Shim wishlist

[saethlin]

I run Miri on the most-downloaded crates, with the flags -Zmiri-panic-on-unsupported and --no-fail-fast which basically asks Miri to try to run as many tests as it can. Searching all my build logs, I find these are the most-encountered can't call foreign function: errors:

117310 counts
(  1)    16419 (14.0%, 14.0%): socket
(  2)     7934 ( 6.8%, 20.8%): TLS_method
(  3)     5867 ( 5.0%, 25.8%): getaddrinfo
(  4)     3964 ( 3.4%, 29.1%): OPENSSL_init_ssl
(  5)     3172 ( 2.7%, 31.8%): fchmod
(  6)     2957 ( 2.5%, 34.4%): ring_core_0_17_8_OPENSSL_cpuid_setup
(  7)     2485 ( 2.1%, 36.5%): rust_psm_stack_pointer
(  8)     2432 ( 2.1%, 38.6%): rocksdb_options_create
(  9)     2167 ( 1.8%, 40.4%): getrlimit
( 10)     1880 ( 1.6%, 42.0%): dlopen
( 11)     1875 ( 1.6%, 43.6%): ts_parser_new
( 12)     1800 ( 1.5%, 45.1%): sodium_init
( 13)     1798 ( 1.5%, 46.7%): Py_IsInitialized
( 14)     1619 ( 1.4%, 48.1%): sqlite3_open_v2
( 15)     1415 ( 1.2%, 49.3%): epoll_create
( 16)     1382 ( 1.2%, 50.4%): sqlite3_threadsafe
( 17)     1365 ( 1.2%, 51.6%): GFp_cpuid_setup
( 18)     1293 ( 1.1%, 52.7%): chmod
( 19)     1155 ( 1.0%, 53.7%): SQLAllocHandle
( 20)     1003 ( 0.9%, 54.5%): geteuid
( 21)      745 ( 0.6%, 55.2%): rustsecp256k1_v0_10_0_context_preallocated_size
( 22)      713 ( 0.6%, 55.8%): InitializeMagick
( 23)      699 ( 0.6%, 56.4%): EVP_sha256
( 24)      694 ( 0.6%, 57.0%): ruby_init_stack
( 25)      629 ( 0.5%, 57.5%): access
( 26)      604 ( 0.5%, 58.0%): JS_NewRuntime
( 27)      600 ( 0.5%, 58.5%): PQconnectdb
( 28)      549 ( 0.5%, 59.0%): ioctl
( 29)      527 ( 0.4%, 59.5%): blst_scalar_from_uint64
( 30)      526 ( 0.4%, 59.9%): v8__Platform__NewDefaultPlatform
( 31)      520 ( 0.4%, 60.3%): __bid128_from_string
( 32)      516 ( 0.4%, 60.8%): nettle_yarrow256_init
( 33)      485 ( 0.4%, 61.2%): mdb_env_create
( 34)      482 ( 0.4%, 61.6%): NK_login_enum
( 35)      479 ( 0.4%, 62.0%): mprotect
( 36)      476 ( 0.4%, 62.4%): tree_sitter_tsx
( 37)      474 ( 0.4%, 62.8%): LLVMCreateMemoryBufferWithContentsOfFile
( 38)      440 ( 0.4%, 63.2%): git_libgit2_init
( 39)      426 ( 0.4%, 63.6%): roaring_bitmap_init_with_capacity
( 40)      407 ( 0.3%, 63.9%): getifaddrs
( 41)      380 ( 0.3%, 64.2%): blst_keygen_v4_5
( 42)      380 ( 0.3%, 64.6%): secp256k1_context_create
( 43)      367 ( 0.3%, 64.9%): decContextDefault
( 44)      367 ( 0.3%, 65.2%): ffopen
( 45)      342 ( 0.3%, 65.5%): SQLSetEnvAttr
( 46)      338 ( 0.3%, 65.8%): sigaction
( 47)      334 ( 0.3%, 66.0%): H5dont_atexit
( 48)      320 ( 0.3%, 66.3%): mrb_open
( 49)      312 ( 0.3%, 66.6%): cuInit

There are some pretty obvious biases in this data. For example, crates with a lot of tests get their favorite symbols counted more than crates with fewer tests.

There are also a lot of things in here which I don't think we will ever support via shims. We're not going to have shims for openssl. We're also not going to shim CUDA or JavaScript, and also all those errors are from 3 crates using CUDA and 1 crate doing some JavaScript thing.

But in any case, this is a starting point for prioritizing what shims should be added. Just in case there isn't anyone out there who already has a pet function they want added.

@drmeepster asked me to run some crates with a Windows target. Here's what the first ~2k crates run into:

2911 counts
(  1)     1583 (54.4%, 54.4%):  GetFullPathNameW
(  2)      485 (16.7%, 71.0%):  CreateIoCompletionPort
(  3)      292 (10.0%, 81.1%):  GetFileInformationByHandleEx
(  4)      183 ( 6.3%, 87.4%):  GetModuleFileNameW
(  5)       46 ( 1.6%, 88.9%):  SleepConditionVariableSRW
(  6)       24 ( 0.8%, 89.8%):  GetTickCount64
(  7)       22 ( 0.8%, 90.5%):  CompareStringOrdinal
(  8)       18 ( 0.6%, 91.1%):  AcquireCredentialsHandleA
(  9)       16 ( 0.5%, 91.7%):  WSAStartup
( 10)       15 ( 0.5%, 92.2%):  CreateNamedPipeW
( 11)       14 ( 0.5%, 92.7%):  Sleep
( 12)       13 ( 0.4%, 93.1%):  CryptAcquireContextW
( 13)       13 ( 0.4%, 93.6%):  log1p
( 14)       11 ( 0.4%, 94.0%):  CreateSemaphoreA
( 15)       10 ( 0.3%, 94.3%):  CreatePipe
( 16)       10 ( 0.3%, 94.6%):  SHGetKnownFolderPath
( 17)       10 ( 0.3%, 95.0%):  WakeAllConditionVariable
( 18)       10 ( 0.3%, 95.3%):  zx_vmo_create
( 19)        8 ( 0.3%, 95.6%):  GetCurrentProcess

I don't know what GetFullPathNameW is coming from, but when crates hit it, they usually have tends to hundreds of tests that attempt to use it. Possibly it's from proptest? prost is one of the crates that hits it a bunch of times.

[RalfJung]

__xpg_strerror_r is something that also comes up when just debugging Miri, I think even some of the tests will debug-print the IO error when the test fails, leading to an annoying double-failure (first the test fails with an assertion, then printing that assertion fails with an "unsupported" error).

[RalfJung]

I think __xpg_strerror_r is from crates that encounter a std::io::Error and try to format it. This is pretty common because a lot of crates attempt to access files in their tests that are not packaged (this is also a huge problem for crater).

Wish granted. ;) #2067

Just N-1 to go...

[mejrs]

( 10) 205 ( 1.3%, 52.8%): Py_IsInitialized

This the first CPython api call that Rust programs embedding the python interpreter will do. I would really like to test pyo3 and these programs with Miri.

I know Python's C api is too big to shim, but I would love to see some solution for this.

[CraftSpider]

I have a similar wishlist for testing a PHP extension library. Currently it fails at pipe2, but after that it would start failing at whatever the first call to PHP is. It would be nice if there was some way to use miri to test the Rust parts of my project, and then just actually call out to the relevant PHP stuff as normal.

[jjl]

mmap() is the one i'm currently missing. for my purposes it could just use a boxed slice. would be a little painful on memory, but enough to get miri running.

[bjorn3]

Read-only mmap where you don't write to the backing file shouldn't be too hard to implement. If writes through either the mapping or through the backing file are allowed, it becomes a lot harder to implement unix compatible semantics.

[jjl]

Ah, I see what you mean. Fortunately, I'm only using anonymous mappings.

[LegNeato]

Thanks for the list! I picked the easiest one I could see near the top (realpath):

Is there any way we can get a couple of example crates for each missing shim in the list so implementers can check the before and after with real code?

[saethlin]

I've manually grabbed a list for you for realpath: realpath-crates.txt

I have a very simple website which is just Cloudfront + S3 at https://miri.saethlin.dev (most people care about https://miri.saethlin.dev/ub). I'm not opposed to making simple additions, like a way to download all the raw logs in a .tar.gz. You can comment here or open a new issue: saethlin/crater-at-home#8