Commit ab0615e2 authored by Rabin Vincent's avatar Rabin Vincent Committed by Kees Cook

arm: use fixmap for text patching when text is RO

Use fixmaps for text patching when the kernel text is read-only,
inspired by x86.  This makes jump labels and kprobes work with the
currently available CONFIG_DEBUG_SET_MODULE_RONX and the upcoming
CONFIG_DEBUG_RODATA options.
Signed-off-by: default avatarRabin Vincent <rabin@rab.in>
[kees: fixed up for merge with "arm: use generic fixmap.h"]
[kees: added parse acquire/release annotations to pass C=1 builds]
[kees: always use stop_machine to keep TLB flushing local]
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Acked-by: default avatarNicolas Pitre <nico@linaro.org>
parent 99b4ac9a
...@@ -11,6 +11,10 @@ enum fixed_addresses { ...@@ -11,6 +11,10 @@ enum fixed_addresses {
FIX_KMAP_BEGIN, FIX_KMAP_BEGIN,
FIX_KMAP_END = FIX_KMAP_BEGIN + (KM_TYPE_NR * NR_CPUS) - 1, FIX_KMAP_END = FIX_KMAP_BEGIN + (KM_TYPE_NR * NR_CPUS) - 1,
/* Support writing RO kernel text via kprobes, jump labels, etc. */
FIX_TEXT_POKE0,
FIX_TEXT_POKE1,
__end_of_fixed_addresses __end_of_fixed_addresses
}; };
......
...@@ -19,7 +19,7 @@ static void __arch_jump_label_transform(struct jump_entry *entry, ...@@ -19,7 +19,7 @@ static void __arch_jump_label_transform(struct jump_entry *entry,
insn = arm_gen_nop(); insn = arm_gen_nop();
if (is_static) if (is_static)
__patch_text(addr, insn); __patch_text_early(addr, insn);
else else
patch_text(addr, insn); patch_text(addr, insn);
} }
......
#include <linux/kernel.h> #include <linux/kernel.h>
#include <linux/spinlock.h>
#include <linux/kprobes.h> #include <linux/kprobes.h>
#include <linux/mm.h>
#include <linux/stop_machine.h> #include <linux/stop_machine.h>
#include <asm/cacheflush.h> #include <asm/cacheflush.h>
#include <asm/fixmap.h>
#include <asm/smp_plat.h> #include <asm/smp_plat.h>
#include <asm/opcodes.h> #include <asm/opcodes.h>
...@@ -13,21 +16,77 @@ struct patch { ...@@ -13,21 +16,77 @@ struct patch {
unsigned int insn; 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)
__acquires(&patch_lock)
{
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);
else
__acquire(&patch_lock);
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)
__releases(&patch_lock)
{
clear_fixmap(fixmap);
if (flags)
spin_unlock_irqrestore(&patch_lock, *flags);
else
__release(&patch_lock);
}
void __kprobes __patch_text_real(void *addr, unsigned int insn, bool remap)
{ {
bool thumb2 = IS_ENABLED(CONFIG_THUMB2_KERNEL); bool thumb2 = IS_ENABLED(CONFIG_THUMB2_KERNEL);
unsigned int uintaddr = (uintptr_t) addr;
bool twopage = false;
unsigned long flags;
void *waddr = addr;
int size; int size;
if (remap)
waddr = patch_map(addr, FIX_TEXT_POKE0, &flags);
else
__acquire(&patch_lock);
if (thumb2 && __opcode_is_thumb16(insn)) { if (thumb2 && __opcode_is_thumb16(insn)) {
*(u16 *)addr = __opcode_to_mem_thumb16(insn); *(u16 *)waddr = __opcode_to_mem_thumb16(insn);
size = sizeof(u16); size = sizeof(u16);
} else if (thumb2 && ((uintptr_t)addr & 2)) { } else if (thumb2 && (uintaddr & 2)) {
u16 first = __opcode_thumb32_first(insn); u16 first = __opcode_thumb32_first(insn);
u16 second = __opcode_thumb32_second(insn); u16 second = __opcode_thumb32_second(insn);
u16 *addrh = addr; u16 *addrh0 = waddr;
u16 *addrh1 = waddr + 2;
twopage = (uintaddr & ~PAGE_MASK) == PAGE_SIZE - 2;
if (twopage && remap)
addrh1 = patch_map(addr + 2, FIX_TEXT_POKE1, NULL);
*addrh0 = __opcode_to_mem_thumb16(first);
*addrh1 = __opcode_to_mem_thumb16(second);
addrh[0] = __opcode_to_mem_thumb16(first); if (twopage && addrh1 != addr + 2) {
addrh[1] = __opcode_to_mem_thumb16(second); flush_kernel_vmap_range(addrh1, 2);
patch_unmap(FIX_TEXT_POKE1, NULL);
}
size = sizeof(u32); size = sizeof(u32);
} else { } else {
...@@ -36,10 +95,16 @@ void __kprobes __patch_text(void *addr, unsigned int insn) ...@@ -36,10 +95,16 @@ void __kprobes __patch_text(void *addr, unsigned int insn)
else else
insn = __opcode_to_mem_arm(insn); insn = __opcode_to_mem_arm(insn);
*(u32 *)addr = insn; *(u32 *)waddr = insn;
size = sizeof(u32); size = sizeof(u32);
} }
if (waddr != addr) {
flush_kernel_vmap_range(waddr, twopage ? size / 2 : size);
patch_unmap(FIX_TEXT_POKE0, &flags);
} else
__release(&patch_lock);
flush_icache_range((uintptr_t)(addr), flush_icache_range((uintptr_t)(addr),
(uintptr_t)(addr) + size); (uintptr_t)(addr) + size);
} }
...@@ -60,16 +125,5 @@ void __kprobes patch_text(void *addr, unsigned int insn) ...@@ -60,16 +125,5 @@ void __kprobes patch_text(void *addr, unsigned int insn)
.insn = insn, .insn = insn,
}; };
if (cache_ops_need_broadcast()) { stop_machine(patch_text_stop_machine, &patch, NULL);
stop_machine(patch_text_stop_machine, &patch, cpu_online_mask);
} else {
bool straddles_word = IS_ENABLED(CONFIG_THUMB2_KERNEL)
&& __opcode_is_thumb32(insn)
&& ((uintptr_t)addr & 2);
if (straddles_word)
stop_machine(patch_text_stop_machine, &patch, NULL);
else
__patch_text(addr, insn);
}
} }
...@@ -2,6 +2,16 @@ ...@@ -2,6 +2,16 @@
#define _ARM_KERNEL_PATCH_H #define _ARM_KERNEL_PATCH_H
void patch_text(void *addr, unsigned int insn); void patch_text(void *addr, unsigned int insn);
void __patch_text(void *addr, unsigned int insn); void __patch_text_real(void *addr, unsigned int insn, bool remap);
static inline void __patch_text(void *addr, unsigned int insn)
{
__patch_text_real(addr, insn, true);
}
static inline void __patch_text_early(void *addr, unsigned int insn)
{
__patch_text_real(addr, insn, false);
}
#endif #endif
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