[PATCH 08/23] x86, kaiser: map cpu entry area

Dave Hansen
2017-11-23T00:36:02Z

From: Dave Hansen <dave.hansen@linux.intel.com>

There is now a special 'struct cpu_entry' area that contains all
of the data needed to enter the kernel. It's mapped in the fixmap
area and contains:

* The GDT (hardware segment descriptor)
* The TSS (thread information structure that points the hardware
to the various stacks, and contains the entry stack).
* The entry trampoline code itself
* The exception stacks (aka IRQ stacks)

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Moritz Lipp <moritz.lipp@iaik.tugraz.at>
Cc: Daniel Gruss <daniel.gruss@iaik.tugraz.at>
Cc: Michael Schwarz <michael.schwarz@iaik.tugraz.at>
Cc: Richard Fellner <richard.fellner@student.tugraz.at>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Kees Cook <keescook@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: x86@kernel.org
---

b/arch/x86/include/asm/kaiser.h | 6 ++++++
b/arch/x86/kernel/cpu/common.c | 4 ++++
b/arch/x86/mm/kaiser.c | 31 +++++++++++++++++++++++++++++++
b/include/linux/kaiser.h | 3 +++
4 files changed, 44 insertions(+)

diff -puN arch/x86/include/asm/kaiser.h~kaiser-user-map-cpu-entry-structure arch/x86/include/asm/kaiser.h
--- a/arch/x86/include/asm/kaiser.h~kaiser-user-map-cpu-entry-structure 2017-11-22 15:45:48.447619740 -0800
+++ b/arch/x86/include/asm/kaiser.h 2017-11-22 15:45:48.456619740 -0800
@@ -34,6 +34,12 @@ extern int kaiser_add_mapping(unsigned l
unsigned long flags);

/**
+ * kaiser_add_mapping_cpu_entry - map the cpu entry area
+ * @cpu: the CPU for which the entry area is being mapped
+ */
+extern void kaiser_add_mapping_cpu_entry(int cpu);
+
+/**
* kaiser_remove_mapping - remove a kernel mapping from the userpage tables
* @addr: the start address of the range
* @size: the size of the range
diff -puN arch/x86/kernel/cpu/common.c~kaiser-user-map-cpu-entry-structure arch/x86/kernel/cpu/common.c
--- a/arch/x86/kernel/cpu/common.c~kaiser-user-map-cpu-entry-structure 2017-11-22 15:45:48.449619740 -0800
+++ b/arch/x86/kernel/cpu/common.c 2017-11-22 15:45:48.457619740 -0800
@@ -4,6 +4,7 @@
#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/percpu.h>
+#include <linux/kaiser.h>
#include <linux/string.h>
#include <linux/ctype.h>
#include <linux/delay.h>
@@ -587,6 +588,9 @@ static inline void setup_cpu_entry_area(
__set_fixmap(get_cpu_entry_area_index(cpu, entry_trampoline),
__pa_symbol(_entry_trampoline), PAGE_KERNEL_RX);
#endif
+ /* CPU 0's mapping is done in kaiser_init() */
+ if (cpu)
+ kaiser_add_mapping_cpu_entry(cpu);
}

/* Load the original GDT from the per-cpu structure */
diff -puN arch/x86/mm/kaiser.c~kaiser-user-map-cpu-entry-structure arch/x86/mm/kaiser.c
--- a/arch/x86/mm/kaiser.c~kaiser-user-map-cpu-entry-structure 2017-11-22 15:45:48.451619740 -0800
+++ b/arch/x86/mm/kaiser.c 2017-11-22 15:45:48.457619740 -0800
@@ -353,6 +353,26 @@ static void __init kaiser_init_all_pgds(
WARN_ON(__ret); \
} while (0)

+void kaiser_add_mapping_cpu_entry(int cpu)
+{
+ kaiser_add_user_map_early(get_cpu_gdt_ro(cpu), PAGE_SIZE,
+ __PAGE_KERNEL_RO);
+
+ /* includes the entry stack */
+ kaiser_add_user_map_early(&get_cpu_entry_area(cpu)->tss,
+ sizeof(get_cpu_entry_area(cpu)->tss),
+ __PAGE_KERNEL | _PAGE_GLOBAL);
+
+ /* Entry code, so needs to be EXEC */
+ kaiser_add_user_map_early(&get_cpu_entry_area(cpu)->entry_trampoline,
+ sizeof(get_cpu_entry_area(cpu)->entry_trampoline),
+ __PAGE_KERNEL_EXEC | _PAGE_GLOBAL);
+
+ kaiser_add_user_map_early(&get_cpu_entry_area(cpu)->exception_stacks,
+ sizeof(get_cpu_entry_area(cpu)->exception_stacks),
+ __PAGE_KERNEL | _PAGE_GLOBAL);
+}
+
extern char __per_cpu_user_mapped_start[], __per_cpu_user_mapped_end[];
/*
* If anything in here fails, we will likely die on one of the
@@ -390,6 +410,17 @@ void __init kaiser_init(void)
kaiser_add_user_map_early((void *)idt_descr.address,
sizeof(gate_desc) * NR_VECTORS,
__PAGE_KERNEL_RO | _PAGE_GLOBAL);
+
+ /*
+ * We delay CPU 0's mappings because these structures are
+ * created before the page allocator is up. Deferring it
+ * until here lets us use the plain page allocator
+ * unconditionally in the page table code above.
+ *
+ * This is OK because kaiser_init() is called long before
+ * we ever run userspace and need the KAISER mappings.
+ */
+ kaiser_add_mapping_cpu_entry(0);
}

int kaiser_add_mapping(unsigned long addr, unsigned long size,
diff -puN include/linux/kaiser.h~kaiser-user-map-cpu-entry-structure include/linux/kaiser.h
--- a/include/linux/kaiser.h~kaiser-user-map-cpu-entry-structure 2017-11-22 15:45:48.453619740 -0800
+++ b/include/linux/kaiser.h 2017-11-22 15:45:48.458619740 -0800
@@ -25,5 +25,8 @@ static inline int kaiser_add_mapping(uns
return 0;
}

+static inline void kaiser_add_mapping_cpu_entry(int cpu)
+{
+}
#endif /* !CONFIG_KAISER */
#endif /* _INCLUDE_KAISER_H */
_