linux-kernel - [PATCH v4 6/8] arm64: Add a compat syscall flag to thread

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Message-Id: <20210430203757.47653-5-amanieu@gmail.com>
Date:   Fri, 30 Apr 2021 21:37:55 +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: [PATCH v4 6/8] arm64: Add a compat syscall flag to thread_info

This flag is used by in_compat_syscall to handle compat syscalls coming
from 64-bit tasks.

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      |  4 ++--
 arch/arm64/include/asm/elf.h         | 13 ++++++++++++-
 arch/arm64/include/asm/thread_info.h |  6 ++++++
 3 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/compat.h b/arch/arm64/include/asm/compat.h
index a2f5001f7793..124f4487dfee 100644
--- a/arch/arm64/include/asm/compat.h
+++ b/arch/arm64/include/asm/compat.h
@@ -190,13 +190,13 @@ static inline bool is_compat_thread(struct thread_info *thread)
 
 static inline bool in_compat_syscall(void)
 {
-	return is_compat_task();
+	return current_thread_info()->use_compat_syscall;
 }
 #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);
+	return thread->use_compat_syscall;
 }
 
 #else /* !CONFIG_COMPAT */
diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h
index e21964898d06..49a9a9db612c 100644
--- a/arch/arm64/include/asm/elf.h
+++ b/arch/arm64/include/asm/elf.h
@@ -158,10 +158,20 @@ typedef struct user_fpsimd_state elf_fpregset_t;
  */
 #define ELF_PLAT_INIT(_r, load_addr)	(_r)->regs[0] = 0
 
+#ifdef CONFIG_COMPAT
+#define CLEAR_COMPAT_SYSCALL()						\
+({									\
+	current_thread_info()->use_compat_syscall = false;		\
+})
+#else
+#define CLEAR_COMPAT_SYSCALL()	((void)0)
+#endif
+
 #define SET_PERSONALITY(ex)						\
 ({									\
 	clear_thread_flag(TIF_32BIT);					\
 	current->personality &= ~READ_IMPLIES_EXEC;			\
+	CLEAR_COMPAT_SYSCALL();						\
 })
 
 /* update AT_VECTOR_SIZE_ARCH if the number of NEW_AUX_ENT entries changes */
@@ -228,7 +238,8 @@ typedef compat_elf_greg_t		compat_elf_gregset_t[COMPAT_ELF_NGREG];
 #define COMPAT_SET_PERSONALITY(ex)					\
 ({									\
 	set_thread_flag(TIF_32BIT);					\
- })
+	current_thread_info()->use_compat_syscall = true;		\
+})
 #ifdef CONFIG_COMPAT_VDSO
 #define COMPAT_ARCH_DLINFO						\
 do {									\
diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
index 6623c99f0984..02310b45900d 100644
--- a/arch/arm64/include/asm/thread_info.h
+++ b/arch/arm64/include/asm/thread_info.h
@@ -42,6 +42,12 @@ struct thread_info {
 	void			*scs_base;
 	void			*scs_sp;
 #endif
+#ifdef CONFIG_COMPAT
+	/*
+	 * compat task or inside a compat syscall from a 64-bit task
+	 */
+	bool			use_compat_syscall;
+#endif
 };
 
 #define thread_saved_pc(tsk)	\
-- 
2.31.1