| Message ID | 20200429020531.20684-4-cmr@informatik.wtf (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Use per-CPU temporary mappings for patching | expand |
Le 29/04/2020 à 04:05, 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 <cmr@informatik.wtf> > --- > arch/powerpc/lib/code-patching.c | 149 ++++++++++++------------------- > 1 file changed, 55 insertions(+), 94 deletions(-) > > diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c > index 259c19480a85..26f06cdb5d7e 100644 > --- a/arch/powerpc/lib/code-patching.c > +++ b/arch/powerpc/lib/code-patching.c > @@ -19,6 +19,7 @@ > #include <asm/page.h> > #include <asm/code-patching.h> > #include <asm/setup.h> > +#include <asm/mmu_context.h> > > static int __patch_instruction(unsigned int *exec_addr, unsigned int instr, > unsigned int *patch_addr) > @@ -72,101 +73,58 @@ 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, > + &patch_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); Why only when CONFIG_PPC_BOOK3S_64 is not set ? PAGE_KERNEL should already be dirty, so making it dirty all the time shouldn't hurt. > + set_pte_at(patching_mm, patching_addr, patch_mapping->ptep, pte); > + > + init_temp_mm(&patch_mapping->temp_mm, patching_mm); > + use_temporary_mm(&patch_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, patch_mapping->ptep); > + unuse_temporary_mm(&patch_mapping->temp_mm); > > - pr_devel("clearing mm %p, pte %p, addr %lx\n", &init_mm, ptep, addr); > - > - /* > - * In hash, pte_clear flushes the tlb, in radix, we have to > - */ > - pte_clear(&init_mm, addr, ptep); > - flush_tlb_kernel_range(addr, addr + PAGE_SIZE); > - > - return 0; > + /* In radix, we have to explicitly flush the tlb (no-op in hash) */ > + local_flush_tlb_mm(patching_mm); > + pte_unmap_unlock(patch_mapping->ptep, patch_mapping->ptl); > } > > static int do_patch_instruction(unsigned int *addr, unsigned int instr) > @@ -174,33 +132,36 @@ static int do_patch_instruction(unsigned int *addr, unsigned int instr) > int err; > unsigned int *patch_addr = NULL; > unsigned long flags; > - unsigned long text_poke_addr; > - unsigned long kaddr = (unsigned long)addr; > + struct patch_mapping patch_mapping; > > /* > - * During early early boot patch_instruction is called > - * when text_poke_area is not ready, but we still need > - * to allow patching. We just do the plain old patching > + * The patching_mm is initialized before calling mark_rodata_ro. Prior > + * to this, patch_instruction is called when we don't have (and don't > + * need) the patching_mm so just do plain old patching. > */ > - if (!this_cpu_read(text_poke_area)) > + if (!patching_mm) > return raw_patch_instruction(addr, instr); > > local_irq_save(flags); > > - text_poke_addr = (unsigned long)__this_cpu_read(text_poke_area)->addr; > - if (map_patch_area(addr, text_poke_addr)) { > - err = -1; > + err = map_patch(addr, &patch_mapping); > + if (err) > goto out; > - } > > - patch_addr = (unsigned int *)(text_poke_addr) + > - ((kaddr & ~PAGE_MASK) / sizeof(unsigned int)); > + patch_addr = (unsigned int *)(patching_addr | offset_in_page(addr)); > > - __patch_instruction(addr, instr, patch_addr); > + if (!radix_enabled()) > + allow_write_to_user(patch_addr, sizeof(instr)); > + err = __patch_instruction(addr, instr, patch_addr); > + if (!radix_enabled()) > + prevent_write_to_user(patch_addr, sizeof(instr)); > > - err = unmap_patch_area(text_poke_addr); > - if (err) > - pr_warn("failed to unmap %lx\n", text_poke_addr); > + unmap_patch(&patch_mapping); > + /* > + * Something is wrong if what we just wrote doesn't match what we > + * think we just wrote. > + */ > + WARN_ON(*addr != instr); > > out: > local_irq_restore(flags); > Christophe
On Wed Apr 29, 2020 at 7:52 AM, Christophe Leroy wrote: > > > > > Le 29/04/2020 à 04:05, 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 <cmr@informatik.wtf> > > --- > > arch/powerpc/lib/code-patching.c | 149 ++++++++++++------------------- > > 1 file changed, 55 insertions(+), 94 deletions(-) > > > > diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c > > index 259c19480a85..26f06cdb5d7e 100644 > > --- a/arch/powerpc/lib/code-patching.c > > +++ b/arch/powerpc/lib/code-patching.c > > @@ -19,6 +19,7 @@ > > #include <asm/page.h> > > #include <asm/code-patching.h> > > #include <asm/setup.h> > > +#include <asm/mmu_context.h> > > > > static int __patch_instruction(unsigned int *exec_addr, unsigned int instr, > > unsigned int *patch_addr) > > @@ -72,101 +73,58 @@ 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, > > + &patch_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); > > > Why only when CONFIG_PPC_BOOK3S_64 is not set ? > > > PAGE_KERNEL should already be dirty, so making it dirty all the time > shouldn't hurt. > > Ok, I'll remove this check to simplify. > > + set_pte_at(patching_mm, patching_addr, patch_mapping->ptep, pte); > > + > > + init_temp_mm(&patch_mapping->temp_mm, patching_mm); > > + use_temporary_mm(&patch_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, patch_mapping->ptep); > > + unuse_temporary_mm(&patch_mapping->temp_mm); > > > > - pr_devel("clearing mm %p, pte %p, addr %lx\n", &init_mm, ptep, addr); > > - > > - /* > > - * In hash, pte_clear flushes the tlb, in radix, we have to > > - */ > > - pte_clear(&init_mm, addr, ptep); > > - flush_tlb_kernel_range(addr, addr + PAGE_SIZE); > > - > > - return 0; > > + /* In radix, we have to explicitly flush the tlb (no-op in hash) */ > > + local_flush_tlb_mm(patching_mm); > > + pte_unmap_unlock(patch_mapping->ptep, patch_mapping->ptl); > > } > > > > static int do_patch_instruction(unsigned int *addr, unsigned int instr) > > @@ -174,33 +132,36 @@ static int do_patch_instruction(unsigned int *addr, unsigned int instr) > > int err; > > unsigned int *patch_addr = NULL; > > unsigned long flags; > > - unsigned long text_poke_addr; > > - unsigned long kaddr = (unsigned long)addr; > > + struct patch_mapping patch_mapping; > > > > /* > > - * During early early boot patch_instruction is called > > - * when text_poke_area is not ready, but we still need > > - * to allow patching. We just do the plain old patching > > + * The patching_mm is initialized before calling mark_rodata_ro. Prior > > + * to this, patch_instruction is called when we don't have (and don't > > + * need) the patching_mm so just do plain old patching. > > */ > > - if (!this_cpu_read(text_poke_area)) > > + if (!patching_mm) > > return raw_patch_instruction(addr, instr); > > > > local_irq_save(flags); > > > > - text_poke_addr = (unsigned long)__this_cpu_read(text_poke_area)->addr; > > - if (map_patch_area(addr, text_poke_addr)) { > > - err = -1; > > + err = map_patch(addr, &patch_mapping); > > + if (err) > > goto out; > > - } > > > > - patch_addr = (unsigned int *)(text_poke_addr) + > > - ((kaddr & ~PAGE_MASK) / sizeof(unsigned int)); > > + patch_addr = (unsigned int *)(patching_addr | offset_in_page(addr)); > > > > - __patch_instruction(addr, instr, patch_addr); > > + if (!radix_enabled()) > > + allow_write_to_user(patch_addr, sizeof(instr)); > > + err = __patch_instruction(addr, instr, patch_addr); > > + if (!radix_enabled()) > > + prevent_write_to_user(patch_addr, sizeof(instr)); > > > > - err = unmap_patch_area(text_poke_addr); > > - if (err) > > - pr_warn("failed to unmap %lx\n", text_poke_addr); > > + unmap_patch(&patch_mapping); > > + /* > > + * Something is wrong if what we just wrote doesn't match what we > > + * think we just wrote. > > + */ > > + WARN_ON(*addr != instr); > > > > out: > > local_irq_restore(flags); > > > > > Christophe > > > >
diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c index 259c19480a85..26f06cdb5d7e 100644 --- a/arch/powerpc/lib/code-patching.c +++ b/arch/powerpc/lib/code-patching.c @@ -19,6 +19,7 @@ #include <asm/page.h> #include <asm/code-patching.h> #include <asm/setup.h> +#include <asm/mmu_context.h> static int __patch_instruction(unsigned int *exec_addr, unsigned int instr, unsigned int *patch_addr) @@ -72,101 +73,58 @@ 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, + &patch_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(&patch_mapping->temp_mm, patching_mm); + use_temporary_mm(&patch_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, patch_mapping->ptep); + unuse_temporary_mm(&patch_mapping->temp_mm); - pr_devel("clearing mm %p, pte %p, addr %lx\n", &init_mm, ptep, addr); - - /* - * In hash, pte_clear flushes the tlb, in radix, we have to - */ - pte_clear(&init_mm, addr, ptep); - flush_tlb_kernel_range(addr, addr + PAGE_SIZE); - - return 0; + /* In radix, we have to explicitly flush the tlb (no-op in hash) */ + local_flush_tlb_mm(patching_mm); + pte_unmap_unlock(patch_mapping->ptep, patch_mapping->ptl); } static int do_patch_instruction(unsigned int *addr, unsigned int instr) @@ -174,33 +132,36 @@ static int do_patch_instruction(unsigned int *addr, unsigned int instr) int err; unsigned int *patch_addr = NULL; unsigned long flags; - unsigned long text_poke_addr; - unsigned long kaddr = (unsigned long)addr; + struct patch_mapping patch_mapping; /* - * During early early boot patch_instruction is called - * when text_poke_area is not ready, but we still need - * to allow patching. We just do the plain old patching + * The patching_mm is initialized before calling mark_rodata_ro. Prior + * to this, patch_instruction is called when we don't have (and don't + * need) the patching_mm so just do plain old patching. */ - if (!this_cpu_read(text_poke_area)) + if (!patching_mm) return raw_patch_instruction(addr, instr); local_irq_save(flags); - text_poke_addr = (unsigned long)__this_cpu_read(text_poke_area)->addr; - if (map_patch_area(addr, text_poke_addr)) { - err = -1; + err = map_patch(addr, &patch_mapping); + if (err) goto out; - } - patch_addr = (unsigned int *)(text_poke_addr) + - ((kaddr & ~PAGE_MASK) / sizeof(unsigned int)); + patch_addr = (unsigned int *)(patching_addr | offset_in_page(addr)); - __patch_instruction(addr, instr, patch_addr); + if (!radix_enabled()) + allow_write_to_user(patch_addr, sizeof(instr)); + err = __patch_instruction(addr, instr, patch_addr); + if (!radix_enabled()) + prevent_write_to_user(patch_addr, sizeof(instr)); - err = unmap_patch_area(text_poke_addr); - if (err) - pr_warn("failed to unmap %lx\n", text_poke_addr); + unmap_patch(&patch_mapping); + /* + * Something is wrong if what we just wrote doesn't match what we + * think we just wrote. + */ + WARN_ON(*addr != instr); out: local_irq_restore(flags);
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 <cmr@informatik.wtf> --- arch/powerpc/lib/code-patching.c | 149 ++++++++++++------------------- 1 file changed, 55 insertions(+), 94 deletions(-)