lkml.org 
[lkml]   [2023]   [Jun]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 1/6] riscv: Implement syscall wrappers
On Thu, Jun 29, 2023 at 11:42:46PM +0000, Sami Tolvanen wrote:
> Commit f0bddf50586d ("riscv: entry: Convert to generic entry") moved
> syscall handling to C code, which exposed function pointer type
> mismatches that trip fine-grained forward-edge Control-Flow Integrity
> (CFI) checks as syscall handlers are all called through the same
> syscall_t pointer type. To fix the type mismatches, implement pt_regs
> based syscall wrappers similarly to x86 and arm64.
>
> This patch is based on arm64 syscall wrappers added in commit
> 4378a7d4be30 ("arm64: implement syscall wrappers"), where the main goal
> was to minimize the risk of userspace-controlled values being used
> under speculation. This may be a concern for riscv in future as well.
>
> Following other architectures, the syscall wrappers generate three
> functions for each syscall; __riscv_<compat_>sys_<name> takes a pt_regs
> pointer and extracts arguments from registers, __se_<compat_>sys_<name>
> is a sign-extension wrapper that casts the long arguments to the
> correct types for the real syscall implementation, which is named
> __do_<compat_>sys_<name>.
>
> Signed-off-by: Sami Tolvanen <samitolvanen@google.com>

This all looks correct to me; though I have not run tested it. I'm glad
to see another arch using this style.

Reviewed-by: Kees Cook <keescook@chromium.org>

--
Kees Cook

\
 
 \ /
  Last update: 2023-06-30 20:30    [W:0.105 / U:1.836 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site