From 01b6fdcecd5a4a9afc93cba4217609b8ae842447 Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Fri, 30 Nov 2018 12:39:17 -0600 Subject: [PATCH] x86_64: Add gap to int3 to allow for call emulation commit 2700fefdb2d9751c416ad56897e27d41e409324a 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: b700e7f03df5 ("livepatch: kernel: add support for live patching") Tested-by: Nicolai Stange Reviewed-by: Nicolai Stange Reviewed-by: Masami Hiramatsu Signed-off-by: Josh Poimboeuf Signed-off-by: Steven Rostedt (VMware) Signed-off-by: Greg Kroah-Hartman --- arch/x86/entry/entry_64.S | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-) diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index 585bbc5..c90e00d 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -905,7 +905,7 @@ apicinterrupt IRQ_WORK_VECTOR irq_work_interrupt smp_irq_work_interrupt */ #define CPU_TSS_IST(x) PER_CPU_VAR(cpu_tss_rw) + (TSS_ist + ((x) - 1) * 8) -.macro idtentry sym do_sym has_error_code:req paranoid=0 shift_ist=-1 +.macro idtentry sym do_sym has_error_code:req paranoid=0 shift_ist=-1 create_gap=0 ENTRY(\sym) UNWIND_HINT_IRET_REGS offset=\has_error_code*8 @@ -925,6 +925,20 @@ ENTRY(\sym) jnz .Lfrom_usermode_switch_stack_\@ .endif + .if \create_gap == 1 + /* + * If coming from kernel space, create a 6-word gap to allow the + * int3 handler to emulate a call instruction. + */ + testb $3, CS-ORIG_RAX(%rsp) + jnz .Lfrom_usermode_no_gap_\@ + .rept 6 + pushq 5*8(%rsp) + .endr + UNWIND_HINT_IRET_REGS offset=8 +.Lfrom_usermode_no_gap_\@: + .endif + .if \paranoid call paranoid_entry .else @@ -1154,7 +1168,7 @@ apicinterrupt3 HYPERV_STIMER0_VECTOR \ #endif /* CONFIG_HYPERV */ idtentry debug do_debug has_error_code=0 paranoid=1 shift_ist=DEBUG_STACK -idtentry int3 do_int3 has_error_code=0 +idtentry int3 do_int3 has_error_code=0 create_gap=1 idtentry stack_segment do_stack_segment has_error_code=1 #ifdef CONFIG_XEN -- 2.7.4