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wasm: align fiber stack pointer to 16 bytes

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In WebAssembly C ABI, the linear stack pointer must be always aligned
to 16 bytes like other archs.
The misaligned stack pointer causes some weird memory corruption since
compiler assumes the aligned stack pointer.
This commit is contained in:
Yuta Saito 2024-01-29 09:49:15 +00:00
parent 8bff7e996c
commit 0d4de0f4b1
1 changed files with 6 additions and 2 deletions
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8
coroutine/asyncify/Context.h
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@ -13,6 +13,7 @@
#include <stddef.h>
#include <stdio.h>
#include <stdint.h>
#include "wasm/asyncify.h"
#include "wasm/machine.h"
#include "wasm/fiber.h"
@ -47,10 +48,13 @@ static inline void coroutine_initialize_main(struct coroutine_context * context)
static inline void coroutine_initialize(struct coroutine_context *context, coroutine_start start, void *stack, size_t size)
{
if (ASYNCIFY_CORO_DEBUG) fprintf(stderr, "[%s] entry (context = %p, stack = %p ... %p)\n", __func__, context, stack, (char *)stack + size);
// Linear stack pointer must be always aligned down to 16 bytes.
// https://github.com/WebAssembly/tool-conventions/blob/c74267a5897c1bdc9aa60adeaf41816387d3cd12/BasicCABI.md#the-linear-stack
uintptr_t sp = ((uintptr_t)stack + size) & ~0xF;
if (ASYNCIFY_CORO_DEBUG) fprintf(stderr, "[%s] entry (context = %p, stack = %p ... %p)\n", __func__, context, stack, (char *)sp);
rb_wasm_init_context(&context->fc, coroutine_trampoline, start, context);
// record the initial stack pointer position to restore it after resumption
context->current_sp = (char *)stack + size;
context->current_sp = (char *)sp;
context->stack_base = stack;
context->size = size;
}