From mboxrd@z Thu Jan 1 00:00:00 1970 From: jonathan.austin@arm.com (Jonathan Austin) Date: Tue, 29 Jan 2013 17:29:06 +0000 Subject: [RFC PATCH] arm: decompressor: initialize PIC offset base register for uClinux tools Message-ID: <1359480546-7033-1-git-send-email-jonathan.austin@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Before jumping to (position independent) C-code from the decompressor's assembler world we set-up the C environment. This setup currently does not set r9, which for arm-none-uclinux-uclibceabi should be the PIC offset base register (IE should point to the beginning of the GOT). Currently, therefore, in order to build working kernels that use the decompressor it is necessary to use an arm-linux-gnueabi toolchain, or similar. uClinux toolchains cause a Prefetch Abort to occur at the beginning of the decompress_kernel function. This patch allows uClinux toolchains to build bootable zImages by setting r9 to the beginning of the GOT when __uClinux__ is defined, allowing the decompressor's C functions to work correctly. Signed-off-by: Jonathan Austin --- One other possibility would be to specify -mno-single-pic-base when building the decompressor. This works around the problem, but forces the compiler to generate less optimal code. arch/arm/boot/compressed/head.S | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S index fe4d9c3..4491e75 100644 --- a/arch/arm/boot/compressed/head.S +++ b/arch/arm/boot/compressed/head.S @@ -410,6 +410,10 @@ wont_overwrite: * sp = stack pointer */ orrs r1, r0, r5 +#ifdef __uClinux__ + mov r9, r11 @ PIC offset base register + addne r9, r9, r0 @ Also needs relocating +#endif beq not_relocated add r11, r11, r0 -- 1.7.9.5