executor.c File Reference

Implements platform-specific memory management for JIT code and execution. More...

#include "common/infix_internals.h"
#include "common/utility.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdint.h>

Include dependency graph for executor.c:

This graph shows which files directly or indirectly include this file:

Go to the source code of this file.

Functions
static int	shm_open_anonymous ()
c23_nodiscard infix_executable_t	infix_executable_alloc (size_t size)
	Allocates a block of executable memory using the platform's W^X strategy.
void	infix_executable_free (infix_executable_t exec)
	Frees a block of executable memory and applies guard pages to prevent use-after-free.
c23_nodiscard bool	infix_executable_make_executable (infix_executable_t exec)
	Makes a block of JIT memory executable, completing the W^X process.
c23_nodiscard infix_protected_t	infix_protected_alloc (size_t size)
	Allocates a block of standard memory for later protection.
void	infix_protected_free (infix_protected_t prot)
	Frees a block of protected memory.
c23_nodiscard bool	infix_protected_make_readonly (infix_protected_t prot)
	Makes a block of memory read-only for security hardening.
void	infix_internal_dispatch_callback_fn_impl (infix_reverse_t *context, void *return_value_ptr, void **args_array)
	The universal C entry point for all reverse call trampolines.

Detailed Description

Implements platform-specific memory management for JIT code and execution.

Copyright (c) 2025 Sanko Robinson

This source code is dual-licensed under the Artistic License 2.0 or the MIT License. You may choose to use this code under the terms of either license.

SPDX-License-Identifier: (Artistic-2.0 OR MIT)

The documentation blocks within this file are licensed under the Creative Commons Attribution 4.0 International License (CC BY 4.0).

SPDX-License-Identifier: CC-BY-4.0

This module serves as the critical OS abstraction layer for the JIT engine. Its primary responsibilities are:

1. Executable Memory Management: It allocates, protects, and frees executable memory in a way that is secure and compliant with modern OS security features like W^X (Write XOR Execute). It implements different strategies (single- vs. dual-mapping) depending on the platform's capabilities and security model.
2. Security Hardening: It provides mechanisms to make memory regions read-only, which is used to protect the infix_reverse_t context from runtime memory corruption. It also implements "guard pages" on freed memory to immediately catch use-after-free bugs.
3. Universal Dispatch: It contains the infix_internal_dispatch_callback_fn_impl, the universal C entry point that is the final target of all reverse trampoline stubs. This function is the bridge between the low-level JIT code and the high-level user-provided C handlers.

Function Documentation

infix_executable_alloc()

c23_nodiscard infix_executable_t infix_executable_alloc

(

size_t

size

)

Allocates a block of executable memory using the platform's W^X strategy.

Located in src/jit/executor.c. This is a platform-specific function that abstracts VirtualAlloc, mmap with MAP_JIT, or shm_open with dual-mapping.

Parameters

size	The number of bytes to allocate.

Returns

An infix_executable_t handle containing pointers to the allocated memory.

infix_executable_free()

void infix_executable_free

(

infix_executable_t

exec

)

Frees a block of executable memory and applies guard pages to prevent use-after-free.

Located in src/jit/executor.c. Before freeing, it attempts to change the memory's protection to be inaccessible, causing an immediate crash on a UAF.

Parameters

exec	The handle to the memory block to free.

infix_executable_make_executable()

c23_nodiscard bool infix_executable_make_executable

(

infix_executable_t

exec

)

Makes a block of JIT memory executable, completing the W^X process.

Located in src/jit/executor.c. For single-map platforms, this calls VirtualProtect or mprotect. For dual-map platforms, this is a no-op. It also handles instruction cache flushing on relevant architectures like AArch64.

Parameters

exec	The handle to the memory block to make executable.

Returns

true on success, false on failure.

infix_internal_dispatch_callback_fn_impl()

void infix_internal_dispatch_callback_fn_impl	(	infix_reverse_t *	context,
		void *	return_value_ptr,
		void **	args_array
	)

The universal C entry point for all reverse call trampolines.

Located in src/jit/executor.c, this function is called by the JIT-compiled stub. It receives the marshalled arguments and dispatches the call to either the type-safe callback (via a cached forward trampoline) or the generic closure handler.

Parameters

[in]	context	The infix_reverse_t context for this call.
[out]	return_value_ptr	A pointer to the stack buffer for the return value.
[in]	args_array	A pointer to the void** array of argument pointers.

infix_protected_alloc()

c23_nodiscard infix_protected_t infix_protected_alloc

(

size_t

size

)

Allocates a block of standard memory for later protection.

Located in src/jit/executor.c. This is used to allocate the memory for an infix_reverse_t context before it is made read-only.

Parameters

size	The number of bytes to allocate.

Returns

An infix_protected_t handle.

infix_protected_free()

void infix_protected_free

(

infix_protected_t

prot

)

Frees a block of protected memory.

Located in src/jit/executor.c.

Parameters

prot	The memory block to free.

infix_protected_make_readonly()

c23_nodiscard bool infix_protected_make_readonly

(

infix_protected_t

prot

)

Makes a block of memory read-only for security hardening.

Located in src/jit/executor.c. This is called on the infix_reverse_t context after it has been fully initialized.

Parameters

prot	The memory block to make read-only.

Returns

true on success, false on failure.

shm_open_anonymous()

static int shm_open_anonymous ( )

static