Swap the r10 and rcx registers in the amd64 trapframe so that the

first six entries are in the same order as syscall arguments, such
that syscall() can just use the trapframe as the argument vector
for mi_syscall() and not need to reorder into another buffer on the
stack.  This doesn't affect coredump layout or ptrace(2), but does
affect kernel crash dumps.

Possibility noted during miod@'s cleanup of the MD syscall()
implementations

ok mlarkin@ kurt@

diff --git a/gnu/usr.bin/binutils/gdb/amd64obsd-tdep.c b/gnu/usr.bin/binutils/gdb/amd64obsd-tdep.c
index b845c2e..726d3e5 100644 (file)
--- a/gnu/usr.bin/binutils/gdb/amd64obsd-tdep.c
+++ b/gnu/usr.bin/binutils/gdb/amd64obsd-tdep.c
@@ -362,7 +362,7 @@ static int amd64obsd_tf_reg_offset[] =
 {
   14 * 8,                      /* %rax */
   13 * 8,                      /* %rbx */
-  3 * 8,                       /* %rcx */
+  6 * 8,                       /* %rcx */
   2 * 8,                       /* %rdx */
   1 * 8,                       /* %rsi */
   0 * 8,                       /* %rdi */
@@ -370,7 +370,7 @@ static int amd64obsd_tf_reg_offset[] =
   20 * 8,                      /* %rsp */
   4 * 8,                       /* %r8 ... */
   5 * 8,
-  6 * 8,
+  3 * 8,
   7 * 8,
   8 * 8,
   9 * 8,

diff --git a/sys/arch/amd64/amd64/trap.c b/sys/arch/amd64/amd64/trap.c
index d64f7c1..4df1748 100644 (file)
--- a/sys/arch/amd64/amd64/trap.c
+++ b/sys/arch/amd64/amd64/trap.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: trap.c,v 1.103 2024/01/11 19:16:26 miod Exp $ */
+/*     $OpenBSD: trap.c,v 1.104 2024/01/31 06:06:28 guenther Exp $     */
 /*     $NetBSD: trap.c,v 1.2 2003/05/04 23:51:56 fvdl Exp $    */
 
 /*-
@@ -553,7 +553,7 @@ syscall(struct trapframe *frame)
        const struct sysent *callp;
        struct proc *p;
        int error = ENOSYS;
-       register_t code, args[6], rval[2], *argp;
+       register_t code, *args, rval[2];
 
        verify_smap(__func__);
        uvmexp.syscalls++;
@@ -565,30 +565,16 @@ syscall(struct trapframe *frame)
        }
 
        code = frame->tf_rax;
-       argp = &args[0];
+       args = (register_t *)&frame->tf_rdi;
 
        if (code <= 0 || code >= SYS_MAXSYSCALL)
                goto bad;
        callp = sysent + code;
-       switch (callp->sy_narg) {
-       case 6:
-               args[5] = frame->tf_r9;
-       case 5:
-               args[4] = frame->tf_r8;
-       case 4:
-               args[3] = frame->tf_r10;
-       case 3:
-               args[2] = frame->tf_rdx;
-       case 2:
-               args[1] = frame->tf_rsi;
-       case 1:
-               args[0] = frame->tf_rdi;
-       }
 
        rval[0] = 0;
        rval[1] = 0;
 
-       error = mi_syscall(p, code, callp, argp, rval);
+       error = mi_syscall(p, code, callp, args, rval);
 
        switch (error) {
        case 0:

diff --git a/sys/arch/amd64/include/frame.h b/sys/arch/amd64/include/frame.h
index 19691ff..d9b0433 100644 (file)
--- a/sys/arch/amd64/include/frame.h
+++ b/sys/arch/amd64/include/frame.h
@@ -1,4 +1,4 @@
-/*     $OpenBSD: frame.h,v 1.10 2018/07/10 08:57:44 guenther Exp $     */
+/*     $OpenBSD: frame.h,v 1.11 2024/01/31 06:06:28 guenther Exp $     */
 /*     $NetBSD: frame.h,v 1.1 2003/04/26 18:39:40 fvdl Exp $   */
 
 /*-
@@ -82,13 +82,13 @@
  * Exception/Trap Stack Frame
  */
 struct trapframe {
-       int64_t tf_rdi;
+       int64_t tf_rdi;         /* ordered by syscall args... */
        int64_t tf_rsi;
        int64_t tf_rdx;
-       int64_t tf_rcx;
-       int64_t tf_r8;
-       int64_t tf_r9;
        int64_t tf_r10;
+       int64_t tf_r8;
+       int64_t tf_r9;          /* ...to here */
+       int64_t tf_rcx;
        int64_t tf_r11;
        int64_t tf_r12;
        int64_t tf_r13;
@@ -115,10 +115,10 @@ struct intrframe {
        int64_t if_rdi;
        int64_t if_rsi;
        int64_t if_rdx;
-       int64_t if_rcx;
+       int64_t if_r10;
        int64_t if_r8;
        int64_t if_r9;
-       int64_t if_r10;
+       int64_t if_rcx;
        int64_t if_r11;
        int64_t if_r12;
        int64_t if_r13;