[PATCH 00/14] x86/alternatives: Nest them

[PATCH 00/14] x86/alternatives: Nest them

[Borislav Petkov]

From: "Borislav Petkov (AMD)" <bp@alien8.de>

Hi,

this is basically peterz's idea to nest the alternative macros with
a fix to an issue I encountered while testing.

For ease of bisection, the old macros are converted to the new, nested
variants in a step-by-step manner so that in case an issue is
encountered during testing, one can pinpoint the place where it fails
easier. Because debugging alternatives is a serious pain.

Testing here on my farm looks good but who knows what happens out there,
in the wild.

Thx.

Borislav Petkov (AMD) (13):
  x86/alternative: Zap alternative_ternary()
  x86/alternative: Convert alternative()
  x86/alternative: Convert alternative_2()
  x86/alternative: Convert alternative_input()
  x86/alternative: Convert alternative_io()
  x86/alternative: Convert alternative_call()
  x86/alternative: Convert alternative_call_2()
  x86/alternative: Convert ALTERNATIVE_TERNARY()
  x86/alternative: Convert ALTERNATIVE_3()
  x86/alternative: Convert the asm ALTERNATIVE() macro
  x86/alternative: Convert the asm ALTERNATIVE_2() macro
  x86/alternative: Convert the asm ALTERNATIVE_3() macro
  x86/alternative: Replace the old macros

Peter Zijlstra (1):
  x86/alternatives: Add nested alternatives macros

 arch/x86/include/asm/alternative.h | 214 ++++++++---------------------
 arch/x86/kernel/alternative.c      |  20 ++-
 arch/x86/kernel/fpu/xstate.h       |   6 +-
 tools/objtool/arch/x86/special.c   |  23 ++++
 tools/objtool/special.c            |  16 +--
 5 files changed, 113 insertions(+), 166 deletions(-)

-- 
2.43.0

[PATCH 01/14] x86/alternative: Zap alternative_ternary()

[Borislav Petkov]

From: "Borislav Petkov (AMD)" <bp@alien8.de>

Unused.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
---
 arch/x86/include/asm/alternative.h | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index ba99ef75f56c..6db78909180a 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -271,9 +271,6 @@ static inline int alternatives_text_reserved(void *start, void *end)
 #define alternative_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \
 	asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) ::: "memory")
 
-#define alternative_ternary(oldinstr, ft_flags, newinstr_yes, newinstr_no) \
-	asm_inline volatile(ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) ::: "memory")
-
 /*
  * Alternative inline assembly with input.
  *
-- 
2.43.0

[PATCH 02/14] x86/alternatives: Add nested alternatives macros

[Borislav Petkov]

From: Peter Zijlstra <peterz@infradead.org>

Instead of making increasingly complicated ALTERNATIVE_n()
implementations, use a nested alternative expression.

The only difference between:

  ALTERNATIVE_2(oldinst, newinst1, flag1, newinst2, flag2)

and

  ALTERNATIVE(ALTERNATIVE(oldinst, newinst1, flag1),
              newinst2, flag2)

is that the outer alternative can add additional padding when the inner
alternative is the shorter one, which then results in
alt_instr::instrlen being inconsistent.

However, this is easily remedied since the alt_instr entries will be
consecutive and it is trivial to compute the max(alt_instr::instrlen) at
runtime while patching.

Specifically, after this the ALTERNATIVE_2 macro, after CPP expansion
(and manual layout), looks like this:

  .macro ALTERNATIVE_2 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2
  740:
  740: \oldinstr ;
  741: .skip -(((744f-743f)-(741b-740b)) > 0) * ((744f-743f)-(741b-740b)),0x90 ;
  742: .pushsection .altinstructions,"a" ;
  	altinstr_entry 740b,743f,\ft_flags1,742b-740b,744f-743f ;
  .popsection ;
  .pushsection .altinstr_replacement,"ax" ;
  743: \newinstr1 ;
  744: .popsection ; ;
  741: .skip -(((744f-743f)-(741b-740b)) > 0) * ((744f-743f)-(741b-740b)),0x90 ;
  742: .pushsection .altinstructions,"a" ;
  altinstr_entry 740b,743f,\ft_flags2,742b-740b,744f-743f ;
  .popsection ;
  .pushsection .altinstr_replacement,"ax" ;
  743: \newinstr2 ;
  744: .popsection ;
  .endm

The only label that is ambiguous is 740, however they all reference the
same spot, so that doesn't matter.

NOTE: obviously only @oldinstr may be an alternative; making @newinstr
an alternative would mean patching .altinstr_replacement which very
likely isn't what is intended, also the labels will be confused in that
case.

  [ bp: Debug an issue where it would match the wrong two insns and
    and consider them nested due to the same signed offsets in the
    .alternative section and use instr_va() to compare the full virtual
    addresses instead.

    - Use new labels to denote that the new, nested
    alternatives are being used when staring at preprocessed output. ]

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Co-developed-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lkml.kernel.org/r/20230628104952.GA2439977@hirez.programming.kicks-ass.net
---
 arch/x86/include/asm/alternative.h | 110 ++++++++++++++++++++++++++++-
 arch/x86/kernel/alternative.c      |  20 +++++-
 tools/objtool/arch/x86/special.c   |  23 ++++++
 tools/objtool/special.c            |  16 ++---
 4 files changed, 158 insertions(+), 11 deletions(-)

diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index 6db78909180a..8554c2c339ff 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -161,8 +161,13 @@ static inline int alternatives_text_reserved(void *start, void *end)
 
 #define alt_end_marker		"663"
 #define alt_slen		"662b-661b"
+#define n_alt_slen		"772b-771b"
+
 #define alt_total_slen		alt_end_marker"b-661b"
+#define n_alt_total_slen	"773b-771b"
+
 #define alt_rlen(num)		e_replacement(num)"f-"b_replacement(num)"f"
+#define n_alt_rlen		"775f-774f"
 
 #define OLDINSTR(oldinstr, num)						\
 	"# ALT: oldnstr\n"						\
@@ -172,6 +177,14 @@ static inline int alternatives_text_reserved(void *start, void *end)
 		"((" alt_rlen(num) ")-(" alt_slen ")),0x90\n"		\
 	alt_end_marker ":\n"
 
+#define N_OLDINSTR(oldinstr)						\
+	"# N_ALT: oldinstr\n"						\
+	"771:\n\t" oldinstr "\n772:\n"					\
+	"# N_ALT: padding\n"						\
+	".skip -(((" n_alt_rlen ")-(" n_alt_slen ")) > 0) * "		\
+		"((" n_alt_rlen ")-(" n_alt_slen ")),0x90\n"		\
+	"773:\n"
+
 /*
  * gas compatible max based on the idea from:
  * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax
@@ -209,10 +222,25 @@ static inline int alternatives_text_reserved(void *start, void *end)
 	" .byte " alt_total_slen "\n"			/* source len      */ \
 	" .byte " alt_rlen(num) "\n"			/* replacement len */
 
+#define N_ALTINSTR_ENTRY(ft_flags)					      \
+	".pushsection .altinstructions,\"a\"\n"				      \
+	" .long 771b - .\n"				/* label           */ \
+	" .long 774f - .\n"				/* new instruction */ \
+	" .4byte " __stringify(ft_flags) "\n"		/* feature + flags */ \
+	" .byte " n_alt_total_slen "\n"			/* source len      */ \
+	" .byte " n_alt_rlen "\n"			/* replacement len */ \
+	".popsection\n"
+
 #define ALTINSTR_REPLACEMENT(newinstr, num)		/* replacement */	\
 	"# ALT: replacement " #num "\n"						\
 	b_replacement(num)":\n\t" newinstr "\n" e_replacement(num) ":\n"
 
+#define N_ALTINSTR_REPLACEMENT(newinstr)		/* replacement */	\
+	".pushsection .altinstr_replacement, \"ax\"\n"				\
+	"# N_ALT: replacement\n"						\
+	"774:\n\t" newinstr "\n775:\n"						\
+	".popsection\n"
+
 /* alternative assembly primitive: */
 #define ALTERNATIVE(oldinstr, newinstr, ft_flags)			\
 	OLDINSTR(oldinstr, 1)						\
@@ -223,6 +251,12 @@ static inline int alternatives_text_reserved(void *start, void *end)
 	ALTINSTR_REPLACEMENT(newinstr, 1)				\
 	".popsection\n"
 
+/* Nested alternatives macro variant */
+#define N_ALTERNATIVE(oldinstr, newinstr, ft_flags)			\
+	N_OLDINSTR(oldinstr)						\
+	N_ALTINSTR_ENTRY(ft_flags)					\
+	N_ALTINSTR_REPLACEMENT(newinstr)
+
 #define ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \
 	OLDINSTR_2(oldinstr, 1, 2)					\
 	".pushsection .altinstructions,\"a\"\n"				\
@@ -234,11 +268,21 @@ static inline int alternatives_text_reserved(void *start, void *end)
 	ALTINSTR_REPLACEMENT(newinstr2, 2)				\
 	".popsection\n"
 
+#define N_ALTERNATIVE_2(oldinst, newinst1, flag1, newinst2, flag2)	\
+	N_ALTERNATIVE(N_ALTERNATIVE(oldinst, newinst1, flag1),		\
+		      newinst2, flag2)
+
 /* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
 #define ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) \
 	ALTERNATIVE_2(oldinstr, newinstr_no, X86_FEATURE_ALWAYS,	\
 		      newinstr_yes, ft_flags)
 
+/* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
+#define N_ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) \
+	N_ALTERNATIVE_2(oldinstr, newinstr_no, X86_FEATURE_ALWAYS,	\
+		      newinstr_yes, ft_flags)
+
+
 #define ALTERNATIVE_3(oldinsn, newinsn1, ft_flags1, newinsn2, ft_flags2, \
 			newinsn3, ft_flags3)				\
 	OLDINSTR_3(oldinsn, 1, 2, 3)					\
@@ -253,6 +297,12 @@ static inline int alternatives_text_reserved(void *start, void *end)
 	ALTINSTR_REPLACEMENT(newinsn3, 3)				\
 	".popsection\n"
 
+
+#define N_ALTERNATIVE_3(oldinst, newinst1, flag1, newinst2, flag2,	\
+		      newinst3, flag3)					\
+	N_ALTERNATIVE(N_ALTERNATIVE_2(oldinst, newinst1, flag1, newinst2, flag2), \
+		      newinst3, flag3)
+
 /*
  * Alternative instructions for different CPU types or capabilities.
  *
@@ -271,6 +321,12 @@ static inline int alternatives_text_reserved(void *start, void *end)
 #define alternative_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \
 	asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) ::: "memory")
 
+#define n_alternative(oldinstr, newinstr, ft_flags)			\
+	asm_inline volatile (N_ALTERNATIVE(oldinstr, newinstr, ft_flags) : : : "memory")
+
+#define n_alternative_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \
+	asm_inline volatile(N_ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) ::: "memory")
+
 /*
  * Alternative inline assembly with input.
  *
@@ -288,11 +344,24 @@ static inline int alternatives_text_reserved(void *start, void *end)
 	asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, ft_flags)	\
 		: output : "i" (0), ## input)
 
+#define n_alternative_io(oldinstr, newinstr, ft_flags, output, input...)	\
+	asm_inline volatile (N_ALTERNATIVE(oldinstr, newinstr, ft_flags)	\
+		: output : "i" (0), ## input)
+
+
 /* Like alternative_io, but for replacing a direct call with another one. */
 #define alternative_call(oldfunc, newfunc, ft_flags, output, input...)	\
 	asm_inline volatile (ALTERNATIVE("call %c[old]", "call %c[new]", ft_flags) \
 		: output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input)
 
+#define n_alternative_input(oldinstr, newinstr, ft_flags, input...)	\
+	asm_inline volatile (N_ALTERNATIVE(oldinstr, newinstr, ft_flags) \
+		: : "i" (0), ## input)
+
+#define n_alternative_call(oldfunc, newfunc, ft_flags, output, input...)	\
+	asm_inline volatile (N_ALTERNATIVE("call %P[old]", "call %P[new]", ft_flags) \
+		: output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input)
+
 /*
  * Like alternative_call, but there are two features and respective functions.
  * If CPU has feature2, function2 is used.
@@ -307,6 +376,15 @@ static inline int alternatives_text_reserved(void *start, void *end)
 		: [old] "i" (oldfunc), [new1] "i" (newfunc1),		\
 		  [new2] "i" (newfunc2), ## input)
 
+#define n_alternative_call_2(oldfunc, newfunc1, ft_flags1, newfunc2, ft_flags2,   \
+			   output, input...)				      \
+	asm_inline volatile (N_ALTERNATIVE_2("call %P[old]", "call %P[new1]", ft_flags1,\
+		"call %P[new2]", ft_flags2)				      \
+		: output, ASM_CALL_CONSTRAINT				      \
+		: [old] "i" (oldfunc), [new1] "i" (newfunc1),		      \
+		  [new2] "i" (newfunc2), ## input)
+
+
 /*
  * use this macro(s) if you need more than one output parameter
  * in alternative_io
@@ -403,6 +481,27 @@ void nop_func(void);
 	.popsection
 .endm
 
+#define __N_ALTERNATIVE(oldinst, newinst, flag)				\
+740:									\
+	oldinst	;							\
+741:									\
+	.skip -(((744f-743f)-(741b-740b)) > 0) * ((744f-743f)-(741b-740b)),0x90	;\
+742:									\
+	.pushsection .altinstructions,"a" ;				\
+	altinstr_entry 740b,743f,flag,742b-740b,744f-743f ;		\
+	.popsection ;							\
+	.pushsection .altinstr_replacement,"ax"	;			\
+743:									\
+	newinst	;							\
+744:									\
+	.popsection ;
+
+
+.macro N_ALTERNATIVE oldinstr, newinstr, ft_flags
+	__N_ALTERNATIVE(\oldinstr, \newinstr, \ft_flags)
+.endm
+
+
 #define old_len			141b-140b
 #define new_len1		144f-143f
 #define new_len2		145f-144f
@@ -417,7 +516,6 @@ void nop_func(void);
 #define alt_max_2(a, b)		((a) ^ (((a) ^ (b)) & -(-((a) < (b)))))
 #define alt_max_3(a, b, c)	(alt_max_2(alt_max_2(a, b), c))
 
-
 /*
  * Same as ALTERNATIVE macro above but for two alternatives. If CPU
  * has @feature1, it replaces @oldinstr with @newinstr1. If CPU has
@@ -445,6 +543,11 @@ void nop_func(void);
 	.popsection
 .endm
 
+.macro N_ALTERNATIVE_2 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2
+	__N_ALTERNATIVE(__N_ALTERNATIVE(\oldinstr, \newinstr1, \ft_flags1),
+		      \newinstr2, \ft_flags2)
+.endm
+
 .macro ALTERNATIVE_3 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2, newinstr3, ft_flags3
 140:
 	\oldinstr
@@ -470,6 +573,11 @@ void nop_func(void);
 	.popsection
 .endm
 
+.macro N_ALTERNATIVE_3 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2, newinstr3, ft_flags3
+	__N_ALTERNATIVE(N_ALTERNATIVE_2(\oldinstr, \newinstr1, \ft_flags1, \newinstr2, \ft_flags2),
+		      \newinstr3, \ft_flags3)
+.endm
+
 /* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
 #define ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) \
 	ALTERNATIVE_2 oldinstr, newinstr_no, X86_FEATURE_ALWAYS,	\
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index 89de61243272..37596a417094 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -432,6 +432,11 @@ static int alt_replace_call(u8 *instr, u8 *insn_buff, struct alt_instr *a)
 	return 5;
 }
 
+static inline u8 * instr_va(struct alt_instr *i)
+{
+	return (u8 *)&i->instr_offset + i->instr_offset;
+}
+
 /*
  * Replace instructions with better alternatives for this CPU type. This runs
  * before SMP is initialized to avoid SMP problems with self modifying code.
@@ -447,7 +452,7 @@ void __init_or_module noinline apply_alternatives(struct alt_instr *start,
 {
 	u8 insn_buff[MAX_PATCH_LEN];
 	u8 *instr, *replacement;
-	struct alt_instr *a;
+	struct alt_instr *a, *b;
 
 	DPRINTK(ALT, "alt table %px, -> %px", start, end);
 
@@ -473,7 +478,18 @@ void __init_or_module noinline apply_alternatives(struct alt_instr *start,
 	for (a = start; a < end; a++) {
 		int insn_buff_sz = 0;
 
-		instr = (u8 *)&a->instr_offset + a->instr_offset;
+		/*
+		 * In case of nested ALTERNATIVE()s the outer alternative might
+		 * add more padding. To ensure consistent patching find the max
+		 * padding for all alt_instr entries for this site (nested
+		 * alternatives result in consecutive entries).
+		 */
+		for (b = a+1; b < end && instr_va(b) == instr_va(a); b++) {
+			u8 len = max(a->instrlen, b->instrlen);
+			a->instrlen = b->instrlen = len;
+		}
+
+		instr = instr_va(a);
 		replacement = (u8 *)&a->repl_offset + a->repl_offset;
 		BUG_ON(a->instrlen > sizeof(insn_buff));
 		BUG_ON(a->cpuid >= (NCAPINTS + NBUGINTS) * 32);
diff --git a/tools/objtool/arch/x86/special.c b/tools/objtool/arch/x86/special.c
index 4134d27c696b..4ea0f9815fda 100644
--- a/tools/objtool/arch/x86/special.c
+++ b/tools/objtool/arch/x86/special.c
@@ -9,6 +9,29 @@
 
 void arch_handle_alternative(unsigned short feature, struct special_alt *alt)
 {
+	static struct special_alt *group, *prev;
+
+	/*
+	 * Recompute orig_len for nested ALTERNATIVE()s.
+	 */
+	if (group && group->orig_sec == alt->orig_sec &&
+	             group->orig_off == alt->orig_off) {
+
+		struct special_alt *iter = group;
+		for (;;) {
+			unsigned int len = max(iter->orig_len, alt->orig_len);
+			iter->orig_len = alt->orig_len = len;
+
+			if (iter == prev)
+				break;
+
+			iter = list_next_entry(iter, list);
+		}
+
+	} else group = alt;
+
+	prev = alt;
+
 	switch (feature) {
 	case X86_FEATURE_SMAP:
 		/*
diff --git a/tools/objtool/special.c b/tools/objtool/special.c
index 91b1950f5bd8..097a69db82a0 100644
--- a/tools/objtool/special.c
+++ b/tools/objtool/special.c
@@ -84,6 +84,14 @@ static int get_alt_entry(struct elf *elf, const struct special_entry *entry,
 						  entry->new_len);
 	}
 
+	orig_reloc = find_reloc_by_dest(elf, sec, offset + entry->orig);
+	if (!orig_reloc) {
+		WARN_FUNC("can't find orig reloc", sec, offset + entry->orig);
+		return -1;
+	}
+
+	reloc_to_sec_off(orig_reloc, &alt->orig_sec, &alt->orig_off);
+
 	if (entry->feature) {
 		unsigned short feature;
 
@@ -94,14 +102,6 @@ static int get_alt_entry(struct elf *elf, const struct special_entry *entry,
 		arch_handle_alternative(feature, alt);
 	}
 
-	orig_reloc = find_reloc_by_dest(elf, sec, offset + entry->orig);
-	if (!orig_reloc) {
-		WARN_FUNC("can't find orig reloc", sec, offset + entry->orig);
-		return -1;
-	}
-
-	reloc_to_sec_off(orig_reloc, &alt->orig_sec, &alt->orig_off);
-
 	if (!entry->group || alt->new_len) {
 		new_reloc = find_reloc_by_dest(elf, sec, offset + entry->new);
 		if (!new_reloc) {
-- 
2.43.0

[PATCH 03/14] x86/alternative: Convert alternative()

[Borislav Petkov]

From: "Borislav Petkov (AMD)" <bp@alien8.de>

Split conversion deliberately into minimal pieces to ease bisection
because debugging alternatives is a nightmare.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
---
 arch/x86/include/asm/alternative.h | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index 8554c2c339ff..c622ec7c4462 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -316,14 +316,11 @@ static inline int alternatives_text_reserved(void *start, void *end)
  * without volatile and memory clobber.
  */
 #define alternative(oldinstr, newinstr, ft_flags)			\
-	asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, ft_flags) : : : "memory")
+	asm_inline volatile(N_ALTERNATIVE(oldinstr, newinstr, ft_flags) : : : "memory")
 
 #define alternative_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \
 	asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) ::: "memory")
 
-#define n_alternative(oldinstr, newinstr, ft_flags)			\
-	asm_inline volatile (N_ALTERNATIVE(oldinstr, newinstr, ft_flags) : : : "memory")
-
 #define n_alternative_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \
 	asm_inline volatile(N_ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) ::: "memory")
 
-- 
2.43.0

[PATCH 04/14] x86/alternative: Convert alternative_2()

[Borislav Petkov]

From: "Borislav Petkov (AMD)" <bp@alien8.de>

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
---
 arch/x86/include/asm/alternative.h | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index c622ec7c4462..1dd445c6e2e1 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -319,9 +319,6 @@ static inline int alternatives_text_reserved(void *start, void *end)
 	asm_inline volatile(N_ALTERNATIVE(oldinstr, newinstr, ft_flags) : : : "memory")
 
 #define alternative_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \
-	asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) ::: "memory")
-
-#define n_alternative_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \
 	asm_inline volatile(N_ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) ::: "memory")
 
 /*
-- 
2.43.0

[PATCH 05/14] x86/alternative: Convert alternative_input()

[Borislav Petkov]

From: "Borislav Petkov (AMD)" <bp@alien8.de>

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
---
 arch/x86/include/asm/alternative.h | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index 1dd445c6e2e1..7f5f26fc42a9 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -330,7 +330,7 @@ static inline int alternatives_text_reserved(void *start, void *end)
  * Leaving an unused argument 0 to keep API compatibility.
  */
 #define alternative_input(oldinstr, newinstr, ft_flags, input...)	\
-	asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, ft_flags)	\
+	asm_inline volatile(N_ALTERNATIVE(oldinstr, newinstr, ft_flags) \
 		: : "i" (0), ## input)
 
 /* Like alternative_input, but with a single output argument */
@@ -348,10 +348,6 @@ static inline int alternatives_text_reserved(void *start, void *end)
 	asm_inline volatile (ALTERNATIVE("call %c[old]", "call %c[new]", ft_flags) \
 		: output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input)
 
-#define n_alternative_input(oldinstr, newinstr, ft_flags, input...)	\
-	asm_inline volatile (N_ALTERNATIVE(oldinstr, newinstr, ft_flags) \
-		: : "i" (0), ## input)
-
 #define n_alternative_call(oldfunc, newfunc, ft_flags, output, input...)	\
 	asm_inline volatile (N_ALTERNATIVE("call %P[old]", "call %P[new]", ft_flags) \
 		: output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input)
-- 
2.43.0

[PATCH 06/14] x86/alternative: Convert alternative_io()

[Borislav Petkov]

From: "Borislav Petkov (AMD)" <bp@alien8.de>

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
---
 arch/x86/include/asm/alternative.h | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index 7f5f26fc42a9..8a0a6ba4b741 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -335,14 +335,9 @@ static inline int alternatives_text_reserved(void *start, void *end)
 
 /* Like alternative_input, but with a single output argument */
 #define alternative_io(oldinstr, newinstr, ft_flags, output, input...)	\
-	asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, ft_flags)	\
+	asm_inline volatile(N_ALTERNATIVE(oldinstr, newinstr, ft_flags)	\
 		: output : "i" (0), ## input)
 
-#define n_alternative_io(oldinstr, newinstr, ft_flags, output, input...)	\
-	asm_inline volatile (N_ALTERNATIVE(oldinstr, newinstr, ft_flags)	\
-		: output : "i" (0), ## input)
-
-
 /* Like alternative_io, but for replacing a direct call with another one. */
 #define alternative_call(oldfunc, newfunc, ft_flags, output, input...)	\
 	asm_inline volatile (ALTERNATIVE("call %c[old]", "call %c[new]", ft_flags) \
-- 
2.43.0

[PATCH 07/14] x86/alternative: Convert alternative_call()

[Borislav Petkov]

From: "Borislav Petkov (AMD)" <bp@alien8.de>

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
---
 arch/x86/include/asm/alternative.h | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index 8a0a6ba4b741..bc696c60848d 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -340,11 +340,7 @@ static inline int alternatives_text_reserved(void *start, void *end)
 
 /* Like alternative_io, but for replacing a direct call with another one. */
 #define alternative_call(oldfunc, newfunc, ft_flags, output, input...)	\
-	asm_inline volatile (ALTERNATIVE("call %c[old]", "call %c[new]", ft_flags) \
-		: output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input)
-
-#define n_alternative_call(oldfunc, newfunc, ft_flags, output, input...)	\
-	asm_inline volatile (N_ALTERNATIVE("call %P[old]", "call %P[new]", ft_flags) \
+	asm_inline volatile(N_ALTERNATIVE("call %P[old]", "call %P[new]", ft_flags) \
 		: output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input)
 
 /*
-- 
2.43.0

[PATCH 08/14] x86/alternative: Convert alternative_call_2()

[Borislav Petkov]

From: "Borislav Petkov (AMD)" <bp@alien8.de>

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
---
 arch/x86/include/asm/alternative.h | 21 ++++++---------------
 1 file changed, 6 insertions(+), 15 deletions(-)

diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index bc696c60848d..bad1558d6382 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -349,23 +349,14 @@ static inline int alternatives_text_reserved(void *start, void *end)
  * Otherwise, if CPU has feature1, function1 is used.
  * Otherwise, old function is used.
  */
-#define alternative_call_2(oldfunc, newfunc1, ft_flags1, newfunc2, ft_flags2, \
-			   output, input...)				\
-	asm_inline volatile (ALTERNATIVE_2("call %c[old]", "call %c[new1]", ft_flags1, \
-		"call %c[new2]", ft_flags2)				\
-		: output, ASM_CALL_CONSTRAINT				\
-		: [old] "i" (oldfunc), [new1] "i" (newfunc1),		\
+#define alternative_call_2(oldfunc, newfunc1, ft_flags1, newfunc2, ft_flags2,		\
+			   output, input...)						\
+	asm_inline volatile(N_ALTERNATIVE_2("call %P[old]", "call %P[new1]", ft_flags1,	\
+		"call %P[new2]", ft_flags2)						\
+		: output, ASM_CALL_CONSTRAINT						\
+		: [old] "i" (oldfunc), [new1] "i" (newfunc1),				\
 		  [new2] "i" (newfunc2), ## input)
 
-#define n_alternative_call_2(oldfunc, newfunc1, ft_flags1, newfunc2, ft_flags2,   \
-			   output, input...)				      \
-	asm_inline volatile (N_ALTERNATIVE_2("call %P[old]", "call %P[new1]", ft_flags1,\
-		"call %P[new2]", ft_flags2)				      \
-		: output, ASM_CALL_CONSTRAINT				      \
-		: [old] "i" (oldfunc), [new1] "i" (newfunc1),		      \
-		  [new2] "i" (newfunc2), ## input)
-
-
 /*
  * use this macro(s) if you need more than one output parameter
  * in alternative_io
-- 
2.43.0

[PATCH 09/14] x86/alternative: Convert ALTERNATIVE_TERNARY()

[Borislav Petkov]

From: "Borislav Petkov (AMD)" <bp@alien8.de>

The C macro.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
---
 arch/x86/include/asm/alternative.h | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index bad1558d6382..73ee18705ef1 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -274,15 +274,9 @@ static inline int alternatives_text_reserved(void *start, void *end)
 
 /* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
 #define ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) \
-	ALTERNATIVE_2(oldinstr, newinstr_no, X86_FEATURE_ALWAYS,	\
-		      newinstr_yes, ft_flags)
-
-/* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
-#define N_ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) \
 	N_ALTERNATIVE_2(oldinstr, newinstr_no, X86_FEATURE_ALWAYS,	\
 		      newinstr_yes, ft_flags)
 
-
 #define ALTERNATIVE_3(oldinsn, newinsn1, ft_flags1, newinsn2, ft_flags2, \
 			newinsn3, ft_flags3)				\
 	OLDINSTR_3(oldinsn, 1, 2, 3)					\
-- 
2.43.0

[PATCH 10/14] x86/alternative: Convert ALTERNATIVE_3()

[Borislav Petkov]

From: "Borislav Petkov (AMD)" <bp@alien8.de>

Fixup label numbering too as the new macros have new label numbers.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
---
 arch/x86/include/asm/alternative.h | 24 ++++--------------------
 arch/x86/kernel/fpu/xstate.h       |  4 ++--
 2 files changed, 6 insertions(+), 22 deletions(-)

diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index 73ee18705ef1..0df99855e003 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -277,26 +277,10 @@ static inline int alternatives_text_reserved(void *start, void *end)
 	N_ALTERNATIVE_2(oldinstr, newinstr_no, X86_FEATURE_ALWAYS,	\
 		      newinstr_yes, ft_flags)
 
-#define ALTERNATIVE_3(oldinsn, newinsn1, ft_flags1, newinsn2, ft_flags2, \
-			newinsn3, ft_flags3)				\
-	OLDINSTR_3(oldinsn, 1, 2, 3)					\
-	".pushsection .altinstructions,\"a\"\n"				\
-	ALTINSTR_ENTRY(ft_flags1, 1)					\
-	ALTINSTR_ENTRY(ft_flags2, 2)					\
-	ALTINSTR_ENTRY(ft_flags3, 3)					\
-	".popsection\n"							\
-	".pushsection .altinstr_replacement, \"ax\"\n"			\
-	ALTINSTR_REPLACEMENT(newinsn1, 1)				\
-	ALTINSTR_REPLACEMENT(newinsn2, 2)				\
-	ALTINSTR_REPLACEMENT(newinsn3, 3)				\
-	".popsection\n"
-
-
-#define N_ALTERNATIVE_3(oldinst, newinst1, flag1, newinst2, flag2,	\
-		      newinst3, flag3)					\
-	N_ALTERNATIVE(N_ALTERNATIVE_2(oldinst, newinst1, flag1, newinst2, flag2), \
-		      newinst3, flag3)
-
+#define ALTERNATIVE_3(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2, \
+			newinstr3, ft_flags3)				\
+	N_ALTERNATIVE(N_ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2), \
+		      newinstr3, ft_flags3)
 /*
  * Alternative instructions for different CPU types or capabilities.
  *
diff --git a/arch/x86/kernel/fpu/xstate.h b/arch/x86/kernel/fpu/xstate.h
index 05df04f39628..4fe8501efc6c 100644
--- a/arch/x86/kernel/fpu/xstate.h
+++ b/arch/x86/kernel/fpu/xstate.h
@@ -108,7 +108,7 @@ static inline u64 xfeatures_mask_independent(void)
  *
  * We use XSAVE as a fallback.
  *
- * The 661 label is defined in the ALTERNATIVE* macros as the address of the
+ * The 771 label is defined in the ALTERNATIVE* macros as the address of the
  * original instruction which gets replaced. We need to use it here as the
  * address of the instruction where we might get an exception at.
  */
@@ -120,7 +120,7 @@ static inline u64 xfeatures_mask_independent(void)
 		     "\n"						\
 		     "xor %[err], %[err]\n"				\
 		     "3:\n"						\
-		     _ASM_EXTABLE_TYPE_REG(661b, 3b, EX_TYPE_EFAULT_REG, %[err]) \
+		     _ASM_EXTABLE_TYPE_REG(771b, 3b, EX_TYPE_EFAULT_REG, %[err]) \
 		     : [err] "=r" (err)					\
 		     : "D" (st), "m" (*st), "a" (lmask), "d" (hmask)	\
 		     : "memory")
-- 
2.43.0

[PATCH 11/14] x86/alternative: Convert the asm ALTERNATIVE() macro

[Borislav Petkov]

From: "Borislav Petkov (AMD)" <bp@alien8.de>

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
---
 arch/x86/include/asm/alternative.h | 22 +---------------------
 1 file changed, 1 insertion(+), 21 deletions(-)

diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index 0df99855e003..4b17267f3f2f 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -413,24 +413,6 @@ void nop_func(void);
  * @newinstr. ".skip" directive takes care of proper instruction padding
  * in case @newinstr is longer than @oldinstr.
  */
-.macro ALTERNATIVE oldinstr, newinstr, ft_flags
-140:
-	\oldinstr
-141:
-	.skip -(((144f-143f)-(141b-140b)) > 0) * ((144f-143f)-(141b-140b)),0x90
-142:
-
-	.pushsection .altinstructions,"a"
-	altinstr_entry 140b,143f,\ft_flags,142b-140b,144f-143f
-	.popsection
-
-	.pushsection .altinstr_replacement,"ax"
-143:
-	\newinstr
-144:
-	.popsection
-.endm
-
 #define __N_ALTERNATIVE(oldinst, newinst, flag)				\
 740:									\
 	oldinst	;							\
@@ -446,12 +428,10 @@ void nop_func(void);
 744:									\
 	.popsection ;
 
-
-.macro N_ALTERNATIVE oldinstr, newinstr, ft_flags
+.macro ALTERNATIVE oldinstr, newinstr, ft_flags
 	__N_ALTERNATIVE(\oldinstr, \newinstr, \ft_flags)
 .endm
 
-
 #define old_len			141b-140b
 #define new_len1		144f-143f
 #define new_len2		145f-144f
-- 
2.43.0

[PATCH 12/14] x86/alternative: Convert the asm ALTERNATIVE_2() macro

[Borislav Petkov]

From: "Borislav Petkov (AMD)" <bp@alien8.de>

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
---
 arch/x86/include/asm/alternative.h | 22 ----------------------
 1 file changed, 22 deletions(-)

diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index 4b17267f3f2f..82a79e17e952 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -452,28 +452,6 @@ void nop_func(void);
  * @feature2, it replaces @oldinstr with @feature2.
  */
 .macro ALTERNATIVE_2 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2
-140:
-	\oldinstr
-141:
-	.skip -((alt_max_2(new_len1, new_len2) - (old_len)) > 0) * \
-		(alt_max_2(new_len1, new_len2) - (old_len)),0x90
-142:
-
-	.pushsection .altinstructions,"a"
-	altinstr_entry 140b,143f,\ft_flags1,142b-140b,144f-143f
-	altinstr_entry 140b,144f,\ft_flags2,142b-140b,145f-144f
-	.popsection
-
-	.pushsection .altinstr_replacement,"ax"
-143:
-	\newinstr1
-144:
-	\newinstr2
-145:
-	.popsection
-.endm
-
-.macro N_ALTERNATIVE_2 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2
 	__N_ALTERNATIVE(__N_ALTERNATIVE(\oldinstr, \newinstr1, \ft_flags1),
 		      \newinstr2, \ft_flags2)
 .endm
-- 
2.43.0

[PATCH 13/14] x86/alternative: Convert the asm ALTERNATIVE_3() macro

[Borislav Petkov]

From: "Borislav Petkov (AMD)" <bp@alien8.de>

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
---
 arch/x86/include/asm/alternative.h | 25 -------------------------
 1 file changed, 25 deletions(-)

diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index 82a79e17e952..19b574331ffd 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -457,31 +457,6 @@ void nop_func(void);
 .endm
 
 .macro ALTERNATIVE_3 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2, newinstr3, ft_flags3
-140:
-	\oldinstr
-141:
-	.skip -((alt_max_3(new_len1, new_len2, new_len3) - (old_len)) > 0) * \
-		(alt_max_3(new_len1, new_len2, new_len3) - (old_len)),0x90
-142:
-
-	.pushsection .altinstructions,"a"
-	altinstr_entry 140b,143f,\ft_flags1,142b-140b,144f-143f
-	altinstr_entry 140b,144f,\ft_flags2,142b-140b,145f-144f
-	altinstr_entry 140b,145f,\ft_flags3,142b-140b,146f-145f
-	.popsection
-
-	.pushsection .altinstr_replacement,"ax"
-143:
-	\newinstr1
-144:
-	\newinstr2
-145:
-	\newinstr3
-146:
-	.popsection
-.endm
-
-.macro N_ALTERNATIVE_3 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2, newinstr3, ft_flags3
 	__N_ALTERNATIVE(N_ALTERNATIVE_2(\oldinstr, \newinstr1, \ft_flags1, \newinstr2, \ft_flags2),
 		      \newinstr3, \ft_flags3)
 .endm
-- 
2.43.0

[PATCH 14/14] x86/alternative: Replace the old macros

[Borislav Petkov]

From: "Borislav Petkov (AMD)" <bp@alien8.de>

Now that the new macros have been gradually put in place, replace the
old ones. Leave the new label numbers starting at 7xx as a hint that the
new nested alternatives are being used now.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
---
 arch/x86/include/asm/alternative.h | 144 +++++++----------------------
 arch/x86/kernel/fpu/xstate.h       |   2 +-
 2 files changed, 33 insertions(+), 113 deletions(-)

diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index 19b574331ffd..f02867092a49 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -156,131 +156,51 @@ static inline int alternatives_text_reserved(void *start, void *end)
 
 #define ALT_CALL_INSTR		"call BUG_func"
 
-#define b_replacement(num)	"664"#num
-#define e_replacement(num)	"665"#num
+#define alt_slen		"772b-771b"
+#define alt_total_slen		"773b-771b"
+#define alt_rlen		"775f-774f"
 
-#define alt_end_marker		"663"
-#define alt_slen		"662b-661b"
-#define n_alt_slen		"772b-771b"
-
-#define alt_total_slen		alt_end_marker"b-661b"
-#define n_alt_total_slen	"773b-771b"
-
-#define alt_rlen(num)		e_replacement(num)"f-"b_replacement(num)"f"
-#define n_alt_rlen		"775f-774f"
-
-#define OLDINSTR(oldinstr, num)						\
-	"# ALT: oldnstr\n"						\
-	"661:\n\t" oldinstr "\n662:\n"					\
-	"# ALT: padding\n"						\
-	".skip -(((" alt_rlen(num) ")-(" alt_slen ")) > 0) * "		\
-		"((" alt_rlen(num) ")-(" alt_slen ")),0x90\n"		\
-	alt_end_marker ":\n"
-
-#define N_OLDINSTR(oldinstr)						\
-	"# N_ALT: oldinstr\n"						\
+#define OLDINSTR(oldinstr)						\
+	"# ALT: oldinstr\n"						\
 	"771:\n\t" oldinstr "\n772:\n"					\
-	"# N_ALT: padding\n"						\
-	".skip -(((" n_alt_rlen ")-(" n_alt_slen ")) > 0) * "		\
-		"((" n_alt_rlen ")-(" n_alt_slen ")),0x90\n"		\
+	"# ALT: padding\n"						\
+	".skip -(((" alt_rlen ")-(" alt_slen ")) > 0) * "		\
+		"((" alt_rlen ")-(" alt_slen ")),0x90\n"		\
 	"773:\n"
 
-/*
- * gas compatible max based on the idea from:
- * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax
- *
- * The additional "-" is needed because gas uses a "true" value of -1.
- */
-#define alt_max_short(a, b)	"((" a ") ^ (((" a ") ^ (" b ")) & -(-((" a ") < (" b ")))))"
-
-/*
- * Pad the second replacement alternative with additional NOPs if it is
- * additionally longer than the first replacement alternative.
- */
-#define OLDINSTR_2(oldinstr, num1, num2) \
-	"# ALT: oldinstr2\n"									\
-	"661:\n\t" oldinstr "\n662:\n"								\
-	"# ALT: padding2\n"									\
-	".skip -((" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")) > 0) * "	\
-		"(" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")), 0x90\n"	\
-	alt_end_marker ":\n"
-
-#define OLDINSTR_3(oldinsn, n1, n2, n3)								\
-	"# ALT: oldinstr3\n"									\
-	"661:\n\t" oldinsn "\n662:\n"								\
-	"# ALT: padding3\n"									\
-	".skip -((" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3))	\
-		" - (" alt_slen ")) > 0) * "							\
-		"(" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3))	\
-		" - (" alt_slen ")), 0x90\n"							\
-	alt_end_marker ":\n"
-
-#define ALTINSTR_ENTRY(ft_flags, num)					      \
-	" .long 661b - .\n"				/* label           */ \
-	" .long " b_replacement(num)"f - .\n"		/* new instruction */ \
-	" .4byte " __stringify(ft_flags) "\n"		/* feature + flags */ \
-	" .byte " alt_total_slen "\n"			/* source len      */ \
-	" .byte " alt_rlen(num) "\n"			/* replacement len */
-
-#define N_ALTINSTR_ENTRY(ft_flags)					      \
+#define ALTINSTR_ENTRY(ft_flags)					      \
 	".pushsection .altinstructions,\"a\"\n"				      \
 	" .long 771b - .\n"				/* label           */ \
 	" .long 774f - .\n"				/* new instruction */ \
 	" .4byte " __stringify(ft_flags) "\n"		/* feature + flags */ \
-	" .byte " n_alt_total_slen "\n"			/* source len      */ \
-	" .byte " n_alt_rlen "\n"			/* replacement len */ \
+	" .byte " alt_total_slen "\n"			/* source len      */ \
+	" .byte " alt_rlen "\n"				/* replacement len */ \
 	".popsection\n"
 
-#define ALTINSTR_REPLACEMENT(newinstr, num)		/* replacement */	\
-	"# ALT: replacement " #num "\n"						\
-	b_replacement(num)":\n\t" newinstr "\n" e_replacement(num) ":\n"
-
-#define N_ALTINSTR_REPLACEMENT(newinstr)		/* replacement */	\
-	".pushsection .altinstr_replacement, \"ax\"\n"				\
-	"# N_ALT: replacement\n"						\
-	"774:\n\t" newinstr "\n775:\n"						\
+#define ALTINSTR_REPLACEMENT(newinstr)		/* replacement */	\
+	".pushsection .altinstr_replacement, \"ax\"\n"			\
+	"# ALT: replacement\n"						\
+	"774:\n\t" newinstr "\n775:\n"					\
 	".popsection\n"
 
 /* alternative assembly primitive: */
 #define ALTERNATIVE(oldinstr, newinstr, ft_flags)			\
-	OLDINSTR(oldinstr, 1)						\
-	".pushsection .altinstructions,\"a\"\n"				\
-	ALTINSTR_ENTRY(ft_flags, 1)					\
-	".popsection\n"							\
-	".pushsection .altinstr_replacement, \"ax\"\n"			\
-	ALTINSTR_REPLACEMENT(newinstr, 1)				\
-	".popsection\n"
-
-/* Nested alternatives macro variant */
-#define N_ALTERNATIVE(oldinstr, newinstr, ft_flags)			\
-	N_OLDINSTR(oldinstr)						\
-	N_ALTINSTR_ENTRY(ft_flags)					\
-	N_ALTINSTR_REPLACEMENT(newinstr)
+	OLDINSTR(oldinstr)						\
+	ALTINSTR_ENTRY(ft_flags)					\
+	ALTINSTR_REPLACEMENT(newinstr)
 
 #define ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \
-	OLDINSTR_2(oldinstr, 1, 2)					\
-	".pushsection .altinstructions,\"a\"\n"				\
-	ALTINSTR_ENTRY(ft_flags1, 1)					\
-	ALTINSTR_ENTRY(ft_flags2, 2)					\
-	".popsection\n"							\
-	".pushsection .altinstr_replacement, \"ax\"\n"			\
-	ALTINSTR_REPLACEMENT(newinstr1, 1)				\
-	ALTINSTR_REPLACEMENT(newinstr2, 2)				\
-	".popsection\n"
-
-#define N_ALTERNATIVE_2(oldinst, newinst1, flag1, newinst2, flag2)	\
-	N_ALTERNATIVE(N_ALTERNATIVE(oldinst, newinst1, flag1),		\
-		      newinst2, flag2)
+	ALTERNATIVE(ALTERNATIVE(oldinstr, newinstr1, ft_flags1), newinstr2, ft_flags2)
 
 /* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
 #define ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) \
-	N_ALTERNATIVE_2(oldinstr, newinstr_no, X86_FEATURE_ALWAYS,	\
-		      newinstr_yes, ft_flags)
+	ALTERNATIVE_2(oldinstr, newinstr_no, X86_FEATURE_ALWAYS, newinstr_yes, ft_flags)
 
 #define ALTERNATIVE_3(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2, \
 			newinstr3, ft_flags3)				\
-	N_ALTERNATIVE(N_ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2), \
+	ALTERNATIVE(ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2), \
 		      newinstr3, ft_flags3)
+
 /*
  * Alternative instructions for different CPU types or capabilities.
  *
@@ -294,10 +214,10 @@ static inline int alternatives_text_reserved(void *start, void *end)
  * without volatile and memory clobber.
  */
 #define alternative(oldinstr, newinstr, ft_flags)			\
-	asm_inline volatile(N_ALTERNATIVE(oldinstr, newinstr, ft_flags) : : : "memory")
+	asm_inline volatile(ALTERNATIVE(oldinstr, newinstr, ft_flags) : : : "memory")
 
 #define alternative_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \
-	asm_inline volatile(N_ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) ::: "memory")
+	asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) ::: "memory")
 
 /*
  * Alternative inline assembly with input.
@@ -308,17 +228,17 @@ static inline int alternatives_text_reserved(void *start, void *end)
  * Leaving an unused argument 0 to keep API compatibility.
  */
 #define alternative_input(oldinstr, newinstr, ft_flags, input...)	\
-	asm_inline volatile(N_ALTERNATIVE(oldinstr, newinstr, ft_flags) \
+	asm_inline volatile(ALTERNATIVE(oldinstr, newinstr, ft_flags) \
 		: : "i" (0), ## input)
 
 /* Like alternative_input, but with a single output argument */
 #define alternative_io(oldinstr, newinstr, ft_flags, output, input...)	\
-	asm_inline volatile(N_ALTERNATIVE(oldinstr, newinstr, ft_flags)	\
+	asm_inline volatile(ALTERNATIVE(oldinstr, newinstr, ft_flags)	\
 		: output : "i" (0), ## input)
 
 /* Like alternative_io, but for replacing a direct call with another one. */
 #define alternative_call(oldfunc, newfunc, ft_flags, output, input...)	\
-	asm_inline volatile(N_ALTERNATIVE("call %P[old]", "call %P[new]", ft_flags) \
+	asm_inline volatile(ALTERNATIVE("call %P[old]", "call %P[new]", ft_flags) \
 		: output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input)
 
 /*
@@ -329,7 +249,7 @@ static inline int alternatives_text_reserved(void *start, void *end)
  */
 #define alternative_call_2(oldfunc, newfunc1, ft_flags1, newfunc2, ft_flags2,		\
 			   output, input...)						\
-	asm_inline volatile(N_ALTERNATIVE_2("call %P[old]", "call %P[new1]", ft_flags1,	\
+	asm_inline volatile(ALTERNATIVE_2("call %P[old]", "call %P[new1]", ft_flags1,	\
 		"call %P[new2]", ft_flags2)						\
 		: output, ASM_CALL_CONSTRAINT						\
 		: [old] "i" (oldfunc), [new1] "i" (newfunc1),				\
@@ -413,7 +333,7 @@ void nop_func(void);
  * @newinstr. ".skip" directive takes care of proper instruction padding
  * in case @newinstr is longer than @oldinstr.
  */
-#define __N_ALTERNATIVE(oldinst, newinst, flag)				\
+#define __ALTERNATIVE(oldinst, newinst, flag)				\
 740:									\
 	oldinst	;							\
 741:									\
@@ -429,7 +349,7 @@ void nop_func(void);
 	.popsection ;
 
 .macro ALTERNATIVE oldinstr, newinstr, ft_flags
-	__N_ALTERNATIVE(\oldinstr, \newinstr, \ft_flags)
+	__ALTERNATIVE(\oldinstr, \newinstr, \ft_flags)
 .endm
 
 #define old_len			141b-140b
@@ -452,12 +372,12 @@ void nop_func(void);
  * @feature2, it replaces @oldinstr with @feature2.
  */
 .macro ALTERNATIVE_2 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2
-	__N_ALTERNATIVE(__N_ALTERNATIVE(\oldinstr, \newinstr1, \ft_flags1),
+	__ALTERNATIVE(__ALTERNATIVE(\oldinstr, \newinstr1, \ft_flags1),
 		      \newinstr2, \ft_flags2)
 .endm
 
 .macro ALTERNATIVE_3 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2, newinstr3, ft_flags3
-	__N_ALTERNATIVE(N_ALTERNATIVE_2(\oldinstr, \newinstr1, \ft_flags1, \newinstr2, \ft_flags2),
+	__ALTERNATIVE(ALTERNATIVE_2(\oldinstr, \newinstr1, \ft_flags1, \newinstr2, \ft_flags2),
 		      \newinstr3, \ft_flags3)
 .endm
 
diff --git a/arch/x86/kernel/fpu/xstate.h b/arch/x86/kernel/fpu/xstate.h
index 4fe8501efc6c..70903c12a911 100644
--- a/arch/x86/kernel/fpu/xstate.h
+++ b/arch/x86/kernel/fpu/xstate.h
@@ -134,7 +134,7 @@ static inline u64 xfeatures_mask_independent(void)
 				 XRSTORS, X86_FEATURE_XSAVES)		\
 		     "\n"						\
 		     "3:\n"						\
-		     _ASM_EXTABLE_TYPE(661b, 3b, EX_TYPE_FPU_RESTORE)	\
+		     _ASM_EXTABLE_TYPE(771b, 3b, EX_TYPE_FPU_RESTORE)	\
 		     :							\
 		     : "D" (st), "m" (*st), "a" (lmask), "d" (hmask)	\
 		     : "memory")
-- 
2.43.0

Re: [PATCH 02/14] x86/alternatives: Add nested alternatives macros

[Uros Bizjak]

> From: Peter Zijlstra <peterz@infradead.org>
> 
> Instead of making increasingly complicated ALTERNATIVE_n()
> implementations, use a nested alternative expression.
> 
> The only difference between:
> 
>    ALTERNATIVE_2(oldinst, newinst1, flag1, newinst2, flag2)
> 
> and
> 
>    ALTERNATIVE(ALTERNATIVE(oldinst, newinst1, flag1),
>                newinst2, flag2)
> 
> is that the outer alternative can add additional padding when the inner
> alternative is the shorter one, which then results in
> alt_instr::instrlen being inconsistent.
> 
> However, this is easily remedied since the alt_instr entries will be
> consecutive and it is trivial to compute the max(alt_instr::instrlen) at
> runtime while patching.
> 
> Specifically, after this the ALTERNATIVE_2 macro, after CPP expansion
> (and manual layout), looks like this:
> 
>    .macro ALTERNATIVE_2 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2
>    740:
>    740: \oldinstr ;
>    741: .skip -(((744f-743f)-(741b-740b)) > 0) * ((744f-743f)-(741b-740b)),0x90 ;
>    742: .pushsection .altinstructions,"a" ;
>    	altinstr_entry 740b,743f,\ft_flags1,742b-740b,744f-743f ;
>    .popsection ;
>    .pushsection .altinstr_replacement,"ax" ;
>    743: \newinstr1 ;
>    744: .popsection ; ;
>    741: .skip -(((744f-743f)-(741b-740b)) > 0) * ((744f-743f)-(741b-740b)),0x90 ;
>    742: .pushsection .altinstructions,"a" ;
>    altinstr_entry 740b,743f,\ft_flags2,742b-740b,744f-743f ;
>    .popsection ;
>    .pushsection .altinstr_replacement,"ax" ;
>    743: \newinstr2 ;
>    744: .popsection ;
>    .endm
> 
> The only label that is ambiguous is 740, however they all reference the
> same spot, so that doesn't matter.
> 
> NOTE: obviously only @oldinstr may be an alternative; making @newinstr
> an alternative would mean patching .altinstr_replacement which very
> likely isn't what is intended, also the labels will be confused in that
> case.
> 
>    [ bp: Debug an issue where it would match the wrong two insns and
>      and consider them nested due to the same signed offsets in the
>      .alternative section and use instr_va() to compare the full virtual
>      addresses instead.
> 
>      - Use new labels to denote that the new, nested
>      alternatives are being used when staring at preprocessed output. ]
> 
> Signed-off-by: Peter Zijlstra <peterz@infradead.org>
> Co-developed-by: Borislav Petkov (AMD) <bp@alien8.de>
> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
> Link: https://lkml.kernel.org/r/20230628104952.GA2439977@hirez.programming.kicks-ass.net
> ---
>   arch/x86/include/asm/alternative.h | 110 ++++++++++++++++++++++++++++-
>   arch/x86/kernel/alternative.c      |  20 +++++-
>   tools/objtool/arch/x86/special.c   |  23 ++++++
>   tools/objtool/special.c            |  16 ++---
>   4 files changed, 158 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
> index 6db78909180a..8554c2c339ff 100644
> --- a/arch/x86/include/asm/alternative.h
> +++ b/arch/x86/include/asm/alternative.h
> @@ -161,8 +161,13 @@ static inline int alternatives_text_reserved(void *start, void *end)
>   
>   #define alt_end_marker		"663"
>   #define alt_slen		"662b-661b"
> +#define n_alt_slen		"772b-771b"
> +
>   #define alt_total_slen		alt_end_marker"b-661b"
> +#define n_alt_total_slen	"773b-771b"
> +
>   #define alt_rlen(num)		e_replacement(num)"f-"b_replacement(num)"f"
> +#define n_alt_rlen		"775f-774f"
>   
>   #define OLDINSTR(oldinstr, num)						\
>   	"# ALT: oldnstr\n"						\
> @@ -172,6 +177,14 @@ static inline int alternatives_text_reserved(void *start, void *end)
>   		"((" alt_rlen(num) ")-(" alt_slen ")),0x90\n"		\
>   	alt_end_marker ":\n"
>   
> +#define N_OLDINSTR(oldinstr)						\
> +	"# N_ALT: oldinstr\n"						\
> +	"771:\n\t" oldinstr "\n772:\n"					\
> +	"# N_ALT: padding\n"						\
> +	".skip -(((" n_alt_rlen ")-(" n_alt_slen ")) > 0) * "		\
> +		"((" n_alt_rlen ")-(" n_alt_slen ")),0x90\n"		\
> +	"773:\n"
> +
>   /*
>    * gas compatible max based on the idea from:
>    * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax
> @@ -209,10 +222,25 @@ static inline int alternatives_text_reserved(void *start, void *end)
>   	" .byte " alt_total_slen "\n"			/* source len      */ \
>   	" .byte " alt_rlen(num) "\n"			/* replacement len */
>   
> +#define N_ALTINSTR_ENTRY(ft_flags)					      \
> +	".pushsection .altinstructions,\"a\"\n"				      \
> +	" .long 771b - .\n"				/* label           */ \
> +	" .long 774f - .\n"				/* new instruction */ \
> +	" .4byte " __stringify(ft_flags) "\n"		/* feature + flags */ \
> +	" .byte " n_alt_total_slen "\n"			/* source len      */ \
> +	" .byte " n_alt_rlen "\n"			/* replacement len */ \
> +	".popsection\n"
> +
>   #define ALTINSTR_REPLACEMENT(newinstr, num)		/* replacement */	\
>   	"# ALT: replacement " #num "\n"						\
>   	b_replacement(num)":\n\t" newinstr "\n" e_replacement(num) ":\n"
>   
> +#define N_ALTINSTR_REPLACEMENT(newinstr)		/* replacement */	\
> +	".pushsection .altinstr_replacement, \"ax\"\n"				\
> +	"# N_ALT: replacement\n"						\
> +	"774:\n\t" newinstr "\n775:\n"						\
> +	".popsection\n"
> +
>   /* alternative assembly primitive: */
>   #define ALTERNATIVE(oldinstr, newinstr, ft_flags)			\
>   	OLDINSTR(oldinstr, 1)						\
> @@ -223,6 +251,12 @@ static inline int alternatives_text_reserved(void *start, void *end)
>   	ALTINSTR_REPLACEMENT(newinstr, 1)				\
>   	".popsection\n"
>   
> +/* Nested alternatives macro variant */
> +#define N_ALTERNATIVE(oldinstr, newinstr, ft_flags)			\
> +	N_OLDINSTR(oldinstr)						\
> +	N_ALTINSTR_ENTRY(ft_flags)					\
> +	N_ALTINSTR_REPLACEMENT(newinstr)
> +
>   #define ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \
>   	OLDINSTR_2(oldinstr, 1, 2)					\
>   	".pushsection .altinstructions,\"a\"\n"				\
> @@ -234,11 +268,21 @@ static inline int alternatives_text_reserved(void *start, void *end)
>   	ALTINSTR_REPLACEMENT(newinstr2, 2)				\
>   	".popsection\n"
>   
> +#define N_ALTERNATIVE_2(oldinst, newinst1, flag1, newinst2, flag2)	\
> +	N_ALTERNATIVE(N_ALTERNATIVE(oldinst, newinst1, flag1),		\
> +		      newinst2, flag2)
> +
>   /* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
>   #define ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) \
>   	ALTERNATIVE_2(oldinstr, newinstr_no, X86_FEATURE_ALWAYS,	\
>   		      newinstr_yes, ft_flags)
>   
> +/* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
> +#define N_ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) \
> +	N_ALTERNATIVE_2(oldinstr, newinstr_no, X86_FEATURE_ALWAYS,	\
> +		      newinstr_yes, ft_flags)
> +
> +
>   #define ALTERNATIVE_3(oldinsn, newinsn1, ft_flags1, newinsn2, ft_flags2, \
>   			newinsn3, ft_flags3)				\
>   	OLDINSTR_3(oldinsn, 1, 2, 3)					\
> @@ -253,6 +297,12 @@ static inline int alternatives_text_reserved(void *start, void *end)
>   	ALTINSTR_REPLACEMENT(newinsn3, 3)				\
>   	".popsection\n"
>   
> +
> +#define N_ALTERNATIVE_3(oldinst, newinst1, flag1, newinst2, flag2,	\
> +		      newinst3, flag3)					\
> +	N_ALTERNATIVE(N_ALTERNATIVE_2(oldinst, newinst1, flag1, newinst2, flag2), \
> +		      newinst3, flag3)
> +
>   /*
>    * Alternative instructions for different CPU types or capabilities.
>    *
> @@ -271,6 +321,12 @@ static inline int alternatives_text_reserved(void *start, void *end)
>   #define alternative_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \
>   	asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) ::: "memory")
>   
> +#define n_alternative(oldinstr, newinstr, ft_flags)			\
> +	asm_inline volatile (N_ALTERNATIVE(oldinstr, newinstr, ft_flags) : : : "memory")
> +
> +#define n_alternative_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \
> +	asm_inline volatile(N_ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) ::: "memory")
> +
>   /*
>    * Alternative inline assembly with input.
>    *
> @@ -288,11 +344,24 @@ static inline int alternatives_text_reserved(void *start, void *end)
>   	asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, ft_flags)	\
>   		: output : "i" (0), ## input)
>   
> +#define n_alternative_io(oldinstr, newinstr, ft_flags, output, input...)	\
> +	asm_inline volatile (N_ALTERNATIVE(oldinstr, newinstr, ft_flags)	\
> +		: output : "i" (0), ## input)
> +
> +
>   /* Like alternative_io, but for replacing a direct call with another one. */
>   #define alternative_call(oldfunc, newfunc, ft_flags, output, input...)	\
>   	asm_inline volatile (ALTERNATIVE("call %c[old]", "call %c[new]", ft_flags) \
>   		: output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input)
>   
> +#define n_alternative_input(oldinstr, newinstr, ft_flags, input...)	\
> +	asm_inline volatile (N_ALTERNATIVE(oldinstr, newinstr, ft_flags) \
> +		: : "i" (0), ## input)
> +
> +#define n_alternative_call(oldfunc, newfunc, ft_flags, output, input...)	\
> +	asm_inline volatile (N_ALTERNATIVE("call %P[old]", "call %P[new]", ft_flags) \
> +		: output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input)

Please don't resurrect the %P modifier, use %c instead.

> +
>   /*
>    * Like alternative_call, but there are two features and respective functions.
>    * If CPU has feature2, function2 is used.
> @@ -307,6 +376,15 @@ static inline int alternatives_text_reserved(void *start, void *end)
>   		: [old] "i" (oldfunc), [new1] "i" (newfunc1),		\
>   		  [new2] "i" (newfunc2), ## input)
>   
> +#define n_alternative_call_2(oldfunc, newfunc1, ft_flags1, newfunc2, ft_flags2,   \
> +			   output, input...)				      \
> +	asm_inline volatile (N_ALTERNATIVE_2("call %P[old]", "call %P[new1]", ft_flags1,\
> +		"call %P[new2]", ft_flags2)				      \
> +		: output, ASM_CALL_CONSTRAINT				      \
> +		: [old] "i" (oldfunc), [new1] "i" (newfunc1),		      \
> +		  [new2] "i" (newfunc2), ## input)

Here too, %P should be avoided in favor of %c.

Uros.

> +
>   /*
>    * use this macro(s) if you need more than one output parameter
>    * in alternative_io
> @@ -403,6 +481,27 @@ void nop_func(void);
>   	.popsection
>   .endm
>   
> +#define __N_ALTERNATIVE(oldinst, newinst, flag)				\
> +740:									\
> +	oldinst	;							\
> +741:									\
> +	.skip -(((744f-743f)-(741b-740b)) > 0) * ((744f-743f)-(741b-740b)),0x90	;\
> +742:									\
> +	.pushsection .altinstructions,"a" ;				\
> +	altinstr_entry 740b,743f,flag,742b-740b,744f-743f ;		\
> +	.popsection ;							\
> +	.pushsection .altinstr_replacement,"ax"	;			\
> +743:									\
> +	newinst	;							\
> +744:									\
> +	.popsection ;
> +
> +
> +.macro N_ALTERNATIVE oldinstr, newinstr, ft_flags
> +	__N_ALTERNATIVE(\oldinstr, \newinstr, \ft_flags)
> +.endm
> +
> +
>   #define old_len			141b-140b
>   #define new_len1		144f-143f
>   #define new_len2		145f-144f
> @@ -417,7 +516,6 @@ void nop_func(void);
>   #define alt_max_2(a, b)		((a) ^ (((a) ^ (b)) & -(-((a) < (b)))))
>   #define alt_max_3(a, b, c)	(alt_max_2(alt_max_2(a, b), c))
>   
> -
>   /*
>    * Same as ALTERNATIVE macro above but for two alternatives. If CPU
>    * has @feature1, it replaces @oldinstr with @newinstr1. If CPU has
> @@ -445,6 +543,11 @@ void nop_func(void);
>   	.popsection
>   .endm
>   
> +.macro N_ALTERNATIVE_2 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2
> +	__N_ALTERNATIVE(__N_ALTERNATIVE(\oldinstr, \newinstr1, \ft_flags1),
> +		      \newinstr2, \ft_flags2)
> +.endm
> +
>   .macro ALTERNATIVE_3 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2, newinstr3, ft_flags3
>   140:
>   	\oldinstr
> @@ -470,6 +573,11 @@ void nop_func(void);
>   	.popsection
>   .endm
>   
> +.macro N_ALTERNATIVE_3 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2, newinstr3, ft_flags3
> +	__N_ALTERNATIVE(N_ALTERNATIVE_2(\oldinstr, \newinstr1, \ft_flags1, \newinstr2, \ft_flags2),
> +		      \newinstr3, \ft_flags3)
> +.endm
> +
>   /* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
>   #define ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) \
>   	ALTERNATIVE_2 oldinstr, newinstr_no, X86_FEATURE_ALWAYS,	\
> diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
> index 89de61243272..37596a417094 100644
> --- a/arch/x86/kernel/alternative.c
> +++ b/arch/x86/kernel/alternative.c
> @@ -432,6 +432,11 @@ static int alt_replace_call(u8 *instr, u8 *insn_buff, struct alt_instr *a)
>   	return 5;
>   }
>   
> +static inline u8 * instr_va(struct alt_instr *i)
> +{
> +	return (u8 *)&i->instr_offset + i->instr_offset;
> +}
> +
>   /*
>    * Replace instructions with better alternatives for this CPU type. This runs
>    * before SMP is initialized to avoid SMP problems with self modifying code.
> @@ -447,7 +452,7 @@ void __init_or_module noinline apply_alternatives(struct alt_instr *start,
>   {
>   	u8 insn_buff[MAX_PATCH_LEN];
>   	u8 *instr, *replacement;
> -	struct alt_instr *a;
> +	struct alt_instr *a, *b;
>   
>   	DPRINTK(ALT, "alt table %px, -> %px", start, end);
>   
> @@ -473,7 +478,18 @@ void __init_or_module noinline apply_alternatives(struct alt_instr *start,
>   	for (a = start; a < end; a++) {
>   		int insn_buff_sz = 0;
>   
> -		instr = (u8 *)&a->instr_offset + a->instr_offset;
> +		/*
> +		 * In case of nested ALTERNATIVE()s the outer alternative might
> +		 * add more padding. To ensure consistent patching find the max
> +		 * padding for all alt_instr entries for this site (nested
> +		 * alternatives result in consecutive entries).
> +		 */
> +		for (b = a+1; b < end && instr_va(b) == instr_va(a); b++) {
> +			u8 len = max(a->instrlen, b->instrlen);
> +			a->instrlen = b->instrlen = len;
> +		}
> +
> +		instr = instr_va(a);
>   		replacement = (u8 *)&a->repl_offset + a->repl_offset;
>   		BUG_ON(a->instrlen > sizeof(insn_buff));
>   		BUG_ON(a->cpuid >= (NCAPINTS + NBUGINTS) * 32);
> diff --git a/tools/objtool/arch/x86/special.c b/tools/objtool/arch/x86/special.c
> index 4134d27c696b..4ea0f9815fda 100644
> --- a/tools/objtool/arch/x86/special.c
> +++ b/tools/objtool/arch/x86/special.c
> @@ -9,6 +9,29 @@
>   
>   void arch_handle_alternative(unsigned short feature, struct special_alt *alt)
>   {
> +	static struct special_alt *group, *prev;
> +
> +	/*
> +	 * Recompute orig_len for nested ALTERNATIVE()s.
> +	 */
> +	if (group && group->orig_sec == alt->orig_sec &&
> +	             group->orig_off == alt->orig_off) {
> +
> +		struct special_alt *iter = group;
> +		for (;;) {
> +			unsigned int len = max(iter->orig_len, alt->orig_len);
> +			iter->orig_len = alt->orig_len = len;
> +
> +			if (iter == prev)
> +				break;
> +
> +			iter = list_next_entry(iter, list);
> +		}
> +
> +	} else group = alt;
> +
> +	prev = alt;
> +
>   	switch (feature) {
>   	case X86_FEATURE_SMAP:
>   		/*
> diff --git a/tools/objtool/special.c b/tools/objtool/special.c
> index 91b1950f5bd8..097a69db82a0 100644
> --- a/tools/objtool/special.c
> +++ b/tools/objtool/special.c
> @@ -84,6 +84,14 @@ static int get_alt_entry(struct elf *elf, const struct special_entry *entry,
>   						  entry->new_len);
>   	}
>   
> +	orig_reloc = find_reloc_by_dest(elf, sec, offset + entry->orig);
> +	if (!orig_reloc) {
> +		WARN_FUNC("can't find orig reloc", sec, offset + entry->orig);
> +		return -1;
> +	}
> +
> +	reloc_to_sec_off(orig_reloc, &alt->orig_sec, &alt->orig_off);
> +
>   	if (entry->feature) {
>   		unsigned short feature;
>   
> @@ -94,14 +102,6 @@ static int get_alt_entry(struct elf *elf, const struct special_entry *entry,
>   		arch_handle_alternative(feature, alt);
>   	}
>   
> -	orig_reloc = find_reloc_by_dest(elf, sec, offset + entry->orig);
> -	if (!orig_reloc) {
> -		WARN_FUNC("can't find orig reloc", sec, offset + entry->orig);
> -		return -1;
> -	}
> -
> -	reloc_to_sec_off(orig_reloc, &alt->orig_sec, &alt->orig_off);
> -
>   	if (!entry->group || alt->new_len) {
>   		new_reloc = find_reloc_by_dest(elf, sec, offset + entry->new);
>   		if (!new_reloc) {

Re: [PATCH 02/14] x86/alternatives: Add nested alternatives macros

[Borislav Petkov]

On Fri, May 31, 2024 at 04:30:31PM +0200, Uros Bizjak wrote:
> Please don't resurrect the %P modifier, use %c instead.
> 
> > +
> >   /*
> >    * Like alternative_call, but there are two features and respective functions.
> >    * If CPU has feature2, function2 is used.
> > @@ -307,6 +376,15 @@ static inline int alternatives_text_reserved(void *start, void *end)
> >   		: [old] "i" (oldfunc), [new1] "i" (newfunc1),		\
> >   		  [new2] "i" (newfunc2), ## input)
> > +#define n_alternative_call_2(oldfunc, newfunc1, ft_flags1, newfunc2, ft_flags2,   \
> > +			   output, input...)				      \
> > +	asm_inline volatile (N_ALTERNATIVE_2("call %P[old]", "call %P[new1]", ft_flags1,\
> > +		"call %P[new2]", ft_flags2)				      \
> > +		: output, ASM_CALL_CONSTRAINT				      \
> > +		: [old] "i" (oldfunc), [new1] "i" (newfunc1),		      \
> > +		  [new2] "i" (newfunc2), ## input)
> 
> Here too, %P should be avoided in favor of %c.

Yeah, will do.

We probably should update our patch checking scripts to catch such
things in the future.

/me adds to todo.

Thx.


-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

Re: [PATCH 02/14] x86/alternatives: Add nested alternatives macros

[Borislav Petkov]

On Fri, May 31, 2024 at 04:30:31PM +0200, Uros Bizjak wrote:
> Please don't resurrect the %P modifier, use %c instead.

Btw, out of curiosity, is %P being phased out?

I'm looking at

41cd2e1ee96e ("x86/asm: Use %c/%n instead of %P operand modifier in asm templates")

and yeah, %c is the generic one while %P is the x86-specific one but
phasing latter out is probably going to take a bunch of gcc releases...

Or is it something else entirely?

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

Re: [PATCH 02/14] x86/alternatives: Add nested alternatives macros

[Uros Bizjak]

Borislav Petkov je 31. 05. 24 ob 16:36 napisal:
> On Fri, May 31, 2024 at 04:30:31PM +0200, Uros Bizjak wrote:
>> Please don't resurrect the %P modifier, use %c instead.
> 
> Btw, out of curiosity, is %P being phased out?

No ;)

> I'm looking at
> 
> 41cd2e1ee96e ("x86/asm: Use %c/%n instead of %P operand modifier in asm templates")
> 
> and yeah, %c is the generic one while %P is the x86-specific one but
> phasing latter out is probably going to take a bunch of gcc releases...

The intention of '%P' operand modifier is primarily to be used with PIC, 
where:

'P'        If used for a function, print the PLT
            suffix and generate PIC code.  For
            example, emit 'foo@PLT' instead of 'foo'
            for the function foo().  If used for a
            constant, drop all syntax-specific
            prefixes and issue the bare constant.  See
            'p' above.

the fact that is handles constants is due to historic reasons.

The '%c' operand modifier will also check its operand that it is indeed 
an immediate integer operand, so should be used with 'i' operand constraint:

'c'        Require a constant operand and print the
            constant expression with no punctuation.

Uros.

Re: [PATCH 10/14] x86/alternative: Convert ALTERNATIVE_3()

[Brian Gerst]

On Fri, May 31, 2024 at 8:41 AM Borislav Petkov <bp@kernel.org> wrote:
>
> From: "Borislav Petkov (AMD)" <bp@alien8.de>
>
> Fixup label numbering too as the new macros have new label numbers.
>
> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
> ---
>  arch/x86/include/asm/alternative.h | 24 ++++--------------------
>  arch/x86/kernel/fpu/xstate.h       |  4 ++--
>  2 files changed, 6 insertions(+), 22 deletions(-)
>
> diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
> index 73ee18705ef1..0df99855e003 100644
> --- a/arch/x86/include/asm/alternative.h
> +++ b/arch/x86/include/asm/alternative.h
> @@ -277,26 +277,10 @@ static inline int alternatives_text_reserved(void *start, void *end)
>         N_ALTERNATIVE_2(oldinstr, newinstr_no, X86_FEATURE_ALWAYS,      \
>                       newinstr_yes, ft_flags)
>
> -#define ALTERNATIVE_3(oldinsn, newinsn1, ft_flags1, newinsn2, ft_flags2, \
> -                       newinsn3, ft_flags3)                            \
> -       OLDINSTR_3(oldinsn, 1, 2, 3)                                    \
> -       ".pushsection .altinstructions,\"a\"\n"                         \
> -       ALTINSTR_ENTRY(ft_flags1, 1)                                    \
> -       ALTINSTR_ENTRY(ft_flags2, 2)                                    \
> -       ALTINSTR_ENTRY(ft_flags3, 3)                                    \
> -       ".popsection\n"                                                 \
> -       ".pushsection .altinstr_replacement, \"ax\"\n"                  \
> -       ALTINSTR_REPLACEMENT(newinsn1, 1)                               \
> -       ALTINSTR_REPLACEMENT(newinsn2, 2)                               \
> -       ALTINSTR_REPLACEMENT(newinsn3, 3)                               \
> -       ".popsection\n"
> -
> -
> -#define N_ALTERNATIVE_3(oldinst, newinst1, flag1, newinst2, flag2,     \
> -                     newinst3, flag3)                                  \
> -       N_ALTERNATIVE(N_ALTERNATIVE_2(oldinst, newinst1, flag1, newinst2, flag2), \
> -                     newinst3, flag3)
> -
> +#define ALTERNATIVE_3(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2, \
> +                       newinstr3, ft_flags3)                           \
> +       N_ALTERNATIVE(N_ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2), \
> +                     newinstr3, ft_flags3)
>  /*
>   * Alternative instructions for different CPU types or capabilities.
>   *
> diff --git a/arch/x86/kernel/fpu/xstate.h b/arch/x86/kernel/fpu/xstate.h
> index 05df04f39628..4fe8501efc6c 100644
> --- a/arch/x86/kernel/fpu/xstate.h
> +++ b/arch/x86/kernel/fpu/xstate.h
> @@ -108,7 +108,7 @@ static inline u64 xfeatures_mask_independent(void)
>   *
>   * We use XSAVE as a fallback.
>   *
> - * The 661 label is defined in the ALTERNATIVE* macros as the address of the
> + * The 771 label is defined in the ALTERNATIVE* macros as the address of the
>   * original instruction which gets replaced. We need to use it here as the
>   * address of the instruction where we might get an exception at.
>   */
> @@ -120,7 +120,7 @@ static inline u64 xfeatures_mask_independent(void)
>                      "\n"                                               \
>                      "xor %[err], %[err]\n"                             \
>                      "3:\n"                                             \
> -                    _ASM_EXTABLE_TYPE_REG(661b, 3b, EX_TYPE_EFAULT_REG, %[err]) \
> +                    _ASM_EXTABLE_TYPE_REG(771b, 3b, EX_TYPE_EFAULT_REG, %[err]) \
>                      : [err] "=r" (err)                                 \
>                      : "D" (st), "m" (*st), "a" (lmask), "d" (hmask)    \
>                      : "memory")
> --
> 2.43.0
>
>

Just add a label at the start of this macro, so it doesn't depend on
the internal labels of ALTERNATIVE().  Something like:
    asm volatile("1:" ALTERNATIVE_3(XSAVE, \
    ...
     _ASM_EXTABLE_TYPE_REG(1b, 3b, EX_TYPE_EFAULT_REG, %[err]) \
    ...


Brian Gerst

Re: [PATCH 02/14] x86/alternatives: Add nested alternatives macros

[Borislav Petkov]

On Fri, May 31, 2024 at 05:10:08PM +0200, Uros Bizjak wrote:
> The intention of '%P' operand modifier is primarily to be used with PIC,
> where ...

Ok, I'll fold in the following. I'd like to have this documented
somewhere in the tree too.

Thx.

diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index f02867092a49..4973edbe9289 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -236,9 +236,18 @@ static inline int alternatives_text_reserved(void *start, void *end)
 	asm_inline volatile(ALTERNATIVE(oldinstr, newinstr, ft_flags)	\
 		: output : "i" (0), ## input)
 
-/* Like alternative_io, but for replacing a direct call with another one. */
+/*
+ * Like alternative_io, but for replacing a direct call with another one.
+ *
+ * Use the %c operand modifier which is the generic way to print a bare
+ * constant expression with all syntax-specific punctuation omitted. %P
+ * is the x86-specific variant which can handle constants too, for
+ * historical reasons, but it should be used primarily for PIC
+ * references: i.e., if used for a function, it would add the PLT
+ * suffix.
+ */
 #define alternative_call(oldfunc, newfunc, ft_flags, output, input...)	\
-	asm_inline volatile(ALTERNATIVE("call %P[old]", "call %P[new]", ft_flags) \
+	asm_inline volatile(ALTERNATIVE("call %c[old]", "call %c[new]", ft_flags) \
 		: output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input)
 
 /*
@@ -249,8 +258,8 @@ static inline int alternatives_text_reserved(void *start, void *end)
  */
 #define alternative_call_2(oldfunc, newfunc1, ft_flags1, newfunc2, ft_flags2,		\
 			   output, input...)						\
-	asm_inline volatile(ALTERNATIVE_2("call %P[old]", "call %P[new1]", ft_flags1,	\
-		"call %P[new2]", ft_flags2)						\
+	asm_inline volatile(ALTERNATIVE_2("call %c[old]", "call %c[new1]", ft_flags1,	\
+		"call %c[new2]", ft_flags2)						\
 		: output, ASM_CALL_CONSTRAINT						\
 		: [old] "i" (oldfunc), [new1] "i" (newfunc1),				\
 		  [new2] "i" (newfunc2), ## input)

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

Re: [PATCH 10/14] x86/alternative: Convert ALTERNATIVE_3()

[Borislav Petkov]

On Fri, May 31, 2024 at 01:00:55PM -0400, Brian Gerst wrote:
> Just add a label at the start of this macro, so it doesn't depend on
> the internal labels of ALTERNATIVE().  Something like:
>     asm volatile("1:" ALTERNATIVE_3(XSAVE, \
>     ...
>      _ASM_EXTABLE_TYPE_REG(1b, 3b, EX_TYPE_EFAULT_REG, %[err]) \
>     ...

Thanks for the cool idea - that use of the asm label outside of the
macro was really nasty but I didn't think of that. Cool.

And yap, it looks good:

------
#APP
# 188 "arch/x86/kernel/fpu/xstate.h" 1
	1: # ALT: oldinstr

<--- the outer label 1:

771:
	# ALT: oldinstr
771:
	# ALT: oldinstr
771:
	.byte 0x48, 0x0f,0xae,0x27
772:
# ALT: padding
.skip -(((775f-774f)-(772b-771b)) > 0) * ((775f-774f)-(772b-771b)),0x90

...

triple-alternative gunk

...

775:
.popsection

xor %edi, %edi	# err
3:
 .pushsection "__ex_table","a"
------

Yap, and boots in the guest.

I'll fold in the below:

diff --git a/arch/x86/kernel/fpu/xstate.h b/arch/x86/kernel/fpu/xstate.h
index 70903c12a911..2ee0b9c53dcc 100644
--- a/arch/x86/kernel/fpu/xstate.h
+++ b/arch/x86/kernel/fpu/xstate.h
@@ -106,21 +106,17 @@ static inline u64 xfeatures_mask_independent(void)
  * Otherwise, if XSAVEOPT is enabled, XSAVEOPT replaces XSAVE because XSAVEOPT
  * supports modified optimization which is not supported by XSAVE.
  *
- * We use XSAVE as a fallback.
- *
- * The 771 label is defined in the ALTERNATIVE* macros as the address of the
- * original instruction which gets replaced. We need to use it here as the
- * address of the instruction where we might get an exception at.
+ * Use XSAVE as a fallback.
  */
 #define XSTATE_XSAVE(st, lmask, hmask, err)				\
-	asm volatile(ALTERNATIVE_3(XSAVE,				\
+	asm volatile("1: " ALTERNATIVE_3(XSAVE,				\
 				   XSAVEOPT, X86_FEATURE_XSAVEOPT,	\
 				   XSAVEC,   X86_FEATURE_XSAVEC,	\
 				   XSAVES,   X86_FEATURE_XSAVES)	\
 		     "\n"						\
 		     "xor %[err], %[err]\n"				\
 		     "3:\n"						\
-		     _ASM_EXTABLE_TYPE_REG(771b, 3b, EX_TYPE_EFAULT_REG, %[err]) \
+		     _ASM_EXTABLE_TYPE_REG(1b, 3b, EX_TYPE_EFAULT_REG, %[err]) \
 		     : [err] "=r" (err)					\
 		     : "D" (st), "m" (*st), "a" (lmask), "d" (hmask)	\
 		     : "memory")
@@ -130,11 +126,11 @@ static inline u64 xfeatures_mask_independent(void)
  * XSAVE area format.
  */
 #define XSTATE_XRESTORE(st, lmask, hmask)				\
-	asm volatile(ALTERNATIVE(XRSTOR,				\
+	asm volatile("1: " ALTERNATIVE(XRSTOR,				\
 				 XRSTORS, X86_FEATURE_XSAVES)		\
 		     "\n"						\
 		     "3:\n"						\
-		     _ASM_EXTABLE_TYPE(771b, 3b, EX_TYPE_FPU_RESTORE)	\
+		     _ASM_EXTABLE_TYPE(1b, 3b, EX_TYPE_FPU_RESTORE)	\
 		     :							\
 		     : "D" (st), "m" (*st), "a" (lmask), "d" (hmask)	\
 		     : "memory")

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette