Messages in this thread | | | Date | Thu, 4 Apr 2019 15:20:07 +0800 | From | Chao Fan <> | Subject | Re: [PATCH v2] x86/boot: Use efi_setup_data for searching RSDP on kexec-ed kernel |
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On Thu, Apr 04, 2019 at 02:41:30PM +0800, Dave Young wrote: >On 04/04/19 at 11:22am, Dave Young wrote: >> On 04/04/19 at 11:10am, Baoquan He wrote: >> > On 04/04/19 at 11:00am, Baoquan He wrote: >> > > On 04/04/19 at 10:52am, Dave Young wrote: >> > > > On 04/04/19 at 01:23am, Junichi Nomura wrote: >> > + /* Save RSDP address for later use. */ >> > + boot_params->acpi_rsdp_addr = get_rsdp_addr(); >> > + >> > + error("Hang kernel for kexec debugging"); >> > >> > Sorry, here I means calling error() to hang kernel after calling >> > get_rsdp_addr(). >> >> Thanks, it did not hang, it always reset to firmware/grub boot menu. >> I'm pretty sure now the bug exists in get_rsdp_addr(). > >static acpi_physical_address kexec_get_rsdp_addr(void) >{ >... > /* Get systab from boot params. */ > systab = (efi_system_table_64_t *) (ei->efi_systab | ((__u64)ei->efi_systab_hi << 32)); > if (!systab) > error("EFI system table not found in kexec boot_params."); > >... > -> add error("hang me") here will have a hang >... > return __efi_get_rsdp_addr((unsigned long)esd->tables, > systab->nr_tables, true); >
I have an idea, but not sure whether is a problem. In code of Nomura:
#if defined(CONFIG_EFI) && defined(CONFIG_X86_64) [...] if (strncmp(sig, EFI64_LOADER_SIGNATURE, 4)) { debug_putstr("Wrong kexec EFI loader signature.\n"); return 0; }
/* Get systab from boot params. */ systab = (efi_system_table_64_t *) (ei->efi_systab | ((__u64)ei->efi_systab_hi << 32)); [...] #endif
After review agian, I wonder what will happen if 32bit-efi boot 64bit OS.
Ever meet a problem: https://lkml.org/lkml/2019/2/8/845
It's a efi32 bootloader to boot a 64bit OS, then a problem happened.
Thanks, Chao Fan
>But add error("hang me") in __efi_get_rsdp_addr it did not hang. > >It seems reference the systab pointer cause a system reset. > >A question is does the identity mapping covered the memory address of >systab? > >In my case it is 0xdad9ef18 > >If the memory is mapped on demand, then there will be problems, it >should cover setup_data and efi table space. > >Thanks >Dave > > >
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