Re: [Qemu-devel] [PATCH] Bug Fix:Segmentation fault when use usb-ehci device

[Peter Maydell]

On 19 July 2013 15:12, Andreas Färber <address@hidden> wrote:
> No, I don't. There were other segfault avoidance patches like yours over
> the past months - they're all fixing individual segfault symptoms.
> Question for Paolo is whether we want to continue to discover them one
> by one or whether to implement a fallback inside memory code if .read or
> .write is NULL.

I think that the correct behaviour is "if neither
.read nor .oldmmio.read[x] are set then behave as if
.valid.accepts returned false" (ie "device has not responded
to the read access, bus error").

That said, if we want to add do-nothing functions instead,
then (a) having memory.c provide a single set of nop functions
that devices can use would be nicer than lots of individual
nop functions and (b) a list to start with:

$ for f in $(find . -name '*.c'); do perl -e '$s = 0; while (<>) { if
(/MemoryRegionOps (.*) =/) { $n = $1; $s = 1; next; } next if $s == 0;
if (/\.read = /) { $s |= 2; } if (/\.write = /) { $s |= 4; } if (/;/)
{ print "$ARGV: $n: missing read\n" unless $s & 2; print "$ARGV: $n:
missing write\n" unless $s & 4; $s = 0; }}' $f; done
./memory.c: unassigned_mem_ops: missing read
./memory.c: unassigned_mem_ops: missing write
./exec.c: notdirty_mem_ops: missing read
./hw/pci-host/prep.c: PPC_intack_ops: missing write
./hw/ssi/xilinx_spips.c: lqspi_ops: missing write
./hw/arm/omap1.c: omap_pwt_ops: missing read
./hw/arm/musicpal.c: mv88w8618_wlan_ops: missing write
./hw/scsi/megasas.c: megasas_queue_ops: missing write
./hw/usb/hcd-ehci.c: ehci_mmio_caps_ops: missing write
./hw/usb/hcd-uhci.c: uhci_ioport_ops: missing read
./hw/intc/openpic_kvm.c: kvm_openpic_mem_ops: missing read
./hw/intc/openpic.c: openpic_glb_ops_le: missing read
./hw/intc/openpic.c: openpic_glb_ops_be: missing read
./hw/intc/openpic.c: openpic_tmr_ops_le: missing read
./hw/intc/openpic.c: openpic_tmr_ops_be: missing read
./hw/intc/openpic.c: openpic_cpu_ops_le: missing read
./hw/intc/openpic.c: openpic_cpu_ops_be: missing read
./hw/intc/openpic.c: openpic_src_ops_le: missing read
./hw/intc/openpic.c: openpic_src_ops_be: missing read
./hw/pci/msix.c: msix_pba_mmio_ops: missing write
./hw/xen/xen_platform.c: xen_pci_io_ops: missing read
./hw/misc/lm32_sys.c: sys_ops: missing read
./hw/misc/pc-testdev.c: test_irq_ops: missing read
./hw/misc/pc-testdev.c: test_flush_ops: missing read
./hw/misc/vfio.c: vfio_ati_3c3_quirk: missing write
./hw/misc/debugexit.c: debug_exit_ops: missing read
./hw/net/lan9118.c: *mem_ops: missing read
./hw/net/lan9118.c: *mem_ops: missing write
./hw/char/grlib_apbuart.c: grlib_apbuart_ops: missing read
./hw/char/grlib_apbuart.c: grlib_apbuart_ops: missing write
./hw/isa/pc87312.c: pc87312_io_ops: missing read
./hw/nvram/fw_cfg.c: fw_cfg_ctl_mem_ops: missing read

No doubt there are some false positives in there (eg fw_cfg.c
provides a valid function so we'll never try to do reads)
and it may miss some.

-- PMM