Commit 6616a147 authored by Josh Poimboeuf's avatar Josh Poimboeuf Committed by Ingo Molnar

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: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nilay Vaish <nilayvaish@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/2588f34b6fbac4ae6f6f9ead2a78d7f8d58a6341.1474480779.git.jpoimboe@redhat.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 4d516f41
...@@ -289,7 +289,8 @@ num_subarch_entries = (. - subarch_entries) / 4 ...@@ -289,7 +289,8 @@ num_subarch_entries = (. - subarch_entries) / 4
ENTRY(start_cpu0) ENTRY(start_cpu0)
movl initial_stack, %ecx movl initial_stack, %ecx
movl %ecx, %esp movl %ecx, %esp
jmp *(initial_code) call *(initial_code)
1: jmp 1b
ENDPROC(start_cpu0) ENDPROC(start_cpu0)
#endif #endif
...@@ -470,8 +471,9 @@ ENTRY(startup_32_smp) ...@@ -470,8 +471,9 @@ ENTRY(startup_32_smp)
xorl %eax,%eax # Clear LDT xorl %eax,%eax # Clear LDT
lldt %ax lldt %ax
pushl $0 # fake return address for unwinder call *(initial_code)
jmp *(initial_code) 1: jmp 1b
ENDPROC(startup_32_smp)
#include "verify_cpu.S" #include "verify_cpu.S"
......
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