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Description of problem:
In certain leaf functions, the code generated by gcc does not allocate a
new stack frame, i.e. it does not subtract from %esp in the function
prelude, yet the remainder of the code accesses stack-allocated local
variables (at negative offsets w.r.t %ebp).  This results in accesses to
stack locations below the stack pointer %esp.  These locations can be wiped
at any time by a signal handler, causing the program to crash.  Also, this
can invalidate the stack growing heuristic in the kernel, causing the
program to be killed on a segmentation violation.

Version-Release number of selected component (if applicable):


How reproducible:
Always

Steps to Reproduce:
1. Compile the attached md5.c file with "gcc -O -S"
2. Look at md5.s, function MD5Transform, and notice the lack of
a "subl $NNN, %esp" instruction in the prelude, and the accesses
" movl %eax, -16(%ebp)" later in the code.


Additional info:

This is the same bug as #55568, but with a much smaller code fragment to
reproduce it.