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memory writes via gdb don't work for memory mapped hardware
When I remote-debug a qemu-guest and attempt to write to a memory mapped location, the
write-handler for the concerned device will not be called. All write-requiests from
gdb are delegated to cpu_physical_memory_write_rom(...). a function that writes to the
underlying ram-block.
I believe requests to memory mapped hardware should be delegated to
address_space_rw().
example:
;; a memory mapped device. No effect, the write-handler is not called
(gdb) set *0xfff3c000 = 48
;; a ram or rom-block. Thos works. The value is changed.
(gdb) set *0x100000 = 48
----------------------------------------
Here's my suggested patch. As noted in the comment, it could perhaps be
improved for the (rare) case when the write-request from gdb spans multiple
memory regions.
$ git diff 85bc2a15121e8bcd9f15eb75794a1eacca9d84bd HEAD ../exec.c
diff --git a/exec.c b/exec.c
index c4f9036..45ef896 100644
--- a/exec.c
+++ b/exec.c
@@ -3676,6 +3676,7 @@ int cpu_memory_rw_debug(CPUState *cpu, target_ulong addr,
int l;
hwaddr phys_addr;
target_ulong page;
+ bool is_memcpy_access;
while (len > 0) {
int asidx;
@@ -3691,13 +3692,32 @@ int cpu_memory_rw_debug(CPUState *cpu, target_ulong addr,
if (l > len)
l = len;
phys_addr += (addr & ~TARGET_PAGE_MASK);
+
if (is_write) {
+ /* if ram/rom region we access the memory
+ via memcpy instead of via the cpu */
+ hwaddr mr_len, addr1;
+ AddressSpace *as = cpu->cpu_ases[asidx].as;
+ MemoryRegion *mr = address_space_translate(as, phys_addr, &addr1, &mr_len, is_write);
+ is_memcpy_access = memory_region_is_ram(mr) || memory_region_is_romd(mr);
+ if(mr_len < len) {
+ /* TODO, mimic more of the loop over mr chunks as
+ done in cpu_physical_memory_write_internal */
+ printf("warning: we dont know whether all bytes "
+ "to be written are ram/rom or io\n");
+ }
+ }
+ else {
+ is_memcpy_access = false;
+ }
+
+ if (is_write && is_memcpy_access) {
cpu_physical_memory_write_rom(cpu->cpu_ases[asidx].as,
phys_addr, buf, l);
} else {
address_space_rw(cpu->cpu_ases[asidx].as, phys_addr,
MEMTXATTRS_UNSPECIFIED,
- buf, l, 0);
+ buf, l, is_write);
}
len -= l;
buf += l;
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