From: Mark Rutland <mark.rutl...@arm.com> commit 3d2403fd10a1dbb359b154af41ffed9f2a7520e8 upstream
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.rutl...@arm.com> Acked-by: James Morse <james.mo...@arm.com> Cc: Christoph Hellwig <h...@lst.de> Cc: Will Deacon <w...@kernel.org> Link: https://lore.kernel.org/r/20201202131558.39270-10-mark.rutl...@arm.com Signed-off-by: Catalin Marinas <catalin.mari...@arm.com> Signed-off-by: Li Wang <li.w...@windriver.com> --- arch/arm64/Kconfig | 1 - arch/arm64/include/asm/exec.h | 1 - arch/arm64/include/asm/processor.h | 4 +-- arch/arm64/include/asm/ptrace.h | 3 +- arch/arm64/include/asm/thread_info.h | 4 --- arch/arm64/include/asm/uaccess.h | 41 ++++------------------------ arch/arm64/kernel/asm-offsets.c | 3 +- arch/arm64/kernel/cpufeature.c | 4 --- arch/arm64/kernel/entry.S | 19 ++----------- arch/arm64/kernel/process.c | 12 -------- arch/arm64/kernel/sdei.c | 7 +---- arch/arm64/kernel/suspend.c | 1 - arch/arm64/mm/fault.c | 5 ---- 13 files changed, 13 insertions(+), 92 deletions(-) diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index e5a08bf262d6..1f8cf5b283fa 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -196,7 +196,6 @@ config ARM64 select PCI_SYSCALL if PCI select POWER_RESET select POWER_SUPPLY - select SET_FS select SPARSE_IRQ select SWIOTLB select SYSCTL_EXCEPTION_TRACE diff --git a/arch/arm64/include/asm/exec.h b/arch/arm64/include/asm/exec.h index 1aae6f9962fc..9a1c22ce664b 100644 --- a/arch/arm64/include/asm/exec.h +++ b/arch/arm64/include/asm/exec.h @@ -10,6 +10,5 @@ #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 */ diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h index 7c546c3487c9..4712b296c45f 100644 --- a/arch/arm64/include/asm/processor.h +++ b/arch/arm64/include/asm/processor.h @@ -8,9 +8,6 @@ #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 @@ -48,6 +45,7 @@ #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) diff --git a/arch/arm64/include/asm/ptrace.h b/arch/arm64/include/asm/ptrace.h index f8347444235f..41b332c054ab 100644 --- a/arch/arm64/include/asm/ptrace.h +++ b/arch/arm64/include/asm/ptrace.h @@ -193,8 +193,7 @@ struct pt_regs { 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]; diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h index cdcf307764aa..accc70eec3c0 100644 --- a/arch/arm64/include/asm/thread_info.h +++ b/arch/arm64/include/asm/thread_info.h @@ -18,14 +18,11 @@ struct task_struct; #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 @@ -122,7 +119,6 @@ void arch_release_task_struct(struct task_struct *tsk); { \ .flags = _TIF_FOREIGN_FPSTATE, \ .preempt_count = INIT_PREEMPT_COUNT, \ - .addr_limit = KERNEL_DS, \ INIT_SCS \ } diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h index 1e0f28568fea..fb0eb16d755f 100644 --- a/arch/arm64/include/asm/uaccess.h +++ b/arch/arm64/include/asm/uaccess.h @@ -26,44 +26,16 @@ #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 @@ -96,7 +68,6 @@ static inline unsigned long __range_ok(const void __user *addr, unsigned long si } #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" \ @@ -226,9 +197,9 @@ static inline void uaccess_enable_not_uao(void) } /* - * 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) @@ -239,7 +210,7 @@ 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"); diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c index 7d32fc959b1a..679b19b8a7ff 100644 --- a/arch/arm64/kernel/asm-offsets.c +++ b/arch/arm64/kernel/asm-offsets.c @@ -30,7 +30,6 @@ int main(void) 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 @@ -70,7 +69,7 @@ int main(void) 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)); diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index 52acabc52523..58f5f8178fb7 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -1809,10 +1809,6 @@ static const struct arm64_cpu_capabilities arm64_features[] = { .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 diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index d5bc1dbdd2fd..37651d55659e 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -225,12 +225,6 @@ alternative_else_nop_endif .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 @@ -290,12 +284,6 @@ alternative_else_nop_endif .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 */ @@ -1078,10 +1066,9 @@ SYM_CODE_START(__sdei_asm_entry_trampoline) 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)] tramp_data_read_var x4, __sdei_asm_handler br x4 @@ -1096,7 +1083,7 @@ NOKPROBE(__sdei_asm_entry_trampoline) * 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 diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index ef7a4d1bbfaf..b969ba997dd8 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -460,17 +460,6 @@ static void tls_thread_switch(struct task_struct *next) 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. @@ -545,7 +534,6 @@ __notrace_funcgraph struct task_struct *__switch_to(struct task_struct *prev, 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(next); diff --git a/arch/arm64/kernel/sdei.c b/arch/arm64/kernel/sdei.c index 551e2f90f6db..2132bd953a87 100644 --- a/arch/arm64/kernel/sdei.c +++ b/arch/arm64/kernel/sdei.c @@ -243,15 +243,12 @@ asmlinkage noinstr unsigned long __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(); arm64_enter_nmi(regs); @@ -259,7 +256,5 @@ __sdei_handler(struct pt_regs *regs, struct sdei_registered_event *arg) arm64_exit_nmi(regs); - force_uaccess_end(orig_addr_limit); - return ret; } diff --git a/arch/arm64/kernel/suspend.c b/arch/arm64/kernel/suspend.c index 9f8cdeccd1ba..d7564891ffe1 100644 --- a/arch/arm64/kernel/suspend.c +++ b/arch/arm64/kernel/suspend.c @@ -58,7 +58,6 @@ void notrace __cpu_suspend_exit(void) * features that might not have been set correctly. */ __uaccess_enable_hw_pan(); - uao_thread_switch(current); /* * Restore HW breakpoint registers to sane values diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c index 795d224f184f..51549a6fae09 100644 --- a/arch/arm64/mm/fault.c +++ b/arch/arm64/mm/fault.c @@ -479,11 +479,6 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr, } 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); -- 2.31.1
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