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arm64: entry: move bulk of ret_to_user to C
In `ret_to_user` we perform some conditional work depending on the thread flags, then perform some IRQ/context tracking which is intended to balance with the IRQ/context tracking performed in the entry C code. For simplicity and consistency, it would be preferable to move this all to C. As a step towards that, this patch moves the conditional work and IRQ/context tracking into a C helper function. To aid bisectability, this is called from the `ret_to_user` assembly, and a subsequent patch will move the call to C code. As local_daif_mask() handles all necessary tracing and PMR manipulation, we no longer need to handle this explicitly. As we call exit_to_user_mode() directly, the `user_enter_irqoff` macro is no longer used, and can be removed. As enter_from_user_mode() and exit_to_user_mode() are no longer called from assembly, these can be made static, and as these are typically very small, they are marked __always_inline to avoid the overhead of a function call. For now, enablement of single-step is left in entry.S, and for this we still need to read the flags in ret_to_user(). It is safe to read this separately as TIF_SINGLESTEP is not part of _TIF_WORK_MASK. There should be no functional change as a result of this patch. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Cc: James Morse <james.morse@arm.com> Cc: Joey Gouly <joey.gouly@arm.com> Cc: Marc Zyngier <maz@kernel.org> Cc: Will Deacon <will@kernel.org> Reviewed-by: Joey Gouly <joey.gouly@arm.com> Link: https://lore.kernel.org/r/20210802140733.52716-4-mark.rutland@arm.com [catalin.marinas@arm.com: removed unused gic_prio_kentry_setup macro] Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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@ -55,8 +55,8 @@ asmlinkage void el0t_32_error_handler(struct pt_regs *regs);
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asmlinkage void call_on_irq_stack(struct pt_regs *regs,
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void (*func)(struct pt_regs *));
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asmlinkage void enter_from_user_mode(void);
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asmlinkage void exit_to_user_mode(void);
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asmlinkage void asm_exit_to_user_mode(struct pt_regs *regs);
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void do_mem_abort(unsigned long far, unsigned int esr, struct pt_regs *regs);
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void do_undefinstr(struct pt_regs *regs);
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void do_bti(struct pt_regs *regs);
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@ -73,6 +73,7 @@ void do_el0_svc(struct pt_regs *regs);
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void do_el0_svc_compat(struct pt_regs *regs);
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void do_ptrauth_fault(struct pt_regs *regs, unsigned int esr);
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void do_serror(struct pt_regs *regs, unsigned int esr);
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void do_notify_resume(struct pt_regs *regs, unsigned long thread_flags);
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void panic_bad_stack(struct pt_regs *regs, unsigned int esr, unsigned long far);
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#endif /* __ASM_EXCEPTION_H */
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@ -104,7 +104,7 @@ static __always_inline void __enter_from_user_mode(void)
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trace_hardirqs_off_finish();
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}
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asmlinkage void noinstr enter_from_user_mode(void)
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static __always_inline void enter_from_user_mode(void)
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{
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__enter_from_user_mode();
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}
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@ -123,12 +123,29 @@ static __always_inline void __exit_to_user_mode(void)
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lockdep_hardirqs_on(CALLER_ADDR0);
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}
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asmlinkage void noinstr exit_to_user_mode(void)
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static __always_inline void exit_to_user_mode(void)
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{
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mte_check_tfsr_exit();
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__exit_to_user_mode();
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}
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static __always_inline void prepare_exit_to_user_mode(struct pt_regs *regs)
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{
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unsigned long flags;
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local_daif_mask();
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flags = READ_ONCE(current_thread_info()->flags);
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if (unlikely(flags & _TIF_WORK_MASK))
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do_notify_resume(regs, flags);
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}
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asmlinkage void noinstr asm_exit_to_user_mode(struct pt_regs *regs)
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{
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prepare_exit_to_user_mode(regs);
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exit_to_user_mode();
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}
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/*
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* Handle IRQ/context state management when entering an NMI from user/kernel
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* mode. Before this function is called it is not safe to call regular kernel
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@ -29,16 +29,6 @@
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#include <asm/asm-uaccess.h>
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#include <asm/unistd.h>
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/*
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* Context tracking and irqflag tracing need to instrument transitions between
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* user and kernel mode.
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*/
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.macro user_enter_irqoff
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#if defined(CONFIG_CONTEXT_TRACKING) || defined(CONFIG_TRACE_IRQFLAGS)
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bl exit_to_user_mode
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#endif
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.endm
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.macro clear_gp_regs
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.irp n,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29
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mov x\n, xzr
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@ -474,18 +464,6 @@ SYM_CODE_END(__swpan_exit_el0)
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/* GPRs used by entry code */
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tsk .req x28 // current thread_info
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/*
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* Interrupt handling.
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*/
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.macro gic_prio_kentry_setup, tmp:req
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#ifdef CONFIG_ARM64_PSEUDO_NMI
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alternative_if ARM64_HAS_IRQ_PRIO_MASKING
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mov \tmp, #(GIC_PRIO_PSR_I_SET | GIC_PRIO_IRQON)
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msr_s SYS_ICC_PMR_EL1, \tmp
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alternative_else_nop_endif
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#endif
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.endm
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.text
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/*
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@ -585,37 +563,17 @@ SYM_CODE_START_LOCAL(ret_to_kernel)
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kernel_exit 1
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SYM_CODE_END(ret_to_kernel)
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/*
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* "slow" syscall return path.
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*/
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SYM_CODE_START_LOCAL(ret_to_user)
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disable_daif
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gic_prio_kentry_setup tmp=x3
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#ifdef CONFIG_TRACE_IRQFLAGS
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bl trace_hardirqs_off
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#endif
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ldr x19, [tsk, #TSK_TI_FLAGS]
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and x2, x19, #_TIF_WORK_MASK
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cbnz x2, work_pending
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finish_ret_to_user:
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user_enter_irqoff
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mov x0, sp
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bl asm_exit_to_user_mode
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/* Ignore asynchronous tag check faults in the uaccess routines */
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clear_mte_async_tcf
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ldr x19, [tsk, #TSK_TI_FLAGS] // re-check for single-step
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enable_step_tsk x19, x2
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#ifdef CONFIG_GCC_PLUGIN_STACKLEAK
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bl stackleak_erase
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#endif
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kernel_exit 0
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/*
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* Ok, we need to do extra processing, enter the slow path.
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*/
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work_pending:
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mov x0, sp // 'regs'
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mov x1, x19
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bl do_notify_resume
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ldr x19, [tsk, #TSK_TI_FLAGS] // re-check for single-step
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b finish_ret_to_user
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SYM_CODE_END(ret_to_user)
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.popsection // .entry.text
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@ -924,8 +924,7 @@ static bool cpu_affinity_invalid(struct pt_regs *regs)
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system_32bit_el0_cpumask());
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}
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asmlinkage void do_notify_resume(struct pt_regs *regs,
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unsigned long thread_flags)
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void do_notify_resume(struct pt_regs *regs, unsigned long thread_flags)
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{
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do {
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if (thread_flags & _TIF_NEED_RESCHED) {
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