From 44b979fa302cab91bdd2cc982823e5c13202cd4e Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Wed, 15 Sep 2021 17:12:59 +0200 Subject: x86/mm/64: Improve stack overflow warnings Current code has an explicit check for hitting the task stack guard; but overflowing any of the other stacks will get you a non-descript general #DF warning. Improve matters by using get_stack_info_noinstr() to detetrmine if and which stack guard page got hit, enabling a better stack warning. In specific, Michael Wang reported what turned out to be an NMI exception stack overflow, which is now clearly reported as such: [] BUG: NMI stack guard page was hit at 0000000085fd977b (stack is 000000003a55b09e..00000000d8cce1a5) Reported-by: Michael Wang Signed-off-by: Peter Zijlstra (Intel) Tested-by: Michael Wang Link: https://lkml.kernel.org/r/YUTE/NuqnaWbST8n@hirez.programming.kicks-ass.net --- arch/x86/mm/fault.c | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-) (limited to 'arch/x86/mm') diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index b2eefdefc108..edb5152f0866 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -32,6 +32,7 @@ #include /* VMALLOC_START, ... */ #include /* kvm_handle_async_pf */ #include /* fixup_vdso_exception() */ +#include #define CREATE_TRACE_POINTS #include @@ -631,6 +632,9 @@ static noinline void page_fault_oops(struct pt_regs *regs, unsigned long error_code, unsigned long address) { +#ifdef CONFIG_VMAP_STACK + struct stack_info info; +#endif unsigned long flags; int sig; @@ -649,9 +653,7 @@ page_fault_oops(struct pt_regs *regs, unsigned long error_code, * that we're in vmalloc space to avoid this. */ if (is_vmalloc_addr((void *)address) && - (((unsigned long)current->stack - 1 - address < PAGE_SIZE) || - address - ((unsigned long)current->stack + THREAD_SIZE) < PAGE_SIZE)) { - unsigned long stack = __this_cpu_ist_top_va(DF) - sizeof(void *); + get_stack_guard_info((void *)address, &info)) { /* * We're likely to be running with very little stack space * left. It's plausible that we'd hit this condition but @@ -662,13 +664,11 @@ page_fault_oops(struct pt_regs *regs, unsigned long error_code, * and then double-fault, though, because we're likely to * break the console driver and lose most of the stack dump. */ - asm volatile ("movq %[stack], %%rsp\n\t" - "call handle_stack_overflow\n\t" - "1: jmp 1b" - : ASM_CALL_CONSTRAINT - : "D" ("kernel stack overflow (page fault)"), - "S" (regs), "d" (address), - [stack] "rm" (stack)); + call_on_stack(__this_cpu_ist_top_va(DF) - sizeof(void*), + handle_stack_overflow, + ASM_CALL_ARG3, + , [arg1] "r" (regs), [arg2] "r" (address), [arg3] "r" (&info)); + unreachable(); } #endif -- cgit From 541ac97186d9ea88491961a46284de3603c914fd Mon Sep 17 00:00:00 2001 From: Borislav Petkov Date: Fri, 1 Oct 2021 21:41:20 +0200 Subject: x86/sev: Make the #VC exception stacks part of the default stacks storage The size of the exception stacks was increased by the commit in Fixes, resulting in stack sizes greater than a page in size. The #VC exception handling was only mapping the first (bottom) page, resulting in an SEV-ES guest failing to boot. Make the #VC exception stacks part of the default exception stacks storage and allocate them with a CONFIG_AMD_MEM_ENCRYPT=y .config. Map them only when a SEV-ES guest has been detected. Rip out the custom VC stacks mapping and storage code. [ bp: Steal and adapt Tom's commit message. ] Fixes: 7fae4c24a2b8 ("x86: Increase exception stack sizes") Signed-off-by: Borislav Petkov Tested-by: Tom Lendacky Tested-by: Brijesh Singh Link: https://lkml.kernel.org/r/YVt1IMjIs7pIZTRR@zn.tnic --- arch/x86/mm/cpu_entry_area.c | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'arch/x86/mm') diff --git a/arch/x86/mm/cpu_entry_area.c b/arch/x86/mm/cpu_entry_area.c index f5e1e60c9095..6c2f1b76a0b6 100644 --- a/arch/x86/mm/cpu_entry_area.c +++ b/arch/x86/mm/cpu_entry_area.c @@ -110,6 +110,13 @@ static void __init percpu_setup_exception_stacks(unsigned int cpu) cea_map_stack(NMI); cea_map_stack(DB); cea_map_stack(MCE); + + if (IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT)) { + if (cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT)) { + cea_map_stack(VC); + cea_map_stack(VC2); + } + } } #else static inline void percpu_setup_exception_stacks(unsigned int cpu) -- cgit