From 6616a147a79c6fc280572f5a993e9e5ebd200d24 Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Wed, 21 Sep 2016 16:04:02 -0500 Subject: [PATCH] x86/boot/32: Fix the end of the stack for idle tasks The frame at the end of each idle task stack is inconsistent with real task stacks, which have a stack frame header and a real return address before the pt_regs area. This inconsistency can be confusing for stack unwinders. It also hides useful information about what asm code was involved in calling into C. Fix that by changing the initial code jumps to calls. Also add infinite loops after the calls to make it clear that the calls don't return, and to hang if they do. Signed-off-by: Josh Poimboeuf Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Nilay Vaish Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/2588f34b6fbac4ae6f6f9ead2a78d7f8d58a6341.1474480779.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar --- arch/x86/kernel/head_32.S | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S index 65e62256df43..9a6f8e820ae1 100644 --- a/arch/x86/kernel/head_32.S +++ b/arch/x86/kernel/head_32.S @@ -289,7 +289,8 @@ num_subarch_entries = (. - subarch_entries) / 4 ENTRY(start_cpu0) movl initial_stack, %ecx movl %ecx, %esp - jmp *(initial_code) + call *(initial_code) +1: jmp 1b ENDPROC(start_cpu0) #endif @@ -470,8 +471,9 @@ ENTRY(startup_32_smp) xorl %eax,%eax # Clear LDT lldt %ax - pushl $0 # fake return address for unwinder - jmp *(initial_code) + call *(initial_code) +1: jmp 1b +ENDPROC(startup_32_smp) #include "verify_cpu.S" -- 2.30.2