[src/trunk]: src/sys/arch/aarch64/aarch64 Fix build failure due to -Werror=st...

[rin <rin%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/893330b7111f
branches:  trunk
changeset: 935168:893330b7111f
user:      rin <rin%NetBSD.org@localhost>
date:      Sat Jun 27 00:43:38 2020 +0000

description:
Fix build failure due to -Werror=stack-usage.

Use db_read_bytes() against particular member of structure in use,
by which we can avoid to have whole structure in the stack.

Now, stack usage shrinks: 4240 --> 1296

diffstat:

 sys/arch/aarch64/aarch64/db_trace.c |  37 +++++++++++++++++++------------------
 1 files changed, 19 insertions(+), 18 deletions(-)

diffs (98 lines):

diff -r ff52d1079a13 -r 893330b7111f sys/arch/aarch64/aarch64/db_trace.c
--- a/sys/arch/aarch64/aarch64/db_trace.c       Fri Jun 26 22:05:05 2020 +0000
+++ b/sys/arch/aarch64/aarch64/db_trace.c       Sat Jun 27 00:43:38 2020 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: db_trace.c,v 1.11 2020/05/22 19:29:26 ryo Exp $ */
+/* $NetBSD: db_trace.c,v 1.12 2020/06/27 00:43:38 rin Exp $ */
 
 /*
  * Copyright (c) 2017 Ryo Shimizu <ryo%nerv.org@localhost>
@@ -28,7 +28,7 @@
 
 #include <sys/cdefs.h>
 
-__KERNEL_RCSID(0, "$NetBSD: db_trace.c,v 1.11 2020/05/22 19:29:26 ryo Exp $");
+__KERNEL_RCSID(0, "$NetBSD: db_trace.c,v 1.12 2020/06/27 00:43:38 rin Exp $");
 
 #include <sys/param.h>
 #include <sys/proc.h>
@@ -174,14 +174,14 @@
 #endif
 
        if (trace_thread) {
-               proc_t *pp, p;
+               proc_t *pp;
 
                if ((pp = db_proc_find((pid_t)addr)) == 0) {
                        (*pr)("trace: pid %d: not found\n", (int)addr);
                        return;
                }
-               db_read_bytes((db_addr_t)pp, sizeof(p), (char *)&p);
-               addr = (db_addr_t)p.p_lwps.lh_first;
+               db_read_bytes((db_addr_t)pp + offsetof(proc_t, p_lwps.lh_first),
+                   sizeof(addr), (char *)&addr);
                trace_thread = false;
                trace_lwp = true;
        }
@@ -193,32 +193,32 @@
 #endif
 
        if (trace_lwp) {
-               proc_t p;
                struct lwp l;
+               pid_t pid;
 
                db_read_bytes(addr, sizeof(l), (char *)&l);
-               db_read_bytes((db_addr_t)l.l_proc, sizeof(p), (char *)&p);
+               db_read_bytes((db_addr_t)l.l_proc + offsetof(proc_t, p_pid),
+                   sizeof(pid), (char *)&pid);
 
 #if defined(_KERNEL)
                if (addr == (db_expr_t)curlwp) {
                        fp = (uint64_t)&DDB_REGS->tf_reg[29];   /* &reg[29]={fp,lr} */
                        tf = DDB_REGS;
                        (*pr)("trace: pid %d lid %d (curlwp) at tf %p\n",
-                           p.p_pid, l.l_lid, tf);
+                           pid, l.l_lid, tf);
                } else
 #endif
                {
-                       struct pcb pcb_buf;
                        struct pcb *pcb = lwp_getpcb(&l);
 
-                       db_read_bytes((db_addr_t)pcb, sizeof(pcb_buf),
-                           (char *)&pcb_buf);
-                       tf = pcb_buf.pcb_tf;
+                       db_read_bytes((db_addr_t)pcb +
+                           offsetof(struct pcb, pcb_tf),
+                           sizeof(tf), (char *)&tf);
                        if (tf != 0) {
                                db_read_bytes((db_addr_t)&tf->tf_reg[29],
                                    sizeof(fp), (char *)&fp);
                                (*pr)("trace: pid %d lid %d at tf %p (in pcb)\n",
-                                   p.p_pid, l.l_lid, tf);
+                                   pid, l.l_lid, tf);
                        }
 #if defined(MULTIPROCESSOR) && defined(_KERNEL)
                        else if (l.l_stat == LSONPROC ||
@@ -226,14 +226,15 @@
 
                                /* running lwp on other cpus */
                                extern struct trapframe *db_readytoswitch[];
-                               struct cpu_info cpuinfobuf;
+                               u_int index;
 
-                               db_read_bytes((db_addr_t)l.l_cpu,
-                                   sizeof(cpuinfobuf), (char *)&cpuinfobuf);
-                               tf = db_readytoswitch[cpuinfobuf.ci_index];
+                               db_read_bytes((db_addr_t)l.l_cpu +
+                                   offsetof(struct cpu_info, ci_index),
+                                   sizeof(index), (char *)&index);
+                               tf = db_readytoswitch[index];
 
                                (*pr)("trace: pid %d lid %d at tf %p (in kdb_trap)\n",
-                                   p.p_pid, l.l_lid, tf);
+                                   pid, l.l_lid, tf);
                        }
 #endif
                        else {