Commit-ID: 6616a147a79c6fc280572f5a993e9e5ebd200d24 Gitweb: http://git.kernel.org/tip/6616a147a79c6fc280572f5a993e9e5ebd200d24 Author: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> AuthorDate: Wed, 21 Sep 2016 16:04:02 -0500 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitDate: Thu, 20 Oct 2016 09:15:23 +0200 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 <jpoimboe@xxxxxxxxxx> Cc: Andy Lutomirski <luto@xxxxxxxxxx> Cc: Borislav Petkov <bp@xxxxxxxxx> Cc: Brian Gerst <brgerst@xxxxxxxxx> Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx> Cc: H. Peter Anvin <hpa@xxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Nilay Vaish <nilayvaish@xxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Link: http://lkml.kernel.org/r/2588f34b6fbac4ae6f6f9ead2a78d7f8d58a6341.1474480779.git.jpoimboe@xxxxxxxxxx Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> --- 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 65e6225..9a6f8e8 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" -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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