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* [PATCH] riscv: Fix syscall wrapper for >word-size arguments
@ 2024-03-11 19:31 ` Sami Tolvanen
  0 siblings, 0 replies; 4+ messages in thread
From: Sami Tolvanen @ 2024-03-11 19:31 UTC (permalink / raw)
  To: Paul Walmsley, Palmer Dabbelt, Albert Ou
  Cc: Kees Cook, linux-riscv, llvm, linux-kernel, Sami Tolvanen, Khem Raj

The current syscall wrapper macros break 64-bit arguments on
rv32 because they only guarantee the first N input registers are
passed to syscalls that accept N arguments. According to the
calling convention, values twice the word size reside in register
pairs and as a result, syscall arguments don't always have a
direct register mapping on rv32.

Instead of using `__MAP(x,__SC_LONG,__VA_ARGS__)` to declare the
type of the `__se(_compat)_sys_*` functions on rv32, change the
function declarations to accept `ulong` arguments and alias them
to the actual syscall implementations, similarly to the existing
macros in include/linux/syscalls.h. This matches previous
behavior and ensures registers are passed to syscalls as-is, no
matter which argument types they expect.

Fixes: 08d0ce30e0e4 ("riscv: Implement syscall wrappers")
Reported-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
 arch/riscv/include/asm/syscall_wrapper.h | 53 +++++++++++++++++-------
 1 file changed, 39 insertions(+), 14 deletions(-)

diff --git a/arch/riscv/include/asm/syscall_wrapper.h b/arch/riscv/include/asm/syscall_wrapper.h
index eeec04b7dae6..980094c2e976 100644
--- a/arch/riscv/include/asm/syscall_wrapper.h
+++ b/arch/riscv/include/asm/syscall_wrapper.h
@@ -12,25 +12,51 @@
 
 asmlinkage long __riscv_sys_ni_syscall(const struct pt_regs *);
 
-#define SC_RISCV_REGS_TO_ARGS(x, ...)				\
-	__MAP(x,__SC_ARGS					\
-	      ,,regs->orig_a0,,regs->a1,,regs->a2		\
+#ifdef CONFIG_64BIT
+
+#define __SYSCALL_SE_DEFINEx(x, prefix, name, ...)					\
+	static long __se_##prefix##name(__MAP(x,__SC_LONG,__VA_ARGS__));		\
+	static long __se_##prefix##name(__MAP(x,__SC_LONG,__VA_ARGS__))
+
+#define SC_RISCV_REGS_TO_ARGS(x, ...)							\
+	__MAP(x,__SC_ARGS								\
+	      ,,regs->orig_a0,,regs->a1,,regs->a2					\
 	      ,,regs->a3,,regs->a4,,regs->a5,,regs->a6)
 
+#else
+/*
+ * Use type aliasing to ensure registers a0-a6 are correctly passed to the syscall
+ * implementation when >word-size arguments are used.
+ */
+#define __SYSCALL_SE_DEFINEx(x, prefix, name, ...)					\
+	__diag_push();									\
+	__diag_ignore(GCC, 8, "-Wattribute-alias",					\
+			"Type aliasing is used to sanitize syscall arguments");		\
+	static long __se_##prefix##name(ulong, ulong, ulong, ulong, ulong, ulong, 	\
+					ulong)						\
+			__attribute__((alias(__stringify(___se_##prefix##name))));	\
+	__diag_pop();									\
+	static long noinline ___se_##prefix##name(__MAP(x,__SC_LONG,__VA_ARGS__));	\
+	static long ___se_##prefix##name(__MAP(x,__SC_LONG,__VA_ARGS__))
+
+#define SC_RISCV_REGS_TO_ARGS(x, ...) \
+	regs->orig_a0,regs->a1,regs->a2,regs->a3,regs->a4,regs->a5,regs->a6
+
+#endif /* CONFIG_64BIT */
+
 #ifdef CONFIG_COMPAT
 
 #define COMPAT_SYSCALL_DEFINEx(x, name, ...)						\
 	asmlinkage long __riscv_compat_sys##name(const struct pt_regs *regs);		\
 	ALLOW_ERROR_INJECTION(__riscv_compat_sys##name, ERRNO);				\
-	static long __se_compat_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__));		\
 	static inline long __do_compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));	\
-	asmlinkage long __riscv_compat_sys##name(const struct pt_regs *regs)		\
+	__SYSCALL_SE_DEFINEx(x, compat_sys, name, __VA_ARGS__)				\
 	{										\
-		return __se_compat_sys##name(SC_RISCV_REGS_TO_ARGS(x,__VA_ARGS__));	\
+		return __do_compat_sys##name(__MAP(x,__SC_DELOUSE,__VA_ARGS__));	\
 	}										\
-	static long __se_compat_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__))		\
+	asmlinkage long __riscv_compat_sys##name(const struct pt_regs *regs)		\
 	{										\
-		return __do_compat_sys##name(__MAP(x,__SC_DELOUSE,__VA_ARGS__));	\
+		return __se_compat_sys##name(SC_RISCV_REGS_TO_ARGS(x,__VA_ARGS__));	\
 	}										\
 	static inline long __do_compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))
 
@@ -51,19 +77,18 @@ asmlinkage long __riscv_sys_ni_syscall(const struct pt_regs *);
 #define __SYSCALL_DEFINEx(x, name, ...)						\
 	asmlinkage long __riscv_sys##name(const struct pt_regs *regs);		\
 	ALLOW_ERROR_INJECTION(__riscv_sys##name, ERRNO);			\
-	static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__));		\
 	static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));	\
-	asmlinkage long __riscv_sys##name(const struct pt_regs *regs)		\
-	{									\
-		return __se_sys##name(SC_RISCV_REGS_TO_ARGS(x,__VA_ARGS__));	\
-	}									\
-	static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__))		\
+	__SYSCALL_SE_DEFINEx(x, sys, name, __VA_ARGS__)				\
 	{									\
 		long ret = __do_sys##name(__MAP(x,__SC_CAST,__VA_ARGS__));	\
 		__MAP(x,__SC_TEST,__VA_ARGS__);					\
 		__PROTECT(x, ret,__MAP(x,__SC_ARGS,__VA_ARGS__));		\
 		return ret;							\
 	}									\
+	asmlinkage long __riscv_sys##name(const struct pt_regs *regs)		\
+	{									\
+		return __se_sys##name(SC_RISCV_REGS_TO_ARGS(x,__VA_ARGS__));	\
+	}									\
 	static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))
 
 #define SYSCALL_DEFINE0(sname)							\
-- 
2.44.0.278.ge034bb2e1d-goog


^ permalink raw reply related	[flat|nested] 4+ messages in thread
* [PATCH] riscv: Fix syscall wrapper for >word-size arguments
@ 2024-03-11 19:31 ` Sami Tolvanen
  0 siblings, 0 replies; 4+ messages in thread
From: Sami Tolvanen @ 2024-03-11 19:31 UTC (permalink / raw)
  To: Paul Walmsley, Palmer Dabbelt, Albert Ou
  Cc: Kees Cook, linux-riscv, llvm, linux-kernel, Sami Tolvanen, Khem Raj

The current syscall wrapper macros break 64-bit arguments on
rv32 because they only guarantee the first N input registers are
passed to syscalls that accept N arguments. According to the
calling convention, values twice the word size reside in register
pairs and as a result, syscall arguments don't always have a
direct register mapping on rv32.

Instead of using `__MAP(x,__SC_LONG,__VA_ARGS__)` to declare the
type of the `__se(_compat)_sys_*` functions on rv32, change the
function declarations to accept `ulong` arguments and alias them
to the actual syscall implementations, similarly to the existing
macros in include/linux/syscalls.h. This matches previous
behavior and ensures registers are passed to syscalls as-is, no
matter which argument types they expect.

Fixes: 08d0ce30e0e4 ("riscv: Implement syscall wrappers")
Reported-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
 arch/riscv/include/asm/syscall_wrapper.h | 53 +++++++++++++++++-------
 1 file changed, 39 insertions(+), 14 deletions(-)

diff --git a/arch/riscv/include/asm/syscall_wrapper.h b/arch/riscv/include/asm/syscall_wrapper.h
index eeec04b7dae6..980094c2e976 100644
--- a/arch/riscv/include/asm/syscall_wrapper.h
+++ b/arch/riscv/include/asm/syscall_wrapper.h
@@ -12,25 +12,51 @@
 
 asmlinkage long __riscv_sys_ni_syscall(const struct pt_regs *);
 
-#define SC_RISCV_REGS_TO_ARGS(x, ...)				\
-	__MAP(x,__SC_ARGS					\
-	      ,,regs->orig_a0,,regs->a1,,regs->a2		\
+#ifdef CONFIG_64BIT
+
+#define __SYSCALL_SE_DEFINEx(x, prefix, name, ...)					\
+	static long __se_##prefix##name(__MAP(x,__SC_LONG,__VA_ARGS__));		\
+	static long __se_##prefix##name(__MAP(x,__SC_LONG,__VA_ARGS__))
+
+#define SC_RISCV_REGS_TO_ARGS(x, ...)							\
+	__MAP(x,__SC_ARGS								\
+	      ,,regs->orig_a0,,regs->a1,,regs->a2					\
 	      ,,regs->a3,,regs->a4,,regs->a5,,regs->a6)
 
+#else
+/*
+ * Use type aliasing to ensure registers a0-a6 are correctly passed to the syscall
+ * implementation when >word-size arguments are used.
+ */
+#define __SYSCALL_SE_DEFINEx(x, prefix, name, ...)					\
+	__diag_push();									\
+	__diag_ignore(GCC, 8, "-Wattribute-alias",					\
+			"Type aliasing is used to sanitize syscall arguments");		\
+	static long __se_##prefix##name(ulong, ulong, ulong, ulong, ulong, ulong, 	\
+					ulong)						\
+			__attribute__((alias(__stringify(___se_##prefix##name))));	\
+	__diag_pop();									\
+	static long noinline ___se_##prefix##name(__MAP(x,__SC_LONG,__VA_ARGS__));	\
+	static long ___se_##prefix##name(__MAP(x,__SC_LONG,__VA_ARGS__))
+
+#define SC_RISCV_REGS_TO_ARGS(x, ...) \
+	regs->orig_a0,regs->a1,regs->a2,regs->a3,regs->a4,regs->a5,regs->a6
+
+#endif /* CONFIG_64BIT */
+
 #ifdef CONFIG_COMPAT
 
 #define COMPAT_SYSCALL_DEFINEx(x, name, ...)						\
 	asmlinkage long __riscv_compat_sys##name(const struct pt_regs *regs);		\
 	ALLOW_ERROR_INJECTION(__riscv_compat_sys##name, ERRNO);				\
-	static long __se_compat_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__));		\
 	static inline long __do_compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));	\
-	asmlinkage long __riscv_compat_sys##name(const struct pt_regs *regs)		\
+	__SYSCALL_SE_DEFINEx(x, compat_sys, name, __VA_ARGS__)				\
 	{										\
-		return __se_compat_sys##name(SC_RISCV_REGS_TO_ARGS(x,__VA_ARGS__));	\
+		return __do_compat_sys##name(__MAP(x,__SC_DELOUSE,__VA_ARGS__));	\
 	}										\
-	static long __se_compat_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__))		\
+	asmlinkage long __riscv_compat_sys##name(const struct pt_regs *regs)		\
 	{										\
-		return __do_compat_sys##name(__MAP(x,__SC_DELOUSE,__VA_ARGS__));	\
+		return __se_compat_sys##name(SC_RISCV_REGS_TO_ARGS(x,__VA_ARGS__));	\
 	}										\
 	static inline long __do_compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))
 
@@ -51,19 +77,18 @@ asmlinkage long __riscv_sys_ni_syscall(const struct pt_regs *);
 #define __SYSCALL_DEFINEx(x, name, ...)						\
 	asmlinkage long __riscv_sys##name(const struct pt_regs *regs);		\
 	ALLOW_ERROR_INJECTION(__riscv_sys##name, ERRNO);			\
-	static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__));		\
 	static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));	\
-	asmlinkage long __riscv_sys##name(const struct pt_regs *regs)		\
-	{									\
-		return __se_sys##name(SC_RISCV_REGS_TO_ARGS(x,__VA_ARGS__));	\
-	}									\
-	static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__))		\
+	__SYSCALL_SE_DEFINEx(x, sys, name, __VA_ARGS__)				\
 	{									\
 		long ret = __do_sys##name(__MAP(x,__SC_CAST,__VA_ARGS__));	\
 		__MAP(x,__SC_TEST,__VA_ARGS__);					\
 		__PROTECT(x, ret,__MAP(x,__SC_ARGS,__VA_ARGS__));		\
 		return ret;							\
 	}									\
+	asmlinkage long __riscv_sys##name(const struct pt_regs *regs)		\
+	{									\
+		return __se_sys##name(SC_RISCV_REGS_TO_ARGS(x,__VA_ARGS__));	\
+	}									\
 	static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))
 
 #define SYSCALL_DEFINE0(sname)							\
-- 
2.44.0.278.ge034bb2e1d-goog


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linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

^ permalink raw reply related	[flat|nested] 4+ messages in thread
* Re: [PATCH] riscv: Fix syscall wrapper for >word-size arguments
  2024-03-11 19:31 ` Sami Tolvanen
@ 2024-03-21  1:50   ` patchwork-bot+linux-riscv
  -1 siblings, 0 replies; 4+ messages in thread
From: patchwork-bot+linux-riscv @ 2024-03-21  1:50 UTC (permalink / raw)
  To: Sami Tolvanen
  Cc: linux-riscv, paul.walmsley, palmer, aou, keescook, llvm,
	linux-kernel, raj.khem

Hello:

This patch was applied to riscv/linux.git (for-next)
by Palmer Dabbelt <palmer@rivosinc.com>:

On Mon, 11 Mar 2024 19:31:44 +0000 you wrote:
> The current syscall wrapper macros break 64-bit arguments on
> rv32 because they only guarantee the first N input registers are
> passed to syscalls that accept N arguments. According to the
> calling convention, values twice the word size reside in register
> pairs and as a result, syscall arguments don't always have a
> direct register mapping on rv32.
> 
> [...]

Here is the summary with links:
  - riscv: Fix syscall wrapper for >word-size arguments
    https://git.kernel.org/riscv/c/a9ad73295cc1

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html



^ permalink raw reply	[flat|nested] 4+ messages in thread
* Re: [PATCH] riscv: Fix syscall wrapper for >word-size arguments
@ 2024-03-21  1:50   ` patchwork-bot+linux-riscv
  0 siblings, 0 replies; 4+ messages in thread
From: patchwork-bot+linux-riscv @ 2024-03-21  1:50 UTC (permalink / raw)
  To: Sami Tolvanen
  Cc: linux-riscv, paul.walmsley, palmer, aou, keescook, llvm,
	linux-kernel, raj.khem

Hello:

This patch was applied to riscv/linux.git (for-next)
by Palmer Dabbelt <palmer@rivosinc.com>:

On Mon, 11 Mar 2024 19:31:44 +0000 you wrote:
> The current syscall wrapper macros break 64-bit arguments on
> rv32 because they only guarantee the first N input registers are
> passed to syscalls that accept N arguments. According to the
> calling convention, values twice the word size reside in register
> pairs and as a result, syscall arguments don't always have a
> direct register mapping on rv32.
> 
> [...]

Here is the summary with links:
  - riscv: Fix syscall wrapper for >word-size arguments
    https://git.kernel.org/riscv/c/a9ad73295cc1

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html



_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

^ permalink raw reply	[flat|nested] 4+ messages in thread
end of thread, other threads:[~2024-03-21  1:50 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2024-03-11 19:31 [PATCH] riscv: Fix syscall wrapper for >word-size arguments Sami Tolvanen
2024-03-11 19:31 ` Sami Tolvanen
2024-03-21  1:50 ` patchwork-bot+linux-riscv
2024-03-21  1:50   ` patchwork-bot+linux-riscv

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