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AJvYcCXTsI3UNr6KguE92xKmP+zUb77vDPuBZKyNC33wXE0bvL0lTuyghElhHmUE5FhZKpVgP8B/fSLTr7eCBT0=@vger.kernel.org X-Gm-Message-State: AOJu0YyHTygh+Mb75JBJRlj1DAIC3jEtIG0bioZp1eIJ+MEl7EKAaMDN Lgbm1OTSGGVrO6NNKP0l1kIfP8opFRA9lGJNSRASSa6/HQyMTXb44ciha65tD6tI6ADuQg== X-Google-Smtp-Source: AGHT+IGNEZwim//wtoUQ0IgEwXQAmuWMXuvjVNrkXztiUbXuSVle0sf2azOpfGly/wGUuNh4kSi9g764 X-Received: from palermo.c.googlers.com ([fda3:e722:ac3:cc00:7b:198d:ac11:8138]) (user=ardb job=sendgmr) by 2002:a05:600c:4b23:b0:42c:b635:9ba7 with SMTP id 5b1f17b1804b1-42e961449f9mr294105e9.3.1727276511763; Wed, 25 Sep 2024 08:01:51 -0700 (PDT) Date: Wed, 25 Sep 2024 17:01:01 +0200 In-Reply-To: <20240925150059.3955569-30-ardb+git@google.com> Precedence: bulk X-Mailing-List: linux-sparse@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240925150059.3955569-30-ardb+git@google.com> X-Developer-Key: i=ardb@kernel.org; a=openpgp; fpr=F43D03328115A198C90016883D200E9CA6329909 X-Developer-Signature: v=1; a=openpgp-sha256; l=1383; i=ardb@kernel.org; h=from:subject; bh=kkus52hb+9U3rGqLGvcTtWiqi7ULiH1wdI2hpFI7/9I=; b=owGbwMvMwCFmkMcZplerG8N4Wi2JIe2L6loPG1eTz6/TRZ+ExF55v9yoPVaMz0DJP05TXvNix 3yvWS87SlkYxDgYZMUUWQRm/3238/REqVrnWbIwc1iZQIYwcHEKwER0vzAyLNdk+Hf0DcN93e0c kou2iV0ReKfEPrsn3ORh04fsoM3R+gz/0yZt5ne4cnJFldTMQpGfLor75ZYczDujFLCs+4iee6Q pMwA= X-Mailer: git-send-email 2.46.0.792.g87dc391469-goog Message-ID: <20240925150059.3955569-31-ardb+git@google.com> Subject: [RFC PATCH 01/28] x86/pvh: Call C code via the kernel virtual mapping From: Ard Biesheuvel To: linux-kernel@vger.kernel.org Cc: Ard Biesheuvel , x86@kernel.org, "H. Peter Anvin" , Andy Lutomirski , Peter Zijlstra , Uros Bizjak , Dennis Zhou , Tejun Heo , Christoph Lameter , Mathieu Desnoyers , Paolo Bonzini , Vitaly Kuznetsov , Juergen Gross , Boris Ostrovsky , Greg Kroah-Hartman , Arnd Bergmann , Masahiro Yamada , Kees Cook , Nathan Chancellor , Keith Packard , Justin Stitt , Josh Poimboeuf , Arnaldo Carvalho de Melo , Namhyung Kim , Jiri Olsa , Ian Rogers , Adrian Hunter , Kan Liang , linux-doc@vger.kernel.org, linux-pm@vger.kernel.org, kvm@vger.kernel.org, xen-devel@lists.xenproject.org, linux-efi@vger.kernel.org, linux-arch@vger.kernel.org, linux-sparse@vger.kernel.org, linux-kbuild@vger.kernel.org, linux-perf-users@vger.kernel.org, rust-for-linux@vger.kernel.org, llvm@lists.linux.dev From: Ard Biesheuvel Calling C code via a different mapping than it was linked at is problematic, because the compiler assumes that RIP-relative and absolute symbol references are interchangeable. GCC in particular may use RIP-relative per-CPU variable references even when not using -fpic. So call xen_prepare_pvh() via its kernel virtual mapping on x86_64, so that those RIP-relative references produce the correct values. This matches the pre-existing behavior for i386, which also invokes xen_prepare_pvh() via the kernel virtual mapping before invoking startup_32 with paging disabled again. Fixes: 7243b93345f7 ("xen/pvh: Bootstrap PVH guest") Signed-off-by: Ard Biesheuvel Tested-by: Jason Andryuk Reviewed-by: Jason Andryuk --- arch/x86/platform/pvh/head.S | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/arch/x86/platform/pvh/head.S b/arch/x86/platform/pvh/head.S index f7235ef87bc3..a308b79a887c 100644 --- a/arch/x86/platform/pvh/head.S +++ b/arch/x86/platform/pvh/head.S @@ -101,7 +101,11 @@ SYM_CODE_START_LOCAL(pvh_start_xen) xor %edx, %edx wrmsr - call xen_prepare_pvh + /* Call xen_prepare_pvh() via the kernel virtual mapping */ + leaq xen_prepare_pvh(%rip), %rax + addq $__START_KERNEL_map, %rax + ANNOTATE_RETPOLINE_SAFE + call *%rax /* startup_64 expects boot_params in %rsi. */ mov $_pa(pvh_bootparams), %rsi