linux-kernel - [PATCH v4 10/21] modpost: simplify find_elf

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Date:   Sun, 14 May 2023 05:44:51 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     linux-kbuild@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nicolas Pitre <npitre@...libre.com>,
        Nicolas Schier <nicolas@...sle.eu>,
        Masahiro Yamada <masahiroy@...nel.org>
Subject: [PATCH v4 10/21] modpost: simplify find_elf_symbol()

I do not know why commit 157c23c80eed ("kbuild: use simpler section
mismatch warnings in modpost") is only applicable to find_elf_symbol2().

Simplify find_elf_symbol() based on find_elf_symbol2().

Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
---

 scripts/mod/modpost.c | 64 +++++++++----------------------------------
 1 file changed, 13 insertions(+), 51 deletions(-)

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 3b7b78e69137..b4fa9e0be4d1 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -1117,57 +1117,7 @@ static inline int is_valid_name(struct elf_info *elf, Elf_Sym *sym)
 	return !is_mapping_symbol(name);
 }
 
-/**
- * Find symbol based on relocation record info.
- * In some cases the symbol supplied is a valid symbol so
- * return refsym. If st_name != 0 we assume this is a valid symbol.
- * In other cases the symbol needs to be looked up in the symbol table
- * based on section and address.
- *  **/
-static Elf_Sym *find_elf_symbol(struct elf_info *elf, Elf64_Sword addr,
-				Elf_Sym *relsym)
-{
-	Elf_Sym *sym;
-	Elf_Sym *near = NULL;
-	Elf64_Sword distance = 20;
-	Elf64_Sword d;
-	unsigned int relsym_secindex;
-
-	if (relsym->st_name != 0)
-		return relsym;
-
-	relsym_secindex = get_secindex(elf, relsym);
-	for (sym = elf->symtab_start; sym < elf->symtab_stop; sym++) {
-		if (get_secindex(elf, sym) != relsym_secindex)
-			continue;
-		if (ELF_ST_TYPE(sym->st_info) == STT_SECTION)
-			continue;
-		if (!is_valid_name(elf, sym))
-			continue;
-		if (sym->st_value == addr)
-			return sym;
-		/* Find a symbol nearby - addr are maybe negative */
-		d = sym->st_value - addr;
-		if (d < 0)
-			d = addr - sym->st_value;
-		if (d < distance) {
-			distance = d;
-			near = sym;
-		}
-	}
-	/* We need a close match */
-	if (distance < 20)
-		return near;
-	else
-		return NULL;
-}
-
-/*
- * Find symbols before or equal addr and after addr - in the section sec.
- * If we find two symbols with equal offset prefer one with a valid name.
- * The ELF format may have a better way to detect what type of symbol
- * it is, but this works for now.
- **/
+/* Look up the nearest symbol based on the section and the address */
 static Elf_Sym *find_elf_symbol2(struct elf_info *elf, Elf_Addr addr,
 				 unsigned int secndx)
 {
@@ -1178,6 +1128,8 @@ static Elf_Sym *find_elf_symbol2(struct elf_info *elf, Elf_Addr addr,
 	for (sym = elf->symtab_start; sym < elf->symtab_stop; sym++) {
 		if (get_secindex(elf, sym) != secndx)
 			continue;
+		if (ELF_ST_TYPE(sym->st_info) == STT_SECTION)
+			continue;
 		if (!is_valid_name(elf, sym))
 			continue;
 		if (sym->st_value <= addr && addr - sym->st_value <= distance) {
@@ -1188,6 +1140,16 @@ static Elf_Sym *find_elf_symbol2(struct elf_info *elf, Elf_Addr addr,
 	return near;
 }
 
+static Elf_Sym *find_elf_symbol(struct elf_info *elf, Elf_Addr addr, Elf_Sym *sym)
+{
+	/* If the supplied symbol is valid, return it */
+	if (sym->st_name != 0)
+		return sym;
+
+	/* Otherwise, look up a better symbol */
+	return find_elf_symbol2(elf, addr, get_secindex(elf, sym));
+}
+
 static bool is_executable_section(struct elf_info *elf, unsigned int secndx)
 {
 	if (secndx > elf->num_sections)
-- 
2.39.2