diff options
Diffstat (limited to 'yjit.c')
| -rw-r--r-- | yjit.c | 51 |
1 files changed, 24 insertions, 27 deletions
@@ -56,7 +56,7 @@ STATIC_ASSERT(pointer_tagging_scheme, USE_FLONUM); // types in C such as int, long, etc. and use `std::os::raw::c_long` and friends on // the Rust side. // -// What's up with the long prefix? The "rb_" part is to apease `make leaked-globals` +// What's up with the long prefix? The "rb_" part is to appease `make leaked-globals` // which runs on upstream CI. The rationale for the check is unclear to Alan as // we build with `-fvisibility=hidden` so only explicitly marked functions end // up as public symbols in libruby.so. Perhaps the check is for the static @@ -66,13 +66,13 @@ STATIC_ASSERT(pointer_tagging_scheme, USE_FLONUM); // The "_yjit_" part is for trying to be informative. We might want different // suffixes for symbols meant for Rust and symbols meant for broader CRuby. -void +bool rb_yjit_mark_writable(void *mem_block, uint32_t mem_size) { if (mprotect(mem_block, mem_size, PROT_READ | PROT_WRITE)) { - rb_bug("Couldn't make JIT page region (%p, %lu bytes) writeable, errno: %s\n", - mem_block, (unsigned long)mem_size, strerror(errno)); + return false; } + return true; } void @@ -209,25 +209,29 @@ align_ptr(uint8_t *ptr, uint32_t multiple) } #endif -// Allocate a block of executable memory +// Address space reservation. Memory pages are mapped on an as needed basis. +// See the Rust mm module for details. uint8_t * -rb_yjit_alloc_exec_mem(uint32_t mem_size) +rb_yjit_reserve_addr_space(uint32_t mem_size) { #ifndef _WIN32 uint8_t *mem_block; // On Linux #if defined(MAP_FIXED_NOREPLACE) && defined(_SC_PAGESIZE) + uint32_t const page_size = (uint32_t)sysconf(_SC_PAGESIZE); + uint8_t *const cfunc_sample_addr = (void *)&rb_yjit_reserve_addr_space; + uint8_t *const probe_region_end = cfunc_sample_addr + INT32_MAX; // Align the requested address to page size - uint32_t page_size = (uint32_t)sysconf(_SC_PAGESIZE); - uint8_t *req_addr = align_ptr((uint8_t*)&rb_yjit_alloc_exec_mem, page_size); + uint8_t *req_addr = align_ptr(cfunc_sample_addr, page_size); + // Probe for addresses close to this function using MAP_FIXED_NOREPLACE + // to improve odds of being in range for 32-bit relative call instructions. do { - // Try to map a chunk of memory as executable - mem_block = (uint8_t*)mmap( - (void*)req_addr, + mem_block = mmap( + req_addr, mem_size, - PROT_READ | PROT_EXEC, + PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED_NOREPLACE, -1, 0 @@ -240,15 +244,15 @@ rb_yjit_alloc_exec_mem(uint32_t mem_size) // +4MB req_addr += 4 * 1024 * 1024; - } while (req_addr < (uint8_t*)&rb_yjit_alloc_exec_mem + INT32_MAX); + } while (req_addr < probe_region_end); // On MacOS and other platforms #else // Try to map a chunk of memory as executable - mem_block = (uint8_t*)mmap( - (void*)rb_yjit_alloc_exec_mem, + mem_block = mmap( + (void *)rb_yjit_reserve_addr_space, mem_size, - PROT_READ | PROT_EXEC, + PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0 @@ -258,10 +262,10 @@ rb_yjit_alloc_exec_mem(uint32_t mem_size) // Fallback if (mem_block == MAP_FAILED) { // Try again without the address hint (e.g., valgrind) - mem_block = (uint8_t*)mmap( + mem_block = mmap( NULL, mem_size, - PROT_READ | PROT_EXEC, + PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0 @@ -270,17 +274,10 @@ rb_yjit_alloc_exec_mem(uint32_t mem_size) // Check that the memory mapping was successful if (mem_block == MAP_FAILED) { - perror("mmap call failed"); - exit(-1); + perror("ruby: yjit: mmap:"); + rb_bug("mmap failed"); } - // Fill the executable memory with PUSH DS (0x1E) so that - // executing uninitialized memory will fault with #UD in - // 64-bit mode. - rb_yjit_mark_writable(mem_block, mem_size); - memset(mem_block, 0x1E, mem_size); - rb_yjit_mark_executable(mem_block, mem_size); - return mem_block; #else // Windows not supported for now |