linux-kernel - [PATCH] modpost, kallsyms: Treat add '$'-prefixed symbols as mapping symbols

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Message-ID: <20230721150147.11720-2-palmer@rivosinc.com>
Date:   Fri, 21 Jul 2023 08:01:48 -0700
From:   Palmer Dabbelt <palmer@...osinc.com>
To:     masahiroy@...nel.org, wangkefeng.wang@...wei.com,
        mcgrof@...nel.org, nathan@...nel.org, ndesaulniers@...gle.com,
        nicolas@...sle.eu
Cc:         linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
            linux-kbuild@...r.kernel.org,
            Palmer Dabbelt <palmer@...osinc.com>
Subject: [PATCH] modpost, kallsyms: Treat add '$'-prefixed symbols as mapping symbols

Trying to restrict the '$'-prefix change to RISC-V caused some fallout,
so let's just treat all those symbols as special.

Fixes: c05780ef3c1 ("module: Ignore RISC-V mapping symbols too")
Link: https://lore.kernel.org/all/20230712015747.77263-1-wangkefeng.wang@huawei.com/
Signed-off-by: Palmer Dabbelt <palmer@...osinc.com>
---
It wasn't clear if we should just revert the original patch and spin a
new one, but looks like this is in at least some trees so I sent a
follow-on patch -- at least this way I can make coffee before forgetting
to send it ;)
---
 include/linux/module_symbol.h | 16 ++--------------
 kernel/module/kallsyms.c      |  2 +-
 scripts/mod/modpost.c         |  2 +-
 3 files changed, 4 insertions(+), 16 deletions(-)

diff --git a/include/linux/module_symbol.h b/include/linux/module_symbol.h
index 5b799942b243..1269543d0634 100644
--- a/include/linux/module_symbol.h
+++ b/include/linux/module_symbol.h
@@ -3,25 +3,13 @@
 #define _LINUX_MODULE_SYMBOL_H
 
 /* This ignores the intensely annoying "mapping symbols" found in ELF files. */
-static inline int is_mapping_symbol(const char *str, int is_riscv)
+static inline int is_mapping_symbol(const char *str)
 {
 	if (str[0] == '.' && str[1] == 'L')
 		return true;
 	if (str[0] == 'L' && str[1] == '0')
 		return true;
-	/*
-	 * RISC-V defines various special symbols that start with "$".  The
-	 * mapping symbols, which exist to differentiate between incompatible
-	 * instruction encodings when disassembling, show up all over the place
-	 * and are generally not meant to be treated like other symbols.  So
-	 * just ignore any of the special symbols.
-	 */
-	if (is_riscv)
-		return str[0] == '$';
-
-	return str[0] == '$' &&
-	       (str[1] == 'a' || str[1] == 'd' || str[1] == 't' || str[1] == 'x')
-	       && (str[2] == '\0' || str[2] == '.');
+	return str[0] == '$';
 }
 
 #endif /* _LINUX_MODULE_SYMBOL_H */
diff --git a/kernel/module/kallsyms.c b/kernel/module/kallsyms.c
index 78a1ffc399d9..ef73ae7c8909 100644
--- a/kernel/module/kallsyms.c
+++ b/kernel/module/kallsyms.c
@@ -289,7 +289,7 @@ static const char *find_kallsyms_symbol(struct module *mod,
 		 * and inserted at a whim.
 		 */
 		if (*kallsyms_symbol_name(kallsyms, i) == '\0' ||
-		    is_mapping_symbol(kallsyms_symbol_name(kallsyms, i), IS_ENABLED(CONFIG_RISCV)))
+		    is_mapping_symbol(kallsyms_symbol_name(kallsyms, i)))
 			continue;
 
 		if (thisval <= addr && thisval > bestval) {
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 7c71429d6502..b29b29707f10 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -1052,7 +1052,7 @@ static inline int is_valid_name(struct elf_info *elf, Elf_Sym *sym)
 
 	if (!name || !strlen(name))
 		return 0;
-	return !is_mapping_symbol(name, elf->hdr->e_machine == EM_RISCV);
+	return !is_mapping_symbol(name);
 }
 
 /* Look up the nearest symbol based on the section and the address */
-- 
2.41.0