On Wed, Feb 2, 2022 at 12:14 PM Heiko Carstens <hca@xxxxxxxxxxxxx> wrote: > > 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. > > > > Signed-off-by: Ilya Leoshkevich <iii@xxxxxxxxxxxxx> > > --- > > arch/s390/include/asm/ptrace.h | 2 +- > > arch/s390/include/uapi/asm/ptrace.h | 1 + > > 2 files changed, 2 insertions(+), 1 deletion(-) > > > > 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; > > Isn't this broken on nearly all architectures? I just checked powerpc, > arm64, and riscv. While powerpc seems to mirror pt_regs as user_pt_regs, > and therefore exports orig_gpr3, the bpf macros still seem to access the > wrong location to access the first syscall parameter(?). > > For arm64 and riscv it seems that orig_x0 or orig_a0 respectively need to > be added to user_pt_regs too, and the same fix like for s390 needs to be > applied as well. We just recently added syscall-specific macros to libbpf and fixed this issue for x86-64. It would be great if people familiar with other architectures contribute fixes for other architectures. Thanks!