On Wed, May 06, 2015 at 02:18:33PM -0400, Steven Rostedt wrote: > From: "Steven Rostedt (Red Hat)" <rostedt@xxxxxxxxxxx> > > The SyS_foo() alias wrapper was added to make sure that system call > arguments were signed extended. The call itself is to never be used > by anything, only the sys_foo() version is. But this symbol is stored > in /proc/kallsyms, and is returned sometimes as the name of system > call functions when a ksym lookup is made, it confuses the function > tracer interface (see available_filter_functions in the tracefs > directory). > > Al Viro even suggested that this should be removed from kallsyms > as well: > > Link: http://lkml.kernel.org/r/20130510211716.GN25399@xxxxxxxxxxxxxxxxxx > > Modify the compile time kallsyms.c to check if the function name > begins with SyS_ and is before or after the same name that starts > with sys_ and if so, do not record it. This saves some space and > more importantly removes the confusing variations of the system > call name. > > wc kallsyms.* > 90151 284644 3819255 kallsyms.orig > 89826 283669 3808628 kallsyms.patched > > size vmlinux* > text data bss dec hex filename > 9990933 2368592 1249280 13608805 cfa765 vmlinux.orig > 9986837 2368592 1249280 13604709 cf9765 vmlinux.patched > > This patch only removes SyS_*, it does not do anything with > compat_SyS_*. > > Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> > Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx> > --- > scripts/kallsyms.c | 43 ++++++++++++++++++++++++++++++++++++++----- > 1 file changed, 38 insertions(+), 5 deletions(-) > > diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c > index 8fa81e84e295..a64d89c6641c 100644 > --- a/scripts/kallsyms.c > +++ b/scripts/kallsyms.c > @@ -193,8 +193,22 @@ static int symbol_in_range(struct sym_entry *s, struct addr_range *ranges, > return 0; > } > > -static int symbol_valid(struct sym_entry *s) > +static const char *skip_prefix(const char *sym) > { > + if (symbol_prefix_char && *sym == symbol_prefix_char) > + return sym + 1; > + return sym; > +} scripts/kallsyms.c: In function ‘symbol_valid’: scripts/kallsyms.c:241:11: warning: assignment discards ‘const’ qualifier from pointer target type sym_name = skip_prefix(sym_name); ^ scripts/kallsyms.c:277:20: warning: assignment discards ‘const’ qualifier from pointer target type sym_name_before = skip_prefix(sym_name_before); ^ scripts/kallsyms.c:282:19: warning: assignment discards ‘const’ qualifier from pointer target type sym_name_after = skip_prefix(sym_name_after); ^ That sym_name should be const? > + > +static int match_sys(const char *sym, const char *sys) > +{ > + return !strncmp(sys, "sys_", 4) && !strcmp(sym + 4, sys + 4); > +} > + > +static int symbol_valid(int idx) > +{ > + struct sym_entry *s = &table[idx]; > + > /* Symbols which vary between passes. Passes 1 and 2 must have > * identical symbol lists. The kallsyms_* symbols below are only added > * after pass 1, they would be included in pass 2 when --all-symbols is > @@ -224,9 +238,7 @@ static int symbol_valid(struct sym_entry *s) > if (s->addr < kernel_start_addr) > return 0; > > - /* skip prefix char */ > - if (symbol_prefix_char && *sym_name == symbol_prefix_char) > - sym_name++; > + sym_name = skip_prefix(sym_name); > > > /* if --all-symbols is not specified, then symbols outside the text > @@ -255,6 +267,27 @@ static int symbol_valid(struct sym_entry *s) > if (strcmp(sym_name, special_symbols[i]) == 0) > return 0; > > + /* Ignore SyS_* alias system calls */ > + if (!strncmp(sym_name, "SyS_", 4)) { I guess we won't have to hide more symbols from kallsyms. If we do, then probably will have to generalize this... Oh well. Other than that, I think this a step in the right direction as the first patch makes the SyS_ symbols local and that's a good way for tools parsing the symbol table to know which symbol to show: readelf -a vmlinux | grep -iE "\Wsys_" | sort -k8 | head -50 77462: ffffffff815928f0 18 FUNC GLOBAL DEFAULT 1 sys_accept 43024: ffffffff815928f0 18 FUNC LOCAL DEFAULT 1 SyS_accept 71564: ffffffff815926e0 526 FUNC GLOBAL DEFAULT 1 sys_accept4 43023: ffffffff815926e0 526 FUNC LOCAL DEFAULT 1 SyS_accept4 50484: ffffffff81181170 26 FUNC GLOBAL DEFAULT 1 sys_access 12656: ffffffff81181170 26 FUNC LOCAL DEFAULT 1 SyS_access ... i.e., the global one, provided all the other attributes are the same. Before that we had them all identical: readelf -a vmlinux | grep -iE "\Wsys_" | sort -k8 | head -50 77446: ffffffff815928f0 18 FUNC GLOBAL DEFAULT 1 sys_accept 69532: ffffffff815928f0 18 FUNC GLOBAL DEFAULT 1 SyS_accept 71484: ffffffff815926e0 526 FUNC GLOBAL DEFAULT 1 sys_accept4 50916: ffffffff815926e0 526 FUNC GLOBAL DEFAULT 1 SyS_accept4 50192: ffffffff81181170 26 FUNC GLOBAL DEFAULT 1 sys_access 59364: ffffffff81181170 26 FUNC GLOBAL DEFAULT 1 SyS_access 52487: ffffffff81078920 18 FUNC WEAK DEFAULT 1 sys_acct 57730: ffffffff812b7d20 629 FUNC GLOBAL DEFAULT 1 sys_add_key 64564: ffffffff812b7d20 629 FUNC GLOBAL DEFAULT 1 SyS_add_key 74229: ffffffff810c7b00 154 FUNC GLOBAL DEFAULT 1 sys_adjtimex 50534: ffffffff810c7b00 154 FUNC GLOBAL DEFAULT 1 SyS_adjtimex 58974: ffffffff810cbab0 18 FUNC GLOBAL DEFAULT 1 sys_alarm 54082: ffffffff810cbab0 18 FUNC GLOBAL DEFAULT 1 SyS_alarm ... -- Regards/Gruss, Boris. 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