linux-kernel - Re: [PATCH v5 18/23] bpf: Use vmalloc special flag

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Message-ID: <49b112b80b211ae05b5f3c36a55f67041783f51e.camel@physik.fu-berlin.de>
Date: Tue, 12 Aug 2025 20:37:15 +0200
From: John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
To: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>, "peterz@...radead.org"
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Subject: Re: [PATCH v5 18/23] bpf: Use vmalloc special flag

Hi,

On Tue, 2025-08-12 at 18:03 +0000, Edgecombe, Rick P wrote:
> On Tue, 2025-08-12 at 18:43 +0200, John Paul Adrian Glaubitz wrote:
> > I suspect that the main issue is to be found in the following patch which introduced VM_FLUSH_RESET_PERMS
> > which may not work as expected on sun4u SPARC systems:
> 
> I think the problem we found with VM_FLUSH_RESET_PERMS was that the sparc64
> kernel TLB flush implementation was broken. Since VM_FLUSH_RESET_PERMS caused
> kernel TLB flushes to happen sooner, it just showed up sooner. [0] 
> 
> This other issue seems to be about userspace memory. So I wonder if these are
> two separate issues? Bisecting to the original VM_FLUSH_RESET_PERMS would have
> had the known sparc kernel range TLB flush issue. So to bisect the other issue
> you might need to apply this [1].

That could be true. I knew about the patch in [1] but I didn't think of applying it.

FWIW, the crashes we're seeing on recent kernel versions look like this:

[   40.992851]               \|/ ____ \|/
[   40.992851]               "@'/ .. \`@"
[   40.992851]               /_| \__/ |_\
[   40.992851]                  \__U_/
[   41.186220] (udev-worker)(88): Kernel illegal instruction [#1]
[   41.262910] CPU: 0 UID: 0 PID: 88 Comm: (udev-worker) Tainted: G        W          6.12.0+ #25
[   41.376151] Tainted: [W]=WARN
[   41.415025] TSTATE: 0000004411001607 TPC: 00000000101c21c0 TNPC: 00000000101c21c4 Y: 00000000    Tainted: G        W         
[   41.563717] TPC: <ehci_init_driver+0x0/0x160 [ehci_hcd]>
[   41.633584] g0: 00000000012005b8 g1: 00000000100a1800 g2: 0000000010206000 g3: 00000000101de000
[   41.747962] g4: fff000000a5af380 g5: 0000000000000000 g6: fff000000aac8000 g7: 0000000000000e7b
[   41.862338] o0: 0000000010060118 o1: 000000001020a000 o2: fff000000aa30ce0 o3: 0000000000000e7a
[   41.976728] o4: 00000000ff000000 o5: 00ff000000000000 sp: fff000000aacb091 ret_pc: 00000000101de028
[   42.095768] RPC: <ehci_pci_init+0x28/0x2000 [ehci_pci]>
[   42.164394] l0: 0000000000000000 l1: 0000000100043fff l2: ffffffffff800000 l3: 0000000000800000
[   42.278768] l4: fff00000001c8008 l5: 0000000000000000 l6: 00000000013358e0 l7: 0000000001002800
[   42.393143] i0: ffffffffffffffed i1: 00000000004db8d8 i2: 0000000000000000 i3: fff000000aa304e0
[   42.507517] i4: 0000000001127250 i5: 0000000010060000 i6: fff000000aacb141 i7: 0000000000427d90
[   42.621893] I7: <do_one_initcall+0x30/0x200>
[   42.677931] Call Trace:
[   42.709953] [<0000000000427d90>] do_one_initcall+0x30/0x200
[   42.783158] [<00000000004db908>] do_init_module+0x48/0x240
[   42.855214] [<00000000004dd82c>] load_module+0x19cc/0x1f20
[   42.927270] [<00000000004ddf8c>] init_module_from_file+0x6c/0xa0
[   43.006189] [<00000000004de1e4>] sys_finit_module+0x1c4/0x2c0
[   43.081677] [<0000000000406174>] linux_sparc_syscall+0x34/0x44
[   43.158307] Disabling lock debugging due to kernel taint
[   43.228077] Caller[0000000000427d90]: do_one_initcall+0x30/0x200
[   43.306995] Caller[00000000004db908]: do_init_module+0x48/0x240
[   43.384772] Caller[00000000004dd82c]: load_module+0x19cc/0x1f20
[   43.462544] Caller[00000000004ddf8c]: init_module_from_file+0x6c/0xa0
[   43.547184] Caller[00000000004de1e4]: sys_finit_module+0x1c4/0x2c0
[   43.628389] Caller[0000000000406174]: linux_sparc_syscall+0x34/0x44
[   43.710741] Caller[fff000010480e2fc]: 0xfff000010480e2fc
[   43.780508] Instruction DUMP:
[   43.780511]  00000000 
[   43.819394]  00000000 
[   43.850273]  00000000 
[   43.881153] <00000000>
[   43.912036]  00000000 
[   43.942917]  00000000 
[   43.973797]  00000000 
[   44.004678]  00000000 
[   44.035561]  00000000 
[   44.066443]

Do you have any suggestion what to bisect?

Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer
`. `'   Physicist
  `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913