Re: [PATCH 3/4] selftests/livepatch: more verification in test-klp-shadow-vars
From: Petr Mladek <pmladek@suse.com>
Date: 2020-06-02 12:36:00
Also in:
linux-kselftest
On Thu 2020-05-28 09:48:48, Yannick Cote wrote:
quoted hunk ↗ jump to hunk
This change makes the test feel more familiar with narrowing to a typical usage by operating on a number of identical structure instances and populating the same two new shadow variables symmetrically while keeping the same testing and verification criteria for the extra variables.@@ -157,122 +165,96 @@ struct test_object { static int test_klp_shadow_vars_init(void) { - struct test_object obj1, obj2, obj3; - char nfield1, nfield2, *pnfield1, *pnfield2, **sv1, **sv2; - int nfield3, nfield4, *pnfield3, *pnfield4, **sv3, **sv4; + struct test_object objs[NUM_OBJS]; + char nfields1[NUM_OBJS], *pnfields1[NUM_OBJS], **sv1[NUM_OBJS]; + char *pndup[NUM_OBJS]; + int nfields2[NUM_OBJS], *pnfields2[NUM_OBJS], **sv2[NUM_OBJS]; void **sv;
+ /* pass 1: init & alloc a char+int pair of svars for each objs */
+ for (i = 0; i < NUM_OBJS; i++) {
+ pnfields1[i] = &nfields1[i];
+ pnfields2[i] = &nfields2[i];
+ ptr_id(pnfields1[i]);
+ ptr_id(pnfields2[i]);
+
+ /* alloc a few svars with different <obj> and <id>. */
+ sv1[i] = shadow_alloc(&objs[i], SV_ID1, sizeof(pnfields1[i]),
+ GFP_KERNEL, shadow_ctor, &pnfields1[i]);
+ if (!sv1[i])
+ return -ENOMEM;Please, put empty line here to delimit ID1 ID2 handling a bit. Also I have got a bit more predictable PTR IDs when I moved pnfields2 initialization here: pnfields2[i] = &nfields2[i]; ptr_id(pnfields2[i]);
+ sv2[i] = shadow_alloc(&objs[i], SV_ID2, sizeof(pnfields2[i]), + GFP_KERNEL, shadow_ctor, &pnfields2[i]); + if (!sv2[i]) + return -ENOMEM; + }
It looks like: test_klp_shadow_vars: klp_shadow_alloc(obj=PTR1, id=0x1234, size=8, gfp_flags=GFP_KERNEL), ctor=PTR4, ctor_data=PTR2 = PTR3 test_klp_shadow_vars: shadow_ctor: PTR6 -> PTR5 test_klp_shadow_vars: klp_shadow_alloc(obj=PTR1, id=0x1235, size=8, gfp_flags=GFP_KERNEL), ctor=PTR4, ctor_data=PTR5 = PTR6 test_klp_shadow_vars: shadow_ctor: PTR8 -> PTR7 test_klp_shadow_vars: klp_shadow_alloc(obj=PTR9, id=0x1234, size=8, gfp_flags=GFP_KERNEL), ctor=PTR4, ctor_data=PTR7 = PTR8 test_klp_shadow_vars: shadow_ctor: PTR11 -> PTR10 instead of test_klp_shadow_vars: klp_shadow_alloc(obj=PTR1, id=0x1234, size=8, gfp_flags=GFP_KERNEL), ctor=PTR5, ctor_data=PTR2 = PTR4 test_klp_shadow_vars: shadow_ctor: PTR6 -> PTR3 test_klp_shadow_vars: klp_shadow_alloc(obj=PTR1, id=0x1235, size=8, gfp_flags=GFP_KERNEL), ctor=PTR5, ctor_data=PTR3 = PTR6 test_klp_shadow_vars: shadow_ctor: PTR9 -> PTR7 test_klp_shadow_vars: klp_shadow_alloc(obj=PTR10, id=0x1234, size=8, gfp_flags=GFP_KERNEL), ctor=PTR5, ctor_data=PTR7 = PTR9 test_klp_shadow_vars: shadow_ctor: PTR11 -> PTR8 By other words, the PTR IDs are incrementing by the same offset for both SV_ID1 and SV_ID2. It looks better even later in the log.
+ /* pass 3: verify that 'get_of_alloc' returns already allocated svars */
+ for (i = 0; i < NUM_OBJS; i++) {
+ sv = shadow_get_or_alloc(&objs[i], SV_ID1, sizeof(pndup[i]),
+ GFP_KERNEL, shadow_ctor, &pndup[i]);
First, the test failed on my system. I have got:
# --- expected
# +++ result
# @@ -27,20 +27,20 @@ test_klp_shadow_vars: klp_shadow_get(obj
# test_klp_shadow_vars: got expected PTR16 -> PTR13 result
# test_klp_shadow_vars: klp_shadow_get_or_alloc(obj=PTR1, id=0x1234, size=8, gfp_flags=GFP_KERNEL), ctor=PTR5, ctor_data=PTR17 = PTR4
# test_klp_shadow_vars: got expected PTR4 -> PTR2 result
# -test_klp_shadow_vars: klp_shadow_get_or_alloc(obj=PTR10, id=0x1234, size=8, gfp_flags=GFP_KERNEL), ctor=PTR5, ctor_data=PTR18 = PTR9
# +test_klp_shadow_vars: klp_shadow_get_or_alloc(obj=PTR10, id=0x1234, size=8, gfp_flags=GFP_KERNEL), ctor=PTR5, ctor_data=PTR0 = PTR9
# test_klp_shadow_vars: got expected PTR9 -> PTR7 result
# -test_klp_shadow_vars: klp_shadow_get_or_alloc(obj=PTR15, id=0x1234, size=8, gfp_flags=GFP_KERNEL), ctor=PTR5, ctor_data=PTR19 = PTR14
# +test_klp_shadow_vars: klp_shadow_get_or_alloc(obj=PTR15, id=0x1234, size=8, gfp_flags=GFP_KERNEL), ctor=PTR5, ctor_data=PTR0 = PTR14
In my build, it uses PTR0 for ctor_data. But it takes a new pointer in
your case.
It is because pndup[i] was not initialized. Note that it is the value (data)
that is stored in the shadow variable.
The solution is to initialize pndup[i] here:
pndup[i] = &nfields1[i];
ptr_id(pndup[i]);
2nd problem, klp_shadow_get_or_alloc() is always
called for already allocated values now. It would be great to test
that they can be created when they are not available.
A solution might be to allocate half of the variables by
shadow_alloc() and the other half with shadow_get_or_alloc().
I would do this in the first cycle, using:
if (i % 2) {
sv1[i] = shadow_alloc(&objs[i], SV_ID1, sizeof(pnfields1[i]),
GFP_KERNEL, shadow_ctor, &pnfields1[i]);
} else {
sv1[i] = shadow_get_or_alloc(&objs[i], SV_ID1, sizeof(pnfields1[i]),
GFP_KERNEL, shadow_ctor, &pnfields1[i]);
}
Otherwise, it is a nice clean up.
Best Regards,
Petr