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Date: Wed, 15 Feb 2023 09:43:10 +0000
To: "cygwin AT cygwin DOT com" <cygwin AT cygwin DOT com>,
        "cygwin-developers AT cygwin DOT com" <cygwin-developers AT cygwin DOT com>
Subject: Re: Why do these mprotect always fail?
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From: w6b7rk5yu4mt25v3 via Cygwin <cygwin AT cygwin DOT com>
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Almost forgot, PAGE_SIZE is set to 4096. This is a Linux application, when I compile on Cygwin it complained that PAGE_SIZE is redefined but the compilation was success nevertheless. Only when I run the application, I always exited with "Unable to mprotect".

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------- Original Message -------
On Wednesday, February 15th, 2023 at 16:38, w6b7rk5yu4mt25v3 <w6b7rk5yu4mt25v3 AT protonmail DOT com> wrote:


> mprotect 1:
> 
> unsigned char* buffer;
> int32_t available, size;
> 
> if(size > PAGE_SIZE) {
> 
> factor = size / PAGE_SIZE + 1;
> }
> available = factor * PAGE_SIZE;
> 
> if(posix_memalign((void**)&buffer, PAGE_SIZE, available)) {
> std::wcerr << L"Unable to allocate JIT memory!" << std::endl;
> exit(1);
> }
> if(mprotect(buffer, available, PROT_READ | PROT_WRITE | PROT_EXEC) < 0) {
> std::wcerr << L"Unable to mprotect" << std::endl;
> exit(1);
> }
> 
> mprotect 2:
> 
> if(posix_memalign((void**)& buffer, PAGE_SIZE, PAGE_SIZE)) {
> std::wcerr << L"Unable to allocate JIT memory!" << std::endl;
> exit(1);
> }
> 
> if(mprotect(buffer, PAGE_SIZE, PROT_READ | PROT_WRITE | PROT_EXEC) < 0) {
> std::wcerr << L"Unable to mprotect" << std::endl;
> exit(1);
> }
> 
> 
> Sent with Proton Mail secure email.

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