[Please wrap commit messages at around 74 columns] On Fri, Aug 07, 2015 at 02:58:10PM +0800, Yuanjie Huang wrote: > PowerPC Book3E processor features hardware-supported single instruction > execution, and it is used for ptrace(PTRACE_SINGLESTEP, ...). When a > debugger loads a debuggee, it typically sets the CPU to yield debug > interrupt on first instruction complete or branch taken. However, the > newly-forked child process could run into instruction TLB miss > exception handler when switched to, and causes a debug interrupt in the > exception entry sequence. This is not expected by caller of > ptrace(PTRACE_SINGLESTEP, ...), so the next instruction address saved > in DSRR0 is checked against the boundary of exception entry sequence, > to ensure the kernel only process the interrupt as a normal exception > if the address does not fall in the exception entry sequence. Failure > in obtaining the correct boundary leads to such debug exception handled > as from privileged mode, and causes kernel oops. > > The LOAD_REG_IMMEDIATE can't be used to load the boundary addresses > when relocatable enabled, so this patch replace them with > LOAD_REG_ADDR_PIC. LR is backed up and restored before and after > calling LOAD_REG_ADDR_PIC, because LOAD_REG_ADDR_PIC clobbers it. > > Signed-off-by: Yuanjie Huang <yuanjie.hu...@windriver.com> > --- > arch/powerpc/kernel/exceptions-64e.S | 24 ++++++++++++++++++++++++ > 1 file changed, 24 insertions(+) > > diff --git a/arch/powerpc/kernel/exceptions-64e.S > b/arch/powerpc/kernel/exceptions-64e.S > index 3e68d1c..c475f569 100644 > --- a/arch/powerpc/kernel/exceptions-64e.S > +++ b/arch/powerpc/kernel/exceptions-64e.S > @@ -735,12 +735,24 @@ END_FTR_SECTION_IFSET(CPU_FTR_ALTIVEC) > andis. r15,r14,(DBSR_IC|DBSR_BT)@h > beq+ 1f > > +#ifdef CONFIG_RELOCATABLE > + mflr r14 > + LOAD_REG_ADDR_PIC(r15,interrupt_base_book3e) > + mtlr r14 > + cmpld cr0,r10,r15 > + blt+ cr0,1f > + LOAD_REG_ADDR_PIC(r15,interrupt_end_book3e) > + mtlr r14 > + cmpld cr0,r10,r15 > + bge+ cr0,1f > +#else
CONFIG_RELOCATABLE is not supported on 64-bit book3e without applying additional patches, such as the RFC patchset I posted recently that contained the patch "powerpc/book3e-64: rename interrupt_end_book3e with __end_interrupts". But if you've applied that patchset, then you wouldn't be working with the name interrupt_base_book3e, so how are you seeing this? Also, why not use the RELOCATABLE version unconditionally? I don't think this is a performance-critical path. -Scott _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
