From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ozlabs.org (ozlabs.org [103.22.144.67]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 0E2F71A0200 for ; Tue, 10 Feb 2015 23:15:16 +1100 (AEDT) Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Subject: [PATCH 3/4] powerpc/boot: Fix stack corruption in epapr entry point Message-Id: <1423570510.219047.52227904007.3.gpush@pablo> In-Reply-To: <1423570510.218330.214724142596.1.gpush@pablo> To: linuxppc-dev@lists.ozlabs.org From: Jeremy Kerr Date: Tue, 10 Feb 2015 20:15:10 +0800 List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Currently, a 64-bit little-endian zImage.epapr won't boot in epapr mode, as 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 corrupt the saved link register: 0000000020c06018 l O .bss 0000000000001000 _bss_stack 0000000020c07018 l O .bss 0000000000000008 fdt This change allocates the minimum of 32 bytes for the base of the stack instead. Signed-off-by: Jeremy Kerr --- arch/powerpc/boot/crt0.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/powerpc/boot/crt0.S b/arch/powerpc/boot/crt0.S index 14de4f8..bf8eeee 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,-32(r1) /* establish a stack frame */ 6: #endif /* __powerpc64__ */ /* Call platform_init() */