`tvOS`/`watchOS` compilation errors

[05nelsonm]

Trying to compile for watchOS and tvOS but keep running into the following errors related to usage of syscall

error: 'syscall' is unavailable: not available on tvOS
    if (syscall(SYS_getentropy, buf, n) == 0)
        ^

note: 'syscall' has been explicitly marked unavailable here
int        syscall(int, ...);
           ^

Everything's working great though for iOS 👍

Seeing in the amalgamations that there is conditional arguments for macOS and iOS only. Would it be possible to also include tvOS and watchOS?

[utelle]

Trying to compile for watchOS and tvOS but keep running into the following errors related to usage of syscall

error: 'syscall' is unavailable: not available on tvOS
    if (syscall(SYS_getentropy, buf, n) == 0)
        ^

note: 'syscall' has been explicitly marked unavailable here
int        syscall(int, ...);
           ^

Everything's working great though for iOS 👍

Seeing in the amalgamations that there is conditional arguments for macOS and iOS only. Would it be possible to also include tvOS and watchOS?

In principle, it should be possible to include tvOS and watchOS. However, I have currently no means to test this myself.

The error you're receiving results from compiling the code in source file chacha20poly1305.c:

static size_t entropy(void* buf, size_t n)
{
#if defined(__APPLE__) && defined(__MAC_10_12) && __MAC_OS_X_VERSION_MAX_ALLOWED >= __MAC_10_12
  if (getentropy(buf, n) == 0)
    return n;
#elif defined(__linux__) && defined(SYS_getrandom)
  if (syscall(SYS_getrandom, buf, n, 0) == n)
    return n;
#elif defined(SYS_getentropy)
  if (syscall(SYS_getentropy, buf, n) == 0)
    return n;
#endif
  return read_urandom(buf, n);
}

Interestingly, the symbol SYS_getentropy seems to be defined for tvOS and watchOS, although the function syscall is not available, and therefore you get a compile time error.

As far as I know the function getentropy is available for tvOS and watchOS. However, at the moment I don't know how to check for tvOS or watchOS via the C preprocessor, so that function getentropy will be used.

[utelle]

Could you please test to change the code for function entropy as follows:

1. Add include for Apple target conditionals (3 lines)
2. Add check for tvOS and watchOS

#if defined(__APPLE__)
#include "TargetConditionals.h"
#endif

static size_t entropy(void* buf, size_t n)
{
#if defined(__APPLE__) && ((defined(__MAC_10_12) && __MAC_OS_X_VERSION_MAX_ALLOWED >= __MAC_10_12) || TARGET_OS_TV || TARGET_OS_WATCH)
  if (getentropy(buf, n) == 0)
    return n;
#elif defined(__linux__) && defined(SYS_getrandom)
  if (syscall(SYS_getrandom, buf, n, 0) == n)
    return n;
#elif defined(SYS_getentropy)
  if (syscall(SYS_getentropy, buf, n) == 0)
    return n;
#endif
  return read_urandom(buf, n);
}

If that works for you please let me know.

[05nelsonm]

Had a few compilation errors

• tvOS and watchOS

  implicit declaration of function 'getentropy' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
    if (getentropy(buf, n) == 0
        ^
  

After adding the following compiler flags to suppress errors, everything built successfully for tvOS and watchOS:

• -Wno-implicit-function-declaration

The following Kotlin Multiplatform targets were compiled successfully:

• iosArm64
• iosSimulatorArm64
• iosX64
• tvosArm64
• tvosSimulatorArm64
• tvosX64
• watchosArm32
• watchosArm64
• watchosX64

My tests that exercised SQLite3MultipleCiphers for all ciphers, rekeying, etc. were run only for only the *X64 targets as I am on x86_64 machine, but I assume that the other architectures work just fine considering the added logic to entropy has nothing to do with architecture.

Have to figure out configuration yet to enable watchosSimulatorArm64, as it throws the following error during compilation:

overriding the module target triple with arm64-apple-watch7.0-simulator [-Woverride-module]

Adding compiler flag -Wno-override-module doesn't do anything, so.

[utelle]

Had a few compilation errors

* `tvOS` and `watchOS`

      implicit declaration of function 'getentropy' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
        if (getentropy(buf, n) == 0
            ^

After adding the following compiler flags to suppress errors, everything built successfully for tvOS and watchOS:

* `-Wno-implicit-function-declaration`

As an alternative you may add an explicit function declaration:

#if TARGET_OS_TV || TARGET_OS_WATCH
extern int getentropy(void* buffer, size_t buflen);
#endif
  if (getentropy(buf, n) == 0)

I will add these modifications in my SQLite3MultipleCiphers repository.

My tests that exercised SQLite3MultipleCiphers for all ciphers, rekeying, etc. were run only for the *X64 targets as I am on x86_64 machine, but I assume that the other architectures work just fine considering the added logic to entropy has nothing to do with architecture.

Right, the other architectures should not be affected.

Have to figure out configuration yet to enable watchosSimulatorArm64, as it throws the following error during compilation:

overriding the module target triple with arm64-apple-watch7.0-simulator [-Woverride-module]

Adding compiler flag -Wno-override-module doesn't do anything, so.

Which target triple is actually defined in your build script? Maybe just specifying the target triple mentioned in the error message in your build script helps, that is:

target triple = "arm64-apple-watch7.0-simulator"

[05nelsonm]

As an alternative you may add an explicit function declaration:

#if TARGET_OS_TV || TARGET_OS_WATCH
extern int getentropy(void* buffer, size_t buflen);
#endif
  if (getentropy(buf, n) == 0)

That worked in that the error suppression is no-longer necessary. 👍

I will add these modifications in my SQLite3MultipleCiphers repository.

🥳

Which target triple is actually defined in your build script? Maybe just specifying the target triple mentioned in the error message in your build script helps, that is:

target triple = "arm64-apple-watch7.0-simulator"

Yeah it's a little problematic as I'm using an older version of kotlin's llvm toolchain. It needs updating (see touchlab/cklib#11) in order to resolve this specific issue so I can add the watchosSimulatorArm64 target.

[utelle]

As an alternative you may add an explicit function declaration:

#if TARGET_OS_TV || TARGET_OS_WATCH
extern int getentropy(void* buffer, size_t buflen);
#endif
  if (getentropy(buf, n) == 0)

That worked in that the error suppression is no-longer necessary. 👍

I will add these modifications in my SQLite3MultipleCiphers repository.

In commit dd508dc I added the precompiler checks for tvOS and watchOS.

I also added the explicit function declaration for getentropy. However, maybe we could avoid that by including

#include <sys/random.h>

Could you please check whether this include is available for tvOS and watchOS? That is, check for tvOS and watchOS like this:

#if defined(__APPLE__) && ((defined(__MAC_10_12) && !defined(__IPHONE_OS_VERSION_MIN_REQUIRED)) || TARGET_OS_TV || TARGET_OS_WATCH)
#include <sys/random.h>
#endif

You have to move the include of the target conditionals in front of the above code:

#if defined(__APPLE__)
#include "TargetConditionals.h"
#endif

#if defined(__APPLE__) && ((defined(__MAC_10_12) && !defined(__IPHONE_OS_VERSION_MIN_REQUIRED)) || TARGET_OS_TV || TARGET_OS_WATCH)
#include <sys/random.h>
#endif

[05nelsonm]

TL;DR >> sys/random.h is available for iOS and tvOS, but not watchOS.

Was not available for watchosArm32, watchosArm64, watchosX64, and presumably watchosSimulatorArm64

fatal error: 'sys/random.h' file not found

I disabled those targets (all watchOS) and recompiled iOS and tvOS targets; everything worked (build, tests).

[utelle]

TL;DR >> sys/random.h is available for iOS and tvOS, but not watchOS.

According to Apple's documentation the function getentropy is available in watchOS. So, in which header file is it defined? Of course, we can define it explicitly (as is currently done), but it would be cleaner to include the correct header file, if it exists, that is.

Was not available for watchosArm32, watchosArm64, watchosX64, and presumably watchosSimulatorArm64

fatal error: 'sys/random.h' file not found

Well, I found this post that indicates that the function is not considered to be part of the public Apple API (contrary to the claim in Apple's documentation). However, it would not be the first flaw in Apple's documentation.

Maybe the function SecRandomCopyBytes could be used instead for tvOS and watchOS?

I disabled those targets (all watchOS) and recompiled iOS and tvOS targets; everything worked (build, tests).

I'm unsure about which approach should be used to support watchOS.

[05nelsonm]

Imo, just use SecRandomCopyBytes for all Apple targets.

https://github.com/KotlinCrypto/secure-random/blob/591ba1dbea955f1a4673cbf3189d8d11ad8fe8bf/secure-random/src/darwinMain/kotlin/org/kotlincrypto/internal/SecRandomDelegate.kt#L40

[utelle]

Imo, just use SecRandomCopyBytes for all Apple targets.

Ok. I'd be fine with that approach. However, I don't know whether this really works for all Apple OS variants or whether checking for certain targets and/or versions is still required. Maybe you could try the following code and report the results:

#if defined(__APPLE__)
#include "TargetConditionals.h"
#endif

#if defined(__APPLE__)
#include <Security/SecRandom.h>
#endif

static size_t entropy(void* buf, size_t n)
{
#if defined(__APPLE__)
  if (SecRandomCopyBytes(kSecRandomDefault, n, (uint8_t*) buf) == 0)
    return n;
#elif defined(__linux__) && defined(SYS_getrandom)
  if (syscall(SYS_getrandom, buf, n, 0) == n)
    return n;
#elif defined(SYS_getentropy)
  if (syscall(SYS_getentropy, buf, n) == 0)
    return n;
#endif
  return read_urandom(buf, n);
}

[05nelsonm]

I don't know whether this really works for all Apple OS variants or whether checking for certain targets and/or versions is still required

Oh it's available 😄

You could (if you so desired to support macOS 10.6 and below) fallback to using getentropy.

Rust for macOS just straight up defaults to getentropy; see HERE. All other apple products they use SecRandomCopyBytes.

Maybe you could try the following code and report the results:

Worked like a charm. Didn't even need the #include "TargetConditionals.h".

[05nelsonm]

Just realized that I am able to enable the watchosSimulatorArm64 target; my compiler issues went away entirely.

No clue what that was about, but it seems to have been something with the inclusion of TargetConditionals.h?

Just so we are on the same page, this is what my sqlite3mc_amalgamation.c was modified to:

#if defined(__APPLE__)
#include <Security/SecRandom.h>
#endif

static size_t entropy(void* buf, size_t n)
{
#if defined(__APPLE__)
  if (SecRandomCopyBytes(kSecRandomDefault, n, (uint8_t*) buf) == 0)
    return n;
#elif defined(__linux__) && defined(SYS_getrandom)
  if (syscall(SYS_getrandom, buf, n, 0) == n)
    return n;
#elif defined(SYS_getentropy)
  if (syscall(SYS_getentropy, buf, n) == 0)
    return n;
#endif
  return read_urandom(buf, n);
}

[05nelsonm]

Another aside about the linux implementation, unless this is being compiled against glibc 2.25 +, it will never use getrandom because SYS_getrandom isn't defined at compile time for the shared lib, right?

https://man7.org/linux/man-pages/man2/getrandom.2.html#HISTORY

Might be worth it to have an actual implementation to check for it where by SYS_getrandom is alternatively defined, and a simple non-blocking check for it is made once to see if it is present on the machine.

https://github.com/KotlinCrypto/secure-random/blob/master/secure-random/src/linuxAndroidMain/kotlin/org/kotlincrypto/internal/GetRandom.kt