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Message-Id: <20241029-arm-generic-entry-v2-5-573519abef38@linaro.org>
Date: Tue, 29 Oct 2024 11:52:45 +0100
From: Linus Walleij <linus.walleij@...aro.org>
To: Oleg Nesterov <oleg@...hat.com>, Russell King <linux@...linux.org.uk>,
Kees Cook <kees@...nel.org>, Andy Lutomirski <luto@...capital.net>,
Will Drewry <wad@...omium.org>, Frederic Weisbecker <frederic@...nel.org>,
"Paul E. McKenney" <paulmck@...nel.org>,
Jinjie Ruan <ruanjinjie@...wei.com>, Arnd Bergmann <arnd@...db.de>,
Ard Biesheuvel <ardb@...nel.org>, Al Viro <viro@...iv.linux.org.uk>
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
Linus Walleij <linus.walleij@...aro.org>
Subject: [PATCH RFC v2 05/28] ARM: process: Remove local restart
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 <linus.walleij@...aro.org>
---
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 8b84092d1518..7acccc96840c 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 df6961a1006b..da5c2d4b62e5 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 79a6730fa0eb..7b1a16e86b23 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)
--
2.46.2
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