Re: [PATCH v2 01/13] audit: log all six syscall arguments in the SYSCALL record

[Will Deacon <will@kernel.org>]

On Wed, Sep 02, 2026 at 11:43:34AM -0300, Ricardo Robaina wrote:
> The SYSCALL record currently logs only four of the six syscall
> arguments (a0-a3). The remaining two are captured but silently
> discarded before reaching the audit context. This leads to the
> need for auxiliary records when audit-relevant data lands in the
> 5th or 6th argument of a syscall.
> 
> Extend the SYSCALL record to log all six arguments, by adding
> arguments a4 and a5 (5th and 6th syscall arguments respectively)
> inline within the existing record. Also add the two new args to
> the audit rules switch case, so audit rules can filter on them.
> 
> Rather than plumbing two more register arguments through every
> architecture's syscall entry path, change __audit_syscall_entry()
> to take a pointer to pt_regs and use syscall_get_arguments() to
> retrieve all six arguments.
> 
>  audit-testsuite# make test
>  audit-testsuite# ausearch -i -m SYSCALL
>  ...
>  type=SYSCALL ... syscall=sendto success=yes exit=1088 a0=0x4
>   a1=0x7ffe43518b60 a2=0x440 a3=0x0 a4=7ffe43518b4c a5=c
>  type=SYSCALL ... syscall=openat2 success=yes exit=4 a0=0x3
>   a1=0x7fffc74692c8 a2=0x7fffc7467390 a3=0x18 a4=0 a5=7fffc74674f8
>  type=SYSCALL ... syscall=openat success=yes exit=3 a0=AT_FDCWD
>   a1=0x557ced4141a2 a2=O_RDWR|O_NONBLOCK a3=0x0 a4=0 a5=0
>  ...
> 
> Suggested-by: Will Deacon <will@kernel.org>
> Link: https://lore.kernel.org/audit/CAHC9VhSjEt_-Bsra4AEqWv+Daw5Ff=gqy7dX4Ah11RVhdyCBUQ@mail.gmail.com/T/#t
> Signed-off-by: Ricardo Robaina <rrobaina@redhat.com>
> ---
>  include/linux/audit.h         | 13 ++++---------
>  include/uapi/linux/audit.h    |  2 ++
>  kernel/audit.h                |  2 +-
>  kernel/auditfilter.c          |  2 ++
>  kernel/auditsc.c              | 19 ++++++++-----------
>  kernel/entry/syscall-common.c |  4 +---
>  6 files changed, 18 insertions(+), 24 deletions(-)
> 
> diff --git a/include/linux/audit.h b/include/linux/audit.h
> index 45abb3722d30..9ce5962bc537 100644
> --- a/include/linux/audit.h
> +++ b/include/linux/audit.h
> @@ -323,8 +323,7 @@ extern int  audit_alloc(struct task_struct *task);
>  extern void __audit_free(struct task_struct *task);
>  extern void __audit_uring_entry(u8 op);
>  extern void __audit_uring_exit(int success, long code);
> -extern void __audit_syscall_entry(int major, unsigned long a0, unsigned long a1,
> -				  unsigned long a2, unsigned long a3);
> +extern void __audit_syscall_entry(int major, struct pt_regs *regs);
>  extern void __audit_syscall_exit(int ret_success, long ret_value);
>  extern void __audit_getname(struct filename *name);
>  extern void __audit_inode(struct filename *name, const struct dentry *dentry,
> @@ -373,12 +372,10 @@ static inline void audit_uring_exit(int success, long code)
>  	if (unlikely(audit_context()))
>  		__audit_uring_exit(success, code);
>  }
> -static inline void audit_syscall_entry(int major, unsigned long a0,
> -				       unsigned long a1, unsigned long a2,
> -				       unsigned long a3)
> +static inline void audit_syscall_entry(int major, struct pt_regs *regs)
>  {
>  	if (unlikely(audit_context()))
> -		__audit_syscall_entry(major, a0, a1, a2, a3);
> +		__audit_syscall_entry(major, regs);
>  }

Won't this (temporarily) break the build? Maybe you need to introduce a
new helper e.g. audit_syscall_entry_regs(), then convert everybody over
to that, then rename it to audit_syscall_entry() at the end to keep the
series bisectable.

Will