Am 02.02.22 um 15:19 schrieb Vasily Gorbik:
On Wed, Feb 02, 2022 at 12:41:58AM +0100, Ilya Leoshkevich wrote:user_pt_regs is used by eBPF in order to access userspace registers - see commit 466698e654e8 ("s390/bpf: correct broken uapi for BPF_PROG_TYPE_PERF_EVENT program type"). In order to access the first syscall argument from eBPF programs, we need to export orig_gpr2.diff --git a/arch/s390/include/asm/ptrace.h b/arch/s390/include/asm/ptrace.h index 4ffa8e7f0ed3..c8698e643904 100644 --- a/arch/s390/include/asm/ptrace.h +++ b/arch/s390/include/asm/ptrace.h @@ -83,9 +83,9 @@ struct pt_regs { unsigned long args[1]; psw_t psw; unsigned long gprs[NUM_GPRS]; + unsigned long orig_gpr2; }; }; - unsigned long orig_gpr2; union { struct { unsigned int int_code; diff --git a/arch/s390/include/uapi/asm/ptrace.h b/arch/s390/include/uapi/asm/ptrace.h index ad64d673b5e6..b3dec603f507 100644 --- a/arch/s390/include/uapi/asm/ptrace.h +++ b/arch/s390/include/uapi/asm/ptrace.h @@ -295,6 +295,7 @@ typedef struct { unsigned long args[1]; psw_t psw; unsigned long gprs[NUM_GPRS]; + unsigned long orig_gpr2; } user_pt_regs;It could be a good opportunity to get rid of that "args[1]" which is not used for syscall parameters handling since commit baa071588c3f ("[S390] cleanup system call parameter setup") [v2.6.37], as well as completely unused now, and shouldn't really be exported to eBPF. And luckily eBPF never used it. So, how about reusing "args[1]" slot for orig_gpr2 instead?
Since this is uapi we certainly have to careful. Reusing this could be ok, though.
