| Message ID | 20220208051635.2160304-12-iii@linux.ibm.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | BPF |
| Headers | show |
| Series | Fix accessing syscall arguments | expand |
On Tue, 2022-02-08 at 06:16 +0100, Ilya Leoshkevich wrote: > On s390, the first syscall argument should be accessed via orig_gpr2 > (see arch/s390/include/asm/syscall.h). Currently gpr[2] is used > instead, leading to bpf_syscall_macro test failure. > > Note that this is unfixable for CO-RE when vmlinux.h is not included. > Simply fail the build in this case. > > Reported-by: Andrii Nakryiko <andrii@kernel.org> > Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com> > --- > tools/lib/bpf/bpf_tracing.h | 15 ++++++++++++++- > 1 file changed, 14 insertions(+), 1 deletion(-) > > diff --git a/tools/lib/bpf/bpf_tracing.h > b/tools/lib/bpf/bpf_tracing.h > index 88ed5ba9510c..5911b177728f 100644 > --- a/tools/lib/bpf/bpf_tracing.h > +++ b/tools/lib/bpf/bpf_tracing.h > @@ -2,6 +2,8 @@ > #ifndef __BPF_TRACING_H__ > #define __BPF_TRACING_H__ > > +#include <bpf/bpf_common_helpers.h> > + > /* Scan the ARCH passed in from ARCH env variable (see Makefile) */ > #if defined(__TARGET_ARCH_x86) > #define bpf_target_x86 > @@ -118,9 +120,20 @@ > > #define __BPF_ARCH_HAS_SYSCALL_WRAPPER > > -#if !defined(__KERNEL__) && !defined(__VMLINUX_H__) > +#if defined(__KERNEL__) || defined(__VMLINUX_H__) > +#define __PT_PARM1_REG_SYSCALL orig_gpr2 > +#else > /* s390 provides user_pt_regs instead of struct pt_regs to userspace > */ > #define __PT_REGS_CAST(x) ((const user_pt_regs *)(x)) > +/* > + * struct pt_regs.orig_gpr2 is not exposed through user_pt_regs, and > the ABI > + * prohibits extending user_pt_regs. In non-CO-RE case, make use of > the fact > + * that orig_gpr2 comes right after gprs in struct pt_regs. CO-RE > does not > + * allow such hacks, so there is no way to access orig_gpr2. > + */ > +#define PT_REGS_PARM1_SYSCALL(x) \ > + (*(unsigned long *)(((char *)(x) + offsetofend(user_pt_regs, > gprs)))) > +#define __PT_PARM1_REG_SYSCALL __unsupported__ > #endif > > #define __PT_PARM1_REG gprs[2] This might be too pessimistic. While I don't see a way to add real CO-RE support here, and doing something like __CORE_RELO(gprs, BYTE_OFFSET) + __CORE_RELO(gprs, BYTE_SIZE) defeats the purpose of using CO-RE, we promise not to move orig_gpr2 around. So just this: #define PT_REGS_PARM1_CORE_SYSCALL(x) ({\ unsigned long __tmp; \ bpf_probe_read_kernel(&tmp, sizeof(__tmp), &PT_REGS_PARM1_SYSCALL(x)); \ tmp; \ }) does the trick here in a sense that, having been compiled once, it would run everywhere. What do you think?
diff --git a/tools/lib/bpf/bpf_tracing.h b/tools/lib/bpf/bpf_tracing.h index 88ed5ba9510c..5911b177728f 100644 --- a/tools/lib/bpf/bpf_tracing.h +++ b/tools/lib/bpf/bpf_tracing.h @@ -2,6 +2,8 @@ #ifndef __BPF_TRACING_H__ #define __BPF_TRACING_H__ +#include <bpf/bpf_common_helpers.h> + /* Scan the ARCH passed in from ARCH env variable (see Makefile) */ #if defined(__TARGET_ARCH_x86) #define bpf_target_x86 @@ -118,9 +120,20 @@ #define __BPF_ARCH_HAS_SYSCALL_WRAPPER -#if !defined(__KERNEL__) && !defined(__VMLINUX_H__) +#if defined(__KERNEL__) || defined(__VMLINUX_H__) +#define __PT_PARM1_REG_SYSCALL orig_gpr2 +#else /* s390 provides user_pt_regs instead of struct pt_regs to userspace */ #define __PT_REGS_CAST(x) ((const user_pt_regs *)(x)) +/* + * struct pt_regs.orig_gpr2 is not exposed through user_pt_regs, and the ABI + * prohibits extending user_pt_regs. In non-CO-RE case, make use of the fact + * that orig_gpr2 comes right after gprs in struct pt_regs. CO-RE does not + * allow such hacks, so there is no way to access orig_gpr2. + */ +#define PT_REGS_PARM1_SYSCALL(x) \ + (*(unsigned long *)(((char *)(x) + offsetofend(user_pt_regs, gprs)))) +#define __PT_PARM1_REG_SYSCALL __unsupported__ #endif #define __PT_PARM1_REG gprs[2]
On s390, the first syscall argument should be accessed via orig_gpr2 (see arch/s390/include/asm/syscall.h). Currently gpr[2] is used instead, leading to bpf_syscall_macro test failure. Note that this is unfixable for CO-RE when vmlinux.h is not included. Simply fail the build in this case. Reported-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com> --- tools/lib/bpf/bpf_tracing.h | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-)