[PATCH v2 1/2] compat32: translate userland PT_* request values into kernel

[Michał Górny <mgorny%gentoo.org@localhost>]

Currently, the compat32 passes PT_* request values to kernel functions
without translation.  This works fine for low PT_* requests that happen
to have the same values both on i386 and amd64.  However, for requests
higher than PT_SETFPREGS, the value passed from userland (matching i386
const) does not match the correct kernel (amd64) request.  As a result,
e.g. when compat32 process calls PT_GETDBREGS, kernel actually processes
it as PT_SETSTEP.

To resolve this, introduce support for compat32 PT_* request
translation.  The interface is based on PTRACE_TRANSLATE_REQUEST32 macro
that is defined to a mapping function on architectures needing it.
In case of amd64, this function maps userland i386 PT_* values into
appropriate amd64 PT_* values.

For the time being, the two additional PT_GETXMMREGS and PT_SETXMMREGS
requests are unsupported due to lack of matching free amd64 constant.
---
 sys/arch/amd64/amd64/netbsd32_machdep.c   | 37 +++++++++++++++++++++++
 sys/arch/amd64/include/netbsd32_machdep.h |  3 ++
 sys/arch/amd64/include/ptrace.h           |  2 ++
 sys/compat/netbsd32/netbsd32_ptrace.c     | 12 +++++++-
 4 files changed, 53 insertions(+), 1 deletion(-)

Changed in v2:
- PTRACE_TRANSLATE_REQUEST32(x) fallback definition has been moved
  from ptrace.h to netbsd32_ptrace.c

diff --git a/sys/arch/amd64/amd64/netbsd32_machdep.c b/sys/arch/amd64/amd64/netbsd32_machdep.c
index 39d671a4b9b6..06f6cbdf3703 100644
--- a/sys/arch/amd64/amd64/netbsd32_machdep.c
+++ b/sys/arch/amd64/amd64/netbsd32_machdep.c
@@ -335,6 +335,43 @@ cpu_coredump32(struct lwp *l, struct coredump_iostate *iocookie,
 }
 #endif
 
+int
+netbsd32_ptrace_translate_request(int req)
+{
+
+	switch (req)
+	{
+	case 0 ... PT_FIRSTMACH - 1:
+		return req;
+	case PT_FIRSTMACH + 0:
+		return PT_STEP;
+	case PT_FIRSTMACH + 1:
+		return PT_GETREGS;
+	case PT_FIRSTMACH + 2:
+		return PT_SETREGS;
+	case PT_FIRSTMACH + 3:
+		return PT_GETFPREGS;
+	case PT_FIRSTMACH + 4:
+		return PT_SETFPREGS;
+	case PT_FIRSTMACH + 5:
+		/* PT_GETXMMREGS */
+		return -1;
+	case PT_FIRSTMACH + 6:
+		/* PT_SETXMMREGS */
+		return -1;
+	case PT_FIRSTMACH + 7:
+		return PT_GETDBREGS;
+	case PT_FIRSTMACH + 8:
+		return PT_SETDBREGS;
+	case PT_FIRSTMACH + 9:
+		return PT_SETSTEP;
+	case PT_FIRSTMACH + 10:
+		return PT_CLEARSTEP;
+	default:
+		return -1;
+	}
+}
+
 int
 netbsd32_process_read_regs(struct lwp *l, struct reg32 *regs)
 {
diff --git a/sys/arch/amd64/include/netbsd32_machdep.h b/sys/arch/amd64/include/netbsd32_machdep.h
index 51691eb7c90f..37019d29134d 100644
--- a/sys/arch/amd64/include/netbsd32_machdep.h
+++ b/sys/arch/amd64/include/netbsd32_machdep.h
@@ -151,6 +151,9 @@ struct x86_64_set_mtrr_args32 {
 
 #define NETBSD32_MID_MACHINE MID_I386
 
+/* Translate ptrace() PT_* request from 32-bit userland to kernel. */
+int netbsd32_ptrace_translate_request(int);
+
 int netbsd32_process_read_regs(struct lwp *, struct reg32 *);
 int netbsd32_process_read_fpregs(struct lwp *, struct fpreg32 *, size_t *);
 int netbsd32_process_read_dbregs(struct lwp *, struct dbreg32 *, size_t *);
diff --git a/sys/arch/amd64/include/ptrace.h b/sys/arch/amd64/include/ptrace.h
index c5cef941fd16..8d0f54dbad24 100644
--- a/sys/arch/amd64/include/ptrace.h
+++ b/sys/arch/amd64/include/ptrace.h
@@ -87,6 +87,8 @@
 #define process_reg32		struct reg32
 #define process_fpreg32		struct fpreg32
 #define process_dbreg32		struct dbreg32
+
+#define PTRACE_TRANSLATE_REQUEST32(x) netbsd32_ptrace_translate_request(x)
 #endif	/* COMPAT_NETBSD32 */
 #endif	/* _KERNEL_OPT */
 
diff --git a/sys/compat/netbsd32/netbsd32_ptrace.c b/sys/compat/netbsd32/netbsd32_ptrace.c
index 614d363c3126..ff5025ceea44 100644
--- a/sys/compat/netbsd32/netbsd32_ptrace.c
+++ b/sys/compat/netbsd32/netbsd32_ptrace.c
@@ -47,6 +47,10 @@ __KERNEL_RCSID(0, "$NetBSD: netbsd32_ptrace.c,v 1.6 2019/01/27 02:08:40 pgoyette
 #include <compat/netbsd32/netbsd32_syscallargs.h>
 #include <compat/netbsd32/netbsd32_conv.h>
 
+#ifndef PTRACE_TRANSLATE_REQUEST32
+#define PTRACE_TRANSLATE_REQUEST32(x) x
+#endif
+
 /*
  * PTRACE methods
  */
@@ -243,6 +247,8 @@ int
 netbsd32_ptrace(struct lwp *l, const struct netbsd32_ptrace_args *uap,
     register_t *retval)
 {
+	int req;
+
 	/* {
 		syscallarg(int) req;
 		syscallarg(pid_t) pid;
@@ -250,7 +256,11 @@ netbsd32_ptrace(struct lwp *l, const struct netbsd32_ptrace_args *uap,
 		syscallarg(int) data;
 	} */
 
-	return do_ptrace(&netbsd32_ptm, l, SCARG(uap, req), SCARG(uap, pid),
+	req = PTRACE_TRANSLATE_REQUEST32(SCARG(uap, req));
+	if (req == -1)
+		return EOPNOTSUPP;
+
+	return do_ptrace(&netbsd32_ptm, l, req, SCARG(uap, pid),
 	    SCARG_P32(uap, addr), SCARG(uap, data), retval);
 }
 
-- 
2.22.0.rc1