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Sat, 19 Apr 2025 15:36:27 -0700 (PDT) From: Linus Walleij Date: Sun, 20 Apr 2025 00:36:11 +0200 Subject: [PATCH v6 24/31] ARM: entry: Complete syscall and IRQ transition to C Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20250420-arm-generic-entry-v6-24-95f1fcdfeeb2@linaro.org> References: <20250420-arm-generic-entry-v6-0-95f1fcdfeeb2@linaro.org> In-Reply-To: <20250420-arm-generic-entry-v6-0-95f1fcdfeeb2@linaro.org> To: Dmitry Vyukov , Oleg Nesterov , Russell King , Kees Cook , Andy Lutomirski , Will Drewry , Frederic Weisbecker , "Paul E. McKenney" , Jinjie Ruan , Arnd Bergmann , Ard Biesheuvel , Al Viro Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Linus Walleij , Thomas Gleixner X-Mailer: b4 0.14.2 This moves over the last few lines of assembly to C. The subtle change is that in return to userspace from syscall (SWI) or interrupt, we need to call do_work_pending() as soon as the thread flags are !=3D 0, just checking for work with _TIF_SYSCALL_WORK is not enough (the machine will freeze if we do that). This is because do_work_pending() does not just handle work: it handles _TIF_NEED_RESCHED, _TIF_SIGPENDING, _TIF_NOTIFY_SIGNAL and _TIF_UPROBE as well. Acked-by: Thomas Gleixner Acked-by: Paul E. McKenney Signed-off-by: Linus Walleij --- arch/arm/kernel/entry-common.S | 13 +------------ arch/arm/kernel/entry.c | 19 +++++++++++++------ arch/arm/kernel/signal.c | 3 +-- 3 files changed, 15 insertions(+), 20 deletions(-) diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S index e2ac6d3216b6828d948d60c424ff95ccdad12331..6b0f86786a7d9e656ecbe8c741f= 2edbcbafd2915 100644 --- a/arch/arm/kernel/entry-common.S +++ b/arch/arm/kernel/entry-common.S @@ -61,12 +61,7 @@ ENTRY(ret_to_user) enable_irq_notrace @ enable interrupts mov r0, sp @ 'regs' bl syscall_exit_to_user_mode - ldr r1, [tsk, #TI_FLAGS] - movs r1, r1, lsl #16 - beq 1f - mov r0, sp @ 'regs' - bl do_work_pending -1: + #ifdef CONFIG_GCC_PLUGIN_STACKLEAK bl stackleak_erase_on_task_stack #endif @@ -74,12 +69,6 @@ ENTRY(ret_to_user) ENDPROC(ret_to_user) =20 ENTRY(ret_to_user_from_irq) - ldr r1, [tsk, #TI_FLAGS] - movs r1, r1, lsl #16 - beq no_work_pending - mov r0, sp @ 'regs' - bl do_work_pending -no_work_pending: asm_irqentry_exit_to_user_mode =20 #ifdef CONFIG_GCC_PLUGIN_STACKLEAK diff --git a/arch/arm/kernel/entry.c b/arch/arm/kernel/entry.c index 88a7a699306ab61153d57333c26266b9161f5466..d7fdb9df33312dd2a914b59512b= 701748f33b597 100644 --- a/arch/arm/kernel/entry.c +++ b/arch/arm/kernel/entry.c @@ -6,11 +6,6 @@ #include #include =20 -static inline bool has_syscall_work(unsigned long flags) -{ - return unlikely(flags & _TIF_SYSCALL_WORK); -} - long syscall_enter_from_user_mode(struct pt_regs *regs, long syscall) { trace_hardirqs_on(); @@ -28,7 +23,11 @@ void syscall_exit_to_user_mode(struct pt_regs *regs) =20 rseq_syscall(regs); local_irq_disable(); - if (has_syscall_work(flags)) + /* + * It really matters that we check for flags !=3D 0 and not + * just for pending work here! + */ + if (flags) do_work_pending(regs, flags); =20 trace_hardirqs_on(); @@ -45,6 +44,14 @@ noinstr void irqentry_enter_from_user_mode(struct pt_reg= s *regs) =20 noinstr void irqentry_exit_to_user_mode(struct pt_regs *regs) { + unsigned long flags =3D read_thread_flags(); + + /* + * It really matters that we check for flags !=3D 0 and not + * just for pending work here! + */ + if (flags) + do_work_pending(regs, flags); trace_hardirqs_on(); /* This context tracking call has inverse naming */ user_enter_callable(); diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c index 03b20637a2e1ca6f327223c9132915a97a9c4697..a39ee14ec5b70b3738ecef53770= 9326ef1e8217c 100644 --- a/arch/arm/kernel/signal.c +++ b/arch/arm/kernel/signal.c @@ -598,8 +598,7 @@ static void arch_do_signal_or_restart(struct pt_regs *r= egs) return; } =20 -asmlinkage void -do_work_pending(struct pt_regs *regs, unsigned int thread_flags) +void do_work_pending(struct pt_regs *regs, unsigned int thread_flags) { /* * The assembly code enters us with IRQs off, but it hasn't --=20 2.49.0