From 58e65b51e6f9b9dd94a25ff2b2772222e0358099 Mon Sep 17 00:00:00 2001 From: Dave Hansen Date: Fri, 20 Apr 2018 15:20:21 -0700 Subject: [PATCH] x86/pti: Fix boot warning from Global-bit setting commit 231df823c4f04176f607afc4576c989895cff40e The pageattr.c code attempts to process "faults" when it goes looking for PTEs to change and finds non-present entries. It allows these faults in the linear map which is "expected to have holes", but WARN()s about them elsewhere, like when called on the kernel image. However, change_page_attr_clear() is now called on the kernel image in the process of trying to clear the Global bit. This trips the warning in __cpa_process_fault() if a non-present PTE is encountered in the kernel image. The "holes" in the kernel image result from free_init_pages()'s use of set_memory_np(). These holes are totally fine, and result from normal operation, just as they would be in the kernel linear map. Just silence the warning when holes in the kernel image are encountered. Fixes: 39114b7a7 (x86/pti: Never implicitly clear _PAGE_GLOBAL for kernel image) Reported-by: Mariusz Ceier Reported-by: Aaro Koskinen Signed-off-by: Dave Hansen Signed-off-by: Thomas Gleixner Tested-by: Aaro Koskinen Acked-by: Ingo Molnar Cc: Andrea Arcangeli Cc: Juergen Gross Cc: Nadav Amit Cc: Kees Cook Cc: Josh Poimboeuf Cc: Peter Zijlstra Cc: David Woodhouse Cc: Hugh Dickins Cc: linux-mm@kvack.org Cc: Linus Torvalds Cc: Andy Lutomirski Cc: Greg Kroah-Hartman Cc: Borislav Petkov Cc: Dan Williams Cc: Arjan van de Ven Link: https://lkml.kernel.org/r/20180420222021.1C7D2B3F@viggo.jf.intel.com --- arch/x86/mm/pageattr.c | 40 ++++++++++++++++++++++++++++++---------- 1 file changed, 30 insertions(+), 10 deletions(-) diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c index 4fadfd2b7017..3bded76e8d5c 100644 --- a/arch/x86/mm/pageattr.c +++ b/arch/x86/mm/pageattr.c @@ -93,6 +93,18 @@ void arch_report_meminfo(struct seq_file *m) static inline void split_page_count(int level) { } #endif +static inline int +within(unsigned long addr, unsigned long start, unsigned long end) +{ + return addr >= start && addr < end; +} + +static inline int +within_inclusive(unsigned long addr, unsigned long start, unsigned long end) +{ + return addr >= start && addr <= end; +} + #ifdef CONFIG_X86_64 static inline unsigned long highmap_start_pfn(void) @@ -106,20 +118,25 @@ static inline unsigned long highmap_end_pfn(void) return __pa_symbol(roundup(_brk_end, PMD_SIZE) - 1) >> PAGE_SHIFT; } -#endif - -static inline int -within(unsigned long addr, unsigned long start, unsigned long end) +static bool __cpa_pfn_in_highmap(unsigned long pfn) { - return addr >= start && addr < end; + /* + * Kernel text has an alias mapping at a high address, known + * here as "highmap". + */ + return within_inclusive(pfn, highmap_start_pfn(), highmap_end_pfn()); } -static inline int -within_inclusive(unsigned long addr, unsigned long start, unsigned long end) +#else + +static bool __cpa_pfn_in_highmap(unsigned long pfn) { - return addr >= start && addr <= end; + /* There is no highmap on 32-bit */ + return false; } +#endif + /* * Flushing functions */ @@ -1183,6 +1200,10 @@ static int __cpa_process_fault(struct cpa_data *cpa, unsigned long vaddr, cpa->numpages = 1; cpa->pfn = __pa(vaddr) >> PAGE_SHIFT; return 0; + + } else if (__cpa_pfn_in_highmap(cpa->pfn)) { + /* Faults in the highmap are OK, so do not warn: */ + return -EFAULT; } else { WARN(1, KERN_WARNING "CPA: called for zero pte. " "vaddr = %lx cpa->vaddr = %lx\n", vaddr, @@ -1335,8 +1356,7 @@ static int cpa_process_alias(struct cpa_data *cpa) * to touch the high mapped kernel as well: */ if (!within(vaddr, (unsigned long)_text, _brk_end) && - within_inclusive(cpa->pfn, highmap_start_pfn(), - highmap_end_pfn())) { + __cpa_pfn_in_highmap(cpa->pfn)) { unsigned long temp_cpa_vaddr = (cpa->pfn << PAGE_SHIFT) + __START_KERNEL_map - phys_base; alias_cpa = *cpa; -- GitLab