objtool: Remove instruction::list

Replace the instruction::list by allocating instructions in arrays of
256 entries and stringing them together by (amortized) find_insn().
This shrinks instruction by 16 bytes and brings it down to 128.

 struct instruction {
-	struct list_head           list;                 /*     0    16 */
-	struct hlist_node          hash;                 /*    16    16 */
-	struct list_head           call_node;            /*    32    16 */
-	struct section *           sec;                  /*    48     8 */
-	long unsigned int          offset;               /*    56     8 */
-	/* --- cacheline 1 boundary (64 bytes) --- */
-	long unsigned int          immediate;            /*    64     8 */
-	unsigned int               len;                  /*    72     4 */
-	u8                         type;                 /*    76     1 */
-
-	/* Bitfield combined with previous fields */
+	struct hlist_node          hash;                 /*     0    16 */
+	struct list_head           call_node;            /*    16    16 */
+	struct section *           sec;                  /*    32     8 */
+	long unsigned int          offset;               /*    40     8 */
+	long unsigned int          immediate;            /*    48     8 */
+	u8                         len;                  /*    56     1 */
+	u8                         prev_len;             /*    57     1 */
+	u8                         type;                 /*    58     1 */
+	s8                         instr;                /*    59     1 */
+	u32                        idx:8;                /*    60: 0  4 */
+	u32                        dead_end:1;           /*    60: 8  4 */
+	u32                        ignore:1;             /*    60: 9  4 */
+	u32                        ignore_alts:1;        /*    60:10  4 */
+	u32                        hint:1;               /*    60:11  4 */
+	u32                        save:1;               /*    60:12  4 */
+	u32                        restore:1;            /*    60:13  4 */
+	u32                        retpoline_safe:1;     /*    60:14  4 */
+	u32                        noendbr:1;            /*    60:15  4 */
+	u32                        entry:1;              /*    60:16  4 */
+	u32                        visited:4;            /*    60:17  4 */
+	u32                        no_reloc:1;           /*    60:21  4 */

-	u16                        dead_end:1;           /*    76: 8  2 */
-	u16                        ignore:1;             /*    76: 9  2 */
-	u16                        ignore_alts:1;        /*    76:10  2 */
-	u16                        hint:1;               /*    76:11  2 */
-	u16                        save:1;               /*    76:12  2 */
-	u16                        restore:1;            /*    76:13  2 */
-	u16                        retpoline_safe:1;     /*    76:14  2 */
-	u16                        noendbr:1;            /*    76:15  2 */
-	u16                        entry:1;              /*    78: 0  2 */
-	u16                        visited:4;            /*    78: 1  2 */
-	u16                        no_reloc:1;           /*    78: 5  2 */
+	/* XXX 10 bits hole, try to pack */

-	/* XXX 2 bits hole, try to pack */
-	/* Bitfield combined with next fields */
-
-	s8                         instr;                /*    79     1 */
-	struct alt_group *         alt_group;            /*    80     8 */
-	struct instruction *       jump_dest;            /*    88     8 */
-	struct instruction *       first_jump_src;       /*    96     8 */
+	/* --- cacheline 1 boundary (64 bytes) --- */
+	struct alt_group *         alt_group;            /*    64     8 */
+	struct instruction *       jump_dest;            /*    72     8 */
+	struct instruction *       first_jump_src;       /*    80     8 */
 	union {
-		struct symbol *    _call_dest;           /*   104     8 */
-		struct reloc *     _jump_table;          /*   104     8 */
-	};                                               /*   104     8 */
-	struct alternative *       alts;                 /*   112     8 */
-	struct symbol *            sym;                  /*   120     8 */
-	/* --- cacheline 2 boundary (128 bytes) --- */
-	struct stack_op *          stack_ops;            /*   128     8 */
-	struct cfi_state *         cfi;                  /*   136     8 */
+		struct symbol *    _call_dest;           /*    88     8 */
+		struct reloc *     _jump_table;          /*    88     8 */
+	};                                               /*    88     8 */
+	struct alternative *       alts;                 /*    96     8 */
+	struct symbol *            sym;                  /*   104     8 */
+	struct stack_op *          stack_ops;            /*   112     8 */
+	struct cfi_state *         cfi;                  /*   120     8 */

-	/* size: 144, cachelines: 3, members: 28 */
-	/* sum members: 142 */
-	/* sum bitfield members: 14 bits, bit holes: 1, sum bit holes: 2 bits */
-	/* last cacheline: 16 bytes */
+	/* size: 128, cachelines: 2, members: 29 */
+	/* sum members: 124 */
+	/* sum bitfield members: 22 bits, bit holes: 1, sum bit holes: 10 bits */
 };

pre:	5:38.18 real,   213.25 user,    124.90 sys,     23449040 mem
post:	5:03.34 real,   210.75 user,    88.80 sys,      20241232 mem

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org> # build only
Tested-by: Thomas Weißschuh <linux@weissschuh.net> # compile and run
Link: https://lore.kernel.org/r/20230208172245.851307606@infradead.org

2 files changed, 27 insertions, 25 deletions

diff --git a/tools/objtool/include/objtool/check.h b/tools/objtool/include/objtool/check.h
index ab6deaed9777..3e7c7004f7df 100644
--- a/tools/objtool/include/objtool/check.h
+++ b/tools/objtool/include/objtool/check.h
@@ -27,7 +27,7 @@ struct alt_group {
 	struct alt_group *orig_group;
 
 	/* First and last instructions in the group */
-	struct instruction *first_insn, *last_insn;
+	struct instruction *first_insn, *last_insn, *nop;
 
 	/*
 	 * Byte-offset-addressed len-sized array of pointers to CFI structs.
@@ -36,31 +36,36 @@ struct alt_group {
 	struct cfi_state **cfi;
 };
 
+#define INSN_CHUNK_BITS		8
+#define INSN_CHUNK_SIZE		(1 << INSN_CHUNK_BITS)
+#define INSN_CHUNK_MAX		(INSN_CHUNK_SIZE - 1)
+
 struct instruction {
-	struct list_head list;
 	struct hlist_node hash;
 	struct list_head call_node;
 	struct section *sec;
 	unsigned long offset;
 	unsigned long immediate;
-	unsigned int len;
-	u8 type;
-
-	u16 dead_end		: 1,
-	   ignore		: 1,
-	   ignore_alts		: 1,
-	   hint			: 1,
-	   save			: 1,
-	   restore		: 1,
-	   retpoline_safe	: 1,
-	   noendbr		: 1,
-	   entry		: 1,
-	   visited		: 4,
-	   no_reloc		: 1;
-		/* 2 bit hole */
 
+	u8 len;
+	u8 prev_len;
+	u8 type;
 	s8 instr;
 
+	u32 idx			: INSN_CHUNK_BITS,
+	    dead_end		: 1,
+	    ignore		: 1,
+	    ignore_alts		: 1,
+	    hint		: 1,
+	    save		: 1,
+	    restore		: 1,
+	    retpoline_safe	: 1,
+	    noendbr		: 1,
+	    entry		: 1,
+	    visited		: 4,
+	    no_reloc		: 1;
+		/* 10 bit hole */
+
 	struct alt_group *alt_group;
 	struct instruction *jump_dest;
 	struct instruction *first_jump_src;
@@ -109,13 +114,11 @@ static inline bool is_jump(struct instruction *insn)
 struct instruction *find_insn(struct objtool_file *file,
 			      struct section *sec, unsigned long offset);
 
-#define for_each_insn(file, insn)					\
-	list_for_each_entry(insn, &file->insn_list, list)
+struct instruction *next_insn_same_sec(struct objtool_file *file, struct instruction *insn);
 
-#define sec_for_each_insn(file, sec, insn)				\
-	for (insn = find_insn(file, sec, 0);				\
-	     insn && &insn->list != &file->insn_list &&			\
-			insn->sec == sec;				\
-	     insn = list_next_entry(insn, list))
+#define sec_for_each_insn(file, _sec, insn)				\
+	for (insn = find_insn(file, _sec, 0);				\
+	     insn && insn->sec == _sec;					\
+	     insn = next_insn_same_sec(file, insn))
 
 #endif /* _CHECK_H */
diff --git a/tools/objtool/include/objtool/objtool.h b/tools/objtool/include/objtool/objtool.h
index 6b40977bcdb1..94a33ee7b363 100644
--- a/tools/objtool/include/objtool/objtool.h
+++ b/tools/objtool/include/objtool/objtool.h
@@ -21,7 +21,6 @@ struct pv_state {
 
 struct objtool_file {
 	struct elf *elf;
-	struct list_head insn_list;
 	DECLARE_HASHTABLE(insn_hash, 20);
 	struct list_head retpoline_call_list;
 	struct list_head return_thunk_list;