使用Xcode 11编译时vm_protect调用失败问题求助

Let's break down why your vm_protect call works smoothly in Xcode 10 but fails in Xcode 11—even after adding entitlements and updating your signing certificate. Below are actionable, targeted steps to resolve this issue:

1. First, Confirm Section Data is Valid #

Before digging into permission issues, make sure getsectiondata is actually returning a valid address and size for your section. Add quick logging to validate this:

section_start = getsectiondata(&_mh_execute_header, "__TEXT", "__mysection", &section_size);
if (!section_start || section_size == 0) {
    os_log_error(my_logger, "Failed to retrieve valid section data");
    return false;
}
os_log_info(my_logger, "Section start: %p, size: %lu", section_start, section_size);

If section_start comes back as NULL, the problem isn't with vm_protect—you're either targeting the wrong section or the Mach-O header lookup is failing.

2. Ensure Entitlements Are Properly Embedded #

Even if you added the required entitlements, Xcode 11 might not be injecting them into your binary correctly. Verify this by running this command in Terminal:

codesign -d --entitlements - /path/to/your/app/binary

Check that com.apple.security.cs.disable-executable-page-protection is listed in the output. If not:

• Double-check that your entitlement file is selected in Build Settings > Code Signing Entitlements for your Debug configuration.
• Ensure Code Signing Inject Base Entitlements is set to YES in Build Settings.

3. Switch to the 64-Bit-Friendly mach_vm_protect API #

Xcode 11 uses an updated toolchain that enforces stricter checks on the older vm_protect API. Try replacing it with mach_vm_protect, which is the recommended API for 64-bit macOS systems:

kern_return_t ret = mach_vm_protect(
    mach_task_self(),
    (mach_vm_address_t)section_start,
    (mach_vm_size_t)section_size,
    FALSE,  // Set to FALSE to modify existing page protections
    VM_PROT_READ | VM_PROT_WRITE
);
if (ret != KERN_SUCCESS) {
    os_log_error(my_logger, "mach_vm_protect failed with error code: %d", ret);
    return false;
}

This API handles modern memory addressing more reliably, which often fixes compatibility issues with Xcode 11's toolchain.

4. Check Hardened Runtime Settings #

Xcode 11 enabled Hardened Runtime by default for many configurations—even Debug. Head to your target's Signing & Capabilities tab:

• If Hardened Runtime is enabled, make sure you've checked Disable Executable Memory Protection (this directly maps to the entitlement you added, but the UI toggle ensures proper configuration).
• Also, enable Disable Library Validation if your section modification interacts with external libraries.

5. Debug the Exact vm_protect Error Code #

Instead of a generic failure message, capture the specific return code from vm_protect to narrow down the issue:

• KERN_PROTECTION_FAILURE: The system blocked the permission change (likely an entitlement or runtime protection issue).
• KERN_INVALID_ADDRESS: Your section address or size is invalid (go back to step 1).
• KERN_INVALID_ARGUMENT: One of your parameters is malformed (check if section_size is 0 or section_start isn't page-aligned).

Logging this code will give you precise insight into what's blocking the call.

6. Verify Linker Flags for Section Attributes #

Xcode 11's linker may apply stricter default attributes to the __TEXT section. Check Build Settings > Other Linker Flags for flags like -Wl,-readonly_relocs,suppress that could lock down the section. If present, remove them for your Debug configuration.

I've seen similar cases where Xcode 11's hardened runtime and updated toolchain tightened memory protections even in Debug builds. Start with validating your section data and entitlement embedding, then switch to mach_vm_protect—that's usually the quick fix for this specific scenario.

内容的提问来源于stack exchange，提问作者MeirS