[PATCH 3/3] ARM: Allow to compile in thumb-2 mode
Sascha Hauer
s.hauer at pengutronix.de
Tue Feb 28 03:56:41 EST 2012
This shrinks the resulting binary size by ~25%. Exceptions
are still handled in arm mode, so we have to explicitely
put .arm directives into the exception code. Thumb-2 mode
has been tested on i.MX51 Babbage board.
Signed-off-by: Sascha Hauer <s.hauer at pengutronix.de>
---
arch/arm/Kconfig | 12 ++++++++++++
arch/arm/Makefile | 11 +++++++++--
arch/arm/cpu/cpu.c | 27 +++++++++++++++++++++++++++
arch/arm/cpu/exceptions.S | 1 +
arch/arm/cpu/start.c | 26 ++++++++++++++++++--------
arch/arm/include/asm/barebox-arm-head.h | 12 ++++++++++++
arch/arm/include/asm/unified.h | 8 ++++----
arch/arm/lib/armlinux.c | 17 ++++++++++++++++-
commands/go.c | 6 +++++-
common/misc.c | 3 +++
include/common.h | 6 ++++++
11 files changed, 113 insertions(+), 16 deletions(-)
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 4c0ee58..adb020a 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -101,6 +101,18 @@ config AEABI
To use this you need GCC version 4.0.0 or later.
+config THUMB2_BAREBOX
+ select ARM_ASM_UNIFIED
+ depends on CPU_V7
+ bool "Compile barebox in thumb-2 mode (read help)"
+ help
+ This enables compilation of barebox in thumb-2 mode which generates
+ ~25% smaller binaries. Arm Assembly code needs some fixups to be able
+ to work correctly in thumb-2 mode. the barebox core should have these
+ fixups since most assembly code is derived from the Kernel. However,
+ your board lowlevel init code may break in thumb-2 mode. You have been
+ warned.
+
endmenu
menu "Arm specific settings "
diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index 9926280..56f21ab 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -39,8 +39,15 @@ ifeq ($(CONFIG_ARM_UNWIND),y)
CFLAGS_ABI +=-funwind-tables
endif
-CPPFLAGS += $(CFLAGS_ABI) $(arch-y) $(tune-y) -msoft-float
-AFLAGS += -include asm/unified.h -msoft-float
+ifeq ($(CONFIG_THUMB2_BAREBOX),y)
+AFLAGS_AUTOIT :=$(call as-option,-Wa$(comma)-mimplicit-it=always,-Wa$(comma)-mauto-it)
+AFLAGS_NOWARN :=$(call as-option,-Wa$(comma)-mno-warn-deprecated,-Wa$(comma)-W)
+CFLAGS_THUMB2 :=-mthumb $(AFLAGS_AUTOIT) $(AFLAGS_NOWARN)
+AFLAGS_THUMB2 :=$(CFLAGS_THUMB2) -Wa$(comma)-mthumb
+endif
+
+CPPFLAGS += $(CFLAGS_ABI) $(arch-y) $(tune-y) -msoft-float $(CFLAGS_THUMB2)
+AFLAGS += -include asm/unified.h -msoft-float $(AFLAGS_THUMB2)
# Machine directory name. This list is sorted alphanumerically
# by CONFIG_* macro name.
diff --git a/arch/arm/cpu/cpu.c b/arch/arm/cpu/cpu.c
index cf31e8b..71ef8c0 100644
--- a/arch/arm/cpu/cpu.c
+++ b/arch/arm/cpu/cpu.c
@@ -26,6 +26,7 @@
*/
#include <common.h>
+#include <init.h>
#include <command.h>
#include <cache.h>
#include <asm/mmu.h>
@@ -89,3 +90,29 @@ void arch_shutdown(void)
);
#endif
}
+
+#ifdef CONFIG_THUMB2_BAREBOX
+static void thumb2_execute(void *func, int argc, char *argv[])
+{
+ /*
+ * Switch back to arm mode before executing external
+ * programs.
+ */
+ __asm__ __volatile__ (
+ "mov r0, #0\n"
+ "mov r1, %0\n"
+ "mov r2, %1\n"
+ "bx %2\n"
+ :
+ : "r" (argc - 1), "r" (&argv[1]), "r" (func)
+ : "r0", "r1", "r2"
+ );
+}
+
+static int execute_init(void)
+{
+ do_execute = thumb2_execute;
+ return 0;
+}
+postcore_initcall(execute_init);
+#endif
diff --git a/arch/arm/cpu/exceptions.S b/arch/arm/cpu/exceptions.S
index 6f35d40..c08537a 100644
--- a/arch/arm/cpu/exceptions.S
+++ b/arch/arm/cpu/exceptions.S
@@ -106,6 +106,7 @@ _STACK_START:
* exception handlers
*/
.section ".text","ax"
+ .arm
.align 5
.globl undefined_instruction
diff --git a/arch/arm/cpu/start.c b/arch/arm/cpu/start.c
index 89aff1d..5011fa2 100644
--- a/arch/arm/cpu/start.c
+++ b/arch/arm/cpu/start.c
@@ -33,26 +33,36 @@ void __naked __section(.text_entry) start(void)
barebox_arm_head();
}
+#ifdef CONFIG_THUMB2_BAREBOX
+#define STOP \
+ "1: bne 1b\n" \
+ "nop\n"
+#else
+#define STOP \
+ "1: bne 1b\n"
+#endif
+
void __naked __section(.text_exceptions) exception_vectors(void)
{
__asm__ __volatile__ (
+ ".arm\n"
"b reset\n" /* reset */
#ifdef CONFIG_ARM_EXCEPTIONS
"ldr pc, =undefined_instruction\n" /* undefined instruction */
"ldr pc, =software_interrupt\n" /* software interrupt (SWI) */
"ldr pc, =prefetch_abort\n" /* prefetch abort */
"ldr pc, =data_abort\n" /* data abort */
- "1: bne 1b\n" /* (reserved) */
+ STOP /* (reserved) */
"ldr pc, =irq\n" /* irq (interrupt) */
"ldr pc, =fiq\n" /* fiq (fast interrupt) */
#else
- "1: bne 1b\n" /* undefined instruction */
- "1: bne 1b\n" /* software interrupt (SWI) */
- "1: bne 1b\n" /* prefetch abort */
- "1: bne 1b\n" /* data abort */
- "1: bne 1b\n" /* (reserved) */
- "1: bne 1b\n" /* irq (interrupt) */
- "1: bne 1b\n" /* fiq (fast interrupt) */
+ STOP /* undefined instruction */
+ STOP /* software interrupt (SWI) */
+ STOP /* prefetch abort */
+ STOP /* data abort */
+ STOP /* (reserved) */
+ STOP /* irq (interrupt) */
+ STOP /* fiq (fast interrupt) */
#endif
);
}
diff --git a/arch/arm/include/asm/barebox-arm-head.h b/arch/arm/include/asm/barebox-arm-head.h
index fdbee8c..0dc3074 100644
--- a/arch/arm/include/asm/barebox-arm-head.h
+++ b/arch/arm/include/asm/barebox-arm-head.h
@@ -4,6 +4,17 @@
static inline void barebox_arm_head(void)
{
__asm__ __volatile__ (
+#ifdef CONFIG_THUMB2_BAREBOX
+ ".arm\n"
+ "adr r9, 1f + 1\n"
+ "bx r9\n"
+ ".thumb\n"
+ "1:\n"
+ "bl reset\n"
+ ".rept 10\n"
+ "1: b 1b\n"
+ ".endr\n"
+#else
"b reset\n"
"1: b 1b\n"
"1: b 1b\n"
@@ -12,6 +23,7 @@ static inline void barebox_arm_head(void)
"1: b 1b\n"
"1: b 1b\n"
"1: b 1b\n"
+#endif
".word 0x65726162\n" /* 'bare' */
".word 0x00786f62\n" /* 'box' */
".word _text\n" /* text base. If copied there,
diff --git a/arch/arm/include/asm/unified.h b/arch/arm/include/asm/unified.h
index bc63116..4d855c8 100644
--- a/arch/arm/include/asm/unified.h
+++ b/arch/arm/include/asm/unified.h
@@ -24,10 +24,10 @@
.syntax unified
#endif
-#ifdef CONFIG_THUMB2_KERNEL
+#ifdef CONFIG_THUMB2_BAREBOX
#if __GNUC__ < 4
-#error Thumb-2 kernel requires gcc >= 4
+#error Thumb-2 barebox requires gcc >= 4
#endif
/* The CPSR bit describing the instruction set (Thumb) */
@@ -40,7 +40,7 @@
#endif
#define BSYM(sym) sym + 1
-#else /* !CONFIG_THUMB2_KERNEL */
+#else /* !CONFIG_THUMB2_BAREBOX */
/* The CPSR bit describing the instruction set (ARM) */
#define PSR_ISETSTATE 0
@@ -52,7 +52,7 @@
#endif
#define BSYM(sym) sym
-#endif /* CONFIG_THUMB2_KERNEL */
+#endif /* CONFIG_THUMB2_BAREBOX */
#ifndef CONFIG_ARM_ASM_UNIFIED
diff --git a/arch/arm/lib/armlinux.c b/arch/arm/lib/armlinux.c
index 85fe2b9..a167036 100644
--- a/arch/arm/lib/armlinux.c
+++ b/arch/arm/lib/armlinux.c
@@ -255,6 +255,7 @@ void start_linux(void *adr, int swap, unsigned long initrd_address,
{
void (*kernel)(int zero, int arch, void *params) = adr;
void *params = NULL;
+ int architecture;
if (oftree) {
printf("booting Linux kernel with devicetree\n");
@@ -272,5 +273,19 @@ void start_linux(void *adr, int swap, unsigned long initrd_address,
__asm__ __volatile__("mcr p15, 0, %0, c1, c0" :: "r" (reg));
}
- kernel(0, armlinux_get_architecture(), params);
+ architecture = armlinux_get_architecture();
+
+#ifdef CONFIG_THUMB2_BAREBOX
+ __asm__ __volatile__ (
+ "mov r0, #0\n"
+ "mov r1, %0\n"
+ "mov r2, %1\n"
+ "bx %2\n"
+ :
+ : "r" (architecture), "r" (params), "r" (kernel)
+ : "r0", "r1", "r2"
+ );
+#else
+ kernel(0, architecture, params);
+#endif
}
diff --git a/commands/go.c b/commands/go.c
index 6082fe5..bc984c8 100644
--- a/commands/go.c
+++ b/commands/go.c
@@ -62,7 +62,11 @@ static int do_go(struct command *cmdtp, int argc, char *argv[])
func = addr;
shutdown_barebox();
- func(argc - 1, &argv[1]);
+
+ if (do_execute)
+ do_execute(func, argc - 1, &argv[1]);
+ else
+ func(argc - 1, &argv[1]);
/*
* The application returned. Since we have shutdown barebox and
diff --git a/common/misc.c b/common/misc.c
index a0059c1..b31a45c 100644
--- a/common/misc.c
+++ b/common/misc.c
@@ -125,3 +125,6 @@ void perror(const char *s)
#endif
}
EXPORT_SYMBOL(perror);
+
+void (*do_execute)(void *func, int argc, char *argv[]);
+EXPORT_SYMBOL(do_execute);
diff --git a/include/common.h b/include/common.h
index d227875..d2347f8 100644
--- a/include/common.h
+++ b/include/common.h
@@ -146,6 +146,12 @@ unsigned long strtoul_suffix(const char *str, char **endp, int base);
void start_barebox(void);
void shutdown_barebox(void);
+/*
+ * architectures which have special calling conventions for
+ * executing programs should set this. Used by the 'go' command
+ */
+extern void (*do_execute)(void *func, int argc, char *argv[]);
+
void arch_shutdown(void);
int run_shell(void);
--
1.7.9.1
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