Now that the uaccess primitives dont take addr_limit into account, we
have no need to manipulate this via set_fs() and get_fs(). Remove
support for these, along with some infrastructure this renders
redundant.
We no longer need to flip UAO to access kernel memory under KERNEL_DS,
and head.S unconditionally clears UAO for all kernel configurations via
an ERET in init_kernel_el. Thus, we don't need to dynamically flip UAO,
nor do we need to context-switch it. However, we still need to adjust
PAN during SDEI entry.
Masking of __user pointers no longer needs to use the dynamic value of
addr_limit, and can use a constant derived from the maximum possible
userspace task size. A new TASK_SIZE_MAX constant is introduced for
this, which is also used by core code. In configurations supporting
52-bit VAs, this may include a region of unusable VA space above a
48-bit TTBR0 limit, but never includes any portion of TTBR1.
Note that TASK_SIZE_MAX is an exclusive limit, while USER_DS and
KERNEL_DS were inclusive limits, and is converted to a mask by
subtracting one.
As the SDEI entry code repurposes the otherwise unnecessary
pt_regs::orig_addr_limit field to store the TTBR1 of the interrupted
context, for now we rename that to pt_regs::sdei_ttbr1. In future we can
consider factoring that out.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: James Morse <james.morse@arm.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20201202131558.39270-10-mark.rutland@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
select PCI_SYSCALL if PCI
select POWER_RESET
select POWER_SUPPLY
- select SET_FS
select SPARSE_IRQ
select SWIOTLB
select SYSCTL_EXCEPTION_TRACE
#include <linux/sched.h>
extern unsigned long arch_align_stack(unsigned long sp);
-void uao_thread_switch(struct task_struct *next);
#endif /* __ASM_EXEC_H */
#ifndef __ASM_PROCESSOR_H
#define __ASM_PROCESSOR_H
-#define KERNEL_DS UL(-1)
-#define USER_DS ((UL(1) << VA_BITS) - 1)
-
/*
* On arm64 systems, unaligned accesses by the CPU are cheap, and so there is
* no point in shifting all network buffers by 2 bytes just to make some IP
#define DEFAULT_MAP_WINDOW_64 (UL(1) << VA_BITS_MIN)
#define TASK_SIZE_64 (UL(1) << vabits_actual)
+#define TASK_SIZE_MAX (UL(1) << VA_BITS)
#ifdef CONFIG_COMPAT
#if defined(CONFIG_ARM64_64K_PAGES) && defined(CONFIG_KUSER_HELPERS)
s32 syscallno;
u32 unused2;
#endif
-
- u64 orig_addr_limit;
+ u64 sdei_ttbr1;
/* Only valid when ARM64_HAS_IRQ_PRIO_MASKING is enabled. */
u64 pmr_save;
u64 stackframe[2];
#include <asm/stack_pointer.h>
#include <asm/types.h>
-typedef unsigned long mm_segment_t;
-
/*
* low level task data that entry.S needs immediate access to.
*/
struct thread_info {
unsigned long flags; /* low level flags */
- mm_segment_t addr_limit; /* address limit */
#ifdef CONFIG_ARM64_SW_TTBR0_PAN
u64 ttbr0; /* saved TTBR0_EL1 */
#endif
{ \
.flags = _TIF_FOREIGN_FPSTATE, \
.preempt_count = INIT_PREEMPT_COUNT, \
- .addr_limit = KERNEL_DS, \
INIT_SCS \
}
#define HAVE_GET_KERNEL_NOFAULT
-#define get_fs() (current_thread_info()->addr_limit)
-
-static inline void set_fs(mm_segment_t fs)
-{
- current_thread_info()->addr_limit = fs;
-
- /*
- * Prevent a mispredicted conditional call to set_fs from forwarding
- * the wrong address limit to access_ok under speculation.
- */
- spec_bar();
-
- /* On user-mode return, check fs is correct */
- set_thread_flag(TIF_FSCHECK);
-
- /*
- * Enable/disable UAO so that copy_to_user() etc can access
- * kernel memory with the unprivileged instructions.
- */
- if (IS_ENABLED(CONFIG_ARM64_UAO) && fs == KERNEL_DS)
- asm(ALTERNATIVE("nop", SET_PSTATE_UAO(1), ARM64_HAS_UAO));
- else
- asm(ALTERNATIVE("nop", SET_PSTATE_UAO(0), ARM64_HAS_UAO,
- CONFIG_ARM64_UAO));
-}
-
-#define uaccess_kernel() (get_fs() == KERNEL_DS)
-
/*
* Test whether a block of memory is a valid user space address.
* Returns 1 if the range is valid, 0 otherwise.
*
* This is equivalent to the following test:
- * (u65)addr + (u65)size <= (u65)current->addr_limit + 1
+ * (u65)addr + (u65)size <= (u65)TASK_SIZE_MAX
*/
static inline unsigned long __range_ok(const void __user *addr, unsigned long size)
{
- unsigned long ret, limit = current_thread_info()->addr_limit;
+ unsigned long ret, limit = TASK_SIZE_MAX - 1;
/*
* Asynchronous I/O running in a kernel thread does not have the
}
#define access_ok(addr, size) __range_ok(addr, size)
-#define user_addr_max get_fs
#define _ASM_EXTABLE(from, to) \
" .pushsection __ex_table, \"a\"\n" \
}
/*
- * Sanitise a uaccess pointer such that it becomes NULL if above the
- * current addr_limit. In case the pointer is tagged (has the top byte set),
- * untag the pointer before checking.
+ * Sanitise a uaccess pointer such that it becomes NULL if above the maximum
+ * user address. In case the pointer is tagged (has the top byte set), untag
+ * the pointer before checking.
*/
#define uaccess_mask_ptr(ptr) (__typeof__(ptr))__uaccess_mask_ptr(ptr)
static inline void __user *__uaccess_mask_ptr(const void __user *ptr)
" bics xzr, %3, %2\n"
" csel %0, %1, xzr, eq\n"
: "=&r" (safe_ptr)
- : "r" (ptr), "r" (current_thread_info()->addr_limit),
+ : "r" (ptr), "r" (TASK_SIZE_MAX - 1),
"r" (untagged_addr(ptr))
: "cc");
BLANK();
DEFINE(TSK_TI_FLAGS, offsetof(struct task_struct, thread_info.flags));
DEFINE(TSK_TI_PREEMPT, offsetof(struct task_struct, thread_info.preempt_count));
- DEFINE(TSK_TI_ADDR_LIMIT, offsetof(struct task_struct, thread_info.addr_limit));
#ifdef CONFIG_ARM64_SW_TTBR0_PAN
DEFINE(TSK_TI_TTBR0, offsetof(struct task_struct, thread_info.ttbr0));
#endif
DEFINE(S_PSTATE, offsetof(struct pt_regs, pstate));
DEFINE(S_PC, offsetof(struct pt_regs, pc));
DEFINE(S_SYSCALLNO, offsetof(struct pt_regs, syscallno));
- DEFINE(S_ORIG_ADDR_LIMIT, offsetof(struct pt_regs, orig_addr_limit));
+ DEFINE(S_SDEI_TTBR1, offsetof(struct pt_regs, sdei_ttbr1));
DEFINE(S_PMR_SAVE, offsetof(struct pt_regs, pmr_save));
DEFINE(S_STACKFRAME, offsetof(struct pt_regs, stackframe));
DEFINE(S_FRAME_SIZE, sizeof(struct pt_regs));
.sys_reg = SYS_ID_AA64MMFR2_EL1,
.field_pos = ID_AA64MMFR2_UAO_SHIFT,
.min_field_value = 1,
- /*
- * We rely on stop_machine() calling uao_thread_switch() to set
- * UAO immediately after patching.
- */
},
#endif /* CONFIG_ARM64_UAO */
#ifdef CONFIG_ARM64_PAN
.else
add x21, sp, #S_FRAME_SIZE
get_current_task tsk
- /* Save the task's original addr_limit and set USER_DS */
- ldr x20, [tsk, #TSK_TI_ADDR_LIMIT]
- str x20, [sp, #S_ORIG_ADDR_LIMIT]
- mov x20, #USER_DS
- str x20, [tsk, #TSK_TI_ADDR_LIMIT]
- /* No need to reset PSTATE.UAO, hardware's already set it to 0 for us */
.endif /* \el == 0 */
mrs x22, elr_el1
mrs x23, spsr_el1
.macro kernel_exit, el
.if \el != 0
disable_daif
-
- /* Restore the task's original addr_limit. */
- ldr x20, [sp, #S_ORIG_ADDR_LIMIT]
- str x20, [tsk, #TSK_TI_ADDR_LIMIT]
-
- /* No need to restore UAO, it will be restored from SPSR_EL1 */
.endif
/* Restore pmr */
mov x4, xzr
/*
- * Use reg->interrupted_regs.addr_limit to remember whether to unmap
- * the kernel on exit.
+ * Remember whether to unmap the kernel on exit.
*/
-1: str x4, [x1, #(SDEI_EVENT_INTREGS + S_ORIG_ADDR_LIMIT)]
+1: str x4, [x1, #(SDEI_EVENT_INTREGS + S_SDEI_TTBR1)]
#ifdef CONFIG_RANDOMIZE_BASE
adr x4, tramp_vectors + PAGE_SIZE
* x4: struct sdei_registered_event argument from registration time.
*/
SYM_CODE_START(__sdei_asm_exit_trampoline)
- ldr x4, [x4, #(SDEI_EVENT_INTREGS + S_ORIG_ADDR_LIMIT)]
+ ldr x4, [x4, #(SDEI_EVENT_INTREGS + S_SDEI_TTBR1)]
cbnz x4, 1f
tramp_unmap_kernel tmp=x4
write_sysreg(*task_user_tls(next), tpidr_el0);
}
-/* Restore the UAO state depending on next's addr_limit */
-void uao_thread_switch(struct task_struct *next)
-{
- if (IS_ENABLED(CONFIG_ARM64_UAO)) {
- if (task_thread_info(next)->addr_limit == KERNEL_DS)
- asm(ALTERNATIVE("nop", SET_PSTATE_UAO(1), ARM64_HAS_UAO));
- else
- asm(ALTERNATIVE("nop", SET_PSTATE_UAO(0), ARM64_HAS_UAO));
- }
-}
-
/*
* Force SSBS state on context-switch, since it may be lost after migrating
* from a CPU which treats the bit as RES0 in a heterogeneous system.
hw_breakpoint_thread_switch(next);
contextidr_thread_switch(next);
entry_task_switch(next);
- uao_thread_switch(next);
ssbs_thread_switch(next);
erratum_1418040_thread_switch(prev, next);
__sdei_handler(struct pt_regs *regs, struct sdei_registered_event *arg)
{
unsigned long ret;
- mm_segment_t orig_addr_limit;
/*
* We didn't take an exception to get here, so the HW hasn't
- * set/cleared bits in PSTATE that we may rely on. Initialize PAN, then
- * use force_uaccess_begin() to reset addr_limit.
+ * set/cleared bits in PSTATE that we may rely on. Initialize PAN.
*/
__sdei_pstate_entry();
- orig_addr_limit = force_uaccess_begin();
nmi_enter();
nmi_exit();
- force_uaccess_end(orig_addr_limit);
-
return ret;
}
* features that might not have been set correctly.
*/
__uaccess_enable_hw_pan();
- uao_thread_switch(current);
/*
* Restore HW breakpoint registers to sane values
}
if (is_ttbr0_addr(addr) && is_el1_permission_fault(addr, esr, regs)) {
- /* regs->orig_addr_limit may be 0 if we entered from EL0 */
- if (regs->orig_addr_limit == KERNEL_DS)
- die_kernel_fault("access to user memory with fs=KERNEL_DS",
- addr, esr, regs);
-
if (is_el1_instruction_abort(esr))
die_kernel_fault("execution of user memory",
addr, esr, regs);
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