From cc6622730be77fa88acc4fb0942cd39e6fa5ca27 Mon Sep 17 00:00:00 2001
From: "Dmitry V. Levin" <ldv@strace.io>
Date: Mon, 3 Mar 2025 13:20:20 +0200
Subject: syscall.h: introduce syscall_set_nr()

Similar to syscall_set_arguments() that complements
syscall_get_arguments(), introduce syscall_set_nr() that complements
syscall_get_nr().

syscall_set_nr() is going to be needed along with syscall_set_arguments()
on all HAVE_ARCH_TRACEHOOK architectures to implement
PTRACE_SET_SYSCALL_INFO API.

Link: https://lkml.kernel.org/r/20250303112020.GD24170@strace.io
Signed-off-by: Dmitry V. Levin <ldv@strace.io>
Tested-by: Charlie Jenkins <charlie@rivosinc.com>
Reviewed-by: Charlie Jenkins <charlie@rivosinc.com>
Acked-by: Helge Deller <deller@gmx.de> # parisc
Reviewed-by: Maciej W. Rozycki <macro@orcam.me.uk> # mips
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Alexey Gladkov (Intel) <legion@kernel.org>
Cc: Andreas Larsson <andreas@gaisler.com>
Cc: anton ivanov <anton.ivanov@cambridgegreys.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Betkov <bp@alien8.de>
Cc: Brian Cain <bcain@quicinc.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Christian Zankel <chris@zankel.net>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Davide Berardi <berardi.dav@gmail.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Dinh Nguyen <dinguyen@kernel.org>
Cc: Eugene Syromiatnikov <esyr@redhat.com>
Cc: Eugene Syromyatnikov <evgsyr@gmail.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Guo Ren <guoren@kernel.org>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc: Jonas Bonn <jonas@southpole.se>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: Naveen N Rao <naveen@kernel.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Renzo Davoi <renzo@cs.unibo.it>
Cc: Richard Weinberger <richard@nod.at>
Cc: Rich Felker <dalias@libc.org>
Cc: Russel King <linux@armlinux.org.uk>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Stafford Horne <shorne@gmail.com>
Cc: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vineet Gupta <vgupta@kernel.org>
Cc: WANG Xuerui <kernel@xen0n.name>
Cc: Will Deacon <will@kernel.org>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
 arch/arm/include/asm/syscall.h | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

(limited to 'arch/arm/include/asm/syscall.h')

diff --git a/arch/arm/include/asm/syscall.h b/arch/arm/include/asm/syscall.h
index 21927fa0ae2b..18b102a30741 100644
--- a/arch/arm/include/asm/syscall.h
+++ b/arch/arm/include/asm/syscall.h
@@ -68,6 +68,30 @@ static inline void syscall_set_return_value(struct task_struct *task,
 	regs->ARM_r0 = (long) error ? error : val;
 }
 
+static inline void syscall_set_nr(struct task_struct *task,
+				  struct pt_regs *regs,
+				  int nr)
+{
+	if (nr == -1) {
+		task_thread_info(task)->abi_syscall = -1;
+		/*
+		 * When the syscall number is set to -1, the syscall will be
+		 * skipped.  In this case the syscall return value has to be
+		 * set explicitly, otherwise the first syscall argument is
+		 * returned as the syscall return value.
+		 */
+		syscall_set_return_value(task, regs, -ENOSYS, 0);
+		return;
+	}
+	if ((IS_ENABLED(CONFIG_AEABI) && !IS_ENABLED(CONFIG_OABI_COMPAT))) {
+		task_thread_info(task)->abi_syscall = nr;
+		return;
+	}
+	task_thread_info(task)->abi_syscall =
+		(task_thread_info(task)->abi_syscall & ~__NR_SYSCALL_MASK) |
+		(nr & __NR_SYSCALL_MASK);
+}
+
 #define SYSCALL_MAX_ARGS 7
 
 static inline void syscall_get_arguments(struct task_struct *task,
-- 
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