From: Borislav Petkov <[email protected]> 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 | 8 ++++++++ include/asm-generic/vmlinux.lds.h | 4 +++- 2 files changed, 11 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S index 22fbf9df61bb..e69742517a54 100644 --- a/arch/x86/kernel/head_64.S +++ b/arch/x86/kernel/head_64.S @@ -64,6 +64,14 @@ startup_64: * tables and then reload them. */ + /* + * Setup stack for verify_cpu(). "-8" because stack_start is defined + * this way, see below. Our best guess is a NULL ptr for stack + * termination heuristics and we don't want to break anything which + * might depend on it (kgdb, ...). + */ + 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 339125bb4d2c..6a67ab94b553 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -245,7 +245,9 @@ #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 -- 2.7.3
