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arm64: entry: move bulk of ret_to_user to C

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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>
This commit is contained in:
Mark Rutland 2021-08-02 15:07:32 +01:00 committed by Catalin Marinas
parent bc29b71f53
commit 4d1c2ee270
4 changed files with 26 additions and 51 deletions
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5
arch/arm64/include/asm/exception.h
View File

@ -55,8 +55,8 @@ asmlinkage void el0t_32_error_handler(struct pt_regs *regs);
asmlinkage void call_on_irq_stack(struct pt_regs *regs,
void (*func)(struct pt_regs *));
asmlinkage void enter_from_user_mode(void);
asmlinkage void exit_to_user_mode(void);
asmlinkage void asm_exit_to_user_mode(struct pt_regs *regs);
void do_mem_abort(unsigned long far, unsigned int esr, struct pt_regs *regs);
void do_undefinstr(struct pt_regs *regs);
void do_bti(struct pt_regs *regs);
@ -73,6 +73,7 @@ void do_el0_svc(struct pt_regs *regs);
void do_el0_svc_compat(struct pt_regs *regs);
void do_ptrauth_fault(struct pt_regs *regs, unsigned int esr);
void do_serror(struct pt_regs *regs, unsigned int esr);
void do_notify_resume(struct pt_regs *regs, unsigned long thread_flags);
void panic_bad_stack(struct pt_regs *regs, unsigned int esr, unsigned long far);
#endif /* __ASM_EXCEPTION_H */

21
arch/arm64/kernel/entry-common.c
View File

@ -104,7 +104,7 @@ static __always_inline void __enter_from_user_mode(void)
trace_hardirqs_off_finish();
}
asmlinkage void noinstr enter_from_user_mode(void)
static __always_inline void enter_from_user_mode(void)
{
__enter_from_user_mode();
}
@ -123,12 +123,29 @@ static __always_inline void __exit_to_user_mode(void)
lockdep_hardirqs_on(CALLER_ADDR0);
}
asmlinkage void noinstr exit_to_user_mode(void)
static __always_inline void exit_to_user_mode(void)
{
mte_check_tfsr_exit();
__exit_to_user_mode();
}
static __always_inline void prepare_exit_to_user_mode(struct pt_regs *regs)
{
unsigned long flags;
local_daif_mask();
flags = READ_ONCE(current_thread_info()->flags);
if (unlikely(flags & _TIF_WORK_MASK))
do_notify_resume(regs, flags);
}
asmlinkage void noinstr asm_exit_to_user_mode(struct pt_regs *regs)
{
prepare_exit_to_user_mode(regs);
exit_to_user_mode();
}
/*
* Handle IRQ/context state management when entering an NMI from user/kernel
* mode. Before this function is called it is not safe to call regular kernel

48
arch/arm64/kernel/entry.S
View File

@ -29,16 +29,6 @@
#include <asm/asm-uaccess.h>
#include <asm/unistd.h>
/*
* Context tracking and irqflag tracing need to instrument transitions between
* user and kernel mode.
*/
.macro user_enter_irqoff
#if defined(CONFIG_CONTEXT_TRACKING) || defined(CONFIG_TRACE_IRQFLAGS)
bl exit_to_user_mode
#endif
.endm
.macro clear_gp_regs
.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
mov x\n, xzr
@ -474,18 +464,6 @@ SYM_CODE_END(__swpan_exit_el0)
/* GPRs used by entry code */
tsk .req x28 // current thread_info
/*
* Interrupt handling.
*/
.macro gic_prio_kentry_setup, tmp:req
#ifdef CONFIG_ARM64_PSEUDO_NMI
alternative_if ARM64_HAS_IRQ_PRIO_MASKING
mov \tmp, #(GIC_PRIO_PSR_I_SET | GIC_PRIO_IRQON)
msr_s SYS_ICC_PMR_EL1, \tmp
alternative_else_nop_endif
#endif
.endm
.text
/*
@ -585,37 +563,17 @@ SYM_CODE_START_LOCAL(ret_to_kernel)
kernel_exit 1
SYM_CODE_END(ret_to_kernel)
/*
* "slow" syscall return path.
*/
SYM_CODE_START_LOCAL(ret_to_user)
disable_daif
gic_prio_kentry_setup tmp=x3
#ifdef CONFIG_TRACE_IRQFLAGS
bl trace_hardirqs_off
#endif
ldr x19, [tsk, #TSK_TI_FLAGS]
and x2, x19, #_TIF_WORK_MASK
cbnz x2, work_pending
finish_ret_to_user:
user_enter_irqoff
mov x0, sp
bl asm_exit_to_user_mode
/* Ignore asynchronous tag check faults in the uaccess routines */
clear_mte_async_tcf
ldr x19, [tsk, #TSK_TI_FLAGS] // re-check for single-step
enable_step_tsk x19, x2
#ifdef CONFIG_GCC_PLUGIN_STACKLEAK
bl stackleak_erase
#endif
kernel_exit 0
/*
* Ok, we need to do extra processing, enter the slow path.
*/
work_pending:
mov x0, sp // 'regs'
mov x1, x19
bl do_notify_resume
ldr x19, [tsk, #TSK_TI_FLAGS] // re-check for single-step
b finish_ret_to_user
SYM_CODE_END(ret_to_user)
.popsection // .entry.text

3
arch/arm64/kernel/signal.c
View File

@ -924,8 +924,7 @@ static bool cpu_affinity_invalid(struct pt_regs *regs)
system_32bit_el0_cpumask());
}
asmlinkage void do_notify_resume(struct pt_regs *regs,
unsigned long thread_flags)
void do_notify_resume(struct pt_regs *regs, unsigned long thread_flags)
{
do {
if (thread_flags & _TIF_NEED_RESCHED) {