Re: [PATCH 17/23] powerpc: Enable compile-time check for syscall handlers

["Nicholas Piggin" <npiggin@gmail.com>]

On Fri Sep 16, 2022 at 3:32 PM AEST, 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>
> Reported-by: Nicholas Piggin <npiggin@gmail.com>
> ---
> V1 -> V2: New patch.
> V4 -> V5: For this patch only, represent handler function pointers as
> unsigned long. Remove reference to syscall wrappers. Use asm/syscalls.h
> which implies asm/syscall.h

Thanks, I think this is the right way to split the patches.

I'm not sure if I reported this issue, but I really like the patch.

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>

> ---
>  arch/powerpc/kernel/{systbl.S => systbl.c} | 28 ++++++++------------
>  1 file changed, 11 insertions(+), 17 deletions(-)
>
> diff --git a/arch/powerpc/kernel/systbl.S b/arch/powerpc/kernel/systbl.c
> similarity index 61%
> rename from arch/powerpc/kernel/systbl.S
> rename to arch/powerpc/kernel/systbl.c
> index 6c1db3b6de2d..ce52bd2ec292 100644
> --- a/arch/powerpc/kernel/systbl.S
> +++ b/arch/powerpc/kernel/systbl.c
> @@ -10,32 +10,26 @@
>   * 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)
> +#define __SYSCALL(nr, entry) [nr] = (unsigned long) &entry,
>  
> -#ifdef CONFIG_PPC64
> -	.p2align	3
> -#define __SYSCALL(nr, entry)	.8byte entry
> -#else
> -	.p2align	2
> -#define __SYSCALL(nr, entry)	.long entry
> -#endif
> -
> -#define __SYSCALL_WITH_COMPAT(nr, native, compat)	__SYSCALL(nr, native)
> -.globl sys_call_table
> -sys_call_table:
> +const unsigned long 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
> +const unsigned long compat_sys_call_table[] = {
>  #include <asm/syscall_table_32.h>
> -#endif
> +};
> +#endif /* CONFIG_COMPAT */
> -- 
> 2.34.1