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AK: Define NAKED more resiliently for AArch64

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This attribute is used for functions in the kernel that are entirely
written in assembly, yet defined in C++ source files.

Without `__attribute__((naked))`, Clang might decide to inline these
functions, making any `ret` instructions within them actually exit the
caller, or discard argument values as they appear "dead". This issue
caused a kernel panic when using the `execve` syscall in AArch64
SerenityOS built by Clang.

While the empty definition so far appears to work fine with GCC, simpler
test cases do similarly suffer from unintended inlining, so define
`NAKED` as a synonym of `NEVER_INLINE` to avert future issues.

Perhaps we should move users of `NAKED` to plain assembly files?

This makes aarch64Clang builds boot :^)
This commit is contained in:
Daniel Bertalan 2023-05-22 11:11:29 +02:00 • committed by Jelle Raaijmakers
parent bafc1193ee
commit fd316945f5
1 changed files with 6 additions and 2 deletions
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8
AK/Platform.h
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@ -145,10 +145,14 @@
#ifdef NAKED
# undef NAKED
#endif
#if !ARCH(AARCH64)
#if !ARCH(AARCH64) || defined(AK_COMPILER_CLANG)
# define NAKED __attribute__((naked))
#else
# define NAKED
// GCC doesn't support __attribute__((naked)) on AArch64. We use NAKED to mark functions
// that are entirely written in inline assembly; having these be inlined would cause
// various problems, such as explicit `ret` instructions accidentally exiting the caller
// function or GCC discarding function arguments as they appear "dead".
# define NAKED NEVER_INLINE
#endif
#ifdef DISALLOW