Random Linux Kernel functions have 16 byte stack alignment at the start of the
function. This stack alignment happens before the
push %ebp
mov %esp, %ebp
sequence and breaks the kernel function graph tracer which needs to manipulate
the return address. When the alignment happens then still 4(%ebp) contains the
return address, but this is only a copy of the real stack entry which is used
by the ret instruction. So the tracer modifies the copy and not the real return
address stack entry.
There are two problems:
1) why is gcc doing 16 byte stack aligment at all
2) why is the stack alignment happening _before_ the "push %ebp, mov %esp %ebp"
sequence.
--
Summary: 16 byte stack alignment on random Linux kernel functions
Product: gcc
Version: 4.4.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: tglx at linutronix dot de
GCC build triplet: i586-redhat-linux
GCC host triplet: i586-redhat-linux
GCC target triplet: i586-redhat-linux
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42109
