linux-kernel - Re: [REGRESSION] module BTF validation failure (Error -22) on next

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Message-ID: <CAFULd4a+GjfN5EgPM-utJNfwo5vQ9Sq+uqXJ62eP9ed7bBJ50w@mail.gmail.com>
Date: Thu, 5 Dec 2024 08:36:33 +0100
From: Uros Bizjak <ubizjak@...il.com>
To: Laura Nao <laura.nao@...labora.com>
Cc: alan.maguire@...cle.com, bpf@...r.kernel.org, 
	chrome-platform@...ts.linux.dev, kernel@...labora.com, 
	linux-kernel@...r.kernel.org, regressions@...ts.linux.dev
Subject: Re: [REGRESSION] module BTF validation failure (Error -22) on next

On Wed, Dec 4, 2024 at 4:52 PM Laura Nao <laura.nao@...labora.com> wrote:
>
> On 11/15/24 18:17, Laura Nao wrote:
> > I managed to reproduce the issue locally and I've uploaded the vmlinux[1]
> > (stripped of DWARF data) and vmlinux.raw[2] files, as well as one of the
> > modules[3] and its btf data[4] extracted with:
> >
> > bpftool -B vmlinux btf dump file cros_kbd_led_backlight.ko > cros_kbd_led_backlight.ko.raw
> >
> > Looking again at the logs[5], I've noticed the following is reported:
> >
> > [    0.415885] BPF:    type_id=115803 offset=177920 size=1152
> > [    0.416029] BPF:
> > [    0.416083] BPF: Invalid offset
> > [    0.416165] BPF:
> >
> > There are two different definitions of rcu_data in '.data..percpu', one
> > is a struct and the other is an integer:
> >
> > type_id=115801 offset=177920 size=1152 (VAR 'rcu_data')
> > type_id=115803 offset=177920 size=1152 (VAR 'rcu_data')
> >
> > [115801] VAR 'rcu_data' type_id=115572, linkage=static
> > [115803] VAR 'rcu_data' type_id=1, linkage=static
> >
> > [115572] STRUCT 'rcu_data' size=1152 vlen=69
> > [1] INT 'long unsigned int' size=8 bits_offset=0 nr_bits=64 encoding=(none)
> >
> > I assume that's not expected, correct?
> >
> > I'll dig a bit deeper and report back if I can find anything else.
>
> I ran a bisection, and it appears the culprit commit is:
> https://lore.kernel.org/all/20241021080856.48746-2-ubizjak@gmail.com/
>
> Hi Uros, do you have any suggestions or insights on resolving this issue?

There is a stray ";" at the end of the #define, perhaps this makes a difference:

+#define PERCPU_PTR(__p) \
+ (typeof(*(__p)) __force __kernel *)(__p);
+

and SHIFT_PERCPU_PTR macro now expands to:

RELOC_HIDE((typeof(*(p)) __force __kernel *)(p);, (offset))

A follow-up patch in the series changes PERCPU_PTR macro to:

#define PERCPU_PTR(__p) \
({ \
unsigned long __pcpu_ptr = (__force unsigned long)(__p); \
(typeof(*(__p)) __force __kernel *)(__pcpu_ptr); \
})

so this should again correctly cast the value.

Uros.