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qemu-i386-static ioctl return -14 (Bad Address)
I use qemu-i386-static on 64 bit ARM.But I don't know how to solve some problems.
First I added some ioctl operations.
Then I tried to do some DRM operations like test.c.
This is successful when I use qemu-x86_64-static,but it failed when I use qemu-i386-static.
I can get some strace info like this:
403 openat(AT_FDCWD,"/dev/dri/card0",O_RDWR|O_LARGEFILE|O_CLOEXEC) = 4
403 ioctl(4,DRM_IOCTL_GET_CAP,{1,0}) = 0 ({1,1})
403 ioctl(4,DRM_IOCTL_MODE_GETRESOURCES,{0,0,0,0,0,0,0,0,0,0,0,0}) = 0 ({0,0,0,0,0,2,2,2,0,16384,0,16384})
403 brk(NULL) = 0x40006000
403 brk(0x40027000) = 0x40027000
403 brk(0x40028000) = 0x40028000
403 ioctl(4,DRM_IOCTL_MODE_GETRESOURCES,{0,1073766816,1073766832,1073766848,0,2,2,2,0,16384,0,16384}) = -1 errno=14 (Bad address)
And there are similar errors in other self driven operations.
I want to know if it is QEMU's problem, so I hope to get some help.
Thank you!
This problem has bothered me for a long time, but I'm not sure whether it's the IOCTL () I added or the QEMU with 32 bits. I hope we can discuss it and help our friends who have other problems.
Thank you,my friends!
My environment is that:
schroot + debian(bullseye-i386)
qemu: 5.1.0-rc3
Please, send your patches to the QEMU devel mailing list, so we can review them and comment.
https://wiki.qemu.org/Contribute/SubmitAPatch
Hi,I found some problems, but I don't know if how to solve it better(I'm not really familiar with the source code).
When I use ioctl() and use a structure like this:
struct drm_mode_card_res {
__u64 fb_id_ptr;
__u64 crtc_id_ptr;
__u64 connector_id_ptr;
__u64 encoder_id_ptr;
__u32 count_fbs;
....
};
Look,"fb_id_ptr" is a pointer,and apply for memory allocation through malloc.But I use qemu-i386 on 64 bit ARM.As a result, my pointer has no problem in QEMU, but it is wrong when I use ioctl(bad address).This address is actually an address in QEMU, but it is not the correct address in a 64 bit machine.
Is there any better way to solve this problem?
Hi,I found some problems, but I don't know if how to solve it better(I'm not really familiar with the source code).
When I use ioctl() and use a structure like this:
struct drm_mode_card_res {
__u64 fb_id_ptr;
__u64 crtc_id_ptr;
__u64 connector_id_ptr;
__u64 encoder_id_ptr;
__u32 count_fbs;
....
};
And in syscall_types.h
STRUCT(drm_mode_card_res,
TYPE_PTRVOID,
TYPE_PTRVOID,
TYPE_PTRVOID,
TYPE_PTRVOID,
TYPE_INT,
...
)
Some code:
...
if (res.count_fbs) {
res.fb_id_ptr = VOID2U64(drmMalloc(res.count_fbs*sizeof(uint32_t)));
if (!res.fb_id_ptr)
goto err_allocs;
}
...
This is strace:
openat(AT_FDCWD,"/dev/dri/card0",O_RDWR|O_LARGEFILE|O_CLOEXEC) = 4
9469 ioctl(4,DRM_IOCTL_GET_CAP,{1,0}) = 0 ({1,1})
9469 ioctl(4,DRM_IOCTL_MODE_GETRESOURCES,{0x0,0x0,0x0,0x0,0,0,0,0,0,0,0,0}) = 0 ({0x0,0x0,0x0,0x0,0,2,2,2,0,16384,0,16384})
9469 brk(NULL) = 0x40006000
9469 brk(0x40027000) = 0x40027000
9469 brk(0x40028000) = 0x40028000
9469 ioctl(4,DRM_IOCTL_MODE_GETRESOURCES,{0x0,0x0,0x400061a0,0x0,0,2,1073832368,0,0,16384,0,16384}) = -1 errno=14 (Bad address)
9469 brk(0x40027000) = 0x40027000
Look
9469 ioctl(4,DRM_IOCTL_MODE_GETRESOURCES,{0x0,0x0,0x400061a0,0x0,0,2,1073832368,0,0,16384,0,16384}) = -1 errno=14 (Bad address)
Why does memory overrun occur here???
I think this is right:
{0x0,0x400061a0,1073832368(0x400061a0),0x400061c0,0,2,2,2,0,16384,0,16384}
Who can help me? Thank you!
You need to use IOCTL_SPECIAL() or STRUCT_SPECIAL() macro to convert the target address to the host address.
Again, share your patches on the qemu-devel mailing list if you want help.
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