Commit 6becb502 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Borislav Petkov (AMD)
Browse files

x86/alternative: Make debug-alternative selective 



Using debug-alternative generates a *LOT* of output, extend it a bit
to select which of the many rewrites it reports on.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230208171431.253636689@infradead.org
parent ac9a7868

arch/x86/kernel/alternative.c

+37 −25
Original line number Diff line number Diff line
@@ -37,11 +37,23 @@ EXPORT_SYMBOL_GPL(alternatives_patched); 


#define MAX_PATCH_LEN (255-1)



static int __initdata_or_module debug_alternative;

#define DA_ALL		(~0)

#define DA_ALT		0x01

#define DA_RET		0x02

#define DA_RETPOLINE	0x04

#define DA_ENDBR	0x08

#define DA_SMP		0x10



static unsigned int __initdata_or_module debug_alternative;



static int __init debug_alt(char *str)

{

	debug_alternative = 1;

	if (str && *str == '=')

		str++;



	if (!str || kstrtouint(str, 0, &debug_alternative))

		debug_alternative = DA_ALL;



	return 1;

}

__setup("debug-alternative", debug_alt);
@@ -55,15 +67,15 @@ static int __init setup_noreplace_smp(char *str) 
}

__setup("noreplace-smp", setup_noreplace_smp);



#define DPRINTK(fmt, args...)						\

#define DPRINTK(type, fmt, args...)					\

do {									\

	if (debug_alternative)						\

	if (debug_alternative & DA_##type)				\

		printk(KERN_DEBUG pr_fmt(fmt) "\n", ##args);		\

} while (0)



#define DUMP_BYTES(buf, len, fmt, args...)				\

#define DUMP_BYTES(type, buf, len, fmt, args...)			\

do {									\

	if (unlikely(debug_alternative)) {				\

	if (unlikely(debug_alternative & DA_##type)) {			\

		int j;							\

									\

		if (!(len))						\
@@ -148,7 +160,7 @@ recompute_jump(struct alt_instr *a, u8 *orig_insn, u8 *repl_insn, u8 *insn_buff) 
	tgt_rip  = next_rip + o_dspl;

	n_dspl = tgt_rip - orig_insn;



	DPRINTK("target RIP: %px, new_displ: 0x%x", tgt_rip, n_dspl);

	DPRINTK(ALT, "target RIP: %px, new_displ: 0x%x", tgt_rip, n_dspl);



	if (tgt_rip - orig_insn >= 0) {

		if (n_dspl - 2 <= 127)
@@ -183,7 +195,7 @@ recompute_jump(struct alt_instr *a, u8 *orig_insn, u8 *repl_insn, u8 *insn_buff) 


done:



	DPRINTK("final displ: 0x%08x, JMP 0x%lx",

	DPRINTK(ALT, "final displ: 0x%08x, JMP 0x%lx",

		n_dspl, (unsigned long)orig_insn + n_dspl + repl_len);

}
@@ -217,7 +229,7 @@ static __always_inline int optimize_nops_range(u8 *instr, u8 instrlen, int off) 
	add_nops(instr + off, nnops);

	local_irq_restore(flags);



	DUMP_BYTES(instr, instrlen, "%px: [%d:%d) optimized NOPs: ", instr, off, i);

	DUMP_BYTES(ALT, instr, instrlen, "%px: [%d:%d) optimized NOPs: ", instr, off, i);



	return nnops;

}
@@ -270,7 +282,7 @@ void __init_or_module noinline apply_alternatives(struct alt_instr *start, 
	u8 *instr, *replacement;

	u8 insn_buff[MAX_PATCH_LEN];



	DPRINTK("alt table %px, -> %px", start, end);

	DPRINTK(ALT, "alt table %px, -> %px", start, end);

	/*

	 * The scan order should be from start to end. A later scanned

	 * alternative code can overwrite previously scanned alternative code.
@@ -297,15 +309,15 @@ void __init_or_module noinline apply_alternatives(struct alt_instr *start, 
		if (!boot_cpu_has(a->cpuid) == !(a->flags & ALT_FLAG_NOT))

			goto next;



		DPRINTK("feat: %s%d*32+%d, old: (%pS (%px) len: %d), repl: (%px, len: %d)",

		DPRINTK(ALT, "feat: %s%d*32+%d, old: (%pS (%px) len: %d), repl: (%px, len: %d)",

			(a->flags & ALT_FLAG_NOT) ? "!" : "",

			a->cpuid >> 5,

			a->cpuid & 0x1f,

			instr, instr, a->instrlen,

			replacement, a->replacementlen);



		DUMP_BYTES(instr, a->instrlen, "%px:   old_insn: ", instr);

		DUMP_BYTES(replacement, a->replacementlen, "%px:   rpl_insn: ", replacement);

		DUMP_BYTES(ALT, instr, a->instrlen, "%px:   old_insn: ", instr);

		DUMP_BYTES(ALT, replacement, a->replacementlen, "%px:   rpl_insn: ", replacement);



		memcpy(insn_buff, replacement, a->replacementlen);

		insn_buff_sz = a->replacementlen;
@@ -318,7 +330,7 @@ void __init_or_module noinline apply_alternatives(struct alt_instr *start, 
		 */

		if (a->replacementlen == 5 && *insn_buff == 0xe8) {

			*(s32 *)(insn_buff + 1) += replacement - instr;

			DPRINTK("Fix CALL offset: 0x%x, CALL 0x%lx",

			DPRINTK(ALT, "Fix CALL offset: 0x%x, CALL 0x%lx",

				*(s32 *)(insn_buff + 1),

				(unsigned long)instr + *(s32 *)(insn_buff + 1) + 5);

		}
@@ -329,7 +341,7 @@ void __init_or_module noinline apply_alternatives(struct alt_instr *start, 
		for (; insn_buff_sz < a->instrlen; insn_buff_sz++)

			insn_buff[insn_buff_sz] = 0x90;



		DUMP_BYTES(insn_buff, insn_buff_sz, "%px: final_insn: ", instr);

		DUMP_BYTES(ALT, insn_buff, insn_buff_sz, "%px: final_insn: ", instr);



		text_poke_early(instr, insn_buff, insn_buff_sz);
@@ -555,15 +567,15 @@ void __init_or_module noinline apply_retpolines(s32 *start, s32 *end) 
			continue;

		}



		DPRINTK("retpoline at: %pS (%px) len: %d to: %pS",

		DPRINTK(RETPOLINE, "retpoline at: %pS (%px) len: %d to: %pS",

			addr, addr, insn.length,

			addr + insn.length + insn.immediate.value);



		len = patch_retpoline(addr, &insn, bytes);

		if (len == insn.length) {

			optimize_nops(bytes, len);

			DUMP_BYTES(((u8*)addr),  len, "%px: orig: ", addr);

			DUMP_BYTES(((u8*)bytes), len, "%px: repl: ", addr);

			DUMP_BYTES(RETPOLINE, ((u8*)addr),  len, "%px: orig: ", addr);

			DUMP_BYTES(RETPOLINE, ((u8*)bytes), len, "%px: repl: ", addr);

			text_poke_early(addr, bytes, len);

		}

	}
@@ -630,14 +642,14 @@ void __init_or_module noinline apply_returns(s32 *start, s32 *end) 
			      addr, dest, 5, addr))

			continue;



		DPRINTK("return thunk at: %pS (%px) len: %d to: %pS",

		DPRINTK(RET, "return thunk at: %pS (%px) len: %d to: %pS",

			addr, addr, insn.length,

			addr + insn.length + insn.immediate.value);



		len = patch_return(addr, &insn, bytes);

		if (len == insn.length) {

			DUMP_BYTES(((u8*)addr),  len, "%px: orig: ", addr);

			DUMP_BYTES(((u8*)bytes), len, "%px: repl: ", addr);

			DUMP_BYTES(RET, ((u8*)addr),  len, "%px: orig: ", addr);

			DUMP_BYTES(RET, ((u8*)bytes), len, "%px: repl: ", addr);

			text_poke_early(addr, bytes, len);

		}

	}
@@ -667,13 +679,13 @@ static void poison_endbr(void *addr, bool warn) 
		return;

	}



	DPRINTK("ENDBR at: %pS (%px)", addr, addr);

	DPRINTK(ENDBR, "ENDBR at: %pS (%px)", addr, addr);



	/*

	 * When we have IBT, the lack of ENDBR will trigger #CP

	 */

	DUMP_BYTES(((u8*)addr), 4, "%px: orig: ", addr);

	DUMP_BYTES(((u8*)&poison), 4, "%px: repl: ", addr);

	DUMP_BYTES(ENDBR, ((u8*)addr), 4, "%px: orig: ", addr);

	DUMP_BYTES(ENDBR, ((u8*)&poison), 4, "%px: repl: ", addr);

	text_poke_early(addr, &poison, 4);

}
@@ -1148,7 +1160,7 @@ void __init_or_module alternatives_smp_module_add(struct module *mod, 
	smp->locks_end	= locks_end;

	smp->text	= text;

	smp->text_end	= text_end;

	DPRINTK("locks %p -> %p, text %p -> %p, name %s\n",

	DPRINTK(SMP, "locks %p -> %p, text %p -> %p, name %s\n",

		smp->locks, smp->locks_end,

		smp->text, smp->text_end, smp->name);