Re: x86/fpu/xsave: protection key test failures

[Dave Kleikamp]

On 5/26/21 10:25 AM, Babu Moger wrote:
> On 5/25/21 7:20 PM, Dave Hansen wrote:
> > On 5/25/21 5:03 PM, Babu Moger wrote:
> > > > What values do PKRU and the shadow have when the test fails?  Is PKRU 0?
> > > It goes back to default value 0x55555554. The test is expecting it to be
> > > 0. Printed them below.
> > >
> > > test_ptrace_of_child()::1346, pkey_reg: 0x0000000055555554 shadow:
> > > 0000000000000000
> > > protection_keys_64: pkey-helpers.h:127: _read_pkey_reg: Assertion
> > > `pkey_reg == shadow_pkey_reg' failed.
> >
> > That's backwards (shadow vs pkru) from what I was expecting.
> >
> > Can you turn on all the debuging?
> >
> > Just compile with -DDEBUG_LEVEL=5
>
>
> Copied the logs at https://pastebin.com/gtQiHg8Q

I think this failed early due to the debug code. I have a patch that 
gets around this.
From: Dave Kleikamp <dave.kleikamp@xxxxxxxxxx>
Subject: [PATCH] selftests/vm/pkeys: fix assert when DEBUG_LEVEL is set to 2
Date: Mon, 12 Apr 2021 17:13:31 -0500

test_implicit_mprotect_exec_only_memory() hits an assert in
_read_pkey_reg() when DEBUG_LEVEL=2.

test 12 starting with pkey: 2
doing malloc_pkey_anon_huge(size=4096, prot=0x3, pkey=2)
new_nr_records: 1
new_size: 24
sys_mprotect_pkey(0x0x7f44144bb000, 400000, prot=3, pkey=2)
mprotect_pkey(0x7f44144bb000, 400000, prot=0x3, pkey=2) ret: 0
mprotect_pkey()::628, ret: 0 pkey_reg: 0x0000000000000000 shadow: 0x0000000000000000
unaligned protection_keys: pkey-helpers.h:127: _read_pkey_reg: Assertion `pkey_reg == shadow_pkey_reg' failed.

This patch provides one way to fix it. Would it be better to make sure
that shadow_pkey_reg is properly set?

Signed-off-by: Dave Kleikamp <dave.kleikamp@xxxxxxxxxx>
Cc: Ram Pai <linuxram@xxxxxxxxxx>
---
 tools/testing/selftests/vm/protection_keys.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/vm/protection_keys.c b/tools/testing/selftests/vm/protection_keys.c
index fdbb602ecf32..070f6f90dcce 100644
--- a/tools/testing/selftests/vm/protection_keys.c
+++ b/tools/testing/selftests/vm/protection_keys.c
@@ -1449,7 +1449,7 @@ void test_implicit_mprotect_exec_only_memory(int *ptr, u16 pkey)
 	ret = mprotect(p1, PAGE_SIZE, PROT_EXEC);
 	pkey_assert(!ret);
 
-	dprintf2("pkey_reg: %016llx\n", read_pkey_reg());
+	dprintf2("pkey_reg: %016llx\n", __read_pkey_reg());
 
 	/* Make sure this is an *instruction* fault */
 	madvise(p1, PAGE_SIZE, MADV_DONTNEED);
-- 
2.31.1