From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joerg Roedel Subject: [PATCH 29/70] x86/head/64: Install boot GDT Date: Thu, 19 Mar 2020 10:13:26 +0100 Message-ID: <20200319091407.1481-30-joro@8bytes.org> References: <20200319091407.1481-1-joro@8bytes.org> Return-path: In-Reply-To: <20200319091407.1481-1-joro@8bytes.org> Sender: linux-kernel-owner@vger.kernel.org To: x86@kernel.org Cc: hpa@zytor.com, Andy Lutomirski , Dave Hansen , Peter Zijlstra , Thomas Hellstrom , Jiri Slaby , Dan Williams , Tom Lendacky , Juergen Gross , Kees Cook , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, Joerg Roedel , Joerg Roedel List-Id: virtualization@lists.linuxfoundation.org From: Joerg Roedel Handling exceptions during boot requires a working GDT. The kernel GDT is not yet ready for use, so install a temporary boot GDT. Signed-off-by: Joerg Roedel --- arch/x86/kernel/head_64.S | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S index 4bbc770af632..5219a70b3fb4 100644 --- a/arch/x86/kernel/head_64.S +++ b/arch/x86/kernel/head_64.S @@ -72,6 +72,26 @@ SYM_CODE_START_NOALIGN(startup_64) /* Set up the stack for verify_cpu(), similar to initial_stack below */ leaq (__end_init_task - SIZEOF_PTREGS)(%rip), %rsp + /* Setup boot GDT descriptor and load boot GDT */ + leaq boot_gdt(%rip), %rax + movq %rax, boot_gdt_base(%rip) + lgdt boot_gdt_descr(%rip) + + /* New GDT is live - reload data segment registers */ + movl $__KERNEL_DS, %eax + movl %eax, %ds + movl %eax, %ss + movl %eax, %es + + /* Now switch to __KERNEL_CS so IRET works reliably */ + pushq $__KERNEL_CS + leaq .Lon_kernel_cs(%rip), %rax + pushq %rax + lretq + +.Lon_kernel_cs: + UNWIND_HINT_EMPTY + /* Sanitize CPU configuration */ call verify_cpu @@ -480,6 +500,18 @@ SYM_DATA_LOCAL(early_gdt_descr_base, .quad INIT_PER_CPU_VAR(gdt_page)) SYM_DATA(phys_base, .quad 0x0) EXPORT_SYMBOL(phys_base) +/* Boot GDT used when kernel addresses are not mapped yet */ +SYM_DATA_LOCAL(boot_gdt_descr, .word boot_gdt_end - boot_gdt) +SYM_DATA_LOCAL(boot_gdt_base, .quad 0) +SYM_DATA_START(boot_gdt) + .quad 0 + .quad 0x00cf9a000000ffff /* __KERNEL32_CS */ + .quad 0x00af9a000000ffff /* __KERNEL_CS */ + .quad 0x00cf92000000ffff /* __KERNEL_DS */ + .quad 0x0080890000000000 /* TS descriptor */ + .quad 0x0000000000000000 /* TS continued */ +SYM_DATA_END_LABEL(boot_gdt, SYM_L_LOCAL, boot_gdt_end) + #include "../../x86/xen/xen-head.S" __PAGE_ALIGNED_BSS -- 2.17.1