Takao Indoh (on Thu, 07 Sep 2006 23:48:51 +0900) wrote: >On Thu, 7 Sep 2006 21:01:17 +0800, "Yu, Luming" wrote: > >>>>Did saved Os gp in SAL OS state somehow get overridden before >>>>ia64_set_kernel_registers prior to invocation of ia64_init_handler? >>>> >>>>I assume the following code (in ia64_set_kernel_registers ) >>>should restore >>>>correct GP value. >>>> >>>>ia64_set_kernel_registers: >>>> ... >>>> ;; >>>> ld8 r1=[temp4] // OS GP from SAL OS state >>> >>>Yes, but this gp value is physical address. >>>In the next line, gp is changed to virtual address. >>> >>>DATA_PA_TO_VA(r1,temp1) >>> >>>This macro just sets region7 bit, so gp value becomes region7 address. >> >>Ok, could you please confirm what is the value of r1 before >>DATA_PA_TO_VA(r1, temp1)? >>I guess we need to set r1 = __gp in ia64_set_kernel_registers. >>If not, this is a bug. Am I right? > >In the ia64_mca_init, the value of ia64_tpa(ia64_getreg(_IA64_REG_GP) >is registered as gp value. When cpu comes into the above code, r1 is set >to this value, I think. Therefore, r1 has physical address of __gp >before DATA_PA_TO_VA(r1, temp1). How do you think? > >I think you are right, I also think r1 has to be set to __gp before >calling ia64_init_handler. It already is set in mca_asm.S. Remember that ia64_init_handler is by definition part of the kernel, it cannot be a module. Therefore before entering ia64_init_handler, r1 must be set to what the kernel expects to be in r1. The standard kernel's r1 is a region 7 address, not a region 5 address. The kernel (including __gp) is compiled as region 5 but relocated to region 7 during kernel load. Is the kexec kernel running in region 5? That may be where the confusion is coming from. - To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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