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x86/mm/cpa: Rework static_protections()
static_protections() is pretty unreadable. Split it up into separate checks for each protection area. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Dave Hansen <dave.hansen@intel.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Bin Yang <bin.yang@intel.com> Cc: Mark Gross <mark.gross@intel.com> Link: https://lkml.kernel.org/r/20180917143545.913005317@linutronix.de
This commit is contained in:
Thomas Gleixner
parent
8679de0959
commit
afd7969a99
@ -286,6 +286,98 @@ static void cpa_flush_array(unsigned long *start, int numpages, int cache,
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}
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}
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#ifdef CONFIG_PCI_BIOS
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/*
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* The BIOS area between 640k and 1Mb needs to be executable for PCI BIOS
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* based config access (CONFIG_PCI_GOBIOS) support.
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*/
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#define BIOS_PFN PFN_DOWN(BIOS_BEGIN)
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#define BIOS_PFN_END PFN_DOWN(BIOS_END)
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static pgprotval_t protect_pci_bios(unsigned long pfn)
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{
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if (pcibios_enabled && within(pfn, BIOS_PFN, BIOS_PFN_END))
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return _PAGE_NX;
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return 0;
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}
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#else
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static pgprotval_t protect_pci_bios(unsigned long pfn)
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{
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return 0;
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}
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#endif
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/*
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* The .rodata section needs to be read-only. Using the pfn catches all
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* aliases. This also includes __ro_after_init, so do not enforce until
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* kernel_set_to_readonly is true.
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*/
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static pgprotval_t protect_rodata(unsigned long pfn)
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{
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unsigned long start_pfn = __pa_symbol(__start_rodata) >> PAGE_SHIFT;
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unsigned long end_pfn = __pa_symbol(__end_rodata) >> PAGE_SHIFT;
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if (kernel_set_to_readonly && within(pfn, start_pfn, end_pfn))
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return _PAGE_RW;
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return 0;
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}
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/*
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* Protect kernel text against becoming non executable by forbidding
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* _PAGE_NX. This protects only the high kernel mapping (_text -> _etext)
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* out of which the kernel actually executes. Do not protect the low
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* mapping.
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*
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* This does not cover __inittext since that is gone after boot.
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*/
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static pgprotval_t protect_kernel_text(unsigned long address)
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{
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if (within(address, (unsigned long)_text, (unsigned long)_etext))
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return _PAGE_NX;
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return 0;
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}
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#if defined(CONFIG_X86_64)
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/*
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* Once the kernel maps the text as RO (kernel_set_to_readonly is set),
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* kernel text mappings for the large page aligned text, rodata sections
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* will be always read-only. For the kernel identity mappings covering the
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* holes caused by this alignment can be anything that user asks.
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*
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* This will preserve the large page mappings for kernel text/data at no
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* extra cost.
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*/
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static pgprotval_t protect_kernel_text_ro(unsigned long address)
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{
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unsigned long end = (unsigned long)__end_rodata_hpage_align;
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unsigned long start = (unsigned long)_text;
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unsigned int level;
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if (!kernel_set_to_readonly || !within(address, start, end))
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return 0;
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/*
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* Don't enforce the !RW mapping for the kernel text mapping, if
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* the current mapping is already using small page mapping. No
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* need to work hard to preserve large page mappings in this case.
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*
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* This also fixes the Linux Xen paravirt guest boot failure caused
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* by unexpected read-only mappings for kernel identity
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* mappings. In this paravirt guest case, the kernel text mapping
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* and the kernel identity mapping share the same page-table pages,
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* so the protections for kernel text and identity mappings have to
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* be the same.
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*/
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if (lookup_address(address, &level) && (level != PG_LEVEL_4K))
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return _PAGE_RW;
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return 0;
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}
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#else
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static pgprotval_t protect_kernel_text_ro(unsigned long address)
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{
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return 0;
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}
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#endif
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/*
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* Certain areas of memory on x86 require very specific protection flags,
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* for example the BIOS area or kernel text. Callers don't always get this
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@ -295,75 +387,17 @@ static void cpa_flush_array(unsigned long *start, int numpages, int cache,
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static inline pgprot_t static_protections(pgprot_t prot, unsigned long address,
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unsigned long pfn)
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{
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pgprot_t forbidden = __pgprot(0);
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pgprotval_t forbidden;
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/*
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* The BIOS area between 640k and 1Mb needs to be executable for
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* PCI BIOS based config access (CONFIG_PCI_GOBIOS) support.
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*/
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#ifdef CONFIG_PCI_BIOS
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if (pcibios_enabled && within(pfn, BIOS_BEGIN >> PAGE_SHIFT, BIOS_END >> PAGE_SHIFT))
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pgprot_val(forbidden) |= _PAGE_NX;
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#endif
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/* Operate on the virtual address */
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forbidden = protect_kernel_text(address);
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forbidden |= protect_kernel_text_ro(address);
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/*
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* The kernel text needs to be executable for obvious reasons
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* Does not cover __inittext since that is gone later on. On
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* 64bit we do not enforce !NX on the low mapping
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*/
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if (within(address, (unsigned long)_text, (unsigned long)_etext))
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pgprot_val(forbidden) |= _PAGE_NX;
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/* Check the PFN directly */
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forbidden |= protect_pci_bios(pfn);
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forbidden |= protect_rodata(pfn);
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/*
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* The .rodata section needs to be read-only. Using the pfn
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* catches all aliases. This also includes __ro_after_init,
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* so do not enforce until kernel_set_to_readonly is true.
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*/
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if (kernel_set_to_readonly &&
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within(pfn, __pa_symbol(__start_rodata) >> PAGE_SHIFT,
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__pa_symbol(__end_rodata) >> PAGE_SHIFT))
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pgprot_val(forbidden) |= _PAGE_RW;
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#if defined(CONFIG_X86_64)
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/*
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* Once the kernel maps the text as RO (kernel_set_to_readonly is set),
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* kernel text mappings for the large page aligned text, rodata sections
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* will be always read-only. For the kernel identity mappings covering
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* the holes caused by this alignment can be anything that user asks.
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*
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* This will preserve the large page mappings for kernel text/data
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* at no extra cost.
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*/
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if (kernel_set_to_readonly &&
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within(address, (unsigned long)_text,
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(unsigned long)__end_rodata_hpage_align)) {
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unsigned int level;
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/*
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* Don't enforce the !RW mapping for the kernel text mapping,
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* if the current mapping is already using small page mapping.
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* No need to work hard to preserve large page mappings in this
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* case.
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*
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* This also fixes the Linux Xen paravirt guest boot failure
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* (because of unexpected read-only mappings for kernel identity
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* mappings). In this paravirt guest case, the kernel text
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* mapping and the kernel identity mapping share the same
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* page-table pages. Thus we can't really use different
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* protections for the kernel text and identity mappings. Also,
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* these shared mappings are made of small page mappings.
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* Thus this don't enforce !RW mapping for small page kernel
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* text mapping logic will help Linux Xen parvirt guest boot
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* as well.
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*/
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if (lookup_address(address, &level) && (level != PG_LEVEL_4K))
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pgprot_val(forbidden) |= _PAGE_RW;
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}
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#endif
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prot = __pgprot(pgprot_val(prot) & ~pgprot_val(forbidden));
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return prot;
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return __pgprot(pgprot_val(prot) & ~forbidden);
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}
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/*
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