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authorVegard Nossum <vegard.nossum@gmail.com>2008-06-27 17:22:17 +0200
committerIngo Molnar <mingo@elte.hu>2008-06-27 17:45:59 +0200
commit9d8ad5d6c7fce31fd2c0fd4fe9977bda3e92e340 (patch)
tree1760e6576072b880a9b1f9c07879a33cce5306f7 /include
parent543cf4cb3fe6f6cae3651ba918b9c56200b257d0 (diff)
x86: don't destroy %rbp on kernel-mode faults
From the code: "B stepping K8s sometimes report an truncated RIP for IRET exceptions returning to compat mode. Check for these here too." The code then proceeds to truncate the upper 32 bits of %rbp. This means that when do_page_fault() is finally called, its prologue, do_page_fault: push %rbp movl %rsp, %rbp will put the truncated base pointer on the stack. This means that the stack tracer will not be able to follow the base-pointer changes and will see all subsequent stack frames as unreliable. This patch changes the code to use a different register (%rcx) for the checking and leaves %rbp untouched. Signed-off-by: Vegard Nossum <vegard.nossum@gmail.com> Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi> Acked-by: Arjan van de Ven <arjan@linux.intel.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Pekka Enberg <penberg@cs.helsinki.fi> Signed-off-by: Ingo Molnar <mingo@elte.hu>
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