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1bdf22580b
There is a selftest that checks if FPRs are corrupted across a fork, aka clone. It was added as part of the series that optimised the clone path to save the parent's FP state without "giving up" (turning off FP). See commit8792468da5("powerpc: Add the ability to save FPU without giving it up"). The test encodes the assumption that FPRs 0-13 are volatile across the syscall, by only checking the volatile FPRs are not changed by the fork. There was also a comment in the fpu_preempt test alluding to that: The check_fpu function in asm only checks the non volatile registers as it is reused from the syscall test It is true that the function call ABI treats f0-f13 as volatile, however the syscall ABI has since been documented as *not* treating those registers as volatile. See commit7b8845a2a2("powerpc/64: Document the syscall ABI"). So change the test to check all FPRs are not corrupted by the syscall. Note that this currently fails, because save_fpu() etc. do not restore f0/vsr0. Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://msgid.link/20231128132748.1990179-5-mpe@ellerman.id.au
88 lines
1.4 KiB
C
88 lines
1.4 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Copyright 2015, Cyril Bur, IBM Corp.
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*
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* This test attempts to see if the FPU registers change across a syscall (fork).
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*/
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#include <stdio.h>
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#include <unistd.h>
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#include <sys/syscall.h>
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#include <sys/time.h>
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#include <sys/types.h>
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#include <sys/wait.h>
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#include <stdlib.h>
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#include "utils.h"
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#include "fpu.h"
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extern int test_fpu(double *darray, pid_t *pid);
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double darray[32];
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int syscall_fpu(void)
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{
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pid_t fork_pid;
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int i;
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int ret;
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int child_ret;
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randomise_darray(darray, ARRAY_SIZE(darray));
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for (i = 0; i < 1000; i++) {
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/* test_fpu will fork() */
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ret = test_fpu(darray, &fork_pid);
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if (fork_pid == -1)
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return -1;
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if (fork_pid == 0)
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exit(ret);
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waitpid(fork_pid, &child_ret, 0);
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if (ret || child_ret)
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return 1;
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}
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return 0;
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}
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int test_syscall_fpu(void)
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{
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/*
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* Setup an environment with much context switching
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*/
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pid_t pid2;
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pid_t pid = fork();
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int ret;
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int child_ret;
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FAIL_IF(pid == -1);
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pid2 = fork();
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/* Can't FAIL_IF(pid2 == -1); because already forked once */
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if (pid2 == -1) {
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/*
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* Couldn't fork, ensure test is a fail
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*/
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child_ret = ret = 1;
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} else {
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ret = syscall_fpu();
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if (pid2)
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waitpid(pid2, &child_ret, 0);
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else
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exit(ret);
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}
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ret |= child_ret;
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if (pid)
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waitpid(pid, &child_ret, 0);
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else
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exit(ret);
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FAIL_IF(ret || child_ret);
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return 0;
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}
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int main(int argc, char *argv[])
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{
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return test_harness(test_syscall_fpu, "syscall_fpu");
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}
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