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6f599d8423
On x86, purgatory() copies the first 640K of memory to a backup region because the kernel needs those first 640K for the real mode trampoline during boot, among others. However, when SME is enabled, the kernel cannot properly copy the old memory to the backup area but reads only its encrypted contents. The result is that the crash tool gets invalid pointers when parsing vmcore: crash> kmem -s|grep -i invalid kmem: dma-kmalloc-512: slab:ffffd77680001c00 invalid freepointer:a6086ac099f0c5a4 kmem: dma-kmalloc-512: slab:ffffd77680001c00 invalid freepointer:a6086ac099f0c5a4 crash> So reserve the remaining low 1M memory when the crashkernel option is specified (after reserving real mode memory) so that allocated memory does not fall into the low 1M area and thus the copying of the contents of the first 640k to a backup region in purgatory() can be avoided altogether. This way, it does not need to be included in crash dumps or used for anything except the trampolines that must live in the low 1M. [ bp: Heavily rewrite commit message, flip check logic in crash_reserve_low_1M().] Signed-off-by: Lianbo Jiang <lijiang@redhat.com> Signed-off-by: Borislav Petkov <bp@suse.de> Cc: bhe@redhat.com Cc: Dave Young <dyoung@redhat.com> Cc: d.hatayama@fujitsu.com Cc: dhowells@redhat.com Cc: ebiederm@xmission.com Cc: horms@verge.net.au Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jürgen Gross <jgross@suse.com> Cc: kexec@lists.infradead.org Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Tom Lendacky <thomas.lendacky@amd.com> Cc: vgoyal@redhat.com Cc: x86-ml <x86@kernel.org> Link: https://lkml.kernel.org/r/20191108090027.11082-2-lijiang@redhat.com Link: https://bugzilla.kernel.org/show_bug.cgi?id=204793
156 lines
3.9 KiB
C
156 lines
3.9 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/io.h>
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#include <linux/slab.h>
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#include <linux/memblock.h>
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#include <linux/mem_encrypt.h>
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#include <asm/set_memory.h>
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#include <asm/pgtable.h>
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#include <asm/realmode.h>
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#include <asm/tlbflush.h>
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#include <asm/crash.h>
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struct real_mode_header *real_mode_header;
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u32 *trampoline_cr4_features;
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/* Hold the pgd entry used on booting additional CPUs */
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pgd_t trampoline_pgd_entry;
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void __init reserve_real_mode(void)
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{
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phys_addr_t mem;
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size_t size = real_mode_size_needed();
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if (!size)
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return;
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WARN_ON(slab_is_available());
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/* Has to be under 1M so we can execute real-mode AP code. */
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mem = memblock_find_in_range(0, 1<<20, size, PAGE_SIZE);
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if (!mem) {
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pr_info("No sub-1M memory is available for the trampoline\n");
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return;
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}
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memblock_reserve(mem, size);
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set_real_mode_mem(mem);
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crash_reserve_low_1M();
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}
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static void __init setup_real_mode(void)
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{
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u16 real_mode_seg;
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const u32 *rel;
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u32 count;
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unsigned char *base;
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unsigned long phys_base;
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struct trampoline_header *trampoline_header;
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size_t size = PAGE_ALIGN(real_mode_blob_end - real_mode_blob);
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#ifdef CONFIG_X86_64
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u64 *trampoline_pgd;
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u64 efer;
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#endif
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base = (unsigned char *)real_mode_header;
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/*
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* If SME is active, the trampoline area will need to be in
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* decrypted memory in order to bring up other processors
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* successfully. This is not needed for SEV.
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*/
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if (sme_active())
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set_memory_decrypted((unsigned long)base, size >> PAGE_SHIFT);
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memcpy(base, real_mode_blob, size);
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phys_base = __pa(base);
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real_mode_seg = phys_base >> 4;
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rel = (u32 *) real_mode_relocs;
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/* 16-bit segment relocations. */
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count = *rel++;
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while (count--) {
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u16 *seg = (u16 *) (base + *rel++);
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*seg = real_mode_seg;
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}
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/* 32-bit linear relocations. */
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count = *rel++;
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while (count--) {
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u32 *ptr = (u32 *) (base + *rel++);
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*ptr += phys_base;
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}
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/* Must be perfomed *after* relocation. */
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trampoline_header = (struct trampoline_header *)
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__va(real_mode_header->trampoline_header);
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#ifdef CONFIG_X86_32
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trampoline_header->start = __pa_symbol(startup_32_smp);
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trampoline_header->gdt_limit = __BOOT_DS + 7;
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trampoline_header->gdt_base = __pa_symbol(boot_gdt);
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#else
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/*
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* Some AMD processors will #GP(0) if EFER.LMA is set in WRMSR
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* so we need to mask it out.
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*/
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rdmsrl(MSR_EFER, efer);
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trampoline_header->efer = efer & ~EFER_LMA;
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trampoline_header->start = (u64) secondary_startup_64;
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trampoline_cr4_features = &trampoline_header->cr4;
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*trampoline_cr4_features = mmu_cr4_features;
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trampoline_header->flags = 0;
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if (sme_active())
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trampoline_header->flags |= TH_FLAGS_SME_ACTIVE;
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trampoline_pgd = (u64 *) __va(real_mode_header->trampoline_pgd);
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trampoline_pgd[0] = trampoline_pgd_entry.pgd;
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trampoline_pgd[511] = init_top_pgt[511].pgd;
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#endif
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}
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/*
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* reserve_real_mode() gets called very early, to guarantee the
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* availability of low memory. This is before the proper kernel page
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* tables are set up, so we cannot set page permissions in that
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* function. Also trampoline code will be executed by APs so we
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* need to mark it executable at do_pre_smp_initcalls() at least,
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* thus run it as a early_initcall().
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*/
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static void __init set_real_mode_permissions(void)
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{
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unsigned char *base = (unsigned char *) real_mode_header;
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size_t size = PAGE_ALIGN(real_mode_blob_end - real_mode_blob);
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size_t ro_size =
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PAGE_ALIGN(real_mode_header->ro_end) -
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__pa(base);
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size_t text_size =
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PAGE_ALIGN(real_mode_header->ro_end) -
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real_mode_header->text_start;
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unsigned long text_start =
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(unsigned long) __va(real_mode_header->text_start);
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set_memory_nx((unsigned long) base, size >> PAGE_SHIFT);
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set_memory_ro((unsigned long) base, ro_size >> PAGE_SHIFT);
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set_memory_x((unsigned long) text_start, text_size >> PAGE_SHIFT);
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}
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static int __init init_real_mode(void)
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{
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if (!real_mode_header)
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panic("Real mode trampoline was not allocated");
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setup_real_mode();
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set_real_mode_permissions();
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return 0;
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}
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early_initcall(init_real_mode);
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