[I've submitted bugzilla 219153 for this libvm issue of not handling powerpc's/powerp64's ET_DYN vmcore.* 's and such.]
On 2017-May-8, at 1:18 PM, Mark Millard <mar...@dsl-only.net> wrote: > [Mostly: Why THING #2 fails: checks for ET_EXEC > but the actual vmcore.* 's have ET_DYN instead.] > > On 2017-May-8, at 11:30 AM, John Baldwin <jhb at freebsd.org> wrote: > >> On Saturday, May 06, 2017 10:03:57 PM Mark Millard wrote: >>> THING #0: >>> >>> It appears that usr.sbin/crashinfo/crashinfo.sh assumes >>> that /usr/local/bin/gdb will work better for all architectures, >>> including for kgdb types of activity: >>> >>> find_gdb() >>> { >>> local binary >>> >>> for binary in /usr/local/bin/gdb /usr/libexec/gdb /usr/bin/gdb; do >>> if [ -x ${binary} ]; then >>> GDB=${binary} >>> return >>> fi >>> done >>> } >>> >>> But it appears that on powerpc /usr/local/bin/gdb and >>> /usr/local/bin/kgdb do not support TARGET_ARCH=powerpc >>> at all for such activity. >> >> Not really. kgdb on powerpc doesn't work period as neither the base nor >> ports >> kgdb can unwind a stack frame. I spent some time last year trying to get the >> unwind out of cpu_switch() to work to no avail. The current hack attempts >> are >> here: >> >> https://github.com/bsdjhb/gdb/compare/freebsd-7.11-kgdb...kgdb-ppc > > Interesting. > >>> THING #1: >>> . . . >> >>> THING #2: >>> >>> /usr/libexec/kgdb (when present) does not support the >>> powerpc architecture for head either . . . >>> >>> On a head -r317820 powerpc I attempted: >>> >>> # /usr/libexec/kgdb /usr/lib/debug/boot/kernel/kernel.debug >>> /var/crash/vmcore.7 >>> GNU gdb 6.1.1 [FreeBSD] >>> Copyright 2004 Free Software Foundation, Inc. >>> GDB is free software, covered by the GNU General Public License, and you are >>> welcome to change it and/or distribute copies of it under certain >>> conditions. >>> Type "show copying" to see the conditions. >>> There is absolutely no warranty for GDB. Type "show warranty" for details. >>> This GDB was configured as "powerpc-marcel-freebsd"... >>> Failed to open vmcore: unsupported architecture >> >> This is a different problem with libkvm. I would start with 'ps -M' and use >> a debugger to step through the _powerpc_probe and _powerpc64_probe routines >> in >> libkvm to see why the appropriate probe routine isn't claiming the core. > > For THING #2: > > I had to use /usr/libexec/gdb as the debugger because /usr/local/bin/gdb > segmentation faulted. > > (gdb) list > 126 int > 127 _kvm_probe_elf_kernel(kvm_t *kd, int class, int machine) > 128 { > 129 > 130 return (kd->nlehdr.e_ident[EI_CLASS] == class && > 131 kd->nlehdr.e_type == ET_EXEC && > 132 kd->nlehdr.e_machine == machine); > 133 } > > gets false via: kd->nlehdr.e_type == ET_EXEC > > (gdb) print kd->nlehdr.e_type > $4 = 3 > > but the comparison is for: > > 0x41882fe0 <_kvm_probe_elf_kernel+32>: cmplwi cr1,r4,2 > > (gdb) disass > Dump of assembler code for function _kvm_probe_elf_kernel: > 0x41882fc0 <_kvm_probe_elf_kernel+0>: stwu r1,-16(r1) > 0x41882fc4 <_kvm_probe_elf_kernel+4>: stw r31,12(r1) > 0x41882fc8 <_kvm_probe_elf_kernel+8>: mr r31,r1 > 0x41882fcc <_kvm_probe_elf_kernel+12>: lbz r6,2076(r3) > 0x41882fd0 <_kvm_probe_elf_kernel+16>: crclr eq > 0x41882fd4 <_kvm_probe_elf_kernel+20>: cmplw cr1,r6,r4 > 0x41882fd8 <_kvm_probe_elf_kernel+24>: bne- cr1,0x41882ff0 > <_kvm_probe_elf_kernel+48> > 0x41882fdc <_kvm_probe_elf_kernel+28>: lhz r4,2088(r3) > 0x41882fe0 <_kvm_probe_elf_kernel+32>: cmplwi cr1,r4,2 > 0x41882fe4 <_kvm_probe_elf_kernel+36>: bne- cr1,0x41882ff0 > <_kvm_probe_elf_kernel+48> > 0x41882fe8 <_kvm_probe_elf_kernel+40>: lhz r3,2090(r3) > 0x41882fec <_kvm_probe_elf_kernel+44>: cmpw r3,r5 > 0x41882ff0 <_kvm_probe_elf_kernel+48>: li r3,1 > 0x41882ff4 <_kvm_probe_elf_kernel+52>: beq- 0x41882ffc > <_kvm_probe_elf_kernel+60> > 0x41882ff8 <_kvm_probe_elf_kernel+56>: li r3,0 > 0x41882ffc <_kvm_probe_elf_kernel+60>: lwz r31,12(r1) > 0x41883000 <_kvm_probe_elf_kernel+64>: addi r1,r1,16 > 0x41883004 <_kvm_probe_elf_kernel+68>: blr > > powerpc and powerpc64 use position independent kernels > these days as I remember, making kd->nlehdr.e_type be > ET_DYN instead of ET_EXEC : > > /* e_type */ > #define ET_REL 1 > #define ET_EXEC 2 > #define ET_DYN 3 > #define ET_CORE 4 > > I do not know if more needs to change than just > the enabling test since the content is ET_DYN > type of material. > > It looks like the conversion to position independent > kernels for powerpc and powerpc64 did not cover all > the related infrastructure, such as libkvm. I've submitted bugzilla 219153 for this libvm issue of not handling powerpc's/powerp64's ET_DYN vmcore.* 's and such. It applies to head , stable/11 , and release/11.0.1 : 20150307: The 32-bit PowerPC kernel has been changed to a position-independent executable. This can only be booted with a version of loader(8) newer than January 31, 2015, so make sure to update both world and kernel before rebooting. . . . 20150131: The powerpc64 kernel has been changed to a position-independent executable. This can only be booted with a new version of loader(8), so make sure to update both world and kernel before rebooting. === Mark Millard markmi at dsl-only.net _______________________________________________ freebsd-toolchain@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-toolchain To unsubscribe, send any mail to "freebsd-toolchain-unsubscr...@freebsd.org"