| Message ID | 20150506182359.216601202@goodmis.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, May 06, 2015 at 02:18:33PM -0400, Steven Rostedt wrote: > From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org> > > 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@ZenIV.linux.org.uk > > 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@zeniv.linux.org.uk> > Signed-off-by: Steven Rostedt <rostedt@goodmis.org> > --- > 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 ...
On Fri, 22 May 2015 12:55:49 +0200 Borislav Petkov <bp@alien8.de> wrote: > > 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? Hmm, thanks. I'll take a look at this. > > > + > > +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. I started writing a more generalize version to begin with, then realized, "why? this isn't something we do every day". Yeah, if we add another one then we should take the time to do so. > > 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: Yep! Thanks, I'll update this patch. -- Steve > > 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 > ... > -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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; +} + +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)) { + char *sym_name_before = ""; + char *sym_name_after = ""; + + if (i > 0) { + sym_name_before = (char *)table[idx-1].sym + 1; + sym_name_before = skip_prefix(sym_name_before); + } + + if (i < table_cnt - 1) { + sym_name_after = (char *)table[idx+1].sym + 1; + sym_name_after = skip_prefix(sym_name_after); + } + + /* If SyS_foo matches a sys_foo, skip it */ + if (match_sys(sym_name, sym_name_before) || + match_sys(sym_name, sym_name_after)) + return 0; + } + for (i = 0; special_suffixes[i]; i++) { int l = strlen(sym_name) - strlen(special_suffixes[i]); @@ -447,7 +480,7 @@ static void build_initial_tok_table(void) pos = 0; for (i = 0; i < table_cnt; i++) { - if ( symbol_valid(&table[i]) ) { + if ( symbol_valid(i) ) { if (pos != i) table[pos] = table[i]; learn_symbol(table[pos].sym, table[pos].len);