uprobes/x86: Emulate unconditional relative jmp's

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Currently we always execute all insns out-of-line, including relative
jmp's and call's. This assumes that even if regs->ip points to nowhere
after the single-step, default_post_xol_op(UPROBE_FIX_IP) logic will
update it correctly.

However, this doesn't work if this regs->ip == xol_vaddr + insn_offset
is not canonical. In this case CPU generates #GP and general_protection()
kills the task which tries to execute this insn out-of-line.

Now that we have uprobe_xol_ops we can teach uprobes to emulate these
insns and solve the problem. This patch adds branch_xol_ops which has
a single branch_emulate_op() hook, so far it can only handle rel8/32
relative jmp's.

TODO: move ->fixup into the union along with rip_rela_target_address.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reported-by: Jonathan Lebon <jlebon@redhat.com>
Reviewed-by: Jim Keniston <jkenisto@us.ibm.com>

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This commit is contained in:

Oleg Nesterov 2014-04-05 20:05:02 +02:00

parent 8faaed1b9f

commit 7ba6db2d68

2 changed files with 45 additions and 1 deletions

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8

arch/x86/include/asm/uprobes.h

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38

arch/x86/kernel/uprobes.c

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