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nubus: generate bus error when attempting to access empty slots

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According to "Designing Cards and Drivers for the Macintosh Family" any attempt
to access an unimplemented address location on Nubus generates a bus error. MacOS
uses a custom bus error handler to detect empty Nubus slots, and with the current
implementation assumes that all slots are occupied as the Nubus transactions
never fail.

Switch nubus_slot_ops and nubus_super_slot_ops over to use {read,write}_with_attrs
and hard-code them to return MEMTX_DECODE_ERROR so that unoccupied Nubus slots
will generate the expected bus error.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20210924073808.1041-9-mark.cave-ayland@ilande.co.uk>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
This commit is contained in:
Mark Cave-Ayland 2021-09-24 08:37:56 +01:00 • committed by Laurent Vivier
parent ce0e6a2c55
commit 1d3d62dff8
1 changed files with 18 additions and 16 deletions
Download patch file Download diff file Expand all files Collapse all files

34
hw/nubus/nubus-bus.c
View file

@ -28,23 +28,23 @@ static NubusBus *nubus_find(void)
return NUBUS_BUS(object_resolve_path_type("", TYPE_NUBUS_BUS, NULL)); return NUBUS_BUS(object_resolve_path_type("", TYPE_NUBUS_BUS, NULL));
} }
static void nubus_slot_write(void *opaque, hwaddr addr, uint64_t val, static MemTxResult nubus_slot_write(void *opaque, hwaddr addr, uint64_t val,
unsigned int size) unsigned size, MemTxAttrs attrs)
{ {
/* read only */
trace_nubus_slot_write(addr, val, size); trace_nubus_slot_write(addr, val, size);
return MEMTX_DECODE_ERROR;
} }
static uint64_t nubus_slot_read(void *opaque, hwaddr addr, static MemTxResult nubus_slot_read(void *opaque, hwaddr addr, uint64_t *data,
unsigned int size) unsigned size, MemTxAttrs attrs)
{ {
trace_nubus_slot_read(addr, size); trace_nubus_slot_read(addr, size);
return 0; return MEMTX_DECODE_ERROR;
} }
static const MemoryRegionOps nubus_slot_ops = { static const MemoryRegionOps nubus_slot_ops = {
.read = nubus_slot_read, .read_with_attrs = nubus_slot_read,
.write = nubus_slot_write, .write_with_attrs = nubus_slot_write,
.endianness = DEVICE_BIG_ENDIAN, .endianness = DEVICE_BIG_ENDIAN,
.valid = { .valid = {
.min_access_size = 1, .min_access_size = 1,
@ -52,23 +52,25 @@ static const MemoryRegionOps nubus_slot_ops = {
}, },
}; };
static void nubus_super_slot_write(void *opaque, hwaddr addr, uint64_t val, static MemTxResult nubus_super_slot_write(void *opaque, hwaddr addr,
unsigned int size) uint64_t val, unsigned size,
MemTxAttrs attrs)
{ {
/* read only */
trace_nubus_super_slot_write(addr, val, size); trace_nubus_super_slot_write(addr, val, size);
return MEMTX_DECODE_ERROR;
} }
static uint64_t nubus_super_slot_read(void *opaque, hwaddr addr, static MemTxResult nubus_super_slot_read(void *opaque, hwaddr addr,
unsigned int size) uint64_t *data, unsigned size,
MemTxAttrs attrs)
{ {
trace_nubus_super_slot_read(addr, size); trace_nubus_super_slot_read(addr, size);
return 0; return MEMTX_DECODE_ERROR;
} }
static const MemoryRegionOps nubus_super_slot_ops = { static const MemoryRegionOps nubus_super_slot_ops = {
.read = nubus_super_slot_read, .read_with_attrs = nubus_super_slot_read,
.write = nubus_super_slot_write, .write_with_attrs = nubus_super_slot_write,
.endianness = DEVICE_BIG_ENDIAN, .endianness = DEVICE_BIG_ENDIAN,
.valid = { .valid = {
.min_access_size = 1, .min_access_size = 1,