linux-kernel - [RESEND PATCH v4 4/8] arm64: Separate in_compat_syscall from is_compat

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Date:   Tue, 18 May 2021 10:06:54 +0100
From:   Amanieu d'Antras <amanieu@...il.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     Amanieu d'Antras <amanieu@...il.com>,
        Ryan Houdek <Houdek.Ryan@...-emu.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Steven Price <steven.price@....com>,
        Arnd Bergmann <arnd@...nel.org>,
        David Laight <David.Laight@...lab.com>,
        Mark Brown <broonie@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [RESEND PATCH v4 4/8] arm64: Separate in_compat_syscall from is_compat_task

This is preliminary work for allowing 64-bit processes to invoke compat
syscalls.

Signed-off-by: Amanieu d'Antras <amanieu@...il.com>
Co-developed-by: Ryan Houdek <Houdek.Ryan@...-emu.org>
Signed-off-by: Ryan Houdek <Houdek.Ryan@...-emu.org>
---
 arch/arm64/include/asm/compat.h  | 24 ++++++++++++++++++++----
 arch/arm64/include/asm/ftrace.h  |  2 +-
 arch/arm64/include/asm/syscall.h |  6 +++---
 arch/arm64/kernel/ptrace.c       |  2 +-
 arch/arm64/kernel/syscall.c      |  2 +-
 5 files changed, 26 insertions(+), 10 deletions(-)

diff --git a/arch/arm64/include/asm/compat.h b/arch/arm64/include/asm/compat.h
index 23a9fb73c04f..a2f5001f7793 100644
--- a/arch/arm64/include/asm/compat.h
+++ b/arch/arm64/include/asm/compat.h
@@ -178,21 +178,37 @@ struct compat_shmid64_ds {
 	compat_ulong_t __unused5;
 };
 
-static inline int is_compat_task(void)
+static inline bool is_compat_task(void)
 {
 	return test_thread_flag(TIF_32BIT);
 }
 
-static inline int is_compat_thread(struct thread_info *thread)
+static inline bool is_compat_thread(struct thread_info *thread)
 {
 	return test_ti_thread_flag(thread, TIF_32BIT);
 }
 
+static inline bool in_compat_syscall(void)
+{
+	return is_compat_task();
+}
+#define in_compat_syscall in_compat_syscall	/* override the generic impl */
+
+static inline bool thread_in_compat_syscall(struct thread_info *thread)
+{
+	return is_compat_thread(thread);
+}
+
 #else /* !CONFIG_COMPAT */
 
-static inline int is_compat_thread(struct thread_info *thread)
+static inline bool is_compat_thread(struct thread_info *thread)
+{
+	return false;
+}
+
+static inline bool thread_in_compat_syscall(struct thread_info *thread)
 {
-	return 0;
+	return false;
 }
 
 #endif /* CONFIG_COMPAT */
diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h
index 91fa4baa1a93..f41aad92c67a 100644
--- a/arch/arm64/include/asm/ftrace.h
+++ b/arch/arm64/include/asm/ftrace.h
@@ -88,7 +88,7 @@ int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec);
 #define ARCH_TRACE_IGNORE_COMPAT_SYSCALLS
 static inline bool arch_trace_is_compat_syscall(struct pt_regs *regs)
 {
-	return is_compat_task();
+	return in_compat_syscall();
 }
 
 #define ARCH_HAS_SYSCALL_MATCH_SYM_NAME
diff --git a/arch/arm64/include/asm/syscall.h b/arch/arm64/include/asm/syscall.h
index cfc0672013f6..0dfc01ea386c 100644
--- a/arch/arm64/include/asm/syscall.h
+++ b/arch/arm64/include/asm/syscall.h
@@ -35,7 +35,7 @@ static inline long syscall_get_error(struct task_struct *task,
 {
 	unsigned long error = regs->regs[0];
 
-	if (is_compat_thread(task_thread_info(task)))
+	if (thread_in_compat_syscall(task_thread_info(task)))
 		error = sign_extend64(error, 31);
 
 	return IS_ERR_VALUE(error) ? error : 0;
@@ -54,7 +54,7 @@ static inline void syscall_set_return_value(struct task_struct *task,
 	if (error)
 		val = error;
 
-	if (is_compat_thread(task_thread_info(task)))
+	if (thread_in_compat_syscall(task_thread_info(task)))
 		val = lower_32_bits(val);
 
 	regs->regs[0] = val;
@@ -88,7 +88,7 @@ static inline void syscall_set_arguments(struct task_struct *task,
  */
 static inline int syscall_get_arch(struct task_struct *task)
 {
-	if (is_compat_thread(task_thread_info(task)))
+	if (thread_in_compat_syscall(task_thread_info(task)))
 		return AUDIT_ARCH_ARM;
 
 	return AUDIT_ARCH_AARCH64;
diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index 170f42fd6101..017a82b24f49 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -1721,7 +1721,7 @@ const struct user_regset_view *task_user_regset_view(struct task_struct *task)
 	 * 32-bit children use an extended user_aarch32_ptrace_view to allow
 	 * access to the TLS register.
 	 */
-	if (is_compat_task())
+	if (in_compat_syscall())
 		return &user_aarch32_view;
 	else if (is_compat_thread(task_thread_info(task)))
 		return &user_aarch32_ptrace_view;
diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c
index b9cf12b271d7..e0e9d54de0a2 100644
--- a/arch/arm64/kernel/syscall.c
+++ b/arch/arm64/kernel/syscall.c
@@ -51,7 +51,7 @@ static void invoke_syscall(struct pt_regs *regs, unsigned int scno,
 		ret = do_ni_syscall(regs, scno);
 	}
 
-	if (is_compat_task())
+	if (in_compat_syscall())
 		ret = lower_32_bits(ret);
 
 	regs->regs[0] = ret;
-- 
2.31.1