[{"id":3675609,"web_url":"http://patchwork.ozlabs.org/comment/3675609/","msgid":"<00b95efa-81de-43e1-811a-0ca63fac4449@linaro.org>","list_archive_url":null,"date":"2026-04-10T02:10:26","subject":"Re: [PATCH v2 1/1] linux-user/mips: sync k0 TLS for\n EF_MIPS_MACH_OCTEON userlands","submitter":{"id":72104,"url":"http://patchwork.ozlabs.org/api/people/72104/","name":"Richard Henderson","email":"richard.henderson@linaro.org"},"content":"On 4/10/26 12:00, James Hilliard wrote:\n> Cavium Octeon userspace is not following a generic MIPS Linux TLS\n> ABI rule here. Older Octeon glibc uses the k0 register as the fast\n> thread pointer, while newer Octeon2 and Octeon3 glibc variants use\n> the normal rdhwr $29 path.\n> \n> linux-user already updates CP0_UserLocal for cpu_set_tls() and\n> TARGET_NR_set_thread_area, but it does not keep gpr[26]\n> synchronized. That leaves EF_MIPS_MACH_OCTEON userlands able to\n> complete set_thread_area() and still reach pthread startup or\n> pthread_self() with a stale k0 value.\n> \n> Use the existing MIPS ELF machine flags from linux-user/elfload.c and\n> mirror CP0_UserLocal into gpr[26] only for EF_MIPS_MACH_OCTEON.\n> \n> Signed-off-by: James Hilliard \n> ---\n> Changes v1 -> v2:\n> - only enable on EF_MIPS_MACH_OCTEON\n> ---\n> linux-user/elfload.c | 3 +++\n> linux-user/mips/target_cpu.h | 5 +++++\n> linux-user/qemu.h | 1 +\n> linux-user/syscall.c | 2 +-\n> 4 files changed, 10 insertions(+), 1 deletion(-)\n> \n> diff --git a/linux-user/elfload.c b/linux-user/elfload.c\n> index 59b543f740..0e757787d2 100644\n> --- a/linux-user/elfload.c\n> +++ b/linux-user/elfload.c\n> @@ -1476,6 +1476,9 @@ static void load_elf_image(const char *image_name, const ImageSource *src,\n> /* Usual start for brk is after all sections of the main executable. */\n> info->brk = TARGET_PAGE_ALIGN(hiaddr + load_bias);\n> info->elf_flags = ehdr->e_flags;\n> +#ifdef TARGET_MIPS\n> + info->use_k0_tls = (ehdr->e_flags & EF_MIPS_MACH) == EF_MIPS_MACH_OCTEON;\n> +#endif\n\nNote that we've just stored e_flags in info->elf_flags.\nBetter placement for this is in mips/cpu_loop.c, init_main_thread.\n\nOtherwise,\nReviewed-by: Richard Henderson \n\n\nr~","headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=linaro.org header.i=@linaro.org header.a=rsa-sha256\n header.s=google header.b=e0NqSodX;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org\n (client-ip=209.51.188.17; helo=lists.gnu.org;\n envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org;\n receiver=patchwork.ozlabs.org)"],"Received":["from lists.gnu.org (lists1p.gnu.org [209.51.188.17])\n\t(using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits))\n\t(No client certificate requested)\n\tby legolas.ozlabs.org (Postfix) with ESMTPS id 4fsKz349hDz1y2d\n\tfor ; Fri, 10 Apr 2026 12:10:55 +1000 (AEST)","from localhost ([::1] helo=lists1p.gnu.org)\n\tby lists.gnu.org with esmtp (Exim 4.90_1)\n\t(envelope-from )\n\tid 1wB1KP-0001cU-CH; Thu, 09 Apr 2026 22:10:37 -0400","from eggs.gnu.org ([2001:470:142:3::10])\n by lists1p.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256)\n (Exim 4.90_1) (envelope-from )\n id 1wB1KN-0001cL-Vm\n for qemu-devel@nongnu.org; Thu, 09 Apr 2026 22:10:36 -0400","from mail-pf1-x42e.google.com ([2607:f8b0:4864:20::42e])\n by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128)\n (Exim 4.90_1) (envelope-from )\n id 1wB1KM-0006nr-9X\n for qemu-devel@nongnu.org; Thu, 09 Apr 2026 22:10:35 -0400","by mail-pf1-x42e.google.com with SMTP id\n d2e1a72fcca58-82748257f5fso861933b3a.1\n for ; Thu, 09 Apr 2026 19:10:33 -0700 (PDT)","from [192.168.1.105] (124-150-69-109.tpgi.com.au. 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