From: Andy Lutomirski <[email protected]> The IST stacks are needed when an IST exception occurs and are accessed before any kernel code at all runs. Move them into struct cpu_entry_area.
Signed-off-by: Andy Lutomirski <[email protected]> Signed-off-by: Thomas Gleixner <[email protected]> Reviewed-by: Thomas Gleixner <[email protected]> Reviewed-by: Borislav Petkov <[email protected]> Cc: Brian Gerst <[email protected]> Cc: Dave Hansen <[email protected]> Cc: Denys Vlasenko <[email protected]> Cc: H. Peter Anvin <[email protected]> Cc: Josh Poimboeuf <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Rik van Riel <[email protected]> Link: https://lkml.kernel.org/r/0ffddccdc0ce1953f950a553142662cf68258fb7.1511497875.git.l...@kernel.org Signed-off-by: Ingo Molnar <[email protected]> --- arch/x86/include/asm/fixmap.h | 10 ++++++++++ arch/x86/kernel/cpu/common.c | 40 +++++++++++++++++++++++++--------------- 2 files changed, 35 insertions(+), 15 deletions(-) diff --git a/arch/x86/include/asm/fixmap.h b/arch/x86/include/asm/fixmap.h index 17be88e73c92..81fdc405ab1f 100644 --- a/arch/x86/include/asm/fixmap.h +++ b/arch/x86/include/asm/fixmap.h @@ -63,6 +63,16 @@ struct cpu_entry_area { struct tss_struct tss; char entry_trampoline[PAGE_SIZE]; + +#ifdef CONFIG_X86_64 + /* + * Exception stacks used for IST entries. + * + * In the future, this should have a separate slot for each stack + * with guard pages between them. + */ + char exception_stacks[(N_EXCEPTION_STACKS - 1) * EXCEPTION_STKSZ + DEBUG_STKSZ]; +#endif }; #define CPU_ENTRY_AREA_PAGES (sizeof(struct cpu_entry_area) / PAGE_SIZE) diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 9af1f176cc5b..f24d13cd73dc 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -503,6 +503,22 @@ static void set_percpu_fixmap_pages(int fixmap_index, void *ptr, int pages, pgpr DEFINE_PER_CPU(struct cpu_entry_area *, cpu_entry_area); #endif +#ifdef CONFIG_X86_64 +/* + * Special IST stacks which the CPU switches to when it calls + * an IST-marked descriptor entry. Up to 7 stacks (hardware + * limit), all of them are 4K, except the debug stack which + * is 8K. + */ +static const unsigned int exception_stack_sizes[N_EXCEPTION_STACKS] = { + [0 ... N_EXCEPTION_STACKS - 1] = EXCEPTION_STKSZ, + [DEBUG_STACK - 1] = DEBUG_STKSZ +}; + +static DEFINE_PER_CPU_PAGE_ALIGNED(char, exception_stacks + [(N_EXCEPTION_STACKS - 1) * EXCEPTION_STKSZ + DEBUG_STKSZ]); +#endif + /* Setup the fixmap mappings only once per-processor */ static inline void setup_cpu_entry_area(int cpu) { @@ -557,6 +573,14 @@ static inline void setup_cpu_entry_area(int cpu) #endif #ifdef CONFIG_X86_64 + BUILD_BUG_ON(sizeof(exception_stacks) % PAGE_SIZE != 0); + BUILD_BUG_ON(sizeof(exception_stacks) != + sizeof(((struct cpu_entry_area *)0)->exception_stacks)); + set_percpu_fixmap_pages(get_cpu_entry_area_index(cpu, exception_stacks), + &per_cpu(exception_stacks, cpu), + sizeof(exception_stacks) / PAGE_SIZE, + PAGE_KERNEL); + __set_fixmap(get_cpu_entry_area_index(cpu, entry_trampoline), __pa_symbol(_entry_trampoline), PAGE_KERNEL_RX); #endif @@ -1407,20 +1431,6 @@ DEFINE_PER_CPU(unsigned int, irq_count) __visible = -1; DEFINE_PER_CPU(int, __preempt_count) = INIT_PREEMPT_COUNT; EXPORT_PER_CPU_SYMBOL(__preempt_count); -/* - * Special IST stacks which the CPU switches to when it calls - * an IST-marked descriptor entry. Up to 7 stacks (hardware - * limit), all of them are 4K, except the debug stack which - * is 8K. - */ -static const unsigned int exception_stack_sizes[N_EXCEPTION_STACKS] = { - [0 ... N_EXCEPTION_STACKS - 1] = EXCEPTION_STKSZ, - [DEBUG_STACK - 1] = DEBUG_STKSZ -}; - -static DEFINE_PER_CPU_PAGE_ALIGNED(char, exception_stacks - [(N_EXCEPTION_STACKS - 1) * EXCEPTION_STKSZ + DEBUG_STKSZ]); - /* May not be marked __init: used by software suspend */ void syscall_init(void) { @@ -1629,7 +1639,7 @@ void cpu_init(void) * set up and load the per-CPU TSS */ if (!oist->ist[0]) { - char *estacks = per_cpu(exception_stacks, cpu); + char *estacks = get_cpu_entry_area(cpu)->exception_stacks; for (v = 0; v < N_EXCEPTION_STACKS; v++) { estacks += exception_stack_sizes[v]; -- 2.14.1
