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kallsyms: strip ThinLTO hashes from static functions

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With CONFIG_CFI_CLANG and ThinLTO, Clang appends a hash to the names
of all static functions not marked __used. This can break userspace
tools that don't expect the function name to change, so strip out the
hash from the output.

Suggested-by: Jack Pham <jackp@codeaurora.org>
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210408182843.1754385-8-samitolvanen@google.com
This commit is contained in:
Sami Tolvanen 2021-04-08 11:28:32 -07:00 committed by Kees Cook
parent 0a5b412891
commit 8b8e6b5d3b
1 changed files with 50 additions and 5 deletions
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55
kernel/kallsyms.c
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@ -161,6 +161,27 @@ static unsigned long kallsyms_sym_address(int idx)
return kallsyms_relative_base - 1 - kallsyms_offsets[idx];
}
#if defined(CONFIG_CFI_CLANG) && defined(CONFIG_LTO_CLANG_THIN)
/*
* LLVM appends a hash to static function names when ThinLTO and CFI are
* both enabled, i.e. foo() becomes foo$707af9a22804d33c81801f27dcfe489b.
* This causes confusion and potentially breaks user space tools, so we
* strip the suffix from expanded symbol names.
*/
static inline bool cleanup_symbol_name(char *s)
{
char *res;
res = strrchr(s, '$');
if (res)
*res = '\0';
return res != NULL;
}
#else
static inline bool cleanup_symbol_name(char *s) { return false; }
#endif
/* Lookup the address for this symbol. Returns 0 if not found. */
unsigned long kallsyms_lookup_name(const char *name)
{
@ -173,6 +194,9 @@ unsigned long kallsyms_lookup_name(const char *name)
if (strcmp(namebuf, name) == 0)
return kallsyms_sym_address(i);
if (cleanup_symbol_name(namebuf) && strcmp(namebuf, name) == 0)
return kallsyms_sym_address(i);
}
return module_kallsyms_lookup_name(name);
}
@ -303,7 +327,9 @@ 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. */
@ -316,11 +342,16 @@ 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';
@ -331,15 +362,23 @@ 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';
@ -351,10 +390,16 @@ 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. */