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Provide and clarify the existing ranges and what you should expect.
Fix the gen_test_kallsyms.sh script to accept different ranges.
Fixes: 84b4a51fce4ccc66 ("selftests: add new kallsyms selftests")
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
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The current arrangement will have the test modules rebuilt on
any make without having the script or code actually change.
Take Masahiro Yamada's suggested fix and cleanups on the Makefile
to fix this.
Suggested-by: Masahiro Yamada <masahiroy@kernel.org>
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Fixes: 84b4a51fce4ccc66 ("selftests: add new kallsyms selftests")
Closes: https://lore.kernel.org/all/CAK7LNATRDODmfz1tE=inV-DQqPA4G9vKH+38zMbaGdpTuFWZFw@mail.gmail.com/T/#me6c8f98e82acbee6e75a31b34bbb543eb4940b15
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
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Use 0 for the values as we use them for the return value on init
to keep the test modules simple. This fixes a splat reported
do_init_module: 'test_kallsyms_b'->init suspiciously returned 255, it should follow 0/-E convention
do_init_module: loading module anyway...
CPU: 5 UID: 0 PID: 1873 Comm: modprobe Not tainted 6.12.0-rc3+ #4
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 2024.08-1 09/18/2024
Call Trace:
<TASK>
dump_stack_lvl+0x56/0x80
do_init_module.cold+0x21/0x26
init_module_from_file+0x88/0xf0
idempotent_init_module+0x108/0x300
__x64_sys_finit_module+0x5a/0xb0
do_syscall_64+0x4b/0x110
entry_SYSCALL_64_after_hwframe+0x76/0x7e
RIP: 0033:0x7f4f3a718839
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff>
RSP: 002b:00007fff97d1a9e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000139
RAX: ffffffffffffffda RBX: 000055b94001ab90 RCX: 00007f4f3a718839
RDX: 0000000000000000 RSI: 000055b910e68a10 RDI: 0000000000000004
RBP: 0000000000000000 R08: 00007f4f3a7f1b20 R09: 000055b94001c5b0
R10: 0000000000000040 R11: 0000000000000246 R12: 000055b910e68a10
R13: 0000000000040000 R14: 000055b94001ad60 R15: 0000000000000000
</TASK>
do_init_module: 'test_kallsyms_b'->init suspiciously returned 255, it should follow 0/-E convention
do_init_module: loading module anyway...
CPU: 1 UID: 0 PID: 1884 Comm: modprobe Not tainted 6.12.0-rc3+ #4
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 2024.08-1 09/18/2024
Call Trace:
<TASK>
dump_stack_lvl+0x56/0x80
do_init_module.cold+0x21/0x26
init_module_from_file+0x88/0xf0
idempotent_init_module+0x108/0x300
__x64_sys_finit_module+0x5a/0xb0
do_syscall_64+0x4b/0x110
entry_SYSCALL_64_after_hwframe+0x76/0x7e
RIP: 0033:0x7ffaa5d18839
Reported-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
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The newly added test script creates modules that are lacking
a description line in order to build cleanly:
WARNING: modpost: missing MODULE_DESCRIPTION() in lib/tests/module/test_kallsyms_a.o
WARNING: modpost: missing MODULE_DESCRIPTION() in lib/tests/module/test_kallsyms_b.o
WARNING: modpost: missing MODULE_DESCRIPTION() in lib/tests/module/test_kallsyms_c.o
WARNING: modpost: missing MODULE_DESCRIPTION() in lib/tests/module/test_kallsyms_d.o
Fixes: 84b4a51fce4c ("selftests: add new kallsyms selftests")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
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We lack find_symbol() selftests, so add one. This let's us stress test
improvements easily on find_symbol() or optimizations. It also inherently
allows us to test the limits of kallsyms on Linux today.
We test a pathalogical use case for kallsyms by introducing modules
which are automatically written for us with a larger number of symbols.
We have 4 kallsyms test modules:
A: has KALLSYSMS_NUMSYMS exported symbols
B: uses one of A's symbols
C: adds KALLSYMS_SCALE_FACTOR * KALLSYSMS_NUMSYMS exported
D: adds 2 * the symbols than C
By using anything much larger than KALLSYSMS_NUMSYMS as 10,000 and
KALLSYMS_SCALE_FACTOR of 8 we segfault today. So we're capped at
around 160000 symbols somehow today. We can inpsect that issue at
our leasure later, but for now the real value to this test is that
this will easily allow us to test improvements on find_symbol().
We want to enable this test on allyesmodconfig builds so we can't
use this combination, so instead just use a safe value for now and
be informative on the Kconfig symbol documentation about where our
thresholds are for testers. We default then to KALLSYSMS_NUMSYMS of
just 100 and KALLSYMS_SCALE_FACTOR of 8.
On x86_64 we can use perf, for other architectures we just use 'time'
and allow for customizations. For example a future enhancements could
be done for parisc to check for unaligned accesses which triggers a
special special exception handler assembler code inside the kernel.
The negative impact on performance is so large on parisc that it
keeps track of its accesses on /proc/cpuinfo as UAH:
IRQ: CPU0 CPU1
3: 1332 0 SuperIO ttyS0
7: 1270013 0 SuperIO pata_ns87415
64: 320023012 320021431 CPU timer
65: 17080507 20624423 CPU IPI
UAH: 10948640 58104 Unaligned access handler traps
While at it, this tidies up lib/ test modules to allow us to have
a new directory for them. The amount of test modules under lib/
is insane.
This should also hopefully showcase how to start doing basic
self module writing code, which may be more useful for more complex
cases later in the future.
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
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