[U-Boot] [PATCH v2 0/2] improve hello_world standalone application for arm
This series addresses - hardcoded load address, use LOADADDR if available as the entry point instead - fix thumb build, jumping with 'go' to the entry point expects arm code
Note that in addition to the two fixes I've seen random freezes or 'random' printed stuff when using an early linaro gcc 6 compiler. Adding an initialized variable helped in that case static int dummy_var_in_text = 1; I assume that this forces alignment of some linker sections. (e.g. I see that __bss_start points to 0x1201027e, with the variable this moves to 0x12010280)
However with the current linaro compilers this does not happen so I don't propose a patch for this issue. Linaro GCC 5.4-2017.05 5.4.1 20170404 Linaro GCC 6.3-2017.05 6.3.1 20170404 Linaro GCC 7.1-2017.05 7.1.1 20170510
This series is available at http://git.toradex.com/cgit/u-boot-toradex.git/log/?h=for-next
Changes in v2: - Don't confuse loadaddr with entry point as reported by Wolfgang. - Change the assembly magic to a C function and use __attribute__ to force arm instruction set. - Keep the entry point name hello_world as reported by Wolfgang.
Max Krummenacher (2): arm: use LOADADDR as the default for STANDALONE_LOAD_ADDR hello_world.c: fix entry point in case of arm thumb binary
arch/arm/config.mk | 4 ++++ doc/README.standalone | 2 +- examples/standalone/hello_world.c | 18 ++++++++++++++++++ 3 files changed, 23 insertions(+), 1 deletion(-)
Different SoCs have different RAM layouts, so using $(CONFIG_LOADADDR) instead of the constant 0xc100000 for CONFIG_STANDALONE_LOAD_ADDR is probably more appropriate.
Signed-off-by: Max Krummenacher max.krummenacher@toradex.com
---
Changes in v2: - Don't confuse loadaddr with entry point as reported by Wolfgang.
arch/arm/config.mk | 4 ++++ doc/README.standalone | 2 +- 2 files changed, 5 insertions(+), 1 deletion(-)
diff --git a/arch/arm/config.mk b/arch/arm/config.mk index 1a77779db4..8f56c7433f 100644 --- a/arch/arm/config.mk +++ b/arch/arm/config.mk @@ -9,7 +9,11 @@ ifndef CONFIG_STANDALONE_LOAD_ADDR ifneq ($(CONFIG_ARCH_OMAP2PLUS),) CONFIG_STANDALONE_LOAD_ADDR = 0x80300000 else +ifndef CONFIG_LOADADDR CONFIG_STANDALONE_LOAD_ADDR = 0xc100000 +else +CONFIG_STANDALONE_LOAD_ADDR = $(CONFIG_LOADADDR) +endif endif endif
diff --git a/doc/README.standalone b/doc/README.standalone index 659a12f6cb..17d740c44b 100644 --- a/doc/README.standalone +++ b/doc/README.standalone @@ -53,7 +53,7 @@ Design Notes on Exporting U-Boot Functions to Standalone Applications: Load address Start address x86 0x00040000 0x00040000 PowerPC 0x00040000 0x00040004 - ARM 0x0c100000 0x0c100000 + ARM CONFIG_LOADADDR CONFIG_LOADADDR MIPS 0x80200000 0x80200000 Blackfin 0x00001000 0x00001000 NDS32 0x00300000 0x00300000
On Mon, Aug 14, 2017 at 06:27:19PM +0200, Max Krummenacher wrote:
Different SoCs have different RAM layouts, so using $(CONFIG_LOADADDR) instead of the constant 0xc100000 for CONFIG_STANDALONE_LOAD_ADDR is probably more appropriate.
Signed-off-by: Max Krummenacher max.krummenacher@toradex.com
Reviewed-by: Tom Rini trini@konsulko.com
For the ARM architecture the U-Boot 'go' command can not jump to code compiled for thumb instruction set. Thus provide a forwarder function to be used as the entry point and have the forwarder deal with how to jump to thumb code.
Note that code which is calling back into the U-Boot binary needs to be compiled in the same instruction set as the U-Boot binary is compiled with.
Signed-off-by: Max Krummenacher max.krummenacher@toradex.com
---
Changes in v2: - Don't confuse loadaddr with entry point as reported by Wolfgang. - Change the assembly magic to a C function and use __attribute__ to force arm instruction set. - Keep the entry point name hello_world as reported by Wolfgang.
examples/standalone/hello_world.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+)
diff --git a/examples/standalone/hello_world.c b/examples/standalone/hello_world.c index bd8b392315..3b58b147ff 100644 --- a/examples/standalone/hello_world.c +++ b/examples/standalone/hello_world.c @@ -8,7 +8,25 @@ #include <common.h> #include <exports.h>
+/* + * Make thumb work by compiling the entry function for arm. + * Only do this if the target CPU is able to execute arm code. + * Note that code which calls back into the U-Boot binary + * must be compiled for thumb. + */ +#if defined(__thumb__) && defined(__ARM_ARCH_ISA_ARM) +static int _hello_world(int argc, char * const argv[]); + +__attribute__((target("arm"))) +int hello_world(int argc, char * const argv[]) +{ + return _hello_world(argc, argv); +} + +static noinline int _hello_world(int argc, char * const argv[]) +#else int hello_world (int argc, char * const argv[]) +#endif { int i;
participants (2)
-
Max Krummenacher -
Tom Rini