From: Mike Rapoport <rppt@xxxxxxxxxxxxx> Subject: x86/mm: simplify init_trampoline() and surrounding logic There are three cases for the trampoline initialization: * 32-bit does nothing * 64-bit with kaslr disabled simply copies a PGD entry from the direct map to the trampoline PGD * 64-bit with kaslr enabled maps the real mode trampoline at PUD level These cases are currently differentiated by a bunch of ifdefs inside asm/include/pgtable.h and the case of 64-bits with kaslr on uses pgd_index() helper. Replacing the ifdefs with a static function in arch/x86/mm/init.c gives clearer code and allows moving pgd_index() to the generic implementation in include/linux/pgtable.h [rppt@xxxxxxxxxxxxx: take CONFIG_RANDOMIZE_MEMORY into account in kaslr_enabled()] Link: http://lkml.kernel.org/r/20200525104045.GB13212@xxxxxxxxxxxxx Link: http://lkml.kernel.org/r/20200514170327.31389-8-rppt@xxxxxxxxxx Signed-off-by: Mike Rapoport <rppt@xxxxxxxxxxxxx> Cc: Arnd Bergmann <arnd@xxxxxxxx> Cc: Borislav Petkov <bp@xxxxxxxxx> Cc: Brian Cain <bcain@xxxxxxxxxxxxxx> Cc: Catalin Marinas <catalin.marinas@xxxxxxx> Cc: Chris Zankel <chris@xxxxxxxxxx> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx> Cc: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> Cc: Greentime Hu <green.hu@xxxxxxxxx> Cc: Greg Ungerer <gerg@xxxxxxxxxxxxxx> Cc: Guan Xuetao <gxt@xxxxxxxxxx> Cc: Guo Ren <guoren@xxxxxxxxxx> Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx> Cc: Helge Deller <deller@xxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Ley Foon Tan <ley.foon.tan@xxxxxxxxx> Cc: Mark Salter <msalter@xxxxxxxxxx> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Cc: Matt Turner <mattst88@xxxxxxxxx> Cc: Max Filippov <jcmvbkbc@xxxxxxxxx> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx> Cc: Michal Simek <monstr@xxxxxxxxx> Cc: Nick Hu <nickhu@xxxxxxxxxxxxx> Cc: Paul Walmsley <paul.walmsley@xxxxxxxxxx> Cc: Richard Weinberger <richard@xxxxxx> Cc: Rich Felker <dalias@xxxxxxxx> Cc: Russell King <linux@xxxxxxxxxxxxxxx> Cc: Stafford Horne <shorne@xxxxxxxxx> Cc: Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Tony Luck <tony.luck@xxxxxxxxx> Cc: Vincent Chen <deanbo422@xxxxxxxxx> Cc: Vineet Gupta <vgupta@xxxxxxxxxxxx> Cc: Will Deacon <will@xxxxxxxxxx> Cc: Yoshinori Sato <ysato@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- arch/x86/include/asm/kaslr.h | 2 + arch/x86/include/asm/pgtable.h | 15 -------------- arch/x86/include/asm/setup.h | 12 ++++++++++- arch/x86/mm/init.c | 22 ++++++++++++++++++++ arch/x86/mm/kaslr.c | 33 ------------------------------- 5 files changed, 37 insertions(+), 47 deletions(-) --- a/arch/x86/include/asm/kaslr.h~x86-mm-simplify-init_trampoline-and-surrounding-logic +++ a/arch/x86/include/asm/kaslr.h @@ -6,8 +6,10 @@ unsigned long kaslr_get_random_long(cons #ifdef CONFIG_RANDOMIZE_MEMORY void kernel_randomize_memory(void); +void init_trampoline_kaslr(void); #else static inline void kernel_randomize_memory(void) { } +static inline void init_trampoline_kaslr(void) {} #endif /* CONFIG_RANDOMIZE_MEMORY */ #endif --- a/arch/x86/include/asm/pgtable.h~x86-mm-simplify-init_trampoline-and-surrounding-logic +++ a/arch/x86/include/asm/pgtable.h @@ -1071,27 +1071,14 @@ void init_mem_mapping(void); void early_alloc_pgt_buf(void); extern void memblock_find_dma_reserve(void); + #ifdef CONFIG_X86_64 -/* Realmode trampoline initialization. */ extern pgd_t trampoline_pgd_entry; -static inline void __meminit init_trampoline_default(void) -{ - /* Default trampoline pgd value */ - trampoline_pgd_entry = init_top_pgt[pgd_index(__PAGE_OFFSET)]; -} void __init poking_init(void); unsigned long init_memory_mapping(unsigned long start, unsigned long end, pgprot_t prot); - -# ifdef CONFIG_RANDOMIZE_MEMORY -void __meminit init_trampoline(void); -# else -# define init_trampoline init_trampoline_default -# endif -#else -static inline void init_trampoline(void) { } #endif /* local pte updates need not use xchg for locking */ --- a/arch/x86/include/asm/setup.h~x86-mm-simplify-init_trampoline-and-surrounding-logic +++ a/arch/x86/include/asm/setup.h @@ -75,7 +75,17 @@ extern char _text[]; static inline bool kaslr_enabled(void) { - return !!(boot_params.hdr.loadflags & KASLR_FLAG); + return IS_ENABLED(CONFIG_RANDOMIZE_MEMORY) && + !!(boot_params.hdr.loadflags & KASLR_FLAG); +} + +/* + * Apply no randomization if KASLR was disabled at boot or if KASAN + * is enabled. KASAN shadow mappings rely on regions being PGD aligned. + */ +static inline bool kaslr_memory_enabled(void) +{ + return kaslr_enabled() && !IS_ENABLED(CONFIG_KASAN); } static inline unsigned long kaslr_offset(void) --- a/arch/x86/mm/init.c~x86-mm-simplify-init_trampoline-and-surrounding-logic +++ a/arch/x86/mm/init.c @@ -680,6 +680,28 @@ static void __init memory_map_bottom_up( } } +/* + * The real mode trampoline, which is required for bootstrapping CPUs + * occupies only a small area under the low 1MB. See reserve_real_mode() + * for details. + * + * If KASLR is disabled the first PGD entry of the direct mapping is copied + * to map the real mode trampoline. + * + * If KASLR is enabled, copy only the PUD which covers the low 1MB + * area. This limits the randomization granularity to 1GB for both 4-level + * and 5-level paging. + */ +static void __init init_trampoline(void) +{ +#ifdef CONFIG_X86_64 + if (!kaslr_memory_enabled()) + trampoline_pgd_entry = init_top_pgt[pgd_index(__PAGE_OFFSET)]; + else + init_trampoline_kaslr(); +#endif +} + void __init init_mem_mapping(void) { unsigned long end; --- a/arch/x86/mm/kaslr.c~x86-mm-simplify-init_trampoline-and-surrounding-logic +++ a/arch/x86/mm/kaslr.c @@ -61,15 +61,6 @@ static inline unsigned long get_padding( return (region->size_tb << TB_SHIFT); } -/* - * Apply no randomization if KASLR was disabled at boot or if KASAN - * is enabled. KASAN shadow mappings rely on regions being PGD aligned. - */ -static inline bool kaslr_memory_enabled(void) -{ - return kaslr_enabled() && !IS_ENABLED(CONFIG_KASAN); -} - /* Initialize base and padding for each memory region randomized with KASLR */ void __init kernel_randomize_memory(void) { @@ -148,7 +139,7 @@ void __init kernel_randomize_memory(void } } -static void __meminit init_trampoline_pud(void) +void __meminit init_trampoline_kaslr(void) { pud_t *pud_page_tramp, *pud, *pud_tramp; p4d_t *p4d_page_tramp, *p4d, *p4d_tramp; @@ -189,25 +180,3 @@ static void __meminit init_trampoline_pu __pgd(_KERNPG_TABLE | __pa(pud_page_tramp))); } } - -/* - * The real mode trampoline, which is required for bootstrapping CPUs - * occupies only a small area under the low 1MB. See reserve_real_mode() - * for details. - * - * If KASLR is disabled the first PGD entry of the direct mapping is copied - * to map the real mode trampoline. - * - * If KASLR is enabled, copy only the PUD which covers the low 1MB - * area. This limits the randomization granularity to 1GB for both 4-level - * and 5-level paging. - */ -void __meminit init_trampoline(void) -{ - if (!kaslr_memory_enabled()) { - init_trampoline_default(); - return; - } - - init_trampoline_pud(); -} _
