Re: [PATCH 3/5] powerpc/lib: Use a temporary mm for code patching
On Wed Jun 3, 2020 at 9:12 AM, Christophe Leroy wrote:
>
>
>
>
> Le 03/06/2020 à 07:19, Christopher M. Riedl a écrit :
> > Currently, code patching a STRICT_KERNEL_RWX exposes the temporary
> > mappings to other CPUs. These mappings should be kept local to the CPU
> > doing the patching. Use the pre-initialized temporary mm and patching
> > address for this purpose. Also add a check after patching to ensure the
> > patch succeeded.
> >
> > Use the KUAP functions on non-BOOKS3_64 platforms since the temporary
> > mapping for patching uses a userspace address (to keep the mapping
> > local). On BOOKS3_64 platforms hash does not implement KUAP and on radix
> > the use of PAGE_KERNEL sets EAA[0] for the PTE which means the AMR
> > (KUAP) protection is ignored (see PowerISA v3.0b, Fig, 35).
> >
> > Based on x86 implementation:
> >
> > commit b3fd8e83ada0
> > ("x86/alternatives: Use temporary mm for text poking")
> >
> > Signed-off-by: Christopher M. Riedl
> > ---
> > arch/powerpc/lib/code-patching.c | 148 ---
> > 1 file changed, 55 insertions(+), 93 deletions(-)
> >
> > diff --git a/arch/powerpc/lib/code-patching.c
> > b/arch/powerpc/lib/code-patching.c
> > index 599114f63b44..df0765845204 100644
> > --- a/arch/powerpc/lib/code-patching.c
> > +++ b/arch/powerpc/lib/code-patching.c
> > @@ -20,6 +20,7 @@
> > #include
> > #include
> > #include
> > +#include
> >
> > static int __patch_instruction(struct ppc_inst *exec_addr, struct
> > ppc_inst instr,
> >struct ppc_inst *patch_addr)
> > @@ -78,101 +79,58 @@ void __init poking_init(void)
> > pte_unmap_unlock(ptep, ptl);
> > }
> >
> > -static DEFINE_PER_CPU(struct vm_struct *, text_poke_area);
> > -
> > -static int text_area_cpu_up(unsigned int cpu)
> > -{
> > - struct vm_struct *area;
> > -
> > - area = get_vm_area(PAGE_SIZE, VM_ALLOC);
> > - if (!area) {
> > - WARN_ONCE(1, "Failed to create text area for cpu %d\n",
> > - cpu);
> > - return -1;
> > - }
> > - this_cpu_write(text_poke_area, area);
> > -
> > - return 0;
> > -}
> > -
> > -static int text_area_cpu_down(unsigned int cpu)
> > -{
> > - free_vm_area(this_cpu_read(text_poke_area));
> > - return 0;
> > -}
> > -
> > -/*
> > - * Run as a late init call. This allows all the boot time patching to be
> > done
> > - * simply by patching the code, and then we're called here prior to
> > - * mark_rodata_ro(), which happens after all init calls are run. Although
> > - * BUG_ON() is rude, in this case it should only happen if ENOMEM, and we
> > judge
> > - * it as being preferable to a kernel that will crash later when someone
> > tries
> > - * to use patch_instruction().
> > - */
> > -static int __init setup_text_poke_area(void)
> > -{
> > - BUG_ON(!cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
> > - "powerpc/text_poke:online", text_area_cpu_up,
> > - text_area_cpu_down));
> > -
> > - return 0;
> > -}
> > -late_initcall(setup_text_poke_area);
> > +struct patch_mapping {
> > + spinlock_t *ptl; /* for protecting pte table */
> > + pte_t *ptep;
> > + struct temp_mm temp_mm;
> > +};
> >
> > /*
> >* This can be called for kernel text or a module.
> >*/
> > -static int map_patch_area(void *addr, unsigned long text_poke_addr)
> > +static int map_patch(const void *addr, struct patch_mapping *patch_mapping)
> > {
> > - unsigned long pfn;
> > - int err;
> > + struct page *page;
> > + pte_t pte;
> > + pgprot_t pgprot;
> >
> > if (is_vmalloc_addr(addr))
> > - pfn = vmalloc_to_pfn(addr);
> > + page = vmalloc_to_page(addr);
> > else
> > - pfn = __pa_symbol(addr) >> PAGE_SHIFT;
> > + page = virt_to_page(addr);
> >
> > - err = map_kernel_page(text_poke_addr, (pfn << PAGE_SHIFT), PAGE_KERNEL);
> > + if (radix_enabled())
> > + pgprot = PAGE_KERNEL;
> > + else
> > + pgprot = PAGE_SHARED;
> >
> > - pr_devel("Mapped addr %lx with pfn %lx:%d\n", text_poke_addr, pfn, err);
> > - if (err)
> > + patch_mapping->ptep = get_locked_pte(patching_mm, patching_addr,
> > +_mapping->ptl);
> > + if (unlikely(!patch_mapping->ptep)) {
> > + pr_warn("map patch: failed to allocate pte for patching\n");
> > return -1;
> > + }
> > +
> > + pte = mk_pte(page, pgprot);
> > + if (!IS_ENABLED(CONFIG_PPC_BOOK3S_64))
> > + pte = pte_mkdirty(pte);
>
>
> Are you should you don't need the DIRTY bit for BOOK3S/64 non radix ?
>
>
> I think the DIRTY bit is needed always, and adding it when it is already
> there is harmless, so it should be done inconditionnnaly.
>
I tested this and it doesn't seem to make a differnce so I can make this
common in the next spin.
>
> > + set_pte_at(patching_mm, patching_addr, patch_mapping->ptep, pte);
> > +
> > + init_temp_mm(_mapping->temp_mm, patching_mm);
> > +
Re: [PATCH 3/5] powerpc/lib: Use a temporary mm for code patching
Le 03/06/2020 à 07:19, Christopher M. Riedl a écrit :
Currently, code patching a STRICT_KERNEL_RWX exposes the temporary
mappings to other CPUs. These mappings should be kept local to the CPU
doing the patching. Use the pre-initialized temporary mm and patching
address for this purpose. Also add a check after patching to ensure the
patch succeeded.
Use the KUAP functions on non-BOOKS3_64 platforms since the temporary
mapping for patching uses a userspace address (to keep the mapping
local). On BOOKS3_64 platforms hash does not implement KUAP and on radix
the use of PAGE_KERNEL sets EAA[0] for the PTE which means the AMR
(KUAP) protection is ignored (see PowerISA v3.0b, Fig, 35).
Based on x86 implementation:
commit b3fd8e83ada0
("x86/alternatives: Use temporary mm for text poking")
Signed-off-by: Christopher M. Riedl
---
arch/powerpc/lib/code-patching.c | 148 ---
1 file changed, 55 insertions(+), 93 deletions(-)
diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
index 599114f63b44..df0765845204 100644
--- a/arch/powerpc/lib/code-patching.c
+++ b/arch/powerpc/lib/code-patching.c
@@ -20,6 +20,7 @@
#include
#include
#include
+#include
static int __patch_instruction(struct ppc_inst *exec_addr, struct ppc_inst instr,
struct ppc_inst *patch_addr)
@@ -78,101 +79,58 @@ void __init poking_init(void)
pte_unmap_unlock(ptep, ptl);
}
-static DEFINE_PER_CPU(struct vm_struct *, text_poke_area);
-
-static int text_area_cpu_up(unsigned int cpu)
-{
- struct vm_struct *area;
-
- area = get_vm_area(PAGE_SIZE, VM_ALLOC);
- if (!area) {
- WARN_ONCE(1, "Failed to create text area for cpu %d\n",
- cpu);
- return -1;
- }
- this_cpu_write(text_poke_area, area);
-
- return 0;
-}
-
-static int text_area_cpu_down(unsigned int cpu)
-{
- free_vm_area(this_cpu_read(text_poke_area));
- return 0;
-}
-
-/*
- * Run as a late init call. This allows all the boot time patching to be done
- * simply by patching the code, and then we're called here prior to
- * mark_rodata_ro(), which happens after all init calls are run. Although
- * BUG_ON() is rude, in this case it should only happen if ENOMEM, and we judge
- * it as being preferable to a kernel that will crash later when someone tries
- * to use patch_instruction().
- */
-static int __init setup_text_poke_area(void)
-{
- BUG_ON(!cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
- "powerpc/text_poke:online", text_area_cpu_up,
- text_area_cpu_down));
-
- return 0;
-}
-late_initcall(setup_text_poke_area);
+struct patch_mapping {
+ spinlock_t *ptl; /* for protecting pte table */
+ pte_t *ptep;
+ struct temp_mm temp_mm;
+};
/*
* This can be called for kernel text or a module.
*/
-static int map_patch_area(void *addr, unsigned long text_poke_addr)
+static int map_patch(const void *addr, struct patch_mapping *patch_mapping)
{
- unsigned long pfn;
- int err;
+ struct page *page;
+ pte_t pte;
+ pgprot_t pgprot;
if (is_vmalloc_addr(addr))
- pfn = vmalloc_to_pfn(addr);
+ page = vmalloc_to_page(addr);
else
- pfn = __pa_symbol(addr) >> PAGE_SHIFT;
+ page = virt_to_page(addr);
- err = map_kernel_page(text_poke_addr, (pfn << PAGE_SHIFT), PAGE_KERNEL);
+ if (radix_enabled())
+ pgprot = PAGE_KERNEL;
+ else
+ pgprot = PAGE_SHARED;
- pr_devel("Mapped addr %lx with pfn %lx:%d\n", text_poke_addr, pfn, err);
- if (err)
+ patch_mapping->ptep = get_locked_pte(patching_mm, patching_addr,
+_mapping->ptl);
+ if (unlikely(!patch_mapping->ptep)) {
+ pr_warn("map patch: failed to allocate pte for patching\n");
return -1;
+ }
+
+ pte = mk_pte(page, pgprot);
+ if (!IS_ENABLED(CONFIG_PPC_BOOK3S_64))
+ pte = pte_mkdirty(pte);
Are you should you don't need the DIRTY bit for BOOK3S/64 non radix ?
I think the DIRTY bit is needed always, and adding it when it is already
there is harmless, so it should be done inconditionnnaly.
+ set_pte_at(patching_mm, patching_addr, patch_mapping->ptep, pte);
+
+ init_temp_mm(_mapping->temp_mm, patching_mm);
+ use_temporary_mm(_mapping->temp_mm);
return 0;
}
-static inline int unmap_patch_area(unsigned long addr)
+static void unmap_patch(struct patch_mapping *patch_mapping)
{
- pte_t *ptep;
- pmd_t *pmdp;
- pud_t *pudp;
- pgd_t *pgdp;
-
- pgdp = pgd_offset_k(addr);
- if (unlikely(!pgdp))
- return -EINVAL;
-
- pudp = pud_offset(pgdp, addr);
- if (unlikely(!pudp))
- return -EINVAL;
-
- pmdp = pmd_offset(pudp, addr);
-
[PATCH 3/5] powerpc/lib: Use a temporary mm for code patching
Currently, code patching a STRICT_KERNEL_RWX exposes the temporary
mappings to other CPUs. These mappings should be kept local to the CPU
doing the patching. Use the pre-initialized temporary mm and patching
address for this purpose. Also add a check after patching to ensure the
patch succeeded.
Use the KUAP functions on non-BOOKS3_64 platforms since the temporary
mapping for patching uses a userspace address (to keep the mapping
local). On BOOKS3_64 platforms hash does not implement KUAP and on radix
the use of PAGE_KERNEL sets EAA[0] for the PTE which means the AMR
(KUAP) protection is ignored (see PowerISA v3.0b, Fig, 35).
Based on x86 implementation:
commit b3fd8e83ada0
("x86/alternatives: Use temporary mm for text poking")
Signed-off-by: Christopher M. Riedl
---
arch/powerpc/lib/code-patching.c | 148 ---
1 file changed, 55 insertions(+), 93 deletions(-)
diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
index 599114f63b44..df0765845204 100644
--- a/arch/powerpc/lib/code-patching.c
+++ b/arch/powerpc/lib/code-patching.c
@@ -20,6 +20,7 @@
#include
#include
#include
+#include
static int __patch_instruction(struct ppc_inst *exec_addr, struct ppc_inst
instr,
struct ppc_inst *patch_addr)
@@ -78,101 +79,58 @@ void __init poking_init(void)
pte_unmap_unlock(ptep, ptl);
}
-static DEFINE_PER_CPU(struct vm_struct *, text_poke_area);
-
-static int text_area_cpu_up(unsigned int cpu)
-{
- struct vm_struct *area;
-
- area = get_vm_area(PAGE_SIZE, VM_ALLOC);
- if (!area) {
- WARN_ONCE(1, "Failed to create text area for cpu %d\n",
- cpu);
- return -1;
- }
- this_cpu_write(text_poke_area, area);
-
- return 0;
-}
-
-static int text_area_cpu_down(unsigned int cpu)
-{
- free_vm_area(this_cpu_read(text_poke_area));
- return 0;
-}
-
-/*
- * Run as a late init call. This allows all the boot time patching to be done
- * simply by patching the code, and then we're called here prior to
- * mark_rodata_ro(), which happens after all init calls are run. Although
- * BUG_ON() is rude, in this case it should only happen if ENOMEM, and we judge
- * it as being preferable to a kernel that will crash later when someone tries
- * to use patch_instruction().
- */
-static int __init setup_text_poke_area(void)
-{
- BUG_ON(!cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
- "powerpc/text_poke:online", text_area_cpu_up,
- text_area_cpu_down));
-
- return 0;
-}
-late_initcall(setup_text_poke_area);
+struct patch_mapping {
+ spinlock_t *ptl; /* for protecting pte table */
+ pte_t *ptep;
+ struct temp_mm temp_mm;
+};
/*
* This can be called for kernel text or a module.
*/
-static int map_patch_area(void *addr, unsigned long text_poke_addr)
+static int map_patch(const void *addr, struct patch_mapping *patch_mapping)
{
- unsigned long pfn;
- int err;
+ struct page *page;
+ pte_t pte;
+ pgprot_t pgprot;
if (is_vmalloc_addr(addr))
- pfn = vmalloc_to_pfn(addr);
+ page = vmalloc_to_page(addr);
else
- pfn = __pa_symbol(addr) >> PAGE_SHIFT;
+ page = virt_to_page(addr);
- err = map_kernel_page(text_poke_addr, (pfn << PAGE_SHIFT), PAGE_KERNEL);
+ if (radix_enabled())
+ pgprot = PAGE_KERNEL;
+ else
+ pgprot = PAGE_SHARED;
- pr_devel("Mapped addr %lx with pfn %lx:%d\n", text_poke_addr, pfn, err);
- if (err)
+ patch_mapping->ptep = get_locked_pte(patching_mm, patching_addr,
+_mapping->ptl);
+ if (unlikely(!patch_mapping->ptep)) {
+ pr_warn("map patch: failed to allocate pte for patching\n");
return -1;
+ }
+
+ pte = mk_pte(page, pgprot);
+ if (!IS_ENABLED(CONFIG_PPC_BOOK3S_64))
+ pte = pte_mkdirty(pte);
+ set_pte_at(patching_mm, patching_addr, patch_mapping->ptep, pte);
+
+ init_temp_mm(_mapping->temp_mm, patching_mm);
+ use_temporary_mm(_mapping->temp_mm);
return 0;
}
-static inline int unmap_patch_area(unsigned long addr)
+static void unmap_patch(struct patch_mapping *patch_mapping)
{
- pte_t *ptep;
- pmd_t *pmdp;
- pud_t *pudp;
- pgd_t *pgdp;
-
- pgdp = pgd_offset_k(addr);
- if (unlikely(!pgdp))
- return -EINVAL;
-
- pudp = pud_offset(pgdp, addr);
- if (unlikely(!pudp))
- return -EINVAL;
-
- pmdp = pmd_offset(pudp, addr);
- if (unlikely(!pmdp))
- return -EINVAL;
-
- ptep = pte_offset_kernel(pmdp, addr);
- if (unlikely(!ptep))
- return -EINVAL;
+ /* In hash, pte_clear flushes the tlb */
+ pte_clear(patching_mm, patching_addr,
