Re: [PATCH v14 0/8] Add additional plugin API functions to read and write memory and registers

[Pierrick Bouvier <pierrick.bouvier@linaro.org>]

On 6/26/25 9:37 AM, Alex Bennée wrote:
> Alex Bennée <alex.bennee@linaro.org> writes:
> 
>> Rowan Hart <rowanbhart@gmail.com> writes:
>>
>>> This patch series adds several new API functions focused on enabling use
>>> cases around reading and writing guest memory from QEMU plugins. To support
>>> these new APIs, some utility functionality around retrieving information about
>>> address spaces is added as well.
>>
>> Queued to plugins/next, thanks.
> 
> So this fails a number of the CI tests, mostly due to 32 bit issues:
> 
>    https://gitlab.com/stsquad/qemu/-/pipelines/1890883927/failures
> 
> The tci failure is easy enough:
> 
> --8<---------------cut here---------------start------------->8---
> modified   tests/tcg/x86_64/Makefile.softmmu-target
> @@ -34,9 +34,11 @@ memory: CFLAGS+=-DCHECK_UNALIGNED=1
>   # Running
>   QEMU_OPTS+=-device isa-debugcon,chardev=output -device isa-debug-exit,iobase=0xf4,iosize=0x4 -kernel
>   
> +ifeq ($(CONFIG_PLUGIN),y)
>   run-plugin-patch-target-with-libpatch.so:		\
>   	PLUGIN_ARGS=$(COMMA)target=ffc0$(COMMA)patch=9090$(COMMA)use_hwaddr=true
>   run-plugin-patch-target-with-libpatch.so:		\
>   	CHECK_PLUGIN_OUTPUT_COMMAND=$(X64_SYSTEM_SRC)/validate-patch.py $@.out
>   run-plugin-patch-target-with-libpatch.so: patch-target libpatch.so
>   EXTRA_RUNS+=run-plugin-patch-target-with-libpatch.so
> +endif
> --8<---------------cut here---------------end--------------->8---
> 
> The other problem is trying to stuff a uint64_t into a void * on 32 bit.
> We did disable plugins for 32 bit but then reverted because we were able
> to fixup the cases:
> 
>   cf2a78cbbb (deprecation: don't enable TCG plugins by default on 32 bit hosts)
>   db7a06ade1 (configure: reenable plugins by default for 32-bit hosts)
> 
> So I don't what is easier:
> 
>   - re-deprecate for 32 bit systems
>   - only build libpatch on 64 bit systems
>   - fix libpatch to handle being built on 32 bit systems
> 

More context:
../tests/tcg/plugins/patch.c: In function ‘patch_hwaddr’:
../tests/tcg/plugins/patch.c:50:21: error: cast from pointer to integer 
of different size [-Werror=pointer-to-int-cast]
    50 |     uint64_t addr = (uint64_t)userdata;
       |                     ^
../tests/tcg/plugins/patch.c: In function ‘patch_vaddr’:
../tests/tcg/plugins/patch.c:93:21: error: cast from pointer to integer 
of different size [-Werror=pointer-to-int-cast]
    93 |     uint64_t addr = (uint64_t)userdata;
       |                     ^
../tests/tcg/plugins/patch.c: In function ‘vcpu_tb_trans_cb’:
../tests/tcg/plugins/patch.c:159:54: error: cast to pointer from integer 
of different size [-Werror=int-to-pointer-cast]
   159 |                                                      (void *)addr);
       |                                                      ^
../tests/tcg/plugins/patch.c:163:54: error: cast to pointer from integer 
of different size [-Werror=int-to-pointer-cast]
   163 |                                                      (void *)addr);
       |

Since we disabled 64 bit targets on 32 bit hosts, and that data passed 
by pointers concern addresses, it should be safe to cast values to 
(uintptr_t) instead of (uint64_t).

Pierrick