Jeremy?
On Jul 21 07:56, Radek Barton via Cygwin-patches wrote:
> Hello.
>
> Sending a patch with AArch64 +/-4GB relocations in mkimport as promised at
> https://sourceware.org/pipermail/cygwin-patches/2025q3/014155.html
>
> Radek
>
> ---
> >From 3ec4e2136942ade5856310ee1f4d9d89359c3c79 Mon Sep 17 00:00:00 2001
> From: =?UTF-8?q?Radek=20Barto=C5=88?= <[email protected]>
> Date: Sat, 19 Jul 2025 19:17:12 +0200
> Subject: [PATCH] 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 Bartoň <[email protected]>
> ---
> winsup/cygwin/mm/malloc_wrapper.cc | 23 ++++++++++++++---------
> winsup/cygwin/scripts/mkimport | 4 ++--
> 2 files changed, 16 insertions(+), 11 deletions(-)
>
> diff --git a/winsup/cygwin/mm/malloc_wrapper.cc
> b/winsup/cygwin/mm/malloc_wrapper.cc
> index 863d3089c..5ca4da587 100644
> --- a/winsup/cygwin/mm/malloc_wrapper.cc
> +++ b/winsup/cygwin/mm/malloc_wrapper.cc
> @@ -51,16 +51,21 @@ 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
> + uint32_t opcode1 = *((uint32_t *) imp);
> + uint32_t opcode2 = *(((uint32_t *) imp) + 1);
> + if (((opcode1 & 0x9f000000) == 0x90000000) && ((opcode2 & 0xbfc00000)
> == 0xb9400000))
> {
> - 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..80594296a 100755
> --- a/winsup/cygwin/scripts/mkimport
> +++ b/winsup/cygwin/scripts/mkimport
> @@ -73,8 +73,8 @@ EOF
> .extern $imp_sym
> .global $glob_sym
> $glob_sym:
> - adr x16, $imp_sym
> - ldr x16, [x16]
> + adrp x16, $imp_sym
> + ldr x16, [x16, #:lo12:$imp_sym]
> br x16
> EOF
> } else {
> --
> 2.50.1.vfs.0.0
>
