Re: [Tarantool-patches] [PATCH luajit 1/2] build: introduce LUAJIT_USE_UBSAN option

[Sergey Bronnikov via Tarantool-patches <tarantool-patches@dev.tarantool.org>]

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Sergey,

thanks for the patch! Please see my comments below.

On 15.05.2024 15:32, Sergey Kaplun wrote:
> This patch adds Undefined Behaviour Sanitizer [1] support. It enables
> all checks except several that are not useful for LuaJIT. Also, it
> instruments all known issues to be fixed in future patches (except
> `kfold_intop()` since cdata arithmetic relies on integer overflow).
>
> [1]:https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html
>
> Resolves tarantool/tarantool#8473
> ---
>   CMakeLists.txt             | 45 ++++++++++++++++++++++++++++++++++++++
>   cmake/SetDynASMFlags.cmake | 11 ++++++++++
>   src/lj_carith.c            |  5 +++++
>   src/lj_opt_fold.c          |  5 +++++
>   src/lj_parse.c             |  5 +++++
>   src/lj_snap.c              |  7 ++++++
>   src/lj_strfmt.c            |  5 +++++
>   7 files changed, 83 insertions(+)

patch in mail is outdated, so I'll copypaste missed part:


diff --git a/src/lj_buf.h b/src/lj_buf.h
index a4051694..aaecc9f8 100644
--- a/src/lj_buf.h
+++ b/src/lj_buf.h
@@ -70,6 +70,13 @@ LJ_FUNC SBuf *lj_buf_putmem(SBuf *sb, const void *q, 
MSize len);
  LJ_FUNC SBuf * LJ_FASTCALL lj_buf_putchar(SBuf *sb, int c);
  LJ_FUNC SBuf * LJ_FASTCALL lj_buf_putstr(SBuf *sb, GCstr *s);

+#if LUAJIT_USE_UBSAN
+/* The `NULL` argument with the zero length, like in the case:
+** | luajit -e 'error("x", 3)'
+*/
+static LJ_AINLINE char *lj_buf_wmem(char *p, const void *q, MSize len)
+  __attribute__((no_sanitize("nonnull-attribute")));
+#endif
  static LJ_AINLINE char *lj_buf_wmem(char *p, const void *q, MSize len)
  {
    return (char *)memcpy(p, q, len) + len;


With this reverted patch tests passed. Do we really need this patch?


>
> diff --git a/CMakeLists.txt b/CMakeLists.txt
> index 2355ce17..edf2012f 100644
> --- a/CMakeLists.txt
> +++ b/CMakeLists.txt
> @@ -300,6 +300,51 @@ if(LUAJIT_USE_ASAN)
>     )
>   endif()
>   
> +option(LUAJIT_USE_UBSAN "Build LuaJIT with UndefinedBehaviorSanitizer" OFF)
> +if(LUAJIT_USE_UBSAN)
> +  # Use all recommendations from the UndefinedBehaviorSanitizer

probably you mean "checks" [1] and not "recommendations"


1. https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html#ubsan-checks

> +  # documentation:
> +  #https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html.
> +  string(JOIN "," UBSAN_IGNORE_OPTIONS
> +    # Misaligned pseudo-pointers are used to determine internal
> +    # variable names inside the `for` cycle.
> +    alignment
> +    # Not interested in float cast overflow errors.
> +    float-cast-overflow
> +    # NULL checking is disabled because this is not a UB and
> +    # raises lots of false-positive fails.
> +    null
> +    # Not interested in checking arithmetic with NULL.
> +    pointer-overflow
> +    # Shifts of negative numbers are widely used in parsing ULEB,
> +    # cdata arithmetic, vmevent hash calculation, etc.
> +    shift-base

Will we report issues produced by these checks to upstream?

Decision "not interested" confuses.

> +  )
> +  if(NOT CMAKE_C_COMPILER_ID STREQUAL "GNU")

please add a link to GCC documentation

https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html#index-fsanitize_003dundefined

> +    string(JOIN "," UBSAN_IGNORE_OPTIONS
> +      ${UBSAN_IGNORE_OPTIONS}
> +      # Not interested in function type mismatch errors.
> +      function
> +    )
> +  endif()
> +  AppendFlags(CMAKE_C_FLAGS
> +    # Enable hints for UndefinedBehaviorSanitizer.
> +    -DLUAJIT_USE_UBSAN
> +    # XXX: To get nicer stack traces in error messages.
> +    -fno-omit-frame-pointer
> +    # Enable UndefinedBehaviorSanitizer support.
> +    # This flag enables all supported options (the documentation
> +    # on cite is not correct about that moment, unfortunately)
typo: cite -> site
> +    # except float-divide-by-zero. Floating point division by zero
> +    # behaviour is defined without -ffast-math and uses the
> +    # IEEE 754 standard on which all NaN tagging is based.
> +    -fsanitize=undefined
> +    -fno-sanitize=${UBSAN_IGNORE_OPTIONS}
> +    # Print a verbose error report and exit the program.
> +    -fno-sanitize-recover=undefined
> +  )
> +endif()
> +
>   # Enable code coverage support.
>   option(LUAJIT_ENABLE_COVERAGE "Enable code coverage support (gcovr)" OFF)
>   if(LUAJIT_ENABLE_COVERAGE)
> diff --git a/cmake/SetDynASMFlags.cmake b/cmake/SetDynASMFlags.cmake
> index 7eead6e9..ae3c75b1 100644
> --- a/cmake/SetDynASMFlags.cmake
> +++ b/cmake/SetDynASMFlags.cmake
> @@ -136,5 +136,16 @@ if(NOT CMAKE_SYSTEM_NAME STREQUAL ${CMAKE_HOST_SYSTEM_NAME})
>     endif()
>   endif()
>   
> +if(LUAJIT_USE_UBSAN)
> +  # XXX: Skip checks for now to avoid build failures due to
> +  # sanitizer errors.
> +  # Need to backprot commits that fix the following issues first:
typo: backprot -> backport
> +  #https://github.com/LuaJIT/LuaJIT/pull/969,
> +  #https://github.com/LuaJIT/LuaJIT/pull/970,
> +  #https://github.com/LuaJIT/LuaJIT/issues/1041,
> +  #https://github.com/LuaJIT/LuaJIT/pull/1044.
> +  AppendFlags(HOST_C_FLAGS -fno-sanitize=undefined)
> +endif()
> +
>   unset(LUAJIT_ARCH)
>   unset(TESTARCH)
> diff --git a/src/lj_carith.c b/src/lj_carith.c
With this reverted patch tests passed. Do we really need this patch?
> index 4e1d450a..1d9d6fe1 100644
> --- a/src/lj_carith.c
> +++ b/src/lj_carith.c
> @@ -159,6 +159,11 @@ static int carith_ptr(lua_State *L, CTState *cts, CDArith *ca, MMS mm)
>   }
>   
>   /* 64 bit integer arithmetic. */
> +#if LUAJIT_USE_UBSAN
> +/* Seehttps://github.com/LuaJIT/LuaJIT/issues/928. */
> +static int carith_int64(lua_State *L, CTState *cts, CDArith *ca, MMS mm)
> +  __attribute__((no_sanitize("signed-integer-overflow")));
> +#endif
>   static int carith_int64(lua_State *L, CTState *cts, CDArith *ca, MMS mm)
>   {
>     if (ctype_isnum(ca->ct[0]->info) && ca->ct[0]->size <= 8 &&
> diff --git a/src/lj_opt_fold.c b/src/lj_opt_fold.c
> index 96780fa2..b9326c65 100644
> --- a/src/lj_opt_fold.c
> +++ b/src/lj_opt_fold.c
> @@ -260,6 +260,11 @@ LJFOLDF(kfold_numcomp)
>   
>   /* -- Constant folding for 32 bit integers -------------------------------- */
>   
> +#if LUAJIT_USE_UBSAN
> +/* Cdata arithmetic depends on the interger overflow. */
> +static int32_t kfold_intop(int32_t k1, int32_t k2, IROp op)
> +  __attribute__((no_sanitize("signed-integer-overflow")));
> +#endif
>   static int32_t kfold_intop(int32_t k1, int32_t k2, IROp op)
>   {
>     switch (op) {
> diff --git a/src/lj_parse.c b/src/lj_parse.c
> index 5a4ab7c8..acceed17 100644
> --- a/src/lj_parse.c
> +++ b/src/lj_parse.c
> @@ -939,6 +939,11 @@ static void bcemit_binop(FuncState *fs, BinOpr op, ExpDesc *e1, ExpDesc *e2)
>   }
>   
>   /* Emit unary operator. */
> +#if LUAJIT_USE_UBSAN
> +/* Seehttps://github.com/LuaJIT/LuaJIT/issues/928. */
> +static void bcemit_unop(FuncState *fs, BCOp op, ExpDesc *e)
> +  __attribute__((no_sanitize("signed-integer-overflow")));
> +#endif
>   static void bcemit_unop(FuncState *fs, BCOp op, ExpDesc *e)
>   {
>     if (op == BC_NOT) {
> diff --git a/src/lj_snap.c b/src/lj_snap.c
> index 5a00b5cd..7dc4fe35 100644
> --- a/src/lj_snap.c
> +++ b/src/lj_snap.c
> @@ -756,6 +756,13 @@ static void snap_restoreval(jit_State *J, GCtrace *T, ExitState *ex,
>   }
>   
>   #if LJ_HASFFI
> +# if LUAJIT_USE_UBSAN
> +/* Seehttps://github.com/LuaJIT/LuaJIT/issues/1193. */
> +static void snap_restoredata(jit_State *J, GCtrace *T, ExitState *ex,
> +			     SnapNo snapno, BloomFilter rfilt,
> +			     IRRef ref, void *dst, CTSize sz)
> +  __attribute__((no_sanitize("bounds")));
> +# endif
>   /* Restore raw data from the trace exit state. */
>   static void snap_restoredata(jit_State *J, GCtrace *T, ExitState *ex,
>   			     SnapNo snapno, BloomFilter rfilt,
> diff --git a/src/lj_strfmt.c b/src/lj_strfmt.c
> index ff5568c3..9592eff1 100644
> --- a/src/lj_strfmt.c
> +++ b/src/lj_strfmt.c
> @@ -93,6 +93,11 @@ retlit:
>     { uint32_t d = (x*(((1<<sh)+sc-1)/sc))>>sh; x -= d*sc; *p++ = (char)('0'+d); }
>   
>   /* Write integer to buffer. */
> +#if LUAJIT_USE_UBSAN
> +/* Seehttps://github.com/LuaJIT/LuaJIT/issues/928. */
> +char * LJ_FASTCALL lj_strfmt_wint(char *p, int32_t k)
> +  __attribute__((no_sanitize("signed-integer-overflow")));
> +#endif
>   char * LJ_FASTCALL lj_strfmt_wint(char *p, int32_t k)
>   {
>     uint32_t u = (uint32_t)k;

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