[PATCH v3 3/7] arm: use fixmap for text patching when text is RO
From: Stephen Boyd <hidden>
Date: 2014-08-13 00:27:52
Also in:
lkml
Subsystem:
arm port, the rest · Maintainers:
Russell King, Linus Torvalds
On 08/12/14 14:47, Kees Cook wrote:
On Tue, Aug 12, 2014 at 2:39 PM, Stephen Boyd [off-list ref] wrote:quoted
On 08/12/14 11:24, Kees Cook wrote:quoted
diff --git a/arch/arm/kernel/patch.c b/arch/arm/kernel/patch.c index 07314af47733..03dd4e39c833 100644 --- a/arch/arm/kernel/patch.c +++ b/arch/arm/kernel/patch.c@@ -13,21 +16,69 @@ struct patch { unsigned int insn; }; -void __kprobes __patch_text(void *addr, unsigned int insn) +static DEFINE_SPINLOCK(patch_lock); + +static void __kprobes *patch_map(void *addr, int fixmap, unsigned long *flags) +{ + unsigned int uintaddr = (uintptr_t) addr; + bool module = !core_kernel_text(uintaddr); + struct page *page; + + if (module && IS_ENABLED(CONFIG_DEBUG_SET_MODULE_RONX)) + page = vmalloc_to_page(addr); + else if (!module && IS_ENABLED(CONFIG_DEBUG_RODATA)) + page = virt_to_page(addr); + else + return addr; + + if (flags) + spin_lock_irqsave(&patch_lock, *flags); + + set_fixmap(fixmap, page_to_phys(page)); + + return (void *) (__fix_to_virt(fixmap) + (uintaddr & ~PAGE_MASK)); +} + +static void __kprobes patch_unmap(int fixmap, unsigned long *flags) +{ + clear_fixmap(fixmap); + + if (flags) + spin_unlock_irqrestore(&patch_lock, *flags); +}Has the kbuildbot complained about this one yet? CHECK arch/arm/kernel/patch.c arch/arm/kernel/patch.c:47:39: warning: context imbalance in 'patch_unmap' - unexpected unlock I guess we're going to ignore it.No, nothing yet from buildbot, let me do a sparse run -- I think we can just add annotation and we'll be okay.
Ok. I tried to move code around but sparse still complains because of conditional locking. ---8<---
diff --git a/arch/arm/kernel/patch.c b/arch/arm/kernel/patch.c
index 03dd4e39c833..f6d4de3826a0 100644
--- a/arch/arm/kernel/patch.c
+++ b/arch/arm/kernel/patch.c@@ -18,33 +18,17 @@ struct patch { static DEFINE_SPINLOCK(patch_lock); -static void __kprobes *patch_map(void *addr, int fixmap, unsigned long *flags) +static struct page __kprobes *patch_page(void *addr) { unsigned int uintaddr = (uintptr_t) addr; bool module = !core_kernel_text(uintaddr); - struct page *page; if (module && IS_ENABLED(CONFIG_DEBUG_SET_MODULE_RONX)) - page = vmalloc_to_page(addr); + return vmalloc_to_page(addr); else if (!module && IS_ENABLED(CONFIG_DEBUG_RODATA)) - page = virt_to_page(addr); - else - return addr; + return virt_to_page(addr); - if (flags) - spin_lock_irqsave(&patch_lock, *flags); - - set_fixmap(fixmap, page_to_phys(page)); - - return (void *) (__fix_to_virt(fixmap) + (uintaddr & ~PAGE_MASK)); -} - -static void __kprobes patch_unmap(int fixmap, unsigned long *flags) -{ - clear_fixmap(fixmap); - - if (flags) - spin_unlock_irqrestore(&patch_lock, *flags); + return NULL; } void __kprobes __patch_text_real(void *addr, unsigned int insn, bool remap)
@@ -54,10 +38,18 @@ void __kprobes __patch_text_real(void *addr, unsigned int insn, bool remap) bool twopage = false; unsigned long flags; void *waddr = addr; + struct page *page = NULL; int size; - if (remap) - waddr = patch_map(addr, FIX_TEXT_POKE0, &flags); + if (remap) { + page = patch_page(addr); + if (page) { + spin_lock_irqsave(&patch_lock, flags); + set_fixmap(FIX_TEXT_POKE0, page_to_phys(page)); + waddr = (void *)(__fix_to_virt(FIX_TEXT_POKE0) + + (uintaddr & ~PAGE_MASK)); + } + } if (thumb2 && __opcode_is_thumb16(insn)) { *(u16 *)waddr = __opcode_to_mem_thumb16(insn);
@@ -69,15 +61,25 @@ void __kprobes __patch_text_real(void *addr, unsigned int insn, bool remap) u16 *addrh1 = waddr + 2; twopage = (uintaddr & ~PAGE_MASK) == PAGE_SIZE - 2; - if (twopage && remap) - addrh1 = patch_map(addr + 2, FIX_TEXT_POKE1, NULL); + if (twopage && remap) { + struct page *page2; + + page2 = patch_page(addr + 2); + if (page2) { + set_fixmap(FIX_TEXT_POKE1, page_to_phys(page)); + addrh1 = (u16 *)(__fix_to_virt(FIX_TEXT_POKE1) + + (uintaddr & ~PAGE_MASK)); + } else { + addrh1 = addr + 2; + } + } *addrh0 = __opcode_to_mem_thumb16(first); *addrh1 = __opcode_to_mem_thumb16(second); if (twopage && addrh1 != addr + 2) { flush_kernel_vmap_range(addrh1, 2); - patch_unmap(FIX_TEXT_POKE1, NULL); + clear_fixmap(FIX_TEXT_POKE1); } size = sizeof(u32);
@@ -91,9 +93,10 @@ void __kprobes __patch_text_real(void *addr, unsigned int insn, bool remap) size = sizeof(u32); } - if (waddr != addr) { + if (page) { flush_kernel_vmap_range(waddr, twopage ? size / 2 : size); - patch_unmap(FIX_TEXT_POKE0, &flags); + clear_fixmap(FIX_TEXT_POKE0); + spin_unlock_irqrestore(&patch_lock, flags); } flush_icache_range((uintptr_t)(addr),
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