Re: kernel stack usage

[Simon Burge <simonb%NetBSD.org@localhost>]

matthew green wrote:

> glad to see this effort and the clean up already!
>
> ideally, we can break the kernel build if large stack consumers
> are added to the kernel.  i'd be OK with it being default on,
> with of course a way to skip it, and if necessary it can have
> a whitelist of "OK large users."

I started to look at -fstack-usage which gives a nice MI way of getting
the data instead of parsing MD objdump output, but didn't get any
further than the below patch.  The find(1) command referenced in the
patch gives the following

  1008 nfs_serv.c:2181:1:nfsrv_link
  1056 procfs_linux.c:422:1:procfs_do_pid_stat
  1056 vfs_subr.c:1521:1:vfs_buf_print
  1072 dl_print.c:80:1:sdl_print
  1104 core_elf32.c:300:1:coredump_getseghdrs_elf32
  1104 core_elf32.c:300:1:coredump_getseghdrs_elf64
  1104 sys_ptrace_common.c:1595:1:proc_regio
  1120 subr_bufq.c:131:1:bufq_alloc
  1136 db_lwp.c:64:1:db_lwp_whatis
  1152 kern_ktrace.c:1269:1:ktrwrite
  1168 uvm_swap.c:768:1:uvm_swap_stats.part.1
  1312 nfs_serv.c:1905:1:nfsrv_rename
  2112 tty_60.c:68:1:compat_60_ptmget_ioctl
  2144 memmem.c:83:14:twoway_memmem

Anyone else want to run with adding a bit more to this to do some build
failure as mrg@ suggests and documenting for options(4)?

Cheers,
Simon.
--
Index: Makefile.kern.inc
===================================================================
RCS file: /cvsroot/src/sys/conf/Makefile.kern.inc,v
retrieving revision 1.270
diff -d -p -u -r1.270 Makefile.kern.inc
--- Makefile.kern.inc	21 May 2020 18:44:19 -0000	1.270
+++ Makefile.kern.inc	31 May 2020 13:34:13 -0000
@@ -104,6 +104,11 @@ CFLAGS+=	-ffreestanding -fno-zero-initia
 CFLAGS+=	${${ACTIVE_CC} == "gcc":? -fno-delete-null-pointer-checks :}
 CFLAGS+=	${DEBUG} ${COPTS}
 AFLAGS+=	-D_LOCORE -Wa,--fatal-warnings
+.if defined(KERN_STACK_USAGE)
+# example usage to find largest stack users in kernel compile directory:
+#    find . -name \*.su | xargs awk '{ printf "%6d %s\n", $2, $1 }' | sort +1n
+CFLAGS+=	-fstack-usage
+.endif
 
 # XXX
 .if defined(HAVE_GCC) || defined(HAVE_LLVM)
@@ -338,8 +343,8 @@ ${_s:T:R}.o: ${_s}
 .if !target(__CLEANKERNEL)
 __CLEANKERNEL: .USE
 	${_MKMSG} "${.TARGET}ing the kernel objects"
-	rm -f ${KERNELS} *.map eddep tags *.[io] *.ko *.ln [a-z]*.s vers.c \
-	    [Ee]rrs linterrs makelinks assym.h.tmp assym.h \
+	rm -f ${KERNELS} *.map *.[io] *.ko *.ln [a-z]*.s *.su vers.c \
+	    eddep tags [Ee]rrs linterrs makelinks assym.h.tmp assym.h \
 	    ${EXTRA_KERNELS} ${EXTRA_CLEAN}
 .endif