The kernel panics early in boot on a x86_64 server if the eXecute Disable (XD) bit is set to disabled in the uEFI firmware. The message in the kernel log buffer looks like below. ------------------------------------------------------------------------ [ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 4.4.0-rc3 #1 [ 0.000000] 0000000000000000 261c6fa13723be1b ffffffff819b7e40 ffffffff8131f320 [ 0.000000] ffffffffffffffff ffffffff819b7f30 ffffffff81b261b0 000000000000001c [ 0.000000] ffffffff81d77a1c 0000000000000010 00000000be35a000 ffffffffff200000 [ 0.000000] Call Trace: [ 0.000000] [<ffffffff8131f320>] dump_stack+0x44/0x64 [ 0.000000] [<ffffffff81b261b0>] early_idt_handler_common+0x90/0xd0 [ 0.000000] [<ffffffff81b2f1c5>] ? setup_arch+0x1f1/0xce0 [ 0.000000] [<ffffffff81b2f1c5>] ? setup_arch+0x1f1/0xce0 [ 0.000000] [<ffffffff81b26120>] ? early_idt_handler_array+0x120/0x120 [ 0.000000] [<ffffffff81b26d81>] start_kernel+0xe6/0x4f0 [ 0.000000] [<ffffffff81b26120>] ? early_idt_handler_array+0x120/0x120 [ 0.000000] [<ffffffff81b26120>] ? early_idt_handler_array+0x120/0x120 [ 0.000000] [<ffffffff81b265ee>] x86_64_start_reservations+0x2a/0x2c [ 0.000000] [<ffffffff81b2673c>] x86_64_start_kernel+0x14c/0x16f [ 0.000000] RIP 0x80000000be359163 ------------------------------------------------------------------------ The panic occurs because __early_set_fixmap() called from parse_setup_data() unconditionally sets the PTE with FIXMAP_PAGE_NORMAL, which contains _PAGE_NX and causes an exception. This patch modifies __early_set_fixmap() to set _PAGE_NX only when the hardware supports it. It also moves the call to x86_configure_nx() earlier in setup_arch() before __early_set_fixmap() is first called. The above problem occurs after __early_set_fixmap() is called from parse_setup_data(). However, since setup_olpc_ofw_pgd() can also call __early_set_fixmap(), the patch moves the call to x86_configure_nx() before that. Signed-off-by: Kosuke Tatsukawa <tatsu@xxxxxxxxxxxxx> --- arch/x86/kernel/setup.c | 18 +++++++++--------- arch/x86/mm/ioremap.c | 3 +++ 2 files changed, 12 insertions(+), 9 deletions(-) diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c index 29db25f..c8b2cdb 100644 --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -894,6 +894,15 @@ void __init setup_arch(char **cmdline_p) early_cpu_init(); early_ioremap_init(); + /* + * x86_configure_nx() is called to detect whether hardware doesn't + * support NX. It has to be called before __early_set_fixmap() is + * called from setup_olpc_ofw_pgd and parse_setup_data. It may + * then be called again from within noexec_setup() during parsing + * early parameters to honor the respective command line option. + */ + x86_configure_nx(); + setup_olpc_ofw_pgd(); ROOT_DEV = old_decode_dev(boot_params.hdr.root_dev); @@ -971,15 +980,6 @@ void __init setup_arch(char **cmdline_p) strlcpy(command_line, boot_command_line, COMMAND_LINE_SIZE); *cmdline_p = command_line; - /* - * x86_configure_nx() is called before parse_early_param() to detect - * whether hardware doesn't support NX (so that the early EHCI debug - * console setup can safely call set_fixmap()). It may then be called - * again from within noexec_setup() during parsing early parameters - * to honor the respective command line option. - */ - x86_configure_nx(); - parse_early_param(); x86_report_nx(); diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c index b9c78f3..9036c8e 100644 --- a/arch/x86/mm/ioremap.c +++ b/arch/x86/mm/ioremap.c @@ -493,6 +493,9 @@ void __init __early_set_fixmap(enum fixed_addresses idx, } pte = early_ioremap_pte(addr); + if (!(__supported_pte_mask & _PAGE_NX)) + pgprot_val(flags) &= ~_PAGE_NX; + if (pgprot_val(flags)) set_pte(pte, pfn_pte(phys >> PAGE_SHIFT, flags)); else -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
