Commit 4531ef6a authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

x86/alternative: Shrink text_poke_loc 



Employ the fact that all text must be within a s32 displacement of one
another to shrink the text_poke_loc::addr field. Make it relative to
_stext.

This then shrinks struct text_poke_loc to 16 bytes, and consequently
increases TP_VEC_MAX from 170 to 256.

Tested-by: default avatarAlexei Starovoitov <ast@kernel.org>
Tested-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20191111132458.047052889@infradead.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 97e6c977

arch/x86/kernel/alternative.c

+14 −9
Original line number Diff line number Diff line
@@ -937,7 +937,7 @@ static void do_sync_core(void *info) 
}



struct text_poke_loc {

	void *addr;

	s32 rel_addr; /* addr := _stext + rel_addr */

	s32 rel32;

	u8 opcode;

	const u8 text[POKE_MAX_OPCODE_SIZE];
@@ -948,13 +948,18 @@ static struct bp_patching_desc { 
	int nr_entries;

} bp_patching;



static inline void *text_poke_addr(struct text_poke_loc *tp)

{

	return _stext + tp->rel_addr;

}



static int notrace patch_cmp(const void *key, const void *elt)

{

	struct text_poke_loc *tp = (struct text_poke_loc *) elt;



	if (key < tp->addr)

	if (key < text_poke_addr(tp))

		return -1;

	if (key > tp->addr)

	if (key > text_poke_addr(tp))

		return 1;

	return 0;

}
@@ -1000,7 +1005,7 @@ int notrace poke_int3_handler(struct pt_regs *regs) 
			return 0;

	} else {

		tp = bp_patching.vec;

		if (tp->addr != ip)

		if (text_poke_addr(tp) != ip)

			return 0;

	}
@@ -1078,7 +1083,7 @@ static void text_poke_bp_batch(struct text_poke_loc *tp, unsigned int nr_entries 
	 * First step: add a int3 trap to the address that will be patched.

	 */

	for (i = 0; i < nr_entries; i++)

		text_poke(tp[i].addr, &int3, sizeof(int3));

		text_poke(text_poke_addr(&tp[i]), &int3, sizeof(int3));



	on_each_cpu(do_sync_core, NULL, 1);
@@ -1089,7 +1094,7 @@ static void text_poke_bp_batch(struct text_poke_loc *tp, unsigned int nr_entries 
		int len = text_opcode_size(tp[i].opcode);



		if (len - sizeof(int3) > 0) {

			text_poke((char *)tp[i].addr + sizeof(int3),

			text_poke(text_poke_addr(&tp[i]) + sizeof(int3),

				  (const char *)tp[i].text + sizeof(int3),

				  len - sizeof(int3));

			do_sync++;
@@ -1113,7 +1118,7 @@ static void text_poke_bp_batch(struct text_poke_loc *tp, unsigned int nr_entries 
		if (tp[i].text[0] == INT3_INSN_OPCODE)

			continue;



		text_poke(tp[i].addr, tp[i].text, sizeof(int3));

		text_poke(text_poke_addr(&tp[i]), tp[i].text, sizeof(int3));

		do_sync++;

	}
@@ -1143,7 +1148,7 @@ void text_poke_loc_init(struct text_poke_loc *tp, void *addr, 
	BUG_ON(!insn_complete(&insn));

	BUG_ON(len != insn.length);



	tp->addr = addr;

	tp->rel_addr = addr - (void *)_stext;

	tp->opcode = insn.opcode.bytes[0];



	switch (tp->opcode) {
@@ -1192,7 +1197,7 @@ static bool tp_order_fail(void *addr) 
		return true;



	tp = &tp_vec[tp_vec_nr - 1];

	if ((unsigned long)tp->addr > (unsigned long)addr)

	if ((unsigned long)text_poke_addr(tp) > (unsigned long)addr)

		return true;



	return false;

CRA Git | Maintained and supported by SUSTech CRA and CCSE