[PATCH v2 07/14] powerpc: Enable compile-time check for syscall handlers

[PATCH v2 07/14] powerpc: Enable compile-time check for syscall handlers

[Rohan McLure]

The table of syscall handlers and registered compatibility syscall
handlers has in past been produced using assembly, with function
references resolved at link time. This moves link-time errors to
compile-time, by rewriting systbl.S in C, and including the
linux/syscalls.h, linux/compat.h and asm/syscalls.h headers for
prototypes.

Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
---
V1 -> V2: New patch.
---
 arch/powerpc/kernel/{systbl.S => systbl.c} | 27 ++++++++++----------
 1 file changed, 14 insertions(+), 13 deletions(-)

diff --git a/arch/powerpc/kernel/systbl.S b/arch/powerpc/kernel/systbl.c
similarity index 59%
rename from arch/powerpc/kernel/systbl.S
rename to arch/powerpc/kernel/systbl.c
index cb3358886203..99ffdfef6b9c 100644
--- a/arch/powerpc/kernel/systbl.S
+++ b/arch/powerpc/kernel/systbl.c
@@ -10,31 +10,32 @@
  * PPC64 updates by Dave Engebretsen (engebret@us.ibm.com) 
  */
 
-#include <asm/ppc_asm.h>
+#include <linux/syscalls.h>
+#include <linux/compat.h>
+#include <asm/unistd.h>
+#include <asm/syscalls.h>
 
-.section .rodata,"a"
+#define __SYSCALL_WITH_COMPAT(nr, entry, compat) __SYSCALL(nr, entry)
 
-#ifdef CONFIG_PPC64
-	.p2align	3
-#define __SYSCALL(nr, entry)	.8byte entry
+#ifdef CONFIG_ARCH_HAS_SYSCALL_WRAPPER
+#define __SYSCALL(nr, entry) [nr] = __powerpc_##entry,
+#define __powerpc_sys_ni_syscall	sys_ni_syscall
 #else
-#define __SYSCALL(nr, entry)	.long entry
+#define __SYSCALL(nr, entry) [nr] = entry,
 #endif
 
-#define __SYSCALL_WITH_COMPAT(nr, native, compat)	__SYSCALL(nr, native)
-.globl sys_call_table
-sys_call_table:
+void *sys_call_table[] = {
 #ifdef CONFIG_PPC64
 #include <asm/syscall_table_64.h>
 #else
 #include <asm/syscall_table_32.h>
 #endif
+};
 
 #ifdef CONFIG_COMPAT
 #undef __SYSCALL_WITH_COMPAT
 #define __SYSCALL_WITH_COMPAT(nr, native, compat)	__SYSCALL(nr, compat)
-.globl compat_sys_call_table
-compat_sys_call_table:
-#define compat_sys_sigsuspend	sys_sigsuspend
+void *compat_sys_call_table[] = {
 #include <asm/syscall_table_32.h>
-#endif
+};
+#endif /* CONFIG_COMPAT */
-- 
2.34.1

Re: [PATCH v2 07/14] powerpc: Enable compile-time check for syscall handlers

[Andrew Donnellan]

On Mon, 2022-07-25 at 16:28 +1000, Rohan McLure wrote:
> The table of syscall handlers and registered compatibility syscall
> handlers has in past been produced using assembly, with function
> references resolved at link time. This moves link-time errors to
> compile-time, by rewriting systbl.S in C, and including the
> linux/syscalls.h, linux/compat.h and asm/syscalls.h headers for
> prototypes.
> 
> Reported-by: Arnd Bergmann <arnd@arndb.de>
> Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
> ---
> V1 -> V2: New patch.
> ---
>  arch/powerpc/kernel/{systbl.S => systbl.c} | 27 ++++++++++----------
>  1 file changed, 14 insertions(+), 13 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/systbl.S
> b/arch/powerpc/kernel/systbl.c
> similarity index 59%
> rename from arch/powerpc/kernel/systbl.S
> rename to arch/powerpc/kernel/systbl.c
> index cb3358886203..99ffdfef6b9c 100644
> --- a/arch/powerpc/kernel/systbl.S
> +++ b/arch/powerpc/kernel/systbl.c
> @@ -10,31 +10,32 @@
>   * PPC64 updates by Dave Engebretsen (engebret@us.ibm.com) 
>   */
>  
> -#include <asm/ppc_asm.h>
> +#include <linux/syscalls.h>
> +#include <linux/compat.h>
> +#include <asm/unistd.h>
> +#include <asm/syscalls.h>
>  
> -.section .rodata,"a"
> +#define __SYSCALL_WITH_COMPAT(nr, entry, compat) __SYSCALL(nr,
> entry)
>  
> -#ifdef CONFIG_PPC64
> -       .p2align        3
> -#define __SYSCALL(nr, entry)   .8byte entry
> +#ifdef CONFIG_ARCH_HAS_SYSCALL_WRAPPER
> +#define __SYSCALL(nr, entry) [nr] = __powerpc_##entry,
> +#define __powerpc_sys_ni_syscall       sys_ni_syscall

Keep this until patch 10.

Otherwise looks alright to me.

>  #else
> -#define __SYSCALL(nr, entry)   .long entry
> +#define __SYSCALL(nr, entry) [nr] = entry,
>  #endif
>  
> -#define __SYSCALL_WITH_COMPAT(nr, native, compat)      __SYSCALL(nr,
> native)
> -.globl sys_call_table
> -sys_call_table:
> +void *sys_call_table[] = {
>  #ifdef CONFIG_PPC64
>  #include <asm/syscall_table_64.h>
>  #else
>  #include <asm/syscall_table_32.h>
>  #endif
> +};
>  
>  #ifdef CONFIG_COMPAT
>  #undef __SYSCALL_WITH_COMPAT
>  #define __SYSCALL_WITH_COMPAT(nr, native, compat)      __SYSCALL(nr,
> compat)
> -.globl compat_sys_call_table
> -compat_sys_call_table:
> -#define compat_sys_sigsuspend  sys_sigsuspend
> +void *compat_sys_call_table[] = {
>  #include <asm/syscall_table_32.h>
> -#endif
> +};
> +#endif /* CONFIG_COMPAT */

-- 
Andrew Donnellan    OzLabs, ADL Canberra
ajd@linux.ibm.com   IBM Australia Limited