From: Jeremy Kerr Date: Wed, 11 Feb 2015 04:55:44 +0000 (+0800) Subject: powerpc/boot: Fix stack corruption in epapr entry point X-Git-Tag: v4.1-rc1~113^2~104 X-Git-Url: https://git.kernelconcepts.de/?p=karo-tx-linux.git;a=commitdiff_plain;h=8c06f0d910ca628b657dc964a7347e70070dc7d6 powerpc/boot: Fix stack corruption in epapr entry point Currently, a 64-bit little-endian zImage.epapr won't boot in epapr mode, as we never return from platform_init. Before entering C, we initialise our stack by setting r1 16 bytes below the end of the _bss_stack: stwu r0,-16(r1) /* establish a stack frame */ However, the called function will save the caller's lr in the caller's frame's lr save area, at -16(r1) to -32(r1). This means that writes to the fdt variable will corrupt the saved link register: 0000000020c06018 l O .bss 0000000000001000 _bss_stack 0000000020c07018 l O .bss 0000000000000008 fdt We'll need at least 32 bytes in the initial stack frame, to handle the LR save area. We bump this to 112 bytes, as that'll be the max required by ABIv1. Thanks to Alistair Popple for debugging help. Signed-off-by: Jeremy Kerr Signed-off-by: Michael Ellerman --- diff --git a/arch/powerpc/boot/crt0.S b/arch/powerpc/boot/crt0.S index 14de4f8778a7..e0040621d00c 100644 --- a/arch/powerpc/boot/crt0.S +++ b/arch/powerpc/boot/crt0.S @@ -218,7 +218,7 @@ p_base: mflr r10 /* r10 now points to runtime addr of p_base */ beq 6f ld r1,0(r8) li r0,0 - stdu r0,-16(r1) /* establish a stack frame */ + stdu r0,-112(r1) /* establish a stack frame */ 6: #endif /* __powerpc64__ */ /* Call platform_init() */