selftests/powerpc: Test the preservation of FPU and VMX regs across s…

…yscall

Test that the non volatile floating point and Altivec registers get
correctly preserved across the fork() syscall.

fork() works nicely for this purpose, the registers should be the same for
both parent and child

Signed-off-by: Cyril Bur <cyrilbur@gmail.com>
[mpe: Add include guards to basic_asm.h, minor formatting]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

tools/testing/selftests/powerpc/Makefile

@@ -22,7 +22,8 @@ SUB_DIRS = benchmarks 		\
 	   switch_endian	\
 	   syscalls		\
 	   tm			\
-	   vphn
+	   vphn         \
+	   math
 
 endif
 

tools/testing/selftests/powerpc/basic_asm.h

@@ -0,0 +1,70 @@
+#ifndef _SELFTESTS_POWERPC_BASIC_ASM_H
+#define _SELFTESTS_POWERPC_BASIC_ASM_H
+
+#include <ppc-asm.h>
+#include <asm/unistd.h>
+
+#define LOAD_REG_IMMEDIATE(reg,expr) \
+	lis	reg,(expr)@highest;	\
+	ori	reg,reg,(expr)@higher;	\
+	rldicr	reg,reg,32,31;	\
+	oris	reg,reg,(expr)@high;	\
+	ori	reg,reg,(expr)@l;
+
+/*
+ * Note: These macros assume that variables being stored on the stack are
+ * doublewords, while this is usually the case it may not always be the
+ * case for each use case.
+ */
+#if defined(_CALL_ELF) && _CALL_ELF == 2
+#define STACK_FRAME_MIN_SIZE 32
+#define STACK_FRAME_TOC_POS  24
+#define __STACK_FRAME_PARAM(_param)  (32 + ((_param)*8))
+#define __STACK_FRAME_LOCAL(_num_params,_var_num)  ((STACK_FRAME_PARAM(_num_params)) + ((_var_num)*8))
+#else
+#define STACK_FRAME_MIN_SIZE 112
+#define STACK_FRAME_TOC_POS  40
+#define __STACK_FRAME_PARAM(i)  (48 + ((i)*8))
+
+/*
+ * Caveat: if a function passed more than 8 doublewords, the caller will have
+ * made more space... which would render the 112 incorrect.
+ */
+#define __STACK_FRAME_LOCAL(_num_params,_var_num)  (112 + ((_var_num)*8))
+#endif
+
+/* Parameter x saved to the stack */
+#define STACK_FRAME_PARAM(var)    __STACK_FRAME_PARAM(var)
+
+/* Local variable x saved to the stack after x parameters */
+#define STACK_FRAME_LOCAL(num_params,var)    __STACK_FRAME_LOCAL(num_params,var)
+#define STACK_FRAME_LR_POS   16
+#define STACK_FRAME_CR_POS   8
+
+/*
+ * It is very important to note here that _extra is the extra amount of
+ * stack space needed. This space can be accessed using STACK_FRAME_PARAM()
+ * or STACK_FRAME_LOCAL() macros.
+ *
+ * r1 and r2 are not defined in ppc-asm.h (instead they are defined as sp
+ * and toc). Kernel programmers tend to prefer rX even for r1 and r2, hence
+ * %1 and %r2. r0 is defined in ppc-asm.h and therefore %r0 gets
+ * preprocessed incorrectly, hence r0.
+ */
+#define PUSH_BASIC_STACK(_extra) \
+	mflr	r0; \
+	std	r0,STACK_FRAME_LR_POS(%r1); \
+	stdu	%r1,-(_extra + STACK_FRAME_MIN_SIZE)(%r1); \
+	mfcr	r0; \
+	stw	r0,STACK_FRAME_CR_POS(%r1); \
+	std	%r2,STACK_FRAME_TOC_POS(%r1);
+
+#define POP_BASIC_STACK(_extra) \
+	ld	%r2,STACK_FRAME_TOC_POS(%r1); \
+	lwz	r0,STACK_FRAME_CR_POS(%r1); \
+	mtcr	r0; \
+	addi	%r1,%r1,(_extra + STACK_FRAME_MIN_SIZE); \
+	ld	r0,STACK_FRAME_LR_POS(%r1); \
+	mtlr	r0;
+
+#endif /* _SELFTESTS_POWERPC_BASIC_ASM_H */

tools/testing/selftests/powerpc/math/.gitignore

@@ -0,0 +1,2 @@
+fpu_syscall
+vmx_syscall

tools/testing/selftests/powerpc/math/Makefile

@@ -0,0 +1,14 @@
+TEST_PROGS := fpu_syscall vmx_syscall
+
+all: $(TEST_PROGS)
+
+$(TEST_PROGS): ../harness.c
+$(TEST_PROGS): CFLAGS += -O2 -g -pthread -m64 -maltivec
+
+fpu_syscall: fpu_asm.S
+vmx_syscall: vmx_asm.S
+
+include ../../lib.mk
+
+clean:
+	rm -f $(TEST_PROGS) *.o

tools/testing/selftests/powerpc/math/fpu_asm.S

@@ -0,0 +1,161 @@
+/*
+ * Copyright 2015, Cyril Bur, IBM Corp.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include "../basic_asm.h"
+
+#define PUSH_FPU(pos) \
+	stfd	f14,pos(sp); \
+	stfd	f15,pos+8(sp); \
+	stfd	f16,pos+16(sp); \
+	stfd	f17,pos+24(sp); \
+	stfd	f18,pos+32(sp); \
+	stfd	f19,pos+40(sp); \
+	stfd	f20,pos+48(sp); \
+	stfd	f21,pos+56(sp); \
+	stfd	f22,pos+64(sp); \
+	stfd	f23,pos+72(sp); \
+	stfd	f24,pos+80(sp); \
+	stfd	f25,pos+88(sp); \
+	stfd	f26,pos+96(sp); \
+	stfd	f27,pos+104(sp); \
+	stfd	f28,pos+112(sp); \
+	stfd	f29,pos+120(sp); \
+	stfd	f30,pos+128(sp); \
+	stfd	f31,pos+136(sp);
+
+#define POP_FPU(pos) \
+	lfd	f14,pos(sp); \
+	lfd	f15,pos+8(sp); \
+	lfd	f16,pos+16(sp); \
+	lfd	f17,pos+24(sp); \
+	lfd	f18,pos+32(sp); \
+	lfd	f19,pos+40(sp); \
+	lfd	f20,pos+48(sp); \
+	lfd	f21,pos+56(sp); \
+	lfd	f22,pos+64(sp); \
+	lfd	f23,pos+72(sp); \
+	lfd	f24,pos+80(sp); \
+	lfd	f25,pos+88(sp); \
+	lfd	f26,pos+96(sp); \
+	lfd	f27,pos+104(sp); \
+	lfd	f28,pos+112(sp); \
+	lfd	f29,pos+120(sp); \
+	lfd	f30,pos+128(sp); \
+	lfd	f31,pos+136(sp);
+
+# Careful calling this, it will 'clobber' fpu (by design)
+# Don't call this from C
+FUNC_START(load_fpu)
+	lfd	f14,0(r3)
+	lfd	f15,8(r3)
+	lfd	f16,16(r3)
+	lfd	f17,24(r3)
+	lfd	f18,32(r3)
+	lfd	f19,40(r3)
+	lfd	f20,48(r3)
+	lfd	f21,56(r3)
+	lfd	f22,64(r3)
+	lfd	f23,72(r3)
+	lfd	f24,80(r3)
+	lfd	f25,88(r3)
+	lfd	f26,96(r3)
+	lfd	f27,104(r3)
+	lfd	f28,112(r3)
+	lfd	f29,120(r3)
+	lfd	f30,128(r3)
+	lfd	f31,136(r3)
+	blr
+FUNC_END(load_fpu)
+
+FUNC_START(check_fpu)
+	mr r4,r3
+	li	r3,1 # assume a bad result
+	lfd	f0,0(r4)
+	fcmpu	cr1,f0,f14
+	bne	cr1,1f
+	lfd	f0,8(r4)
+	fcmpu	cr1,f0,f15
+	bne	cr1,1f
+	lfd	f0,16(r4)
+	fcmpu	cr1,f0,f16
+	bne	cr1,1f
+	lfd	f0,24(r4)
+	fcmpu	cr1,f0,f17
+	bne	cr1,1f
+	lfd	f0,32(r4)
+	fcmpu	cr1,f0,f18
+	bne	cr1,1f
+	lfd	f0,40(r4)
+	fcmpu	cr1,f0,f19
+	bne	cr1,1f
+	lfd	f0,48(r4)
+	fcmpu	cr1,f0,f20
+	bne	cr1,1f
+	lfd	f0,56(r4)
+	fcmpu	cr1,f0,f21
+	bne	cr1,1f
+	lfd	f0,64(r4)
+	fcmpu	cr1,f0,f22
+	bne	cr1,1f
+	lfd	f0,72(r4)
+	fcmpu	cr1,f0,f23
+	bne	cr1,1f
+	lfd	f0,80(r4)
+	fcmpu	cr1,f0,f24
+	bne	cr1,1f
+	lfd	f0,88(r4)
+	fcmpu	cr1,f0,f25
+	bne	cr1,1f
+	lfd	f0,96(r4)
+	fcmpu	cr1,f0,f26
+	bne	cr1,1f
+	lfd	f0,104(r4)
+	fcmpu	cr1,f0,f27
+	bne	cr1,1f
+	lfd	f0,112(r4)
+	fcmpu	cr1,f0,f28
+	bne	cr1,1f
+	lfd	f0,120(r4)
+	fcmpu	cr1,f0,f29
+	bne	cr1,1f
+	lfd	f0,128(r4)
+	fcmpu	cr1,f0,f30
+	bne	cr1,1f
+	lfd	f0,136(r4)
+	fcmpu	cr1,f0,f31
+	bne	cr1,1f
+	li	r3,0 # Success!!!
+1:	blr
+
+FUNC_START(test_fpu)
+	# r3 holds pointer to where to put the result of fork
+	# r4 holds pointer to the pid
+	# f14-f31 are non volatiles
+	PUSH_BASIC_STACK(256)
+	std	r3,STACK_FRAME_PARAM(0)(sp) # Address of darray
+	std r4,STACK_FRAME_PARAM(1)(sp) # Address of pid
+	PUSH_FPU(STACK_FRAME_LOCAL(2,0))
+
+	bl load_fpu
+	nop
+	li	r0,__NR_fork
+	sc
+
+	# pass the result of the fork to the caller
+	ld	r9,STACK_FRAME_PARAM(1)(sp)
+	std	r3,0(r9)
+
+	ld r3,STACK_FRAME_PARAM(0)(sp)
+	bl check_fpu
+	nop
+
+	POP_FPU(STACK_FRAME_LOCAL(2,0))
+	POP_BASIC_STACK(256)
+	blr
+FUNC_END(test_fpu)

tools/testing/selftests/powerpc/math/fpu_syscall.c

@@ -0,0 +1,90 @@
+/*
+ * Copyright 2015, Cyril Bur, IBM Corp.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ *
+ * This test attempts to see if the FPU registers change across a syscall (fork).
+ */
+
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/syscall.h>
+#include <sys/time.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <stdlib.h>
+
+#include "utils.h"
+
+extern int test_fpu(double *darray, pid_t *pid);
+
+double darray[] = {0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0,
+		     1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0,
+		     2.1};
+
+int syscall_fpu(void)
+{
+	pid_t fork_pid;
+	int i;
+	int ret;
+	int child_ret;
+	for (i = 0; i < 1000; i++) {
+		/* test_fpu will fork() */
+		ret = test_fpu(darray, &fork_pid);
+		if (fork_pid == -1)
+			return -1;
+		if (fork_pid == 0)
+			exit(ret);
+		waitpid(fork_pid, &child_ret, 0);
+		if (ret || child_ret)
+			return 1;
+	}
+
+	return 0;
+}
+
+int test_syscall_fpu(void)
+{
+	/*
+	 * Setup an environment with much context switching
+	 */
+	pid_t pid2;
+	pid_t pid = fork();
+	int ret;
+	int child_ret;
+	FAIL_IF(pid == -1);
+
+	pid2 = fork();
+	/* Can't FAIL_IF(pid2 == -1); because already forked once */
+	if (pid2 == -1) {
+		/*
+		 * Couldn't fork, ensure test is a fail
+		 */
+		child_ret = ret = 1;
+	} else {
+		ret = syscall_fpu();
+		if (pid2)
+			waitpid(pid2, &child_ret, 0);
+		else
+			exit(ret);
+	}
+
+	ret |= child_ret;
+
+	if (pid)
+		waitpid(pid, &child_ret, 0);
+	else
+		exit(ret);
+
+	FAIL_IF(ret || child_ret);
+	return 0;
+}
+
+int main(int argc, char *argv[])
+{
+	return test_harness(test_syscall_fpu, "syscall_fpu");
+
+}