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x86_64: Add gap to int3 to allow for call emulation
commit2700fefdb2
upstream. To allow an int3 handler to emulate a call instruction, it must be able to push a return address onto the stack. Add a gap to the stack to allow the int3 handler to push the return address and change the return from int3 to jump straight to the emulated called function target. Link: http://lkml.kernel.org/r/20181130183917.hxmti5josgq4clti@treble Link: http://lkml.kernel.org/r/20190502162133.GX2623@hirez.programming.kicks-ass.net [ Note, this is needed to allow Live Kernel Patching to not miss calling a patched function when tracing is enabled. -- Steven Rostedt ] Cc: stable@vger.kernel.org Fixes:b700e7f03d
("livepatch: kernel: add support for live patching") Tested-by: Nicolai Stange <nstange@suse.de> Reviewed-by: Nicolai Stange <nstange@suse.de> Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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1 changed files with 16 additions and 2 deletions
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@ -853,7 +853,7 @@ ENTRY(switch_to_thread_stack)
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ret
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END(switch_to_thread_stack)
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.macro idtentry sym do_sym has_error_code:req paranoid=0 shift_ist=-1
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.macro idtentry sym do_sym has_error_code:req paranoid=0 shift_ist=-1 create_gap=0
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ENTRY(\sym)
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UNWIND_HINT_IRET_REGS offset=\has_error_code*8
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@ -873,6 +873,20 @@ ENTRY(\sym)
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jnz .Lfrom_usermode_switch_stack_\@
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.endif
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.if \create_gap == 1
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/*
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* If coming from kernel space, create a 6-word gap to allow the
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* int3 handler to emulate a call instruction.
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*/
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testb $3, CS-ORIG_RAX(%rsp)
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jnz .Lfrom_usermode_no_gap_\@
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.rept 6
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pushq 5*8(%rsp)
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.endr
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UNWIND_HINT_IRET_REGS offset=8
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.Lfrom_usermode_no_gap_\@:
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.endif
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.if \paranoid
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call paranoid_entry
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.else
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@ -1093,7 +1107,7 @@ apicinterrupt3 HYPERVISOR_CALLBACK_VECTOR \
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#endif /* CONFIG_HYPERV */
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idtentry debug do_debug has_error_code=0 paranoid=1 shift_ist=DEBUG_STACK
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idtentry int3 do_int3 has_error_code=0
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idtentry int3 do_int3 has_error_code=0 create_gap=1
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idtentry stack_segment do_stack_segment has_error_code=1
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#ifdef CONFIG_XEN
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