linux-kernel - Re: [PATCH v2] tracing/x86: Update syscall trace events to handle new x86 syscall func names

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Date:   Tue, 17 Apr 2018 17:41:28 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Dominik Brodowski <linux@...inikbrodowski.net>,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org
Subject: Re: [PATCH v2] tracing/x86: Update syscall trace events to handle
 new x86 syscall func names

On Tue, 17 Apr 2018 15:13:04 -0300
Arnaldo Carvalho de Melo <acme@...nel.org> wrote:

> Em Tue, Apr 17, 2018 at 03:04:30PM -0300, Arnaldo Carvalho de Melo escreveu:
> > Em Tue, Apr 17, 2018 at 07:22:36PM +0200, Dominik Brodowski escreveu:  
> > > >   Added back original compare to not miss 32bit kernel syscalls  
> > > 
> > > s/32bit/32bit and 0-parameter syscalls.  
> > 
> > So this should have covered 0-parameter syscalls, ok, I'm double
> > checking that the last patch is the one I have running... Because
> > 0-parameter syscalls are not working for me, i.e. no
> > syscalls:sys_enter_getppid, for instance.  
> 
> Yeah, failing:
> 
> [root@...et ~]# strace -e openat -e file perf test -F -v "mmap interface" |& grep syscalls
> openat(AT_FDCWD, "/sys/kernel/debug/tracing/events/syscalls/sys_enter_getsid/format", O_RDONLY) = 3
> openat(AT_FDCWD, "/sys/kernel/debug/tracing/events/syscalls/sys_enter_getppid/format", O_RDONLY) = -1 ENOENT (No such file or directory)
> [root@...et ~]# 
> 
> [root@...et ~]# ls -la /sys/kernel/debug/tracing/events/syscalls/sys_enter_getppid/format
> ls: cannot access '/sys/kernel/debug/tracing/events/syscalls/sys_enter_getppid/format': No such file or directory
> [root@...et ~]#
> 
> With:
> 
> +#define ARCH_HAS_SYSCALL_MATCH_SYM_NAME
> +static inline bool arch_syscall_match_sym_name(const char *sym, const char *name)
> +{
> +       /*
> +        * Compare the symbol name with the system call name. Skip the
> +        * "__x64_sys" prefix.
> +        */
> +       return !strcmp(sym + 9, name + 3) || !strcmp(sym + 3, name + 3);
> +}
> 
> in place.

It doesn't have to do with the number of parameters, not everything has
"__x64" on it.

Try this patch:

-- Steve

diff --git a/arch/x86/include/asm/ftrace.h b/arch/x86/include/asm/ftrace.h
index 09ad88572746..15582648887f 100644
--- a/arch/x86/include/asm/ftrace.h
+++ b/arch/x86/include/asm/ftrace.h
@@ -31,6 +31,19 @@ static inline unsigned long ftrace_call_adjust(unsigned long addr)
 	return addr;
 }
 
+#define ARCH_HAS_SYSCALL_MATCH_SYM_NAME
+static inline bool arch_syscall_match_sym_name(const char *sym, const char *name)
+{
+	/*
+	 * Compare the symbol name with the system call name. Skip the
+	 * "__x64_sys", "__ia32_sys" or simple "sys" prefix.
+	 */
+	return !strcmp(sym + 3, name + 3) ||
+		(!strncmp(sym, "__x64_", 6) && !strcmp(sym + 9, name + 3)) ||
+		(!strncmp(sym, "__ia32_", 7) && !strcmp(sym + 10, name + 3));
+
+}
+
 #ifdef CONFIG_DYNAMIC_FTRACE
 
 struct dyn_arch_ftrace {