On Tue, Sep 10, 2019 at 03:40:44PM -0700, Sami Tolvanen wrote:
> Define a weak function in COND_SYSCALL instead of a weak alias to
> sys_ni_syscall, which has an incompatible type. This fixes indirect
> call mismatches with Control-Flow Integrity (CFI) checking.
>
> Signed-off-by: Sami Tolvanen <samitolva...@google.com>
This looks correct to me, builds fine, and I asume has been tested, so FWIW:
Acked-by: Mark Rutland <mark.rutl...@arm.com>
In looking at this, I came to the conclusion that we can drop the ifdeffery
around our SYSCALL_DEFINE0(), COND_SYSCALL(), and SYS_NI(), which I evidently
cargo-culted from x86 (where the ifdeffery is actually necessary).
I can send a follow up for that.
Thanks,
Mark.
> ---
> arch/arm64/include/asm/syscall_wrapper.h | 15 ++++++++++++---
> 1 file changed, 12 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm64/include/asm/syscall_wrapper.h
> b/arch/arm64/include/asm/syscall_wrapper.h
> index 507d0ee6bc69..06d880b3526c 100644
> --- a/arch/arm64/include/asm/syscall_wrapper.h
> +++ b/arch/arm64/include/asm/syscall_wrapper.h
> @@ -8,6 +8,8 @@
> #ifndef __ASM_SYSCALL_WRAPPER_H
> #define __ASM_SYSCALL_WRAPPER_H
>
> +struct pt_regs;
> +
> #define SC_ARM64_REGS_TO_ARGS(x, ...) \
> __MAP(x,__SC_ARGS \
> ,,regs->regs[0],,regs->regs[1],,regs->regs[2] \
> @@ -35,8 +37,11 @@
> ALLOW_ERROR_INJECTION(__arm64_compat_sys_##sname, ERRNO);
> \
> asmlinkage long __arm64_compat_sys_##sname(const struct pt_regs
> *__unused)
>
> -#define COND_SYSCALL_COMPAT(name) \
> - cond_syscall(__arm64_compat_sys_##name);
> +#define COND_SYSCALL_COMPAT(name)
> \
> + asmlinkage long __weak __arm64_compat_sys_##name(const struct pt_regs
> *regs) \
> + {
> \
> + return sys_ni_syscall();
> \
> + }
>
> #define COMPAT_SYS_NI(name) \
> SYSCALL_ALIAS(__arm64_compat_sys_##name, sys_ni_posix_timers);
> @@ -70,7 +75,11 @@
> #endif
>
> #ifndef COND_SYSCALL
> -#define COND_SYSCALL(name) cond_syscall(__arm64_sys_##name)
> +#define COND_SYSCALL(name)
> \
> + asmlinkage long __weak __arm64_sys_##name(const struct pt_regs *regs)
> \
> + {
> \
> + return sys_ni_syscall();
> \
> + }
> #endif
>
> #ifndef SYS_NI
> --
> 2.23.0.162.g0b9fbb3734-goog
>
