[PATCH RFC v3 05/30] ARM: process: Remove local restart
From: Linus Walleij <hidden>
Date: 2025-01-07 09:41:34
Also in:
lkml
Subsystem:
arm port, the rest · Maintainers:
Russell King, Linus Torvalds
The ARM kernel contains a quirk to handle syscall restarts inside the kernel without exiting to userspace. The generic entry cannot handle this. Rename do_signal() to arch_do_signal_or_restart() to fit with the upcoming generic entry conversion. This is essentially a revert of commit 81783786d5cf "ARM: 7473/1: deal with handlerless restarts without leaving the kernel" from 2012. Other solutions may be possible, such as checking the PC after do_work_pending and assume it is a local restart if that address is inside the kernel, or modifying the generic entry code to track local restarts like ARM does and pass that information back. Signed-off-by: Linus Walleij <redacted> --- arch/arm/include/asm/signal.h | 3 +-- arch/arm/kernel/entry-common.S | 9 +-------- arch/arm/kernel/signal.c | 28 +++++++++------------------- 3 files changed, 11 insertions(+), 29 deletions(-)
diff --git a/arch/arm/include/asm/signal.h b/arch/arm/include/asm/signal.h
index 8b84092d151800cb4076672d1c31f0a83777d0d8..7acccc96840c8a17744cc3f2894f19d142aba4fd 100644
--- a/arch/arm/include/asm/signal.h
+++ b/arch/arm/include/asm/signal.h@@ -24,7 +24,6 @@ typedef struct { #include <asm/sigcontext.h> void do_rseq_syscall(struct pt_regs *regs); -int do_work_pending(struct pt_regs *regs, unsigned int thread_flags, - int syscall); +void do_work_pending(struct pt_regs *regs, unsigned int thread_flags); #endif
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index df6961a1006b7a0f3522728812bf52ccb849e511..da5c2d4b62e56cce644b15e329ab4149d69c5b79 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S@@ -86,14 +86,8 @@ ENDPROC(ret_fast_syscall) bne __sys_trace_return_nosave slow_work_pending: mov r0, sp @ 'regs' - mov r2, why @ 'syscall' bl do_work_pending - cmp r0, #0 - beq no_work_pending - movlt scno, #(__NR_restart_syscall - __NR_SYSCALL_BASE) - str scno, [tsk, #TI_ABI_SYSCALL] @ make sure tracers see update - ldmia sp, {r0 - r6} @ have to reload r0 - r6 - b local_restart @ ... and off we go + b no_work_pending ENDPROC(ret_fast_syscall) /*
@@ -266,7 +260,6 @@ ENTRY(vector_swi) */ TRACE( ldmia sp, {r0 - r3} ) -local_restart: ldr r10, [tsk, #TI_FLAGS] @ check for syscall tracing stmdb sp!, {r4, r5} @ push fifth and sixth args
diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
index 79a6730fa0eb7d6581343bdbbeb6834dcaabb9f8..7b1a16e86b236575efdc29cda9b751e8e2a3f64e 100644
--- a/arch/arm/kernel/signal.c
+++ b/arch/arm/kernel/signal.c@@ -18,6 +18,7 @@ #include <asm/traps.h> #include <asm/unistd.h> #include <asm/vfp.h> +#include <asm/syscall.h> #include <asm/syscalls.h> #include "signal.h"
@@ -534,9 +535,10 @@ static void handle_signal(struct ksignal *ksig, struct pt_regs *regs) * the kernel can handle, and then we build all the user-level signal handling * stack-frames in one go after that. */ -static int do_signal(struct pt_regs *regs, int syscall) +static void arch_do_signal_or_restart(struct pt_regs *regs) { unsigned int retval = 0, continue_addr = 0, restart_addr = 0; + bool syscall = (syscall_get_nr(current, regs) != -1); struct ksignal ksig; int restart = 0;
@@ -590,16 +592,14 @@ static int do_signal(struct pt_regs *regs, int syscall) } else { /* no handler */ restore_saved_sigmask(); - if (unlikely(restart) && regs->ARM_pc == restart_addr) { + if (unlikely(restart) && regs->ARM_pc == restart_addr) regs->ARM_pc = continue_addr; - return restart; - } } - return 0; + return; } -asmlinkage int -do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall) +asmlinkage void +do_work_pending(struct pt_regs *regs, unsigned int thread_flags) { /* * The assembly code enters us with IRQs off, but it hasn't
@@ -612,19 +612,10 @@ do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall) schedule(); } else { if (unlikely(!user_mode(regs))) - return 0; + return; local_irq_enable(); if (thread_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL)) { - int restart = do_signal(regs, syscall); - if (unlikely(restart)) { - /* - * Restart without handlers. - * Deal with it without leaving - * the kernel space. - */ - return restart; - } - syscall = 0; + arch_do_signal_or_restart(regs); } else if (thread_flags & _TIF_UPROBE) { uprobe_notify_resume(regs); } else {
@@ -634,7 +625,6 @@ do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall) local_irq_disable(); thread_flags = read_thread_flags(); } while (thread_flags & _TIF_WORK_MASK); - return 0; } struct page *get_signal_page(void)
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2.47.1