Re: [RFC PATCH 6/6] powerpc/64s: Enable CONFIG_VMAP_STACK
From: Christophe Leroy <hidden>
Date: 2022-11-05 17:08:53
Also in:
linux-hardening
Le 04/11/2022 à 18:27, Andrew Donnellan a écrit :
Enable CONFIG_VMAP_STACK for book3s64. To do this, we need to make some slight adjustments to set the stack SLB entry up for vmalloc rather than linear. For now, only enable if KVM_BOOK3S_64_HV is disabled (there's some real mode handlers we need to fix there).
There is one missing point : with VMAP_STACK, a stack overflow will generate a page fault. You have to handle it at interrupt entry, before going back to virtual mode, otherwise it will fault forever. See how it is done in arch/powerpc/kernel/head_32.h, in macro EXCEPTION_PROLOG_1
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Signed-off-by: Andrew Donnellan <redacted> --- arch/powerpc/kernel/process.c | 4 ++++ arch/powerpc/mm/book3s64/slb.c | 11 +++++++++-- arch/powerpc/platforms/Kconfig.cputype | 1 + 3 files changed, 14 insertions(+), 2 deletions(-)diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index 07917726c629..cadf2db5a2a8 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c@@ -1685,7 +1685,11 @@ static void setup_ksp_vsid(struct task_struct *p, unsigned long sp) { #ifdef CONFIG_PPC_64S_HASH_MMU unsigned long sp_vsid; +#ifdef CONFIG_VMAP_STACK + unsigned long llp = mmu_psize_defs[mmu_vmalloc_psize].sllp; +#else /* CONFIG_VMAP_STACK */ unsigned long llp = mmu_psize_defs[mmu_linear_psize].sllp; +#endif /* CONFIG_VMAP_STACK */
I think you could use IS_ENABLED() instead of an ifdef: unsigned long llp; if (IS_ENABLED(CONFIG_VMAP_STACK)) llp = mmu_psize_defs[mmu_vmalloc_psize].sllp; else llp = mmu_psize_defs[mmu_linear_psize].sllp;
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if (radix_enabled()) return;diff --git a/arch/powerpc/mm/book3s64/slb.c b/arch/powerpc/mm/book3s64/slb.c index 6956f637a38c..0e21f0eaa7bb 100644 --- a/arch/powerpc/mm/book3s64/slb.c +++ b/arch/powerpc/mm/book3s64/slb.c@@ -541,7 +541,7 @@ void slb_set_size(u16 size) void slb_initialize(void) { unsigned long linear_llp, vmalloc_llp, io_llp; - unsigned long lflags; + unsigned long lflags, kstack_flags; static int slb_encoding_inited; #ifdef CONFIG_SPARSEMEM_VMEMMAP unsigned long vmemmap_llp;@@ -582,11 +582,18 @@ void slb_initialize(void) * get_paca()->kstack hasn't been initialized yet. * For secondary cpus, we need to bolt the kernel stack entry now. */ + +#ifdef CONFIG_VMAP_STACK + kstack_flags = SLB_VSID_KERNEL | vmalloc_llp; +#else + kstack_flags = SLB_VSID_KERNEL | linear_llp; +#endif
Same, should be if (IS_ENABLED(CONFIG_VMAP_STACK)) kstack_flags = SLB_VSID_KERNEL | vmalloc_llp; else kstack_flags = SLB_VSID_KERNEL | linear_llp;
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slb_shadow_clear(KSTACK_INDEX); if (raw_smp_processor_id() != boot_cpuid && (get_paca()->kstack & slb_esid_mask(mmu_kernel_ssize)) > PAGE_OFFSET) create_shadowed_slbe(get_paca()->kstack, - mmu_kernel_ssize, lflags, KSTACK_INDEX); + mmu_kernel_ssize, kstack_flags, + KSTACK_INDEX); asm volatile("isync":::"memory"); }diff --git a/arch/powerpc/platforms/Kconfig.cputype b/arch/powerpc/platforms/Kconfig.cputype index 0c4eed9aea80..998317257797 100644 --- a/arch/powerpc/platforms/Kconfig.cputype +++ b/arch/powerpc/platforms/Kconfig.cputype@@ -104,6 +104,7 @@ config PPC_BOOK3S_64 select IRQ_WORK select PPC_64S_HASH_MMU if !PPC_RADIX_MMU select KASAN_VMALLOC if KASAN + select HAVE_ARCH_VMAP_STACK if KVM_BOOK3S_64_HV = n
Is it different from select HAVE_ARCH_VMAP_STACK if !KVM_BOOK3S_64_HV ?
config PPC_BOOK3E_64 bool "Embedded processors"