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4185b3b927
Add a selftest for the usage of FPU code in kernel mode.
Currently only implemented for x86. In the future, kernel FPU testing
could be unified between the different architectures supporting it.
[ bp:
- Split out from a conglomerate patch, put comments over statements.
- run the test only on debugfs write.
- Add bare-minimum run_test_fpu.sh, run 1000 iterations on all CPUs
by default.
- Add conditionally -msse2 so that clang doesn't generate library
calls.
- Use cc-option to detect gcc 7.1 not supporting -mpreferred-stack-boundary=3 (amluto).
- Document stuff so that we don't forget.
- Fix:
ld: lib/test_fpu.o: in function `test_fpu_get':
>> test_fpu.c:(.text+0x16e): undefined reference to `__sanitizer_cov_trace_cmpd'
>> ld: test_fpu.c:(.text+0x1a7): undefined reference to `__sanitizer_cov_trace_cmpd'
ld: test_fpu.c:(.text+0x1e0): undefined reference to `__sanitizer_cov_trace_cmpd'
]
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Petteri Aimonen <jpa@git.mail.kapsi.fi>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Link: https://lkml.kernel.org/r/20200624114646.28953-3-bp@alien8.de
62 lines
1.5 KiB
C
62 lines
1.5 KiB
C
// SPDX-License-Identifier: GPL-2.0+
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/* This testcase operates with the test_fpu kernel driver.
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* It modifies the FPU control register in user mode and calls the kernel
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* module to perform floating point operations in the kernel. The control
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* register value should be independent between kernel and user mode.
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*/
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#define _GNU_SOURCE
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#include <stdio.h>
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#include <errno.h>
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#include <string.h>
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#include <fenv.h>
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#include <unistd.h>
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#include <fcntl.h>
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const char *test_fpu_path = "/sys/kernel/debug/selftest_helpers/test_fpu";
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int main(void)
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{
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char dummy[1];
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int fd = open(test_fpu_path, O_RDONLY);
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if (fd < 0) {
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printf("[SKIP]\tcan't access %s: %s\n",
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test_fpu_path, strerror(errno));
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return 0;
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}
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if (read(fd, dummy, 1) < 0) {
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printf("[FAIL]\taccess with default rounding mode failed\n");
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return 1;
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}
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fesetround(FE_DOWNWARD);
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if (read(fd, dummy, 1) < 0) {
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printf("[FAIL]\taccess with downward rounding mode failed\n");
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return 2;
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}
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if (fegetround() != FE_DOWNWARD) {
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printf("[FAIL]\tusermode rounding mode clobbered\n");
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return 3;
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}
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/* Note: the tests up to this point are quite safe and will only return
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* an error. But the exception mask setting can cause misbehaving kernel
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* to crash.
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*/
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feclearexcept(FE_ALL_EXCEPT);
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feenableexcept(FE_ALL_EXCEPT);
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if (read(fd, dummy, 1) < 0) {
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printf("[FAIL]\taccess with fpu exceptions unmasked failed\n");
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return 4;
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}
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if (fegetexcept() != FE_ALL_EXCEPT) {
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printf("[FAIL]\tusermode fpu exception mask clobbered\n");
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return 5;
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}
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printf("[OK]\ttest_fpu\n");
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return 0;
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}
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