Messages in this thread Patch in this message | | | Date | Wed, 3 Jan 2018 19:52:04 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: CONFIG_PAGE_TABLE_ISOLATION=y on x86_64 causes gcc to segfault when building x86_32 binaries |
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On Wed, 3 Jan 2018, Thomas Gleixner wrote:
> On Wed, 3 Jan 2018, Lars Wendler wrote: > > Am Wed, 3 Jan 2018 13:05:38 +0100 (CET) > > schrieb Thomas Gleixner <tglx@linutronix.de>: > > > Also can you please try Linus v4.15-rc6 with PTI enabled so we can see > > > whether that's a backport issue or a general one? > > > > Same problem with 4.15-rc6. So I suppose that means it's a general > > issue. > > Just a shot in the dark as I just decoded another issue on a AMD CPU. Can > you please try the patch below?
Ok. Found the real issue. This is a problem on AMD boxen.
Fix below.
Can Xen folks please have a look at that as well?
Thanks,
tglx
8<-------------------
arch/x86/entry/entry_64_compat.S | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-)
--- a/arch/x86/entry/entry_64_compat.S +++ b/arch/x86/entry/entry_64_compat.S @@ -190,8 +190,13 @@ ENTRY(entry_SYSCALL_compat) /* Interrupts are off on entry. */ swapgs - /* Stash user ESP and switch to the kernel stack. */ + /* Stash user ESP */ movl %esp, %r8d + + /* Use %rsp as scratch reg. User ESP is stashed in r8 */ + SWITCH_TO_KERNEL_CR3 scratch_reg=%rsp + + /* Switch to the kernel stack */ movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp /* Construct struct pt_regs on stack */ @@ -220,12 +225,6 @@ GLOBAL(entry_SYSCALL_compat_after_hwfram pushq $0 /* pt_regs->r15 = 0 */ /* - * We just saved %rdi so it is safe to clobber. It is not - * preserved during the C calls inside TRACE_IRQS_OFF anyway. - */ - SWITCH_TO_KERNEL_CR3 scratch_reg=%rdi - - /* * User mode is traced as though IRQs are on, and SYSENTER * turned them off. */
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