On Tue, 2022-02-08 at 14:08 -0800, Andrii Nakryiko wrote: > On Mon, Feb 7, 2022 at 9:16 PM Ilya Leoshkevich <iii@xxxxxxxxxxxxx> > wrote: > > > > Depending on whether or not an arch has ARCH_HAS_SYSCALL_WRAPPER, > > syscall arguments must be accessed through a different set of > > registers. Provide PT_REGS_SYSCALL_REGS macro to abstract away > > that difference. > > > > Reported-by: Heiko Carstens <hca@xxxxxxxxxxxxx> > > Co-developed-by: Naveen N. Rao <naveen.n.rao@xxxxxxxxxxxxxxxxxx> > > Signed-off-by: Naveen N. Rao <naveen.n.rao@xxxxxxxxxxxxxxxxxx> > > Signed-off-by: Ilya Leoshkevich <iii@xxxxxxxxxxxxx> > > --- > > Again, there was nothing wrong with the way you did it in v3, please > revert to that one. I've realized that, even though fully correct, v3 looked somewhat ad-hoc: it defined PT_REGS_SYSCALL_REGS for different architectures without explaining why this particular arch has this parciular way to access syscall arguments. So I've decided to switch to the existing terminology, as Naveen proposed [1]: - arches that select ARCH_HAS_SYSCALL_WRAPPER in Kconfig get a __BPF_ARCH_HAS_SYSCALL_WRAPPER in bpf_tracing.h - syscall handler calling convention is (at least partially) determined by whether or not an arch has a sycall wrapper as described in ARCH_HAS_SYSCALL_WRAPPER help text I can, of course, switch back to v3 - both patches look functionally identical - but this one seems to be a bit easier to understand. [1] https://lore.kernel.org/bpf/1643991537.bfyv1b2oym.naveen@xxxxxxxxxxxxx/#t > > > tools/lib/bpf/bpf_tracing.h | 17 +++++++++++++++++ > > 1 file changed, 17 insertions(+) > > > > diff --git a/tools/lib/bpf/bpf_tracing.h > > b/tools/lib/bpf/bpf_tracing.h > > index 82f1e935d549..7a015ee8fb11 100644 > > --- a/tools/lib/bpf/bpf_tracing.h > > +++ b/tools/lib/bpf/bpf_tracing.h > > @@ -64,6 +64,8 @@ > > > > #if defined(bpf_target_x86) > > > > +#define __BPF_ARCH_HAS_SYSCALL_WRAPPER > > + > > #if defined(__KERNEL__) || defined(__VMLINUX_H__) > > > > #define __PT_PARM1_REG di > > @@ -114,6 +116,8 @@ > > > > #elif defined(bpf_target_s390) > > > > +#define __BPF_ARCH_HAS_SYSCALL_WRAPPER > > + > > /* s390 provides user_pt_regs instead of struct pt_regs to > > userspace */ > > #define __PT_REGS_CAST(x) ((const user_pt_regs *)(x)) > > #define __PT_PARM1_REG gprs[2] > > @@ -142,6 +146,8 @@ > > > > #elif defined(bpf_target_arm64) > > > > +#define __BPF_ARCH_HAS_SYSCALL_WRAPPER > > + > > /* arm64 provides struct user_pt_regs instead of struct pt_regs to > > userspace */ > > #define __PT_REGS_CAST(x) ((const struct user_pt_regs *)(x)) > > #define __PT_PARM1_REG regs[0] > > @@ -344,6 +350,17 @@ struct pt_regs; > > > > #endif /* defined(bpf_target_defined) */ > > > > +/* > > + * When invoked from a syscall handler BPF_KPROBE, returns a > > pointer to a > > + * struct pt_regs containing syscall arguments, that is suitable > > for passing to > > + * PT_REGS_PARMn_SYSCALL() and PT_REGS_PARMn_CORE_SYSCALL(). > > + */ > > +#ifdef __BPF_ARCH_HAS_SYSCALL_WRAPPER > > +#define PT_REGS_SYSCALL_REGS(ctx) ((struct pt_regs > > *)PT_REGS_PARM1(ctx)) > > +#else > > +#define PT_REGS_SYSCALL_REGS(ctx) ctx > > +#endif > > + > > #ifndef ___bpf_concat > > #define ___bpf_concat(a, b) a ## b > > #endif > > -- > > 2.34.1 > >
