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[209.132.180.67]) by mx.google.com with ESMTP id b133si3905140oif.244.2019.12.06.14.14.51; Fri, 06 Dec 2019 14:14:52 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20161025 header.b=JVSCGAex; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726566AbfLFWOH (ORCPT + 27 others); Fri, 6 Dec 2019 17:14:07 -0500 Received: from mail-pj1-f73.google.com ([209.85.216.73]:56990 "EHLO mail-pj1-f73.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726374AbfLFWOE (ORCPT ); Fri, 6 Dec 2019 17:14:04 -0500 Received: by mail-pj1-f73.google.com with SMTP id y11so4319794pjr.23 for ; Fri, 06 Dec 2019 14:14:04 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=uHQktI1tJwpSEASWzTTpFz8grSSRR6XNFC+ZxIDfRWA=; b=JVSCGAexBdlmEE06N3xdBo1mMgDCQUAzeCFTnY/Fb4PUF3CdyU+S+dJmoeOBcQpskt pQlHMRe4/NoGMN6dRiHhDHP+i8N5fTr0akNG7dMtVlPdnkUgBYg1bOqnIs57w9tpOppn h3P6tDLRd1yFYEckmEJJCQxo0n3g9pJcL6H74Uh/VtTUvo+6MeQgSW2zhKMH+sCUToFI o7GV9ZRZyjNs77Qgw277M/tmmzzGpVVT9AYDXnhrnJbeuQt5uYXmjyR4tDv50Ia46lse OEhmSLK0RFYITFtLphqOwtnwFPc0VNKCOUxoxB5FuaqN/pL+ZqeV8gr3z7A4mE8JaAQ2 ESHQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=uHQktI1tJwpSEASWzTTpFz8grSSRR6XNFC+ZxIDfRWA=; b=Qtl9ui0KA2U3hQ4WgdxKaaRfPJBQ4o6Ij1kEYpnzHxgwqqOzFIpxdSurJBItvfJmBB 6YVVWehjUVGKUUFgkI48ECG7BBphryuylpUAvb3K4FMEEfwRYiLiBNb8FZcyHyuPokt8 EgGiuKh9+TWwn0jIsbgWTO9x7yex9Z28j6JWIqcK2scy6LGeCWJ1jrb6XPn9nNr1E3lf ZPCLvW31x7/wfzNSHc2BgA/UhD3xDY5MwykOStAkIzaM7wFA3glnjSPlYqLkZgRgkqIM 5gsoL8OsNe6yd0ZWegWZrUzbmoUuJhqbgkMkXG80DyBJsPhrRIlJwZFkt1AO4wTNIAK3 dbVA== X-Gm-Message-State: APjAAAURwGHxN2zp04WzSmV9WMHeoSw88EYVqZaY5iA1TUVDQH9fn9N9 phb92uj0ucyiXNUG0SNu6GQ11SZbWxArIctytSk= X-Received: by 2002:a63:ed56:: with SMTP id m22mr5943958pgk.261.1575670443383; Fri, 06 Dec 2019 14:14:03 -0800 (PST) Date: Fri, 6 Dec 2019 14:13:39 -0800 In-Reply-To: <20191206221351.38241-1-samitolvanen@google.com> Message-Id: <20191206221351.38241-4-samitolvanen@google.com> Mime-Version: 1.0 References: <20191018161033.261971-1-samitolvanen@google.com> <20191206221351.38241-1-samitolvanen@google.com> X-Mailer: git-send-email 2.24.0.393.g34dc348eaf-goog Subject: [PATCH v6 03/15] arm64: kvm: stop treating register x18 as caller save From: Sami Tolvanen To: Will Deacon , Catalin Marinas , Steven Rostedt , Masami Hiramatsu , Ard Biesheuvel , Mark Rutland Cc: Dave Martin , Kees Cook , Laura Abbott , Marc Zyngier , Nick Desaulniers , Jann Horn , Miguel Ojeda , Masahiro Yamada , clang-built-linux@googlegroups.com, kernel-hardening@lists.openwall.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Sami Tolvanen Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Ard Biesheuvel In preparation of reserving x18, stop treating it as caller save in the KVM guest entry/exit code. Currently, the code assumes there is no need to preserve it for the host, given that it would have been assumed clobbered anyway by the function call to __guest_enter(). Instead, preserve its value and restore it upon return. Link: https://patchwork.kernel.org/patch/9836891/ Signed-off-by: Ard Biesheuvel [Sami: updated commit message, switched from x18 to x29 for the guest context] Signed-off-by: Sami Tolvanen Reviewed-by: Kees Cook Reviewed-by: Marc Zyngier Reviewed-by: Mark Rutland --- arch/arm64/kvm/hyp/entry.S | 45 ++++++++++++++++++++------------------ 1 file changed, 24 insertions(+), 21 deletions(-) -- 2.24.0.393.g34dc348eaf-goog diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S index e5cc8d66bf53..0c6832ec52b1 100644 --- a/arch/arm64/kvm/hyp/entry.S +++ b/arch/arm64/kvm/hyp/entry.S @@ -22,7 +22,12 @@ .text .pushsection .hyp.text, "ax" +/* + * We treat x18 as callee-saved as the host may use it as a platform + * register (e.g. for shadow call stack). + */ .macro save_callee_saved_regs ctxt + str x18, [\ctxt, #CPU_XREG_OFFSET(18)] stp x19, x20, [\ctxt, #CPU_XREG_OFFSET(19)] stp x21, x22, [\ctxt, #CPU_XREG_OFFSET(21)] stp x23, x24, [\ctxt, #CPU_XREG_OFFSET(23)] @@ -32,6 +37,8 @@ .endm .macro restore_callee_saved_regs ctxt + // We require \ctxt is not x18-x28 + ldr x18, [\ctxt, #CPU_XREG_OFFSET(18)] ldp x19, x20, [\ctxt, #CPU_XREG_OFFSET(19)] ldp x21, x22, [\ctxt, #CPU_XREG_OFFSET(21)] ldp x23, x24, [\ctxt, #CPU_XREG_OFFSET(23)] @@ -48,7 +55,7 @@ ENTRY(__guest_enter) // x0: vcpu // x1: host context // x2-x17: clobbered by macros - // x18: guest context + // x29: guest context // Store the host regs save_callee_saved_regs x1 @@ -67,31 +74,28 @@ alternative_else_nop_endif ret 1: - add x18, x0, #VCPU_CONTEXT + add x29, x0, #VCPU_CONTEXT // Macro ptrauth_switch_to_guest format: // ptrauth_switch_to_guest(guest cxt, tmp1, tmp2, tmp3) // The below macro to restore guest keys is not implemented in C code // as it may cause Pointer Authentication key signing mismatch errors // when this feature is enabled for kernel code. - ptrauth_switch_to_guest x18, x0, x1, x2 + ptrauth_switch_to_guest x29, x0, x1, x2 // Restore guest regs x0-x17 - ldp x0, x1, [x18, #CPU_XREG_OFFSET(0)] - ldp x2, x3, [x18, #CPU_XREG_OFFSET(2)] - ldp x4, x5, [x18, #CPU_XREG_OFFSET(4)] - ldp x6, x7, [x18, #CPU_XREG_OFFSET(6)] - ldp x8, x9, [x18, #CPU_XREG_OFFSET(8)] - ldp x10, x11, [x18, #CPU_XREG_OFFSET(10)] - ldp x12, x13, [x18, #CPU_XREG_OFFSET(12)] - ldp x14, x15, [x18, #CPU_XREG_OFFSET(14)] - ldp x16, x17, [x18, #CPU_XREG_OFFSET(16)] - - // Restore guest regs x19-x29, lr - restore_callee_saved_regs x18 - - // Restore guest reg x18 - ldr x18, [x18, #CPU_XREG_OFFSET(18)] + ldp x0, x1, [x29, #CPU_XREG_OFFSET(0)] + ldp x2, x3, [x29, #CPU_XREG_OFFSET(2)] + ldp x4, x5, [x29, #CPU_XREG_OFFSET(4)] + ldp x6, x7, [x29, #CPU_XREG_OFFSET(6)] + ldp x8, x9, [x29, #CPU_XREG_OFFSET(8)] + ldp x10, x11, [x29, #CPU_XREG_OFFSET(10)] + ldp x12, x13, [x29, #CPU_XREG_OFFSET(12)] + ldp x14, x15, [x29, #CPU_XREG_OFFSET(14)] + ldp x16, x17, [x29, #CPU_XREG_OFFSET(16)] + + // Restore guest regs x18-x29, lr + restore_callee_saved_regs x29 // Do not touch any register after this! eret @@ -114,7 +118,7 @@ ENTRY(__guest_exit) // Retrieve the guest regs x0-x1 from the stack ldp x2, x3, [sp], #16 // x0, x1 - // Store the guest regs x0-x1 and x4-x18 + // Store the guest regs x0-x1 and x4-x17 stp x2, x3, [x1, #CPU_XREG_OFFSET(0)] stp x4, x5, [x1, #CPU_XREG_OFFSET(4)] stp x6, x7, [x1, #CPU_XREG_OFFSET(6)] @@ -123,9 +127,8 @@ ENTRY(__guest_exit) stp x12, x13, [x1, #CPU_XREG_OFFSET(12)] stp x14, x15, [x1, #CPU_XREG_OFFSET(14)] stp x16, x17, [x1, #CPU_XREG_OFFSET(16)] - str x18, [x1, #CPU_XREG_OFFSET(18)] - // Store the guest regs x19-x29, lr + // Store the guest regs x18-x29, lr save_callee_saved_regs x1 get_host_ctxt x2, x3