From d0cd64b02aa854d68ce517cb7da1fe4e4fff2653 Mon Sep 17 00:00:00 2001 From: Yonghong Song Date: Wed, 8 Nov 2017 11:28:45 -0800 Subject: [PATCH] x86/idt: Remove X86_TRAP_BP initialization in idt_setup_traps() Commit b70543a0b2b6("x86/idt: Move regular trap init to tables") moves regular trap init for each trap vector into a table based initialization. It introduced the initialization for vector X86_TRAP_BP which was not in the code which it replaced. This breaks uprobe functionality for x86_32; the probed program segfaults instead of handling the probe proper. The reason for this is that TRAP_BP is set up as system interrupt gate (DPL3) in the early IDT and then replaced by a regular interrupt gate (DPL0) in idt_setup_traps(). The DPL0 restriction causes the int3 trap to fail with a #GP resulting in a SIGSEGV of the probed program. On 64bit this does not cause a problem because the IDT entry is replaced with a system interrupt gate (DPL3) with interrupt stack afterwards. Remove X86_TRAP_BP from the def_idts table which is used in idt_setup_traps(). Remove a redundant entry for X86_TRAP_NMI in def_idts while at it. Tested on both x86_64 and x86_32. [ tglx: Amended changelog with a description of the root cause ] Fixes: b70543a0b2b6("x86/idt: Move regular trap init to tables") Reported-and-tested-by: Yonghong Song Signed-off-by: Yonghong Song Signed-off-by: Thomas Gleixner Cc: a.p.zijlstra@chello.nl Cc: ast@fb.com Cc: oleg@redhat.com Cc: luto@kernel.org Cc: kernel-team@fb.com Link: https://lkml.kernel.org/r/20171108192845.552709-1-yhs@fb.com --- arch/x86/kernel/idt.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/arch/x86/kernel/idt.c b/arch/x86/kernel/idt.c index 6107ee1cb8d5..014cb2fc47ff 100644 --- a/arch/x86/kernel/idt.c +++ b/arch/x86/kernel/idt.c @@ -92,8 +92,6 @@ static const __initdata struct idt_data def_idts[] = { INTG(X86_TRAP_DF, double_fault), #endif INTG(X86_TRAP_DB, debug), - INTG(X86_TRAP_NMI, nmi), - INTG(X86_TRAP_BP, int3), #ifdef CONFIG_X86_MCE INTG(X86_TRAP_MC, &machine_check),