On Thu, Dec 03, 2020 at 01:19:16PM +0100, Geert Uytterhoeven wrote: > diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S > index d9cce7238a365081..1b6425df87e84e71 100644 > --- a/arch/arm/boot/compressed/head.S > +++ b/arch/arm/boot/compressed/head.S > @@ -282,10 +282,36 @@ not_angel: > * are already placing their zImage in (eg) the top 64MB > * of this range. > */ > - mov r4, pc > - and r4, r4, #0xf8000000 > + mov r0, pc > + and r0, r0, #0xf8000000 > +#ifdef CONFIG_USE_OF > + adr r1, LC1 > +#ifdef CONFIG_ARM_APPENDED_DTB > + /* > + * Look for an appended DTB. If found, we cannot use it to > + * validate the calculated start of physical memory, as its > + * memory nodes may need to be augmented by ATAGS stored at > + * an offset from the same start of physical memory. > + */ > + ldr r2, [r1, #4] @ get &_edata > + add r2, r2, r1 @ relocate it > + ldr r2, [r2] @ get DTB signature > + ldr r3, =OF_DT_MAGIC > + cmp r2, r3 @ do we have a DTB there? > + beq 1f @ if yes, skip validation > +#endif /* CONFIG_ARM_APPENDED_DTB */ > + > + /* Make sure we have some stack */ > + ldr sp, [r1] @ get stack location > + add sp, sp, r1 @ apply relocation > + > + /* Validate calculated start against passed DTB */ > + mov r1, r8 > + bl fdt_check_mem_start
I don't think this is going to work. You can only run C code when it has been linked for a specific address and is loaded at the correct address as it contains absolute addresses. We work around that in the decompressor by (ab)using the GOT table, and the code that fixes up the GOT table is run later, after you've called out to some C code here. Quite how this works for you without the GOT fixups having been done, I'm not sure. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!
