Commit-ID: a6b744f3ce9d017dd86b28355de2d8e0d36496d4 Gitweb: https://git.kernel.org/tip/a6b744f3ce9d017dd86b28355de2d8e0d36496d4 Author: Joerg Roedel <jroe...@suse.de> AuthorDate: Wed, 18 Jul 2018 11:40:40 +0200 Committer: Thomas Gleixner <t...@linutronix.de> CommitDate: Fri, 20 Jul 2018 01:11:36 +0200
x86/entry/32: Load task stack from x86_tss.sp1 in SYSENTER handler x86_tss.sp0 will be used to point to the entry stack later to use it as a trampoline stack for other kernel entry points besides SYSENTER. So store the real task stack pointer in x86_tss.sp1, which is otherwise unused by the hardware, as Linux doesn't make use of Ring 1. Signed-off-by: Joerg Roedel <jroe...@suse.de> Signed-off-by: Thomas Gleixner <t...@linutronix.de> Tested-by: Pavel Machek <pa...@ucw.cz> Cc: "H . Peter Anvin" <h...@zytor.com> Cc: linux...@kvack.org Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Andy Lutomirski <l...@kernel.org> Cc: Dave Hansen <dave.han...@intel.com> Cc: Josh Poimboeuf <jpoim...@redhat.com> Cc: Juergen Gross <jgr...@suse.com> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Borislav Petkov <b...@alien8.de> Cc: Jiri Kosina <jkos...@suse.cz> Cc: Boris Ostrovsky <boris.ostrov...@oracle.com> Cc: Brian Gerst <brge...@gmail.com> Cc: David Laight <david.lai...@aculab.com> Cc: Denys Vlasenko <dvlas...@redhat.com> Cc: Eduardo Valentin <edu...@amazon.com> Cc: Greg KH <gre...@linuxfoundation.org> Cc: Will Deacon <will.dea...@arm.com> Cc: aligu...@amazon.com Cc: daniel.gr...@iaik.tugraz.at Cc: hu...@google.com Cc: keesc...@google.com Cc: Andrea Arcangeli <aarca...@redhat.com> Cc: Waiman Long <ll...@redhat.com> Cc: "David H . Gutteridge" <dhgutteri...@sympatico.ca> Cc: j...@8bytes.org Link: https://lkml.kernel.org/r/1531906876-13451-4-git-send-email-j...@8bytes.org --- arch/x86/kernel/asm-offsets_32.c | 9 +++++++-- arch/x86/kernel/process_32.c | 2 ++ 2 files changed, 9 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/asm-offsets_32.c b/arch/x86/kernel/asm-offsets_32.c index 15b3f45b69cd..82826f2275cc 100644 --- a/arch/x86/kernel/asm-offsets_32.c +++ b/arch/x86/kernel/asm-offsets_32.c @@ -46,9 +46,14 @@ void foo(void) OFFSET(saved_context_gdt_desc, saved_context, gdt_desc); BLANK(); - /* Offset from the entry stack to task stack stored in TSS */ + /* + * Offset from the entry stack to task stack stored in TSS. Kernel entry + * happens on the per-cpu entry-stack, and the asm code switches to the + * task-stack pointer stored in x86_tss.sp1, which is a copy of + * task->thread.sp0 where entry code can find it. + */ DEFINE(TSS_entry2task_stack, - offsetof(struct cpu_entry_area, tss.x86_tss.sp0) - + offsetof(struct cpu_entry_area, tss.x86_tss.sp1) - offsetofend(struct cpu_entry_area, entry_stack_page.stack)); #ifdef CONFIG_STACKPROTECTOR diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c index 0ae659de21eb..ec62cc77388d 100644 --- a/arch/x86/kernel/process_32.c +++ b/arch/x86/kernel/process_32.c @@ -290,6 +290,8 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p) this_cpu_write(cpu_current_top_of_stack, (unsigned long)task_stack_page(next_p) + THREAD_SIZE); + /* SYSENTER reads the task-stack from tss.sp1 */ + this_cpu_write(cpu_tss_rw.x86_tss.sp1, next_p->thread.sp0); /* * Restore %gs if needed (which is common)
