[PATCH v3] um: switch to regset API and depend on XSTATE

[Johannes Berg]

On Wed, 2024-10-23 at 10:29 +0200, Benjamin Berg wrote:
> From: Benjamin Berg <benjamin.berg at intel.com>
> 
> The PTRACE_GETREGSET API has now existed since Linux 2.6.33. The XSAVE
> CPU feature should also be sufficiently common to be able to rely on it.
> 
> With this, define our internal FP state to be the hosts XSAVE data. Add
> discovery for the hosts XSAVE size and place the FP registers at the end
> of task_struct so that we can adjust the size at runtime.
> 
> Next we can implement the regset API on top and update the signal
> handling as well as ptrace APIs to use them. Also switch coredump
> creation to use the regset API and finally set HAVE_ARCH_TRACEHOOK.
> 
> This considerably improves the signal frames. Previously they might not
> have contained all the registers (i386) and also did not have the
> sizes and magic values set to the correct values to permit userspace to
> decode the frame.
> 
> As a side effect, this will permit UML to run on hosts with newer CPU
> extensions (such as AMX) that need even more register state.
> 
> Signed-off-by: Benjamin Berg <benjamin.berg at intel.com>
> 
> ---
> 
> v3:
> * Fix FP register initialization, thanks to Johannes Berg
> 

Still causes problems with new userspace processes being killed due to:

userspace - ptrace set fp regs failed, errno = 22

(at least on 32-bit, hadn't seen it on 64-bit yet)

I dumped the FP state that couldn't be set in case that helps anything:

fp state:00000000: 7f 02 20 40 00 00 00 00 12 a0 06 08 00 00 00 00
fp state:00000010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000030: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000040: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000050: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000060: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000070: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000090: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000000a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000000b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000000c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000000d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000000e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000000f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000110: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000120: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000130: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000140: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000150: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000160: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000170: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000180: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000190: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000001a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000001b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000001c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000001d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000001e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000001f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000200: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000210: 00 00 00 00 00 00 00 00 80 49 8b 47 00 10 00 00
fp state:00000220: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000230: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000240: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000250: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000260: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000270: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000280: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000290: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000002a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000002b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000002c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000002d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000002e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000002f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000300: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000310: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000320: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000330: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000340: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000350: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000360: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000370: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000380: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000390: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000003a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000003b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000003c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000003d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000003e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000003f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000400: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000410: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000420: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000430: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000440: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000450: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000460: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000470: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000480: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000490: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000004a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000004b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000004c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000004d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000004e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000004f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000510: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000520: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000530: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000540: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000550: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000560: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000570: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000580: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000590: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000005a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000005b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000005c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000005d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000005e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000005f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000600: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000610: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000620: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000630: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000640: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000650: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000660: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000670: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000680: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000690: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000006a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000006b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000006c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000006d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000006e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000006f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000700: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000710: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000720: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000730: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000740: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000750: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000760: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000770: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000780: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000790: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000007a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000007b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000007c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000007d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000007e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000007f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000800: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000810: 00 00 00 00 00 00 00 00 00 bc 32 0a 00 00 00 00
fp state:00000820: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000830: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000840: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000850: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000860: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000870: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000880: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000890: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000008a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000008b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000008c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000008d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000008e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000008f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000900: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000910: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000920: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000930: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000940: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000950: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000960: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000970: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000980: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000990: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000009a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000009b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000009c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000009d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000009e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:000009f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000a00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000a10: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000a20: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000a30: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000a40: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000a50: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000a60: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000a70: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
fp state:00000a80: 00 00 00 00 00 00 00 00


johannes