On Mon, May 18, 2020 at 10:23:13AM +0200, Borislav Petkov wrote: > On Tue, Apr 28, 2020 at 05:16:41PM +0200, Joerg Roedel wrote: > > @@ -480,6 +500,22 @@ 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 0 /* __USER32_CS - unused */ > > + .quad 0 /* __USER_DS - unused */ > > + .quad 0 /* __USER_CS - unused */ > > + .quad 0 /* unused */ > > + .quad 0x0080890000000000 /* TSS descriptor */ > > + .quad 0x0000000000000000 /* TSS continued */ > > Any chance you could use macros ala GDT_ENTRY_INIT() for those instead > of the naked values?
Yeah, seems to work. Updated patch attached. >From 1350746f9063147a33156c0b56a7b12b1794f555 Mon Sep 17 00:00:00 2001 From: Joerg Roedel <[email protected]> Date: Fri, 15 Nov 2019 13:49:55 +0100 Subject: [PATCH 31/74] x86/head/64: Install boot GDT 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 <[email protected]> --- arch/x86/kernel/head64.c | 19 +++++++++++++++++++ arch/x86/kernel/head_64.S | 25 +++++++++++++++++++++++++ 2 files changed, 44 insertions(+) diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c index 206a4b6144c2..900c3372cc6a 100644 --- a/arch/x86/kernel/head64.c +++ b/arch/x86/kernel/head64.c @@ -61,6 +61,25 @@ unsigned long vmemmap_base __ro_after_init = __VMEMMAP_BASE_L4; EXPORT_SYMBOL(vmemmap_base); #endif +/* + * GDT used before %gs is set up and the kernel can use gdt_page. Needed for + * early exception handling. + */ +struct desc_struct boot_gdt[GDT_ENTRIES] = { + [GDT_ENTRY_KERNEL32_CS] = GDT_ENTRY_INIT(0xc09b, 0, 0xfffff), + [GDT_ENTRY_KERNEL_CS] = GDT_ENTRY_INIT(0xa09b, 0, 0xfffff), + [GDT_ENTRY_KERNEL_DS] = GDT_ENTRY_INIT(0xc093, 0, 0xfffff), +}; + +/* + * Address needs to be set at runtime because it references the boot_gdt while + * the kernel still uses a direct mapping. + */ +struct desc_ptr boot_gdt_descr = { + .size = sizeof(boot_gdt), + .address = 0, +}; + #define __head __section(.head.text) static void __head *fixup_pointer(void *ptr, unsigned long physaddr) diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S index 4bbc770af632..62513dd1e0e4 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_descr+2(%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 @@ -143,6 +163,11 @@ SYM_CODE_START(secondary_startup_64) 1: UNWIND_HINT_EMPTY + /* Setup boot GDT descriptor and load boot GDT */ + leaq boot_gdt(%rip), %rax + movq %rax, boot_gdt_descr+2(%rip) + lgdt boot_gdt_descr(%rip) + /* Check if nx is implemented */ movl $0x80000001, %eax cpuid -- 2.26.2 _______________________________________________ Virtualization mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/virtualization
