This patch adds support for and demonstrates the usage of an embedded position independent executable (PIE). The goal is to allow the use of C code in situations where carefully written position independent assembly was previously required. The example used is the suspend/resume code for the am335x, a Texas Instruments ARM SoC. In order to save the maximum amount of power during suspend, the am335x has to perform several power saving operations after SDRAM has been disabled, and undo those steps at resume time. The am335x provides an SRAM region for the processor to execute such code. A PIE executable was chosen because it limits the types of relocations that must be performed before the code is executed. In the case of ARM, the only required relocation type is a relative relocation of pointers. The kernel is provided symbols into the PIE executable by way of exporting those symbols from the PIE and then importing them into vmlinux at final link time. Because the PIE is loaded dynamically at runtime, any access to PIE functions or data must pass through special accessor macros that apply the necessary offset. Code within the PIE does not have access to symbols outside of the PIE, but it still can access code and data outside the PIE so long as it is passed pointers to that code/data. The PIE executable is provided its own set of functions required by gcc, such as memcpy, memmove, etc. The different PIE sections are collected together in the linker script as an overlay so that the kernel only needs one copy of these functions. When the PIE is loaded, the library functions and appropriate sections are copied into a genalloc pool (in the case of the example, backed by SRAM). The PIE code then applies the necessary relocations to the loaded code. Because the relocations are just relative offsets to pointers, the relocations can be reapplied to allow the code to run with the MMU enabled or disabled. This patchset is a complete rethinking of an earlier patchset [1]. Ard Biesheuvel provided the suggestion to use the PIE executable format for storing the relocatable code within the kernel. Russell King and Dave Martin pointed out the shortcomings of my initial naive approach. This patchset depends on Rajendra Nayak's SRAM DT-ification patch series [2], Suman Anna's am335x mailbox series [3], and a portion of Dave Gerlach's am335x suspend/resume patchset [4]. I've collected together the necessary dependances and applied this patch series on top of them here [5]. Because special ioremap variants are required on ARM for io mappings that allow code execution, the first two patches provide generic accessors for those variants. The third patch provides a DT and pdata method for instructing misc/sram to map the memory in such a way that allows code execution. The 4th patch provides a generic set of functions for handling function pointers as addresses and vice versa. This is necessary on ARM because of the way that Thumb2 function pointers are handled by gcc. The PIE framework requires this functionality because it performs translations of function pointers. The 5th patch is the general PIE framework. The 6th patch is the addition of ARM support for PIE. The 7th patch provides the ability of ARM to fixup PIE code on the fly. This is necessary since at suspend time the MMU will be working, but at resume time, it will be off. The 8th patch provides a predefined trampoline that utilizes the on the fly fixup. The 9th patch configures the SRAM DT entries for am335x so that they can be easily found by the PM code, and so that they are mapped with exec enabled. The 10th patch adds PIE entries for am335x, and the 11th patch finally adds suspend/resume support for am33xx utilizing C code for suspend/resume paths. [1] http://www.spinics.net/lists/arm-kernel/msg271525.html [2] http://comments.gmane.org/gmane.linux.ports.arm.omap/103774 [3] http://www.spinics.net/lists/devicetree/msg00227.html [4] http://www.spinics.net/lists/linux-omap/msg95305.html [5] https://github.com/russdill/linux/commits/sram Russ Dill (10): asm-generic: io: Add exec versions of ioremap lib: devres: Add exec versions of devm_ioremap_resource and friends misc: SRAM: Add option to map SRAM to allow code execution asm-generic: fncpy: Add function copying macros PIE: Support embedding position independent executables ARM: PIE: Add position independent executable embedding to ARM ARM: PIE: Add support for updating PIE relocations ARM: PIE: Add macro for generating PIE resume trampoline ARM: dts: AM33XX: Associate SRAM with MPU and mark it exec ARM: OMAP2+: AM33XX: Add PIE support for AM33XX Vaibhav Bedia (1): ARM: OMAP2+: AM33XX: Basic suspend resume support Documentation/devicetree/bindings/misc/sram.txt | 4 + Documentation/pie.txt | 167 ++++++++ Makefile | 17 +- arch/alpha/include/asm/fncpy.h | 1 + arch/arc/include/asm/fncpy.h | 1 + arch/arm/Kconfig | 1 + arch/arm/Makefile | 5 + arch/arm/boot/dts/am33xx.dtsi | 2 + arch/arm/configs/omap2plus_defconfig | 1 + arch/arm/include/asm/elf.h | 1 + arch/arm/include/asm/fncpy.h | 76 +--- arch/arm/include/asm/io.h | 2 + arch/arm/include/asm/pie.h | 42 ++ arch/arm/include/asm/suspend.h | 25 ++ arch/arm/kernel/.gitignore | 1 + arch/arm/kernel/Makefile | 4 +- arch/arm/kernel/pie.c | 92 +++++ arch/arm/kernel/pie.lds.S | 41 ++ arch/arm/kernel/vmlinux.lds.S | 2 + arch/arm/libpie/.gitignore | 3 + arch/arm/libpie/Makefile | 32 ++ arch/arm/libpie/empty.S | 12 + arch/arm/libpie/relocate.S | 76 ++++ arch/arm/mach-omap2/Kconfig | 7 +- arch/arm/mach-omap2/Makefile | 2 + arch/arm/mach-omap2/board-generic.c | 1 + arch/arm/mach-omap2/common.h | 10 + arch/arm/mach-omap2/io.c | 5 + arch/arm/mach-omap2/pm.c | 3 +- arch/arm/mach-omap2/pm33xx.c | 486 ++++++++++++++++++++++++ arch/arm/mach-omap2/pm33xx.h | 68 ++++ arch/arm/mach-omap2/sleep33xx.c | 314 +++++++++++++++ arch/arm/mach-omap2/wkup_m3.c | 183 +++++++++ arch/arm/plat-omap/sram.c | 2 +- arch/arm64/include/asm/fncpy.h | 1 + arch/avr32/include/asm/fncpy.h | 1 + arch/blackfin/include/asm/fncpy.h | 1 + arch/c6x/include/asm/fncpy.h | 1 + arch/cris/include/asm/fncpy.h | 1 + arch/frv/include/asm/fncpy.h | 1 + arch/h8300/include/asm/fncpy.h | 1 + arch/hexagon/include/asm/fncpy.h | 1 + arch/ia64/include/asm/fncpy.h | 1 + arch/m32r/include/asm/fncpy.h | 1 + arch/m68k/include/asm/fncpy.h | 1 + arch/metag/include/asm/fncpy.h | 1 + arch/microblaze/include/asm/fncpy.h | 1 + arch/mips/include/asm/fncpy.h | 1 + arch/mn10300/include/asm/fncpy.h | 1 + arch/openrisc/include/asm/fncpy.h | 1 + arch/parisc/include/asm/fncpy.h | 1 + arch/powerpc/include/asm/fncpy.h | 1 + arch/s390/include/asm/fncpy.h | 1 + arch/score/include/asm/fncpy.h | 1 + arch/sh/include/asm/fncpy.h | 1 + arch/sparc/include/asm/fncpy.h | 1 + arch/tile/include/asm/fncpy.h | 1 + arch/um/include/asm/fncpy.h | 1 + arch/unicore32/include/asm/fncpy.h | 1 + arch/x86/include/asm/fncpy.h | 1 + arch/xtensa/include/asm/fncpy.h | 1 + drivers/misc/sram.c | 13 +- include/asm-generic/fncpy.h | 104 +++++ include/asm-generic/iomap.h | 5 + include/asm-generic/pie.lds.h | 82 ++++ include/asm-generic/vmlinux.lds.h | 1 + include/linux/device.h | 17 +- include/linux/io.h | 4 + include/linux/pie.h | 196 ++++++++++ include/linux/platform_data/sram.h | 8 + lib/Kconfig | 14 + lib/Makefile | 2 + lib/devres.c | 97 ++++- lib/pie.c | 138 +++++++ pie/.gitignore | 3 + pie/Makefile | 85 +++++ scripts/link-vmlinux.sh | 11 +- 77 files changed, 2425 insertions(+), 71 deletions(-) create mode 100644 Documentation/pie.txt create mode 100644 arch/alpha/include/asm/fncpy.h create mode 100644 arch/arc/include/asm/fncpy.h create mode 100644 arch/arm/include/asm/pie.h create mode 100644 arch/arm/kernel/pie.c create mode 100644 arch/arm/kernel/pie.lds.S create mode 100644 arch/arm/libpie/.gitignore create mode 100644 arch/arm/libpie/Makefile create mode 100644 arch/arm/libpie/empty.S create mode 100644 arch/arm/libpie/relocate.S create mode 100644 arch/arm/mach-omap2/pm33xx.c create mode 100644 arch/arm/mach-omap2/pm33xx.h create mode 100644 arch/arm/mach-omap2/sleep33xx.c create mode 100644 arch/arm/mach-omap2/wkup_m3.c create mode 100644 arch/arm64/include/asm/fncpy.h create mode 100644 arch/avr32/include/asm/fncpy.h create mode 100644 arch/blackfin/include/asm/fncpy.h create mode 100644 arch/c6x/include/asm/fncpy.h create mode 100644 arch/cris/include/asm/fncpy.h create mode 100644 arch/frv/include/asm/fncpy.h create mode 100644 arch/h8300/include/asm/fncpy.h create mode 100644 arch/hexagon/include/asm/fncpy.h create mode 100644 arch/ia64/include/asm/fncpy.h create mode 100644 arch/m32r/include/asm/fncpy.h create mode 100644 arch/m68k/include/asm/fncpy.h create mode 100644 arch/metag/include/asm/fncpy.h create mode 100644 arch/microblaze/include/asm/fncpy.h create mode 100644 arch/mips/include/asm/fncpy.h create mode 100644 arch/mn10300/include/asm/fncpy.h create mode 100644 arch/openrisc/include/asm/fncpy.h create mode 100644 arch/parisc/include/asm/fncpy.h create mode 100644 arch/powerpc/include/asm/fncpy.h create mode 100644 arch/s390/include/asm/fncpy.h create mode 100644 arch/score/include/asm/fncpy.h create mode 100644 arch/sh/include/asm/fncpy.h create mode 100644 arch/sparc/include/asm/fncpy.h create mode 100644 arch/tile/include/asm/fncpy.h create mode 100644 arch/um/include/asm/fncpy.h create mode 100644 arch/unicore32/include/asm/fncpy.h create mode 100644 arch/x86/include/asm/fncpy.h create mode 100644 arch/xtensa/include/asm/fncpy.h create mode 100644 include/asm-generic/fncpy.h create mode 100644 include/asm-generic/pie.lds.h create mode 100644 include/linux/pie.h create mode 100644 include/linux/platform_data/sram.h create mode 100644 lib/pie.c create mode 100644 pie/.gitignore create mode 100644 pie/Makefile -- 1.8.3.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
