Commit 72e213a7 authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

x86/ibt: Clean up is_endbr() 



Pretty much every caller of is_endbr() actually wants to test something at an
address and ends up doing get_kernel_nofault(). Fold the lot into a more
convenient helper.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarSami Tolvanen <samitolvanen@google.com>
Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Acked-by: default avatar"Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Link: https://lore.kernel.org/r/20250207122546.181367417@infradead.org
parent 92d2da37

arch/x86/events/core.c

+1 −1
Original line number Diff line number Diff line
@@ -2844,7 +2844,7 @@ static bool is_uprobe_at_func_entry(struct pt_regs *regs) 
		return true;



	/* endbr64 (64-bit only) */

	if (user_64bit_mode(regs) && is_endbr(*(u32 *)auprobe->insn))

	if (user_64bit_mode(regs) && is_endbr((u32 *)auprobe->insn))

		return true;



	return false;

arch/x86/include/asm/ftrace.h

+2 −14
Original line number Diff line number Diff line
@@ -36,21 +36,9 @@ static inline unsigned long ftrace_call_adjust(unsigned long addr) 


static inline unsigned long arch_ftrace_get_symaddr(unsigned long fentry_ip)

{

#ifdef CONFIG_X86_KERNEL_IBT

	u32 instr;



	/* We want to be extra safe in case entry ip is on the page edge,

	 * but otherwise we need to avoid get_kernel_nofault()'s overhead.

	 */

	if ((fentry_ip & ~PAGE_MASK) < ENDBR_INSN_SIZE) {

		if (get_kernel_nofault(instr, (u32 *)(fentry_ip - ENDBR_INSN_SIZE)))

			return fentry_ip;

	} else {

		instr = *(u32 *)(fentry_ip - ENDBR_INSN_SIZE);

	}

	if (is_endbr(instr))

	if (is_endbr((void*)(fentry_ip - ENDBR_INSN_SIZE)))

		fentry_ip -= ENDBR_INSN_SIZE;

#endif



	return fentry_ip;

}

#define ftrace_get_symaddr(fentry_ip)	arch_ftrace_get_symaddr(fentry_ip)

arch/x86/include/asm/ibt.h

+3 −2
Original line number Diff line number Diff line
@@ -65,7 +65,7 @@ static inline __attribute_const__ u32 gen_endbr_poison(void) 
	return 0x001f0f66; /* osp nopl (%rax) */

}



static inline bool is_endbr(u32 val)

static inline bool __is_endbr(u32 val)

{

	if (val == gen_endbr_poison())

		return true;
@@ -74,6 +74,7 @@ static inline bool is_endbr(u32 val) 
	return val == gen_endbr();

}



extern __noendbr bool is_endbr(u32 *val);

extern __noendbr u64 ibt_save(bool disable);

extern __noendbr void ibt_restore(u64 save);
@@ -98,7 +99,7 @@ extern __noendbr void ibt_restore(u64 save); 


#define __noendbr



static inline bool is_endbr(u32 val) { return false; }

static inline bool is_endbr(u32 *val) { return false; }



static inline u64 ibt_save(bool disable) { return 0; }

static inline void ibt_restore(u64 save) { }

arch/x86/kernel/alternative.c

+14 −6
Original line number Diff line number Diff line
@@ -852,16 +852,24 @@ void __init_or_module noinline apply_returns(s32 *start, s32 *end) { } 


#ifdef CONFIG_X86_KERNEL_IBT



__noendbr bool is_endbr(u32 *val)

{

	u32 endbr;



	__get_kernel_nofault(&endbr, val, u32, Efault);

	return __is_endbr(endbr);



Efault:

	return false;

}



static void poison_cfi(void *addr);



static void __init_or_module poison_endbr(void *addr, bool warn)

{

	u32 endbr, poison = gen_endbr_poison();



	if (WARN_ON_ONCE(get_kernel_nofault(endbr, addr)))

		return;

	u32 poison = gen_endbr_poison();



	if (!is_endbr(endbr)) {

	if (!is_endbr(addr)) {

		WARN_ON_ONCE(warn);

		return;

	}
@@ -988,7 +996,7 @@ static u32 cfi_seed __ro_after_init; 
static u32 cfi_rehash(u32 hash)

{

	hash ^= cfi_seed;

	while (unlikely(is_endbr(hash) || is_endbr(-hash))) {

	while (unlikely(__is_endbr(hash) || __is_endbr(-hash))) {

		bool lsb = hash & 1;

		hash >>= 1;

		if (lsb)

arch/x86/kernel/kprobes/core.c

+1 −10
Original line number Diff line number Diff line
@@ -373,16 +373,7 @@ static bool can_probe(unsigned long paddr) 
kprobe_opcode_t *arch_adjust_kprobe_addr(unsigned long addr, unsigned long offset,

					 bool *on_func_entry)

{

	u32 insn;



	/*

	 * Since 'addr' is not guaranteed to be safe to access, use

	 * copy_from_kernel_nofault() to read the instruction:

	 */

	if (copy_from_kernel_nofault(&insn, (void *)addr, sizeof(u32)))

		return NULL;



	if (is_endbr(insn)) {

	if (is_endbr((u32 *)addr)) {

		*on_func_entry = !offset || offset == 4;

		if (*on_func_entry)

			offset = 4;