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Message-ID: <20160419142741.GI3886@suse.de>
Date: Tue, 19 Apr 2016 16:27:41 +0200
From: Joerg Roedel <jroedel@...e.de>
To: Thomas Garnier <thgarnie@...gle.com>
Cc: "H . Peter Anvin" <hpa@...or.com>, Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...e.de>,
Andy Lutomirski <luto@...nel.org>,
Dmitry Vyukov <dvyukov@...gle.com>,
Paolo Bonzini <pbonzini@...hat.com>,
Dan Williams <dan.j.williams@...el.com>,
Kees Cook <keescook@...omium.org>,
Stephen Smalley <sds@...ho.nsa.gov>,
Seth Jennings <sjennings@...iantweb.net>,
Kefeng Wang <wangkefeng.wang@...wei.com>,
Jonathan Corbet <corbet@....net>,
Matt Fleming <matt@...eblueprint.co.uk>,
Toshi Kani <toshi.kani@....com>,
Alexander Kuleshov <kuleshovmail@...il.com>,
Alexander Popov <alpopov@...ecurity.com>,
Dave Young <dyoung@...hat.com>, Baoquan He <bhe@...hat.com>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Mark Salter <msalter@...hat.com>,
Boris Ostrovsky <boris.ostrovsky@...cle.com>, x86@...nel.org,
linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
gthelen@...gle.com, kernel-hardening@...ts.openwall.com
Subject: Re: [RFC v1 3/4] x86, boot: Implement ASLR for kernel memory
sections (x86_64)
Hi Thomas,
On Fri, Apr 15, 2016 at 03:03:12PM -0700, Thomas Garnier wrote:
> +/*
> + * Create PGD aligned trampoline table to allow real mode initialization
> + * of additional CPUs. Consume only 1 additonal low memory page.
> + */
> +void __meminit kaslr_trampoline_init(unsigned long page_size_mask)
> +{
> + unsigned long addr, next, end;
> + pgd_t *pgd;
> + pud_t *pud_page, *tr_pud_page;
> + int i;
> +
> + if (!kaslr_enabled()) {
> + trampoline_pgd_entry = init_level4_pgt[pgd_index(PAGE_OFFSET)];
> + return;
> + }
> +
> + tr_pud_page = alloc_low_page();
> + set_pgd(&trampoline_pgd_entry, __pgd(_PAGE_TABLE | __pa(tr_pud_page)));
> +
> + addr = 0;
> + end = ISA_END_ADDRESS;
> + pgd = pgd_offset_k((unsigned long)__va(addr));
> + pud_page = (pud_t *) pgd_page_vaddr(*pgd);
> +
> + for (i = pud_index(addr); i < PTRS_PER_PUD; i++, addr = next) {
> + pud_t *pud, *tr_pud;
> + pmd_t *pmd;
> +
> + tr_pud = tr_pud_page + pud_index(addr);
> + pud = pud_page + pud_index((unsigned long)__va(addr));
> + next = (addr & PUD_MASK) + PUD_SIZE;
> +
> + if (addr >= end || !pud_val(*pud)) {
> + if (!after_bootmem &&
> + !e820_any_mapped(addr & PUD_MASK, next, E820_RAM) &&
> + !e820_any_mapped(addr & PUD_MASK, next,
> + E820_RESERVED_KERN))
> + set_pud(tr_pud, __pud(0));
> + continue;
> + }
> +
> + if (page_size_mask & (1<<PG_LEVEL_1G)) {
> + set_pte((pte_t *)tr_pud,
> + pfn_pte((__pa(addr) & PUD_MASK) >> PAGE_SHIFT,
Hmm, why do you treat addr as virtual here, before it was a physical
address, no?
> + PAGE_KERNEL_LARGE));
> + continue;
> + }
Why do you need to check these two cases above, can't you just copy the
pud-entries like done below? The direct mapping should already take care
of unmapped regions and 1gb pages.
> + pmd = pmd_offset(pud, 0);
> + set_pud(tr_pud, __pud(_PAGE_TABLE | __pa(pmd)));
> + }
> +}
Joerg
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