address from the code object (see JumpTableAssembler::EmitFarJumpSlot). There is no workaround for that, so if you want to support WebAssembly, you would have to change how the far jump table works on x64.
To view this discussion on the web visit https://groups.google.com/d/msgid/v8-users/9ec8f5b4-ac7c-4ad1-9a52-7d73819a84a7n%40googlegroups.com.
Clemens Backes
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martin dobrev
Jun 1, 2021, 8:28:29 AM6/1/21
to v8-users
Currently I don't need support for wasm.
But just in case I set `--no--expose_wasm` and `--jitless` flags.
Thank you for extra information!
But just in case I set `--no--expose_wasm` and `--jitless` flags.
Thank you for extra information!
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