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Commit f683c8dc authored by Sami Tolvanen's avatar Sami Tolvanen
Browse files

ANDROID: kallsyms: strip hashes from static functions with ThinLTO and CFI 



With CONFIG_THINLTO and CFI both enabled, LLVM appends a hash to the
names of all static functions. This breaks userspace tools, so strip
out the hash from output.

Bug: 147422318
Change-Id: Ie19a59d9d0681298be54e73064badc361c0f7014
Signed-off-by: default avatarSami Tolvanen <samitolvanen@google.com>
parent 383f53ee

kernel/kallsyms.c

+44 −5
Original line number Diff line number Diff line
@@ -271,6 +271,24 @@ int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize, 
	       !!__bpf_address_lookup(addr, symbolsize, offset, namebuf);

}



#if defined(CONFIG_CFI_CLANG) && defined(CONFIG_THINLTO)

/*

 * LLVM appends a hash to static function names when ThinLTO and CFI are

 * both enabled, which causes confusion and potentially breaks user space

 * tools, so we will strip the postfix from expanded symbol names.

 */

static inline void cleanup_symbol_name(char *s)

{

	char *res;



	res = strrchr(s, '$');

	if (res)

		*res = '\0';

}

#else

static inline void cleanup_symbol_name(char *s) {}

#endif



/*

 * Lookup an address

 * - modname is set to NULL if it's in the kernel.
@@ -297,7 +315,9 @@ const char *kallsyms_lookup(unsigned long addr, 
				       namebuf, KSYM_NAME_LEN);

		if (modname)

			*modname = NULL;

		return namebuf;



		ret = namebuf;

		goto found;

	}



	/* See if it's in a module or a BPF JITed image. */
@@ -310,11 +330,16 @@ const char *kallsyms_lookup(unsigned long addr, 
	if (!ret)

		ret = ftrace_mod_address_lookup(addr, symbolsize,

						offset, modname, namebuf);



found:

	cleanup_symbol_name(namebuf);

	return ret;

}



int lookup_symbol_name(unsigned long addr, char *symname)

{

	int res;



	symname[0] = '\0';

	symname[KSYM_NAME_LEN - 1] = '\0';
@@ -325,15 +350,23 @@ int lookup_symbol_name(unsigned long addr, char *symname) 
		/* Grab name */

		kallsyms_expand_symbol(get_symbol_offset(pos),

				       symname, KSYM_NAME_LEN);

		return 0;

		goto found;

	}

	/* See if it's in a module. */

	return lookup_module_symbol_name(addr, symname);

	res = lookup_module_symbol_name(addr, symname);

	if (res)

		return res;



found:

	cleanup_symbol_name(symname);

	return 0;

}



int lookup_symbol_attrs(unsigned long addr, unsigned long *size,

			unsigned long *offset, char *modname, char *name)

{

	int res;



	name[0] = '\0';

	name[KSYM_NAME_LEN - 1] = '\0';
@@ -345,10 +378,16 @@ int lookup_symbol_attrs(unsigned long addr, unsigned long *size, 
		kallsyms_expand_symbol(get_symbol_offset(pos),

				       name, KSYM_NAME_LEN);

		modname[0] = '\0';

		return 0;

		goto found;

	}

	/* See if it's in a module. */

	return lookup_module_symbol_attrs(addr, size, offset, modname, name);

	res = lookup_module_symbol_attrs(addr, size, offset, modname, name);

	if (res)

		return res;



found:

	cleanup_symbol_name(name);

	return 0;

}



/* Look up a kernel symbol and return it in a text buffer. */