@@ -63,6 +63,118 @@ static codeblock_t *ocb = NULL;
6363//
6464// The "_yjit_" part is for trying to be informative. We might want different
6565// suffixes for symbols meant for Rust and symbols meant for broader CRuby.
66+
67+ /*
68+ void rb_yjit_mark_all_writable(uint8_t *mem_block, uint32_t mem_size) {
69+ if (mprotect(mem_block, mem_size, PROT_READ | PROT_WRITE)) {
70+ fprintf(stderr, "Couldn't make JIT page (%p) writeable, errno: %s", (void *)mem_block, strerror(errno));
71+ abort();
72+ }
73+ }
74+
75+ void rb_yjit_mark_all_executable(uint8_t *mem_block, uint32_t mem_size) {
76+ if (mprotect(mem_block, mem_size, PROT_READ | PROT_EXEC)) {
77+ fprintf(stderr, "Couldn't make JIT page (%p) executable, errno: %s", (void *)mem_block, strerror(errno));
78+ abort();
79+ }
80+ }
81+
82+ #if defined(MAP_FIXED_NOREPLACE) && defined(_SC_PAGESIZE)
83+ // Align the current write position to a multiple of bytes
84+ static uint8_t *align_ptr(uint8_t *ptr, uint32_t multiple)
85+ {
86+ // Compute the pointer modulo the given alignment boundary
87+ uint32_t rem = ((uint32_t)(uintptr_t)ptr) % multiple;
88+
89+ // If the pointer is already aligned, stop
90+ if (rem == 0)
91+ return ptr;
92+
93+ // Pad the pointer by the necessary amount to align it
94+ uint32_t pad = multiple - rem;
95+
96+ return ptr + pad;
97+ }
98+ #endif
99+
100+ // Allocate a block of executable memory
101+ uint8_t *rb_yjit_alloc_exec_mem(uint32_t mem_size) {
102+ #ifndef _WIN32
103+ uint8_t *mem_block;
104+
105+ // On Linux
106+ #if defined(MAP_FIXED_NOREPLACE) && defined(_SC_PAGESIZE)
107+ // Align the requested address to page size
108+ uint32_t page_size = (uint32_t)sysconf(_SC_PAGESIZE);
109+ uint8_t *req_addr = align_ptr((uint8_t*)&rb_yjit_alloc_exec_mem, page_size);
110+
111+ do {
112+ // Try to map a chunk of memory as executable
113+ mem_block = (uint8_t*)mmap(
114+ (void*)req_addr,
115+ mem_size,
116+ PROT_READ | PROT_EXEC,
117+ MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED_NOREPLACE,
118+ -1,
119+ 0
120+ );
121+
122+ // If we succeeded, stop
123+ if (mem_block != MAP_FAILED) {
124+ break;
125+ }
126+
127+ // +4MB
128+ req_addr += 4 * 1024 * 1024;
129+ } while (req_addr < (uint8_t*)&rb_yjit_alloc_exec_mem + INT32_MAX);
130+
131+ // On MacOS and other platforms
132+ #else
133+ // Try to map a chunk of memory as executable
134+ mem_block = (uint8_t*)mmap(
135+ (void*)yjit_alloc_exec_mem,
136+ mem_size,
137+ PROT_READ | PROT_EXEC,
138+ MAP_PRIVATE | MAP_ANONYMOUS,
139+ -1,
140+ 0
141+ );
142+ #endif
143+
144+ // Fallback
145+ if (mem_block == MAP_FAILED) {
146+ // Try again without the address hint (e.g., valgrind)
147+ mem_block = (uint8_t*)mmap(
148+ NULL,
149+ mem_size,
150+ PROT_READ | PROT_EXEC,
151+ MAP_PRIVATE | MAP_ANONYMOUS,
152+ -1,
153+ 0
154+ );
155+ }
156+
157+ // Check that the memory mapping was successful
158+ if (mem_block == MAP_FAILED) {
159+ perror("mmap call failed");
160+ exit(-1);
161+ }
162+
163+ // Fill the executable memory with PUSH DS (0x1E) so that
164+ // executing uninitialized memory will fault with #UD in
165+ // 64-bit mode.
166+ yjit_mark_all_writable(mem_block, mem_size);
167+ memset(mem_block, 0x1E, mem_size);
168+ yjit_mark_all_executable(mem_block, mem_size);
169+
170+ return mem_block;
171+ #else
172+ // Windows not supported for now
173+ return NULL;
174+ #endif
175+ }
176+ */
177+
66178uint8_t *
67179rb_yjit_alloc_exec_mem (uint32_t mem_size )
68180{
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