Naveen N. Rao wrote:
Hi Heiko,
Heiko Carstens 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(?).
On powerpc, gpr[3] continues to be valid on syscall entry (so this test
passes on powerpc), though orig_gpr3 will remain valid throughout.
Hmm.. we can't use orig_gpr3 since we don't use a syscall wrapper. All
system calls just receive the parameters directly.
- Naveen
