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AJvYcCWG2pRGfAtXAWa9P4b1+XdlL0MfvWFzTOxuvd/EQnLZ8iWw1orP/qsC7QUxdKZI3gmmKDHEOwvnVp8=@vger.kernel.org X-Gm-Message-State: AOJu0YzwkB5cgxjUH1eCra0477hTFsRnIb9qzidEEz/YBgF4gkBcc3nN JB7Et0WesBjhjGUhWsZHt9gKEEiM4iava+j4ka7WmHdOyz59YvWS33JRTbMSKzjEH9rLzw== X-Google-Smtp-Source: AGHT+IHCtqA+oNLQfmXqpM//kOUUkVuRiayEu9UAQA8X933VnnJ2JGMGIKXjp5QscVvSLG685e3KtDKL X-Received: from palermo.c.googlers.com ([fda3:e722:ac3:cc00:7b:198d:ac11:8138]) (user=ardb job=sendgmr) by 2002:a05:6902:1782:b0:e0b:958a:3344 with SMTP id 3f1490d57ef6-e24da39b0c3mr17940276.10.1727276578847; Wed, 25 Sep 2024 08:02:58 -0700 (PDT) Date: Wed, 25 Sep 2024 17:01:27 +0200 In-Reply-To: <20240925150059.3955569-30-ardb+git@google.com> Precedence: bulk X-Mailing-List: linux-efi@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=4280; i=ardb@kernel.org; h=from:subject; bh=Qfoxr/CYN1brA02vZLn1djUOVE7sfU2DhAxM/gB47SE=; b=owGbwMvMwCFmkMcZplerG8N4Wi2JIe2L6qUIX51znF3nJyzZfmoB13+eT2d+37/IY95y8cys2 5n+JYzJHaUsDGIcDLJiiiwCs/++23l6olSt8yxZmDmsTCBDGLg4BWAifvYMv5jZZ0me+ya2VVnU Ozku0cJESLKOW+VHtMSKvW8vdx2dKMfIsJzzq0hJkqFDXdOunnmqwir812MtQuf0H13yi9n0fe8 DLgA= X-Mailer: git-send-email 2.46.0.792.g87dc391469-goog Message-ID: <20240925150059.3955569-57-ardb+git@google.com> Subject: [RFC PATCH 27/28] x86/kernel: Switch to PIE linking for the core kernel 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 Build the kernel as a Position Independent Executable (PIE). This results in more efficient relocation processing for the virtual displacement of the kernel (for KASLR). More importantly, it instructs the linker to generate what is actually needed (a program that can be moved around in memory before execution), which is better than having to rely on the linker to create a position dependent binary that happens to tolerate being moved around after poking it in exactly the right manner. Note that this means that all codegen should be compatible with PIE, including Rust objects, so this needs to switch to the small code model with the PIE relocation model as well. Signed-off-by: Ard Biesheuvel --- arch/x86/Kconfig | 2 +- arch/x86/Makefile | 11 +++++++---- arch/x86/boot/compressed/misc.c | 2 ++ arch/x86/kernel/vmlinux.lds.S | 5 +++++ drivers/firmware/efi/libstub/x86-stub.c | 2 ++ 5 files changed, 17 insertions(+), 5 deletions(-) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 54cb1f14218b..dbb4d284b0e1 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -2187,7 +2187,7 @@ config RANDOMIZE_BASE # Relocation on x86 needs some additional build support config X86_NEED_RELOCS def_bool y - depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE) + depends on X86_32 && RELOCATABLE config PHYSICAL_ALIGN hex "Alignment value to which kernel should be aligned" diff --git a/arch/x86/Makefile b/arch/x86/Makefile index 83d20f402535..c1dcff444bc8 100644 --- a/arch/x86/Makefile +++ b/arch/x86/Makefile @@ -206,9 +206,8 @@ else PIE_CFLAGS-$(CONFIG_SMP) += -mstack-protector-guard-reg=gs endif - # Don't emit relaxable GOTPCREL relocations - KBUILD_AFLAGS_KERNEL += -Wa,-mrelax-relocations=no - KBUILD_CFLAGS_KERNEL += -Wa,-mrelax-relocations=no $(PIE_CFLAGS-y) + KBUILD_CFLAGS_KERNEL += $(PIE_CFLAGS-y) + KBUILD_RUSTFLAGS_KERNEL += -Ccode-model=small -Crelocation-model=pie endif # @@ -264,12 +263,16 @@ else LDFLAGS_vmlinux := endif +ifdef CONFIG_X86_64 +ldflags-pie-$(CONFIG_LD_IS_LLD) := --apply-dynamic-relocs +ldflags-pie-$(CONFIG_LD_IS_BFD) := -z call-nop=suffix-nop +LDFLAGS_vmlinux += --pie -z text $(ldflags-pie-y) + # # The 64-bit kernel must be aligned to 2MB. Pass -z max-page-size=0x200000 to # the linker to force 2MB page size regardless of the default page size used # by the linker. # -ifdef CONFIG_X86_64 LDFLAGS_vmlinux += -z max-page-size=0x200000 endif diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c index 89f01375cdb7..79e3ffe16f61 100644 --- a/arch/x86/boot/compressed/misc.c +++ b/arch/x86/boot/compressed/misc.c @@ -495,6 +495,8 @@ asmlinkage __visible void *extract_kernel(void *rmode, unsigned char *output) error("Destination virtual address changed when not relocatable"); #endif + boot_params_ptr->kaslr_va_shift = virt_addr - LOAD_PHYSICAL_ADDR; + debug_putstr("\nDecompressing Linux... "); if (init_unaccepted_memory()) { diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S index f7e832c2ac61..d172e6e8eaaf 100644 --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -459,6 +459,11 @@ xen_elfnote_phys32_entry_offset = DISCARDS + /DISCARD/ : { + *(.dynsym .gnu.hash .hash .dynamic .dynstr) + *(.interp .dynbss .eh_frame .sframe) + } + /* * Make sure that the .got.plt is either completely empty or it * contains only the lazy dispatch entries. diff --git a/drivers/firmware/efi/libstub/x86-stub.c b/drivers/firmware/efi/libstub/x86-stub.c index f8e465da344d..5c03954924fe 100644 --- a/drivers/firmware/efi/libstub/x86-stub.c +++ b/drivers/firmware/efi/libstub/x86-stub.c @@ -912,6 +912,8 @@ static efi_status_t efi_decompress_kernel(unsigned long *kernel_entry) if (status != EFI_SUCCESS) return status; + boot_params_ptr->kaslr_va_shift = virt_addr - LOAD_PHYSICAL_ADDR; + entry = decompress_kernel((void *)addr, virt_addr, error); if (entry == ULONG_MAX) { efi_free(alloc_size, addr);