On Wed, Mar 02, 2016 at 02:32:54PM -0800, H. Peter Anvin wrote: > I'm trying to think of any reason why we couldn't simply have a symbol > at the top of the initial stack? Then a simple leaq would suffice; > this is for the BSP after all.
How about something like this: --- From: Borislav Petkov <[email protected]> Date: Sun, 28 Feb 2016 21:35:44 +0100 Subject: [PATCH -v2] x86/asm: Make sure verify_cpu() has a good stack MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 04633df0c43d ("x86/cpu: Call verify_cpu() after having entered long mode too") added the call to verify_cpu() for sanitizing CPU configuration. The latter uses the stack minimally and it can happen that we land in startup_64() directly from a 64-bit bootloader. Then we want to use our own, known good stack. Do that. APs don't need this as the trampoline sets up a stack for them. Reported-by: Tom Lendacky <[email protected]> Signed-off-by: Borislav Petkov <[email protected]> Cc: Brian Gerst <[email protected]> Cc: "H. Peter Anvin" <[email protected]> Cc: Mika Penttilä <[email protected]> --- arch/x86/kernel/head_64.S | 3 +++ include/asm-generic/vmlinux.lds.h | 4 +++- 2 files changed, 6 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S index 22fbf9df61bb..968d6408b887 100644 --- a/arch/x86/kernel/head_64.S +++ b/arch/x86/kernel/head_64.S @@ -64,6 +64,9 @@ startup_64: * tables and then reload them. */ + /* Setup stack for verify_cpu(). */ + leaq (__end_init_task - 8)(%rip), %rsp + /* Sanitize CPU configuration */ call verify_cpu diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index 772c784ba763..cba2a26628fc 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -246,7 +246,9 @@ #define INIT_TASK_DATA(align) \ . = ALIGN(align); \ - *(.data..init_task) + VMLINUX_SYMBOL(__start_init_task) = .; \ + *(.data..init_task) \ + VMLINUX_SYMBOL(__end_init_task) = .; /* * Read only Data -- 2.3.5 -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply.
