From: James Morse james.morse@arm.com
[ Upstream commit 2671828c3ff4ffadf777f793a1f3232d6e51394a ]
When taking an SError or Debug exception from EL0, we run the C handler for these exceptions before updating the context tracking code and unmasking lower priority interrupts.
When booting with nohz_full lockdep tells us we got this wrong: | ============================= | WARNING: suspicious RCU usage | 5.3.0-rc2-00010-gb4b5e9dcb11b-dirty #11271 Not tainted | ----------------------------- | include/linux/rcupdate.h:643 rcu_read_unlock() used illegally wh! | | other info that might help us debug this: | | | RCU used illegally from idle CPU! | rcu_scheduler_active = 2, debug_locks = 1 | RCU used illegally from extended quiescent state! | 1 lock held by a.out/432: | #0: 00000000c7a79515 (rcu_read_lock){....}, at: brk_handler+0x00 | | stack backtrace: | CPU: 1 PID: 432 Comm: a.out Not tainted 5.3.0-rc2-00010-gb4b5e9d1 | Hardware name: ARM LTD ARM Juno Development Platform/ARM Juno De8 | Call trace: | dump_backtrace+0x0/0x140 | show_stack+0x14/0x20 | dump_stack+0xbc/0x104 | lockdep_rcu_suspicious+0xf8/0x108 | brk_handler+0x164/0x1b0 | do_debug_exception+0x11c/0x278 | el0_dbg+0x14/0x20
Moving the ct_user_exit calls to be before do_debug_exception() means they are also before trace_hardirqs_off() has been updated. Add a new ct_user_exit_irqoff macro to avoid the context-tracking code using irqsave/restore before we've updated trace_hardirqs_off(). To be consistent, do this everywhere.
The C helper is called enter_from_user_mode() to match x86 in the hope we can merge them into kernel/context_tracking.c later.
Cc: Masami Hiramatsu mhiramat@kernel.org Fixes: 6c81fe7925cc4c42 ("arm64: enable context tracking") Signed-off-by: James Morse james.morse@arm.com Signed-off-by: Will Deacon will@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- arch/arm64/include/asm/exception.h | 2 ++ arch/arm64/kernel/entry.S | 36 ++++++++++++++++-------------- arch/arm64/kernel/traps.c | 9 ++++++++ 3 files changed, 30 insertions(+), 17 deletions(-)
diff --git a/arch/arm64/include/asm/exception.h b/arch/arm64/include/asm/exception.h index ed57b760f38cf..a17393ff66774 100644 --- a/arch/arm64/include/asm/exception.h +++ b/arch/arm64/include/asm/exception.h @@ -30,4 +30,6 @@ static inline u32 disr_to_esr(u64 disr) return esr; }
+asmlinkage void enter_from_user_mode(void); + #endif /* __ASM_EXCEPTION_H */ diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 320a30dbe35ef..84a822748c84e 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -30,9 +30,9 @@ * Context tracking subsystem. Used to instrument transitions * between user and kernel mode. */ - .macro ct_user_exit + .macro ct_user_exit_irqoff #ifdef CONFIG_CONTEXT_TRACKING - bl context_tracking_user_exit + bl enter_from_user_mode #endif .endm
@@ -792,8 +792,8 @@ el0_cp15: /* * Trapped CP15 (MRC, MCR, MRRC, MCRR) instructions */ + ct_user_exit_irqoff enable_daif - ct_user_exit mov x0, x25 mov x1, sp bl do_cp15instr @@ -805,8 +805,8 @@ el0_da: * Data abort handling */ mrs x26, far_el1 + ct_user_exit_irqoff enable_daif - ct_user_exit clear_address_tag x0, x26 mov x1, x25 mov x2, sp @@ -818,11 +818,11 @@ el0_ia: */ mrs x26, far_el1 gic_prio_kentry_setup tmp=x0 + ct_user_exit_irqoff enable_da_f #ifdef CONFIG_TRACE_IRQFLAGS bl trace_hardirqs_off #endif - ct_user_exit mov x0, x26 mov x1, x25 mov x2, sp @@ -832,8 +832,8 @@ el0_fpsimd_acc: /* * Floating Point or Advanced SIMD access */ + ct_user_exit_irqoff enable_daif - ct_user_exit mov x0, x25 mov x1, sp bl do_fpsimd_acc @@ -842,8 +842,8 @@ el0_sve_acc: /* * Scalable Vector Extension access */ + ct_user_exit_irqoff enable_daif - ct_user_exit mov x0, x25 mov x1, sp bl do_sve_acc @@ -852,8 +852,8 @@ el0_fpsimd_exc: /* * Floating Point, Advanced SIMD or SVE exception */ + ct_user_exit_irqoff enable_daif - ct_user_exit mov x0, x25 mov x1, sp bl do_fpsimd_exc @@ -868,11 +868,11 @@ el0_sp_pc: * Stack or PC alignment exception handling */ gic_prio_kentry_setup tmp=x0 + ct_user_exit_irqoff enable_da_f #ifdef CONFIG_TRACE_IRQFLAGS bl trace_hardirqs_off #endif - ct_user_exit mov x0, x26 mov x1, x25 mov x2, sp @@ -882,8 +882,8 @@ el0_undef: /* * Undefined instruction */ + ct_user_exit_irqoff enable_daif - ct_user_exit mov x0, sp bl do_undefinstr b ret_to_user @@ -891,8 +891,8 @@ el0_sys: /* * System instructions, for trapped cache maintenance instructions */ + ct_user_exit_irqoff enable_daif - ct_user_exit mov x0, x25 mov x1, sp bl do_sysinstr @@ -902,17 +902,18 @@ el0_dbg: * Debug exception handling */ tbnz x24, #0, el0_inv // EL0 only + mrs x24, far_el1 gic_prio_kentry_setup tmp=x3 - mrs x0, far_el1 + ct_user_exit_irqoff + mov x0, x24 mov x1, x25 mov x2, sp bl do_debug_exception enable_da_f - ct_user_exit b ret_to_user el0_inv: + ct_user_exit_irqoff enable_daif - ct_user_exit mov x0, sp mov x1, #BAD_SYNC mov x2, x25 @@ -925,13 +926,13 @@ el0_irq: kernel_entry 0 el0_irq_naked: gic_prio_irq_setup pmr=x20, tmp=x0 + ct_user_exit_irqoff enable_da_f
#ifdef CONFIG_TRACE_IRQFLAGS bl trace_hardirqs_off #endif
- ct_user_exit #ifdef CONFIG_HARDEN_BRANCH_PREDICTOR tbz x22, #55, 1f bl do_el0_irq_bp_hardening @@ -958,13 +959,14 @@ ENDPROC(el1_error) el0_error: kernel_entry 0 el0_error_naked: - mrs x1, esr_el1 + mrs x25, esr_el1 gic_prio_kentry_setup tmp=x2 + ct_user_exit_irqoff enable_dbg mov x0, sp + mov x1, x25 bl do_serror enable_da_f - ct_user_exit b ret_to_user ENDPROC(el0_error)
diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c index 32893b3d9164e..742a636861e77 100644 --- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -7,9 +7,11 @@ */
#include <linux/bug.h> +#include <linux/context_tracking.h> #include <linux/signal.h> #include <linux/personality.h> #include <linux/kallsyms.h> +#include <linux/kprobes.h> #include <linux/spinlock.h> #include <linux/uaccess.h> #include <linux/hardirq.h> @@ -900,6 +902,13 @@ asmlinkage void do_serror(struct pt_regs *regs, unsigned int esr) nmi_exit(); }
+asmlinkage void enter_from_user_mode(void) +{ + CT_WARN_ON(ct_state() != CONTEXT_USER); + user_exit_irqoff(); +} +NOKPROBE_SYMBOL(enter_from_user_mode); + void __pte_error(const char *file, int line, unsigned long val) { pr_err("%s:%d: bad pte %016lx.\n", file, line, val);