Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit ccb1ce32 authored by Jiyong Park's avatar Jiyong Park Committed by Gerrit Code Review
Browse files

Merge "Enhance documentation about SetMmapRndBitsAction"

parents 2d79c6c0 5b16ccb3

init/security.cpp

+10 −3
Original line number Diff line number Diff line
@@ -90,7 +90,7 @@ static bool SetMmapRndBitsMin(int start, int min, bool compat) { 


// Set /proc/sys/vm/mmap_rnd_bits and potentially

// /proc/sys/vm/mmap_rnd_compat_bits to the maximum supported values.

// Returns -1 if unable to set these to an acceptable value.

// Returns an error if unable to set these to an acceptable value.

//

// To support this sysctl, the following upstream commits are needed:

//
@@ -106,12 +106,19 @@ Result<void> SetMmapRndBitsAction(const BuiltinArguments&) { 
    // uml does not support mmap_rnd_bits

    return {};

#elif defined(__aarch64__)

    // arm64 supports 18 - 33 bits depending on pagesize and VA_SIZE

    // arm64 architecture supports 18 - 33 rnd bits depending on pagesize and

    // VA_SIZE. However the kernel might have been compiled with a narrower

    // range using CONFIG_ARCH_MMAP_RND_BITS_MIN/MAX. To use the maximum

    // supported number of bits, we start from the theoretical maximum of 33

    // bits and try smaller values until we reach 24 bits which is the

    // Android-specific minimum. Don't go lower even if the configured maximum

    // is smaller than 24.

    if (SetMmapRndBitsMin(33, 24, false) && (!Has32BitAbi() || SetMmapRndBitsMin(16, 16, true))) {

        return {};

    }

#elif defined(__x86_64__)

    // x86_64 supports 28 - 32 bits

    // x86_64 supports 28 - 32 rnd bits, but Android wants to ensure that the

    // theoretical maximum of 32 bits is always supported and used.

    if (SetMmapRndBitsMin(32, 32, false) && (!Has32BitAbi() || SetMmapRndBitsMin(16, 16, true))) {

        return {};

    }