Hello. Sending another version with suggestion to use more strict conditions for instructions detection applied.
Radek --- >From fed90421a5c9c8539a7aad92588730f0a84fd306 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Radek=20Barto=C5=88?= <radek.bar...@microsoft.com> Date: Sat, 19 Jul 2025 19:17:12 +0200 Subject: [PATCH v4] Cygwin: mkimport: implement AArch64 +/-4GB relocations MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Based on https://sourceware.org/pipermail/cygwin-patches/2025q3/014154.html suggestion, this patch implements +/-4GB relocations for AArch64 in the mkimport script by using adrp and ldr instructions. This change required update in winsup/cygwin/mm/malloc_wrapper.cc where those instructions are decoded to get target import address. Signed-off-by: Radek BartoĊ <radek.bar...@microsoft.com> --- winsup/cygwin/mm/malloc_wrapper.cc | 29 ++++++++++++++++++++--------- winsup/cygwin/scripts/mkimport | 7 +++++-- 2 files changed, 25 insertions(+), 11 deletions(-) diff --git a/winsup/cygwin/mm/malloc_wrapper.cc b/winsup/cygwin/mm/malloc_wrapper.cc index 863d3089c..db6ffb5a0 100644 --- a/winsup/cygwin/mm/malloc_wrapper.cc +++ b/winsup/cygwin/mm/malloc_wrapper.cc @@ -51,16 +51,27 @@ import_address (void *imp) __try { #if defined(__aarch64__) - // If opcode is an adr instruction. - uint32_t opcode = *(uint32_t *) imp; - if ((opcode & 0x9f000000) == 0x10000000) + /* If opcode1 is an adrp and opcode2 is ldr instruction: + - https://www.scs.stanford.edu/~zyedidia/arm64/adrp.html + - https://www.scs.stanford.edu/~zyedidia/arm64/ldr_imm_gen.html + NOTE: This implementation assumes that the relocation table is made of + those specific AArch64 instructions as generated by the + winsup/cygwin/scripts/mkimport script. Please, keep it in sync. */ + uint32_t opcode1 = *((uint32_t *) imp); + uint32_t opcode2 = *(((uint32_t *) imp) + 1); + uint32_t opcode3 = *(((uint32_t *) imp) + 2); + if (((opcode1 & 0x9f00001f) == 0x90000010) && + ((opcode2 & 0xffc003ff) == 0xf9400210) && + (opcode3 == 0xd61f0200)) { - uint32_t immhi = (opcode >> 5) & 0x7ffff; - uint32_t immlo = (opcode >> 29) & 0x3; - int64_t sign_extend = (0l - (immhi >> 18)) << 21; - int64_t imm = sign_extend | (immhi << 2) | immlo; - uintptr_t jmpto = *(uintptr_t *) ((uint8_t *) imp + imm); - return (void *) jmpto; + uint32_t immhi = (opcode1 >> 5) & 0x7ffff; + uint32_t immlo = (opcode1 >> 29) & 0x3; + uint32_t imm12 = ((opcode2 >> 10) & 0xfff) * 8; // 64 bit scale + int64_t sign_extend = (0l - ((int64_t) immhi >> 32)) << 33; // sign extend from 33 to 64 bits + int64_t imm = sign_extend | (((immhi << 2) | immlo) << 12); + int64_t base = (int64_t) imp & ~0xfff; + uintptr_t* jmpto = (uintptr_t *) (base + imm + imm12); + return (void *) *jmpto; } #else if (*((uint16_t *) imp) == 0x25ff) diff --git a/winsup/cygwin/scripts/mkimport b/winsup/cygwin/scripts/mkimport index 0c1bcafbf..33d8b08fb 100755 --- a/winsup/cygwin/scripts/mkimport +++ b/winsup/cygwin/scripts/mkimport @@ -73,8 +73,11 @@ EOF .extern $imp_sym .global $glob_sym $glob_sym: - adr x16, $imp_sym - ldr x16, [x16] + # NOTE: Using instructions that are used by MSVC and LLVM. Binutils are + # using adrp/add/ldr-0-offset though. Please, keep it in sync with + # import_address implementation in winsup/cygwin/mm/malloc_wrapper.cc. + adrp x16, $imp_sym + ldr x16, [x16, #:lo12:$imp_sym] br x16 EOF } else { -- 2.50.1.vfs.0.0
v4-0001-Cygwin-mkimport-implement-AArch64-4GB-relocations.patch
Description: v4-0001-Cygwin-mkimport-implement-AArch64-4GB-relocations.patch
