[PATCH 3/3] arm: vectors support

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Add support for tests to use exception handlers.

Signed-off-by: Andrew Jones <drjones@xxxxxxxxxx>
---
 arm/boot.c            | 128 ++++++++++++++++++++++++++++++++++++--
 arm/cstart.S          | 168 ++++++++++++++++++++++++++++++++++++++++++++++++--
 arm/flat.lds          |   7 ++-
 arm/unittests.cfg     |  19 ++++++
 config/config-arm.mak |   1 +
 lib/arm/processor.c   |  97 +++++++++++++++++++++++++++++
 lib/arm/processor.h   |  29 +++++++++
 lib/arm/sysinfo.h     |   4 ++
 lib/libcflat.h        |   2 +
 9 files changed, 443 insertions(+), 12 deletions(-)
 create mode 100644 lib/arm/processor.c
 create mode 100644 lib/arm/processor.h

diff --git a/arm/boot.c b/arm/boot.c
index dc42dfc232366..fd3e3412669fe 100644
--- a/arm/boot.c
+++ b/arm/boot.c
@@ -1,17 +1,133 @@
 #include "libcflat.h"
 #include "test_util.h"
 #include "arm/sysinfo.h"
+#include "arm/ptrace.h"
+#include "arm/processor.h"
+#include "arm/asm-offsets.h"
+
+static struct pt_regs expected_regs;
+/* NOTE: update clobber list if passed insns needs more than r0,r1 */
+#define test_excptn(pre_insns, excptn_insn, post_insns)		\
+	asm volatile(						\
+		pre_insns "\n"					\
+		"mov	r0, %0\n"				\
+		"stmia	r0, { r0-lr }\n"			\
+		"mrs	r1, cpsr\n"				\
+		"str	r1, [r0, #" __stringify(S_PSR) "]\n"	\
+		"mov	r1, #-1\n"				\
+		"str	r1, [r0, #" __stringify(S_OLD_R0) "]\n"	\
+		"add	r1, pc, #8\n"				\
+		"str	r1, [r0, #" __stringify(S_R1) "]\n"	\
+		"str	r1, [r0, #" __stringify(S_PC) "]\n"	\
+		excptn_insn "\n"				\
+		post_insns "\n"					\
+	:: "r" (&expected_regs) : "r0", "r1")
+
+#define svc_mode() ((get_cpsr() & MODE_MASK) == SVC_MODE)
+
+static bool check_regs(struct pt_regs *regs)
+{
+	unsigned i;
+
+	if (!svc_mode())
+		return false;
+
+	for (i = 0; i < ARRAY_SIZE(regs->uregs); ++i)
+		if (regs->uregs[i] != expected_regs.uregs[i])
+			return false;
+
+	return true;
+}
+
+static bool und_works;
+static void und_handler(struct pt_regs *regs)
+{
+	if (check_regs(regs))
+		und_works = true;
+}
+
+static bool check_und(void)
+{
+	handle_exception(EXCPTN_UND, und_handler);
+
+	/* issue an instruction to a coprocessor we don't have */
+	test_excptn("", "mcr p2, 0, r0, c0, c0", "");
+
+	handle_exception(EXCPTN_UND, NULL);
+
+	return und_works;
+}
+
+static bool svc_works;
+static void svc_handler(struct pt_regs *regs)
+{
+	u32 svc = *(u32 *)(regs->ARM_pc - 4) & 0xffffff;
+
+	if (!user_mode(regs)) {
+		/*
+		 * When issuing an svc from supervisor mode lr_svc will
+		 * get corrupted. So before issuing the svc, callers must
+		 * always push it on the stack. We pushed it to offset 4.
+		 */
+		regs->ARM_lr = *(unsigned long *)(regs->ARM_sp + 4);
+	}
+
+	if (check_regs(regs) && svc == 123)
+		svc_works = true;
+}
+
+static bool check_svc(void)
+{
+	handle_exception(EXCPTN_SVC, svc_handler);
+
+	if (svc_mode()) {
+		/*
+		 * An svc from supervisor mode will corrupt lr_svc and
+		 * spsr_svc. We need to save/restore them separately.
+		 */
+		test_excptn(
+			"mrs	r0, spsr\n"
+			"push	{ r0,lr }\n",
+			"svc	#123\n",
+			"pop	{ r0,lr }\n"
+			"msr	spsr, r0\n"
+		);
+	} else {
+		test_excptn("", "svc #123", "");
+	}
+
+	handle_exception(EXCPTN_SVC, NULL);
+
+	return svc_works;
+}
+
+static void check_vectors(void)
+{
+	int ret = check_und() && check_svc() ? PASS : FAIL;
+	exit(ret);
+}
 
 int main(int argc, char **argv)
 {
 	int ret = FAIL;
 
-	if (argc >= 1) {
-		--argc;
-		if (!strcmp(argv[0], "mem") && enough_args(argc, 1)) {
-			if (check_u32(mem32.size/1024/1024, 10, argv[1]))
-				ret = PASS;
-		}
+	if (!enough_args(argc, 1))
+		return ret;
+
+	if (strcmp(argv[0], "mem") == 0 && enough_args(argc, 2)) {
+
+		if (check_u32(mem32.size/1024/1024, 10, argv[1]))
+			ret = PASS;
+
+	} else if (strcmp(argv[0], "vectors") == 0) {
+
+		check_vectors(); /* doesn't return */
+
+	} else if (strcmp(argv[0], "vectors_usr") == 0) {
+
+		start_usr(check_vectors); /* doesn't return */
+
 	}
+
 	return ret;
 }
diff --git a/arm/cstart.S b/arm/cstart.S
index 05d4bb5becaa0..951c3c2768076 100644
--- a/arm/cstart.S
+++ b/arm/cstart.S
@@ -1,5 +1,7 @@
-
-#define CR_B	(1 << 7)	/* Big endian */
+#define __ASSEMBLY__
+#include "arm/asm-offsets.h"
+#include "arm/ptrace.h"
+#include "arm/cp15.h"
 
 .arm
 
@@ -9,13 +11,23 @@
 start:
 	/* bootloader params are in r0-r2 */
 	ldr	sp, =stacktop
+	mrc	p15, 0, r8, c1, c0, 0	@ r8 := sctrl
 
-	mrc	p15, 0, r8, c1, c0, 0	@r8 = sctrl
-	ands	r3, r8, #CR_B		@set BE, if necessary
+	/* set BE, if necessary */
+	tst	r8, #CR_B
 	ldrne	r3, =cpu_is_be
 	movne	r4, #1
 	strne	r4, [r3]
-	bl	setup			@complete setup
+
+	/* set up vector table */
+	bl	exceptions_init
+	bic	r8, #CR_V		@ sctrl.V := 0
+	mcr	p15, 0, r8, c1, c0, 0
+	ldr	r3, =vector_table	@ vbar := vector_table
+	mcr	p15, 0, r3, c12, c0, 0
+
+	/* complete setup */
+	bl	setup
 
 	/* start the test */
 	ldr	r0, =__argc
@@ -25,6 +37,25 @@ start:
 	bl	exit
 	b	halt
 
+exceptions_init:
+	mrs	r3, cpsr
+	ldr	r4, =exception_stacks
+		/* first frame for svc mode */
+	msr	cpsr_c, #(UND_MODE | PSR_I_BIT | PSR_F_BIT)
+	add	r4, #S_FRAME_SIZE
+	mov	sp, r4
+	msr	cpsr_c, #(ABT_MODE | PSR_I_BIT | PSR_F_BIT)
+	add	r4, #S_FRAME_SIZE
+	mov	sp, r4
+	msr	cpsr_c, #(IRQ_MODE | PSR_I_BIT | PSR_F_BIT)
+	add	r4, #S_FRAME_SIZE
+	mov	sp, r4
+	msr	cpsr_c, #(FIQ_MODE | PSR_I_BIT | PSR_F_BIT)
+	add	r4, #S_FRAME_SIZE
+	mov	sp, r4
+	msr	cpsr_cxsf, r3	@ back to svc mode
+	mov	pc, lr
+
 .text
 
 .globl halt
@@ -32,6 +63,133 @@ halt:
 1:	wfi
 	b	1b
 
+/*
+ * Vector stubs.
+ * Simplified version of the Linux kernel implementation
+ *   arch/arm/kernel/entry-armv.S
+ *
+ * Each mode has an S_FRAME_SIZE sized stack initialized
+ * in exceptions_init
+ */
+.macro vector_stub, name, vec, mode, correction=0
+.align 5
+vector_\name:
+.if \correction
+	sub	lr, lr, #\correction
+.endif
+	/*
+	 * Save r0, r1, lr_<exception> (parent PC)
+	 * and spsr_<exception> (parent CPSR)
+	 */
+	str	r0, [sp, #S_R0]
+	str	r1, [sp, #S_R1]
+	str	lr, [sp, #S_PC]
+	mrs	r0, spsr
+	str	r0, [sp, #S_PSR]
+
+	/* Prepare for SVC32 mode. */
+	mrs	r0, cpsr
+	bic	r0, #MODE_MASK
+	orr	r0, #SVC_MODE
+	msr	spsr_cxsf, r0
+
+	/* Branch to handler in SVC mode */
+	mov	r0, #\vec
+	mov	r1, sp
+	ldr	lr, =vector_common
+	movs	pc, lr
+.endm
+
+vector_stub 	rst,	0, UND_MODE
+vector_stub	und,	1, UND_MODE
+vector_stub	pabt,	3, ABT_MODE, 4
+vector_stub	dabt,	4, ABT_MODE, 8
+vector_stub	irq,	6, IRQ_MODE, 4
+vector_stub	fiq,	7, FIQ_MODE, 4
+
+.align 5
+vector_svc:
+	/*
+	 * Save r0, r1, lr_<exception> (parent PC)
+	 * and spsr_<exception> (parent CPSR)
+	 */
+	push	{ r1 }
+	ldr	r1, =exception_stacks
+	str	r0, [r1, #S_R0]
+	pop	{ r0 }
+	str	r0, [r1, #S_R1]
+	str	lr, [r1, #S_PC]
+	mrs	r0, spsr
+	str	r0, [r1, #S_PSR]
+
+	/* Branch to handler, still in SVC mode */
+	mov	r0, #2
+	ldr	lr, =vector_common
+	mov	pc, lr
+
+vector_common:
+	/* make room for pt_regs */
+	sub	sp, #S_FRAME_SIZE
+	tst	sp, #4			@ check stack alignment
+	subne	sp, #4
+
+	/* store registers r0-r12 */
+	stmia	sp, { r0-r12 }		@ stored wrong r0 and r1, fix later
+
+	/* get registers saved in the stub */
+	ldr	r2, [r1, #S_R0]		@ r0
+	ldr	r3, [r1, #S_R1]		@ r1
+	ldr	r4, [r1, #S_PC] 	@ lr_<exception> (parent PC)
+	ldr	r5, [r1, #S_PSR]	@ spsr_<exception> (parent CPSR)
+
+	/* fix r0 and r1 */
+	str	r2, [sp, #S_R0]
+	str	r3, [sp, #S_R1]
+
+	/* store sp_svc, if we were in usr mode we'll fix this later */
+	add	r2, sp, #S_FRAME_SIZE
+	addne	r2, #4			@ stack wasn't aligned
+	str	r2, [sp, #S_SP]
+
+	str	lr, [sp, #S_LR]		@ store lr_svc, fix later for usr mode
+	str	r4, [sp, #S_PC]		@ store lr_<exception>
+	str	r5, [sp, #S_PSR]	@ store spsr_<exception>
+
+	/* set ORIG_r0 */
+	mov	r2, #-1
+	str	r2, [sp, #S_OLD_R0]
+
+	/* if we were in usr mode then we need sp_usr and lr_usr instead */
+	and	r1, r5, #MODE_MASK
+	cmp	r1, #USR_MODE
+	bne	1f
+	add	r1, sp, #S_SP
+	stmia	r1, { sp,lr }^
+
+	/* Call the handler. r0 is the vector number, r1 := pt_regs */
+1:	mov	r1, sp
+	bl	do_handle_exception
+
+	/* return from exception */
+	msr	spsr_cxsf, r5
+	ldmia	sp, { r0-pc }^
+
+.align 5
+vector_addrexcptn:
+	b	vector_addrexcptn
+
+.section .text.ex
+.align 5
+vector_table:
+	b	vector_rst
+	b	vector_und
+	b	vector_svc
+	b	vector_pabt
+	b	vector_dabt
+	b	vector_addrexcptn	@ should never happen
+	b	vector_irq
+	b	vector_fiq
+
 .data
 
 .globl cpu_is_be
diff --git a/arm/flat.lds b/arm/flat.lds
index 3e5d72e24989b..ee9fc0ab79abc 100644
--- a/arm/flat.lds
+++ b/arm/flat.lds
@@ -3,7 +3,12 @@ SECTIONS
 {
     .text : { *(.init) *(.text) *(.text.*) }
     . = ALIGN(4K);
-    .data : { *(.data) }
+    .data : {
+        exception_stacks = .;
+        . += 4K;
+        exception_stacks_end = .;
+        *(.data)
+    }
     . = ALIGN(16);
     .rodata : { *(.rodata) }
     . = ALIGN(16);
diff --git a/arm/unittests.cfg b/arm/unittests.cfg
index c328657b7944a..3a42bbeb3cb38 100644
--- a/arm/unittests.cfg
+++ b/arm/unittests.cfg
@@ -6,6 +6,25 @@
 # arch = arm/arm64 # Only if the test case works only on one of them
 # groups = group1 group2 # Used to identify test cases with run_tests -g ...
 
+#
+# The boot group tests the initial booting of a guest, as well as
+# the test framework itself.
+#
+
+# Test bootinfo reading; configured mem-size should equal expected mem-size
 [boot_info]
 file = boot.flat
 extra_params = -m 256 -append 'mem 256'
+groups = boot
+
+# Test vector setup and exception handling (svc mode).
+[boot_vectors]
+file = boot.flat
+extra_params = -append 'vectors'
+groups = boot
+
+# Test vector setup and exception handling (usr mode).
+[boot_vectors_usr]
+file = boot.flat
+extra_params = -append 'vectors_usr'
+groups = boot
diff --git a/config/config-arm.mak b/config/config-arm.mak
index 173e606fbe64c..4a05519f495c5 100644
--- a/config/config-arm.mak
+++ b/config/config-arm.mak
@@ -20,6 +20,7 @@ cflatobjs += \
 	lib/virtio-testdev.o \
 	lib/test_util.o \
 	lib/arm/io.o \
+	lib/arm/processor.o \
 	lib/arm/setup.o
 
 libeabi := lib/arm/libeabi.a
diff --git a/lib/arm/processor.c b/lib/arm/processor.c
new file mode 100644
index 0000000000000..d37231df19690
--- /dev/null
+++ b/lib/arm/processor.c
@@ -0,0 +1,97 @@
+#include "libcflat.h"
+#include "arm/sysinfo.h"
+#include "arm/ptrace.h"
+#include "heap.h"
+
+static const char *processor_modes[] = {
+	"USER_26", "FIQ_26" , "IRQ_26" , "SVC_26" ,
+	"UK4_26" , "UK5_26" , "UK6_26" , "UK7_26" ,
+	"UK8_26" , "UK9_26" , "UK10_26", "UK11_26",
+	"UK12_26", "UK13_26", "UK14_26", "UK15_26",
+	"USER_32", "FIQ_32" , "IRQ_32" , "SVC_32" ,
+	"UK4_32" , "UK5_32" , "UK6_32" , "ABT_32" ,
+	"UK8_32" , "UK9_32" , "UK10_32", "UND_32" ,
+	"UK12_32", "UK13_32", "UK14_32", "SYS_32"
+};
+
+static char *vector_names[] = {
+	"rst", "und", "svc", "pabt", "dabt", "addrexcptn", "irq", "fiq"
+};
+
+void show_regs(struct pt_regs *regs)
+{
+	unsigned long flags;
+	char buf[64];
+
+	printf("pc : [<%08lx>]    lr : [<%08lx>]    psr: %08lx\n"
+	       "sp : %08lx  ip : %08lx  fp : %08lx\n",
+		regs->ARM_pc, regs->ARM_lr, regs->ARM_cpsr,
+		regs->ARM_sp, regs->ARM_ip, regs->ARM_fp);
+	printf("r10: %08lx  r9 : %08lx  r8 : %08lx\n",
+		regs->ARM_r10, regs->ARM_r9, regs->ARM_r8);
+	printf("r7 : %08lx  r6 : %08lx  r5 : %08lx  r4 : %08lx\n",
+		regs->ARM_r7, regs->ARM_r6, regs->ARM_r5, regs->ARM_r4);
+	printf("r3 : %08lx  r2 : %08lx  r1 : %08lx  r0 : %08lx\n",
+		regs->ARM_r3, regs->ARM_r2, regs->ARM_r1, regs->ARM_r0);
+
+	flags = regs->ARM_cpsr;
+	buf[0] = flags & PSR_N_BIT ? 'N' : 'n';
+	buf[1] = flags & PSR_Z_BIT ? 'Z' : 'z';
+	buf[2] = flags & PSR_C_BIT ? 'C' : 'c';
+	buf[3] = flags & PSR_V_BIT ? 'V' : 'v';
+	buf[4] = '\0';
+
+	printf("Flags: %s  IRQs o%s  FIQs o%s  Mode %s\n",
+		buf, interrupts_enabled(regs) ? "n" : "ff",
+		fast_interrupts_enabled(regs) ? "n" : "ff",
+		processor_modes[processor_mode(regs)]);
+
+	if (!user_mode(regs)) {
+		unsigned int ctrl, transbase, dac;
+		asm volatile(
+			"mrc p15, 0, %0, c1, c0\n"
+			"mrc p15, 0, %1, c2, c0\n"
+			"mrc p15, 0, %2, c3, c0\n"
+		: "=r" (ctrl), "=r" (transbase), "=r" (dac));
+		printf("Control: %08x  Table: %08x  DAC: %08x\n",
+			ctrl, transbase, dac);
+	}
+}
+
+static void (*exception_handlers[8])(struct pt_regs *regs);
+
+void handle_exception(u8 v, void (*func)(struct pt_regs *regs))
+{
+	if (v < 8)
+		exception_handlers[v] = func;
+}
+
+void do_handle_exception(u8 v, struct pt_regs *regs)
+{
+	if (v < 8 && exception_handlers[v]) {
+		exception_handlers[v](regs);
+		return;
+	}
+
+	if (v < 8)
+		printf("Unhandled exception %d (%s)\n", v, vector_names[v]);
+	else
+		printf("%s called with vector=%d\n", __func__, v);
+
+	printf("Exception frame registers:\n");
+	show_regs(regs);
+	exit(EINTR);
+}
+
+void start_usr(void (*func)(void))
+{
+	void *sp_usr = alloc_page() + PAGE_SIZE;
+	asm volatile(
+		"mrs	r0, cpsr\n"
+		"bic	r0, #" __stringify(MODE_MASK) "\n"
+		"orr	r0, #" __stringify(USR_MODE) "\n"
+		"msr	cpsr_c, r0\n"
+		"mov	sp, %0\n"
+		"mov	pc, %1\n"
+	:: "r" (sp_usr), "r" (func) : "r0");
+}
diff --git a/lib/arm/processor.h b/lib/arm/processor.h
new file mode 100644
index 0000000000000..66cc7363a2f10
--- /dev/null
+++ b/lib/arm/processor.h
@@ -0,0 +1,29 @@
+#ifndef _ARM_PROCESSOR_H_
+#define _ARM_PROCESSOR_H_
+#include "libcflat.h"
+#include "ptrace.h"
+
+enum {
+	EXCPTN_RST,
+	EXCPTN_UND,
+	EXCPTN_SVC,
+	EXCPTN_PABT,
+	EXCPTN_DABT,
+	EXCPTN_ADDREXCPTN,
+	EXCPTN_IRQ,
+	EXCPTN_FIQ,
+};
+
+extern void handle_exception(u8 v, void (*func)(struct pt_regs *regs));
+extern void show_regs(struct pt_regs *regs);
+
+extern void start_usr(void (*func)(void));
+
+static inline unsigned long get_cpsr(void)
+{
+	unsigned long cpsr;
+	asm volatile("mrs %0, cpsr" : "=r" (cpsr));
+	return cpsr;
+}
+
+#endif
diff --git a/lib/arm/sysinfo.h b/lib/arm/sysinfo.h
index f3b076e1a34c4..91bb17dca0c86 100644
--- a/lib/arm/sysinfo.h
+++ b/lib/arm/sysinfo.h
@@ -16,4 +16,8 @@ struct tag_mem32 {
 extern u32 mach_type_id;
 extern struct tag_core core;
 extern struct tag_mem32 mem32;
+
+#ifndef PAGE_SIZE
+#define PAGE_SIZE core.pagesize
+#endif
 #endif
diff --git a/lib/libcflat.h b/lib/libcflat.h
index 8c6cf1f0735ba..951559b6d69e6 100644
--- a/lib/libcflat.h
+++ b/lib/libcflat.h
@@ -62,6 +62,8 @@ extern long atol(const char *ptr);
 		(type *)( (char *)__mptr - offsetof(type,member) );})
 
 #define __unused __attribute__((__unused__))
+#define __stringify_1(x...)	#x
+#define __stringify(x...)	__stringify_1(x)
 #define NULL ((void *)0UL)
 #include "errno.h"
 #endif
-- 
1.8.1.4

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