Message ID | 4995c6bc655337598b88bef025cd48b320c2ada0.1349235619.git.pratyush.anand@st.com (mailing list archive) |
---|---|
State | New, archived |
Headers | show |
On 3 October 2012 04:43, Pratyush Anand <pratyush.anand@st.com> wrote: > From: Neha MAKHIJA <neha.makhija-ext@st.com> > > ARM supports 32Mb jump. Hence branch instruction has a limited range. > > For MMU systems, the module area is located just before the kernel memory > because this allows function calls to be linked directly without any indirect > branches. > > In case of MMU-less system, Module area is given whole of the DDR address > space. Since, module_alloc() calls vmalloc(), the module area goes outside the > allowed jump range. Due to this insmod will not be able to load the modules > giving out of range relocation errors. > > Solution - Add the mlong-calls flags while compiling the modules. This tells > the compiler to perform function calls by first loading the address of the > function and then performing a subroutine function call on this register. Do we need the module loader to handle additional relocations or they are all already handled?
On Wed, Oct 03, 2012 at 10:25:09AM +0100, Catalin Marinas wrote: > On 3 October 2012 04:43, Pratyush Anand <pratyush.anand@st.com> wrote: > > From: Neha MAKHIJA <neha.makhija-ext@st.com> > > > > ARM supports 32Mb jump. Hence branch instruction has a limited range. > > > > For MMU systems, the module area is located just before the kernel memory > > because this allows function calls to be linked directly without any indirect > > branches. > > > > In case of MMU-less system, Module area is given whole of the DDR address > > space. Since, module_alloc() calls vmalloc(), the module area goes outside the > > allowed jump range. Due to this insmod will not be able to load the modules > > giving out of range relocation errors. > > > > Solution - Add the mlong-calls flags while compiling the modules. This tells > > the compiler to perform function calls by first loading the address of the > > function and then performing a subroutine function call on this register. > > Do we need the module loader to handle additional relocations or they > are all already handled? I have explained this extensively when the 2.6 module loader came into being. It's not about additional relocations, it's about the addressible range of the 'b' instruction. Please search the archives for the explanation.
On Wed, Oct 03, 2012 at 10:48:02AM +0100, Russell King - ARM Linux wrote: > On Wed, Oct 03, 2012 at 10:25:09AM +0100, Catalin Marinas wrote: > > On 3 October 2012 04:43, Pratyush Anand <pratyush.anand@st.com> wrote: > > > From: Neha MAKHIJA <neha.makhija-ext@st.com> > > > > > > ARM supports 32Mb jump. Hence branch instruction has a limited range. > > > > > > For MMU systems, the module area is located just before the kernel memory > > > because this allows function calls to be linked directly without any indirect > > > branches. > > > > > > In case of MMU-less system, Module area is given whole of the DDR address > > > space. Since, module_alloc() calls vmalloc(), the module area goes outside the > > > allowed jump range. Due to this insmod will not be able to load the modules > > > giving out of range relocation errors. > > > > > > Solution - Add the mlong-calls flags while compiling the modules. This tells > > > the compiler to perform function calls by first loading the address of the > > > function and then performing a subroutine function call on this register. > > > > Do we need the module loader to handle additional relocations or they > > are all already handled? > > I have explained this extensively when the 2.6 module loader came into > being. It's not about additional relocations, it's about the addressible > range of the 'b' instruction. But doesn't -mlong-calls generate the function calls by first loading the address in a register?
diff --git a/arch/arm/Makefile b/arch/arm/Makefile index 88eec8f..78b5c12 100644 --- a/arch/arm/Makefile +++ b/arch/arm/Makefile @@ -112,6 +112,10 @@ CFLAGS_MODULE +=-fno-optimize-sibling-calls endif endif +ifeq ($(CONFIG_MMU),) +CFLAGS_MODULE +=-mlong-calls +endif + # Need -Uarm for gcc < 3.x KBUILD_CFLAGS +=$(CFLAGS_ABI) $(CFLAGS_THUMB2) $(arch-y) $(tune-y) $(call cc-option,-mshort-load-bytes,$(call cc-option,-malignment-traps,)) -msoft-float -Uarm KBUILD_AFLAGS +=$(CFLAGS_ABI) $(AFLAGS_THUMB2) $(arch-y) $(tune-y) -include asm/unified.h -msoft-float