--- /dev/null
+Memory Protection Keys for Userspace (PKU aka PKEYs) is a CPU feature
+which will be found on future Intel CPUs.
+
+Memory Protection Keys provides a mechanism for enforcing page-based
+protections, but without requiring modification of the page tables
+when an application changes protection domains. It works by
+dedicating 4 previously ignored bits in each page table entry to a
+"protection key", giving 16 possible keys.
+
+There is also a new user-accessible register (PKRU) with two separate
+bits (Access Disable and Write Disable) for each key. Being a CPU
+register, PKRU is inherently thread-local, potentially giving each
+thread a different set of protections from every other thread.
+
+There are two new instructions (RDPKRU/WRPKRU) for reading and writing
+to the new register. The feature is only available in 64-bit mode,
+even though there is theoretically space in the PAE PTEs. These
+permissions are enforced on data access only and have no effect on
+instruction fetches.
+
+=========================== Config Option ===========================
+
+This config option adds approximately 1.5kb of text. and 50 bytes of
+data to the executable. A workload which does large O_DIRECT reads
+of holes in XFS files was run to exercise get_user_pages_fast(). No
+performance delta was observed with the config option
+enabled or disabled.
vmlinux.bin.xz vmlinux.bin.lzo vmlinux.bin.lz4
KBUILD_CFLAGS := -m$(BITS) -D__KERNEL__ $(LINUX_INCLUDE) -O2
-KBUILD_CFLAGS += -fno-strict-aliasing -fPIC
+KBUILD_CFLAGS += -fno-strict-aliasing $(call cc-option, -fPIE, -fPIC)
KBUILD_CFLAGS += -DDISABLE_BRANCH_PROFILING
cflags-$(CONFIG_X86_32) := -march=i386
cflags-$(CONFIG_X86_64) := -mcmodel=small
UBSAN_SANITIZE :=n
LDFLAGS := -m elf_$(UTS_MACHINE)
+ifeq ($(CONFIG_RELOCATABLE),y)
+# If kernel is relocatable, build compressed kernel as PIE.
+ifeq ($(CONFIG_X86_32),y)
+LDFLAGS += $(call ld-option, -pie) $(call ld-option, --no-dynamic-linker)
+else
+# To build 64-bit compressed kernel as PIE, we disable relocation
+# overflow check to avoid relocation overflow error with a new linker
+# command-line option, -z noreloc-overflow.
+LDFLAGS += $(shell $(LD) --help 2>&1 | grep -q "\-z noreloc-overflow" \
+ && echo "-z noreloc-overflow -pie --no-dynamic-linker")
+endif
+endif
LDFLAGS_vmlinux := -T
hostprogs-y := mkpiggy
#include <asm/asm-offsets.h>
#include <asm/bootparam.h>
+/*
+ * The 32-bit x86 assembler in binutils 2.26 will generate R_386_GOT32X
+ * relocation to get the symbol address in PIC. When the compressed x86
+ * kernel isn't built as PIC, the linker optimizes R_386_GOT32X
+ * relocations to their fixed symbol addresses. However, when the
+ * compressed x86 kernel is loaded at a different address, it leads
+ * to the following load failure:
+ *
+ * Failed to allocate space for phdrs
+ *
+ * during the decompression stage.
+ *
+ * If the compressed x86 kernel is relocatable at run-time, it should be
+ * compiled with -fPIE, instead of -fPIC, if possible and should be built as
+ * Position Independent Executable (PIE) so that linker won't optimize
+ * R_386_GOT32X relocation to its fixed symbol address. Older
+ * linkers generate R_386_32 relocations against locally defined symbols,
+ * _bss, _ebss, _got and _egot, in PIE. It isn't wrong, just less
+ * optimal than R_386_RELATIVE. But the x86 kernel fails to properly handle
+ * R_386_32 relocations when relocating the kernel. To generate
+ * R_386_RELATIVE relocations, we mark _bss, _ebss, _got and _egot as
+ * hidden:
+ */
+ .hidden _bss
+ .hidden _ebss
+ .hidden _got
+ .hidden _egot
+
__HEAD
ENTRY(startup_32)
#ifdef CONFIG_EFI_STUB
#include <asm/asm-offsets.h>
#include <asm/bootparam.h>
+/*
+ * Locally defined symbols should be marked hidden:
+ */
+ .hidden _bss
+ .hidden _ebss
+ .hidden _got
+ .hidden _egot
+
__HEAD
.code32
ENTRY(startup_32)
void mce_gen_pool_process(void)
{
struct llist_node *head;
- struct mce_evt_llist *node;
+ struct mce_evt_llist *node, *tmp;
struct mce *mce;
head = llist_del_all(&mce_event_llist);
return;
head = llist_reverse_order(head);
- llist_for_each_entry(node, head, llnode) {
+ llist_for_each_entry_safe(node, tmp, head, llnode) {
mce = &node->mce;
atomic_notifier_call_chain(&x86_mce_decoder_chain, 0, mce);
gen_pool_free(mce_evt_pool, (unsigned long)node, sizeof(*node));
* Actually now I think of it, it's possible that Ron *is* half the Plan 9
* userbase. Oh well.
*/
-static bool could_be_syscall(unsigned int num)
+bool could_be_syscall(unsigned int num)
{
/* Normal Linux IA32_SYSCALL_VECTOR or reserved vector? */
return num == IA32_SYSCALL_VECTOR || num == syscall_vector;
*
* This routine indicates if a particular trap number could be delivered
* directly.
+ *
+ * Unfortunately, Linux 4.6 started using an interrupt gate instead of a
+ * trap gate for syscalls, so this trick is ineffective. See Mastery for
+ * how we could do this anyway...
*/
static bool direct_trap(unsigned int num)
{
bool send_notify_to_eventfd(struct lg_cpu *cpu);
void init_clockdev(struct lg_cpu *cpu);
bool check_syscall_vector(struct lguest *lg);
+bool could_be_syscall(unsigned int num);
int init_interrupts(void);
void free_interrupts(void);
return;
break;
case 32 ... 255:
+ /* This might be a syscall. */
+ if (could_be_syscall(cpu->regs->trapnum))
+ break;
+
/*
- * These values mean a real interrupt occurred, in which case
+ * Other values mean a real interrupt occurred, in which case
* the Host handler has already been run. We just do a
* friendly check if another process should now be run, then
* return to run the Guest again.
projects / deliverable / linux.git / commitdiff
