linux-kernel - [PATCH RFT v12 1/8] arm64/gcs: Return a success value from gcs_alloc_thread

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Message-Id: <20241031-clone3-shadow-stack-v12-1-7183eb8bee17@kernel.org>
Date: Thu, 31 Oct 2024 19:25:02 +0000
From: Mark Brown <broonie@...nel.org>
To: "Rick P. Edgecombe" <rick.p.edgecombe@...el.com>, 
 Deepak Gupta <debug@...osinc.com>, Szabolcs Nagy <Szabolcs.Nagy@....com>, 
 "H.J. Lu" <hjl.tools@...il.com>, Florian Weimer <fweimer@...hat.com>, 
 Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, 
 Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, 
 x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>, 
 Peter Zijlstra <peterz@...radead.org>, Juri Lelli <juri.lelli@...hat.com>, 
 Vincent Guittot <vincent.guittot@...aro.org>, 
 Dietmar Eggemann <dietmar.eggemann@....com>, 
 Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>, 
 Mel Gorman <mgorman@...e.de>, Valentin Schneider <vschneid@...hat.com>, 
 Christian Brauner <brauner@...nel.org>, Shuah Khan <shuah@...nel.org>
Cc: linux-kernel@...r.kernel.org, Catalin Marinas <catalin.marinas@....com>, 
 Will Deacon <will@...nel.org>, jannh@...gle.com, bsegall@...gle.com, 
 Yury Khrustalev <yury.khrustalev@....com>, 
 Wilco Dijkstra <wilco.dijkstra@....com>, linux-kselftest@...r.kernel.org, 
 linux-api@...r.kernel.org, Mark Brown <broonie@...nel.org>, 
 Kees Cook <kees@...nel.org>
Subject: [PATCH RFT v12 1/8] arm64/gcs: Return a success value from
 gcs_alloc_thread_stack()

Currently as a result of templating from x86 code gcs_alloc_thread_stack()
returns a pointer as an unsigned int however on arm64 we don't actually use
this pointer value as anything other than a pass/fail flag. Simplify the
interface to just return an int with 0 on success and a negative error code
on failure.

Acked-by: Deepak Gupta <debug@...osinc.com>
Signed-off-by: Mark Brown <broonie@...nel.org>
---
 arch/arm64/include/asm/gcs.h | 8 ++++----
 arch/arm64/kernel/process.c  | 8 ++++----
 arch/arm64/mm/gcs.c          | 8 ++++----
 3 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/arch/arm64/include/asm/gcs.h b/arch/arm64/include/asm/gcs.h
index f50660603ecf5dc09a92740062df3a089b02b219..d8923b5f03b776252aca76ce316ef57399d71fa9 100644
--- a/arch/arm64/include/asm/gcs.h
+++ b/arch/arm64/include/asm/gcs.h
@@ -64,8 +64,8 @@ static inline bool task_gcs_el0_enabled(struct task_struct *task)
 void gcs_set_el0_mode(struct task_struct *task);
 void gcs_free(struct task_struct *task);
 void gcs_preserve_current_state(void);
-unsigned long gcs_alloc_thread_stack(struct task_struct *tsk,
-				     const struct kernel_clone_args *args);
+int gcs_alloc_thread_stack(struct task_struct *tsk,
+			   const struct kernel_clone_args *args);

 static inline int gcs_check_locked(struct task_struct *task,
 				   unsigned long new_val)
@@ -91,8 +91,8 @@ static inline bool task_gcs_el0_enabled(struct task_struct *task)
 static inline void gcs_set_el0_mode(struct task_struct *task) { }
 static inline void gcs_free(struct task_struct *task) { }
 static inline void gcs_preserve_current_state(void) { }
-static inline unsigned long gcs_alloc_thread_stack(struct task_struct *tsk,
-						   const struct kernel_clone_args *args)
+static inline int gcs_alloc_thread_stack(struct task_struct *tsk,
+					 const struct kernel_clone_args *args)
 {
 	return -ENOTSUPP;
 }
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index fdd095480c3ffb8c13fd4e7c9abc79e88143e08b..8ebd11c29792524dfeeade9cc7826b007329aa6a 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -297,7 +297,7 @@ static void flush_gcs(void)
 static int copy_thread_gcs(struct task_struct *p,
 			   const struct kernel_clone_args *args)
 {
-	unsigned long gcs;
+	int ret;

 	if (!system_supports_gcs())
 		return 0;
@@ -305,9 +305,9 @@ static int copy_thread_gcs(struct task_struct *p,
 	p->thread.gcs_base = 0;
 	p->thread.gcs_size = 0;

-	gcs = gcs_alloc_thread_stack(p, args);
-	if (IS_ERR_VALUE(gcs))
-		return PTR_ERR((void *)gcs);
+	ret = gcs_alloc_thread_stack(p, args);
+	if (ret != 0)
+		return ret;

 	p->thread.gcs_el0_mode = current->thread.gcs_el0_mode;
 	p->thread.gcs_el0_locked = current->thread.gcs_el0_locked;
diff --git a/arch/arm64/mm/gcs.c b/arch/arm64/mm/gcs.c
index 5c46ec527b1cdaa8f52cff445d70ba0f8509d086..1f633a482558b59aac5427963d42b37fce08c8a6 100644
--- a/arch/arm64/mm/gcs.c
+++ b/arch/arm64/mm/gcs.c
@@ -38,8 +38,8 @@ static unsigned long gcs_size(unsigned long size)
 	return max(PAGE_SIZE, size);
 }

-unsigned long gcs_alloc_thread_stack(struct task_struct *tsk,
-				     const struct kernel_clone_args *args)
+int gcs_alloc_thread_stack(struct task_struct *tsk,
+			   const struct kernel_clone_args *args)
 {
 	unsigned long addr, size;

@@ -59,13 +59,13 @@ unsigned long gcs_alloc_thread_stack(struct task_struct *tsk,
 	size = gcs_size(size);
 	addr = alloc_gcs(0, size);
 	if (IS_ERR_VALUE(addr))
-		return addr;
+		return PTR_ERR((void *)addr);

 	tsk->thread.gcs_base = addr;
 	tsk->thread.gcs_size = size;
 	tsk->thread.gcspr_el0 = addr + size - sizeof(u64);

-	return addr;
+	return 0;
 }

 SYSCALL_DEFINE3(map_shadow_stack, unsigned long, addr, unsigned long, size, unsigned int, flags)

-- 
2.39.2