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From:   Michael Ellerman <mpe@ellerman.id.au>
To:     "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc:     Linus Torvalds <torvalds@linux-foundation.org>, ajd@linux.ibm.com,
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Subject: Re: [GIT PULL] Please pull powerpc/linux.git powerpc-6.1-1 tag
In-Reply-To: <Y0Tbsh7Zeodxueux@zx2c4.com>
References: <87edvhntv0.fsf@mpe.ellerman.id.au> <Y0RxpSFyn9m68zIb@zx2c4.com>
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 <Y0Tbsh7Zeodxueux@zx2c4.com>
Date:   Tue, 11 Oct 2022 20:35:51 +1100
Message-ID: <87y1tmn1mw.fsf@mpe.ellerman.id.au>
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"Jason A. Donenfeld" <Jason@zx2c4.com> writes:
> On Tue, Oct 11, 2022 at 12:53:17PM +1100, Michael Ellerman wrote:
>> "Jason A. Donenfeld" <Jason@zx2c4.com> writes:
>> > On Mon, Oct 10, 2022 at 01:25:25PM -0600, Jason A. Donenfeld wrote:
>> >> Hi Michael,
>> >> 
>> >> On Sun, Oct 09, 2022 at 10:01:39PM +1100, Michael Ellerman wrote:
>> >> > powerpc updates for 6.1
>> >> > 
>> >> >  - Remove our now never-true definitions for pgd_huge() and p4d_leaf().
>> >> > 
>> >> >  - Add pte_needs_flush() and huge_pmd_needs_flush() for 64-bit.
>> >> > 
>> >> >  - Add support for syscall wrappers.
>> >> > 
>> >> >  - Add support for KFENCE on 64-bit.
>> >> > 
>> >> >  - Update 64-bit HV KVM to use the new guest state entry/exit accounting API.
>> >> > 
>> >> >  - Support execute-only memory when using the Radix MMU (P9 or later).
>> >> > 
>> >> >  - Implement CONFIG_PARAVIRT_TIME_ACCOUNTING for pseries guests.
>> >> > 
>> >> >  - Updates to our linker script to move more data into read-only sections.
>> >> > 
>> >> >  - Allow the VDSO to be randomised on 32-bit.
>> >> > 
>> >> >  - Many other small features and fixes.
>> >> 
>> >> FYI, something in here broke the wireguard test suite, which runs the
>> >> iperf3 networking utility. The full log is here [1], but the relevant part
>> >> is: 
>> >> 
>> >> [+] NS1: iperf3 -Z -t 3 -c 192.168.241.2
>> >> Connecting to host 192.168.241.2, port 5201
>> >> iperf3: error - failed to read /dev/urandom: Bad address
>> >> 
>> >> I'll see if I can narrow it down a bit more and bisect. But just FYI, in
>> >> case you have an intuition.
>> >
>> > Huh. From iov_iter.c:
>> >
>> > static int copyout(void __user *to, const void *from, size_t n)
>> > {
>> >         size_t before = n;
>> >         if (should_fail_usercopy())
>> >                 return n;
>> >         if (access_ok(to, n)) {
>> >                 instrument_copy_to_user(to, from, n);
>> >                 n = raw_copy_to_user(to, from, n);
>> >                 if (n == before)
>> >                         pr_err("SARU n still %zu pointer is %lx\n", n, (unsigned long)to);
>> >         }
>> >         return n;
>> > }
>> >
>> > I added the pr_err() there to catch the failure:
>> > [    3.443506] SARU n still 64 pointer is b78db000
>> >
>> > Also I managed to extract the failing portion of iperf3 into something
>> > smaller:
>> >
>> >         int temp;
>> >         char *x;
>> >         ssize_t l;
>> >         FILE *f;
>> >         char template[] = "/blah-XXXXXX";
>> >
>> >         temp = mkstemp(template);
>> >         if (temp < 0)
>> >                 panic("mkstemp");
>> >         if (unlink(template) < 0)
>> >                 panic("unlink");
>> >         if (ftruncate(temp, 0x20000) < 0)
>> >                 panic("ftruncate");
>> >         x = mmap(NULL, 0x20000, PROT_READ|PROT_WRITE, MAP_PRIVATE, temp, 0);
>> >         if (x == MAP_FAILED)
>> >                 panic("mmap");
>> >         f = fopen("/dev/urandom", "rb");
>> >         if (!f)
>> >                 panic("fopen");
>> >         setbuf(f, NULL);
>> >         if (fread(x, 1, 0x20000, f) != 0x20000)
>> >                 panic("fread");
>> 
>> Does that fail for you reliably?
>> 
>> It succeeds for me running under qemu ppce500, though I'm not using your
>> kernel config yet.
>
> Yes, every time without fail, across two systems and two qemu builds.

OK. Joel worked out that it only fails when built with musl, so that's
why it's succeeding for me (built with glibc).

cheers