* Tony Lindgren <[email protected]> [110509 07:47]: > * Tony Lindgren <[email protected]> [110509 14:16]: > > Do this before relocating the compressed kernel + device tree data. > > Otherwise we would have to split the copying into two parts, or copy > > the device tree data twice. > > > > As we only have one register available, pass the size of kernel BSS > > via linker and do the following calculation using r1. > > Blah, this still needs a bit more work.. The calculation is wrong > and we can get multiple relocations now.
Here's a better version that also makes the stack usable early. That might become handy for further changes. Will still do a bit more testing on this on Friday. Tony From: Tony Lindgren <[email protected]> Date: Thu, 12 May 2011 05:29:49 -0700 Subject: [PATCH] ARM: Make sure appended device tree data won't overlap kernel BSS Do this before relocating the compressed kernel + device tree data. Otherwise we would have to split the copying into two parts, or copy the device tree data twice. As we only have one register available, pass the size of kernel BSS via linker and do the calculation using r1, then save it to the stack. Note that this patch now makes the stack also usable earlier for CONFIG_ARM_APPENDED_DTB. Not-Yet-Signed-off-by: Tony Lindgren <[email protected]> --- a/arch/arm/boot/compressed/Makefile +++ b/arch/arm/boot/compressed/Makefile @@ -98,6 +98,9 @@ endif ccflags-y := -fpic -fno-builtin asflags-y := -Wa,-march=all +# Supply kernel BSS size to the decompressor via a linker symbol. +KBSS_SZ = $(shell size $(obj)/../../../../vmlinux | awk 'END{print $$3}') +LDFLAGS_vmlinux = --defsym _kbss_sz=$(KBSS_SZ) # Supply ZRELADDR to the decompressor via a linker symbol. ifneq ($(CONFIG_AUTO_ZRELADDR),y) LDFLAGS_vmlinux += --defsym zreladdr=$(ZRELADDR) --- a/arch/arm/boot/compressed/head.S +++ b/arch/arm/boot/compressed/head.S @@ -266,6 +266,25 @@ restart: adr r0, LC0 add lr, lr, #7 bic lr, lr, #7 + /* + * Compensate for the appended device tree and make stack + * usable. Note if the linker script changes so the stack is + * not after the bss section, this code will be wrong. + */ + add sp, sp, lr + + /* + * Calculate and save the offset between kernel BSS end and + * device tree data start for later use to check they won't + * overlap. + */ + adr r1, kbss_sz + ldr r1, [r1, #0] @ kernel BSS size + add r1, r1, r4 @ add inflated kernel start + add r1, r1, r9 @ add inflated kernel size + sub r1, r1, r6 @ kbss end - dt start + str r1, [sp, #0] @ save offset into stack + add r10, r10, lr add r6, r6, lr dtb_check_done: @@ -273,17 +292,29 @@ dtb_check_done: /* * Check to see if we will overwrite ourselves. + * r1 = corrupted * r4 = final kernel address * r9 = size of decompressed image * r10 = end of this image, including bss/stack/malloc space if non XIP * We basically want: * r4 - 16k page directory >= r10 -> OK * r4 + image length <= current position (pc) -> OK + * For the appended device tree case, check that the device tree data does + * not overlap the kernel BSS area. */ add r10, r10, #16384 cmp r4, r10 bhs wont_overwrite add r10, r4, r9 +#if defined(CONFIG_ARM_APPENDED_DTB) + cmp lr, #0 @ device tree appended? + beq no_kbss_check @ no, skip check + ldr r1, [sp, #0] @ get kbss offset + add r1, r10, r1 @ inflated end + kbss offset + cmp r10, r1 @ DT start < kernel BSS end? + movlt r10, r1 @ yes, move past kernel BSS end +no_kbss_check: +#endif cmp r10, pc bls wont_overwrite @@ -331,6 +362,10 @@ dtb_check_done: add r0, r0, r6 mov pc, r0 +#ifdef CONFIG_ARM_APPENDED_DTB +kbss_sz: .word _kbss_sz @ kernel BSS size +#endif + wont_overwrite: /* * If delta is zero, we are running at the address we were linked at. @@ -376,13 +411,6 @@ wont_overwrite: add r2, r2, lr add r3, r3, lr - /* - * bump the stack pinter - * - * If the linker script changes so the stack is not after - * the bss section, this code will be wrong. - */ - add sp, sp, lr #else /* _______________________________________________ devicetree-discuss mailing list [email protected] https://lists.ozlabs.org/listinfo/devicetree-discuss
