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Subject[for-next][PATCH 02/12] tracing: Show address when function names are not found
From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

Currently, when a function is not found in kallsyms, instead of simply
showing the function address, it shows nothing at all:

# echo ':mod:kvm_intel' > /sys/kernel/tracing/set_ftrace_filter
# echo function > /sys/kernel/tracing/set_ftrace_filter
# qemu -enable-kvm /home/my-qemu-image
<Ctrl-C>
# rmmod kvm_intel
# cat /sys/kernel/tracing/trace
qemu-system-x86-2408 [001] d..2 135.013238: <-kvm_arch_hardware_enable
qemu-system-x86-2408 [001] .... 135.014574: <-kvm_arch_vm_ioctl
qemu-system-x86-2408 [001] .... 135.015420: <-kvm_vm_ioctl_check_extension
qemu-system-x86-2408 [001] .... 135.045411: <-__do_cpuid_ent
qemu-system-x86-2408 [001] .... 135.045412: <-__do_cpuid_ent
qemu-system-x86-2408 [001] .... 135.045412: <-__do_cpuid_ent
qemu-system-x86-2408 [001] .... 135.045412: <-__do_cpuid_ent
qemu-system-x86-2408 [001] ...1 135.045413: <-__do_cpuid_ent
qemu-system-x86-2408 [001] .... 135.045413: <-__do_cpuid_ent

When it should show:

qemu-system-x86-2408 [001] d..2 135.013238: 0xffffffffa02a39f0 <-kvm_arch_hardware_enable
qemu-system-x86-2408 [001] .... 135.014574: 0xffffffffa02a2ba0 <-kvm_arch_vm_ioctl
qemu-system-x86-2408 [001] .... 135.015420: 0xffffffffa029e4e0 <-kvm_vm_ioctl_check_extension
qemu-system-x86-2408 [001] .... 135.045411: 0xffffffffa02a1380 <-__do_cpuid_ent
qemu-system-x86-2408 [001] .... 135.045412: 0xffffffffa029e160 <-__do_cpuid_ent
qemu-system-x86-2408 [001] .... 135.045412: 0xffffffffa029e180 <-__do_cpuid_ent
qemu-system-x86-2408 [001] .... 135.045412: 0xffffffffa029e520 <-__do_cpuid_ent
qemu-system-x86-2408 [001] ...1 135.045413: 0xffffffffa02a13b0 <-__do_cpuid_ent
qemu-system-x86-2408 [001] .... 135.045413: 0xffffffffa02a1380 <-__do_cpuid_ent

instead.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
kernel/trace/trace_output.c | 18 ++++++++++++++----
1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index 08f9bab8089e..01ff99969ca7 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -340,31 +340,41 @@ static inline const char *kretprobed(const char *name)
static void
seq_print_sym_short(struct trace_seq *s, const char *fmt, unsigned long address)
{
-#ifdef CONFIG_KALLSYMS
char str[KSYM_SYMBOL_LEN];
+#ifdef CONFIG_KALLSYMS
const char *name;

kallsyms_lookup(address, NULL, NULL, NULL, str);

name = kretprobed(str);

- trace_seq_printf(s, fmt, name);
+ if (name && strlen(name)) {
+ trace_seq_printf(s, fmt, name);
+ return;
+ }
#endif
+ snprintf(str, KSYM_SYMBOL_LEN, "0x%08lx", address);
+ trace_seq_printf(s, fmt, str);
}

static void
seq_print_sym_offset(struct trace_seq *s, const char *fmt,
unsigned long address)
{
-#ifdef CONFIG_KALLSYMS
char str[KSYM_SYMBOL_LEN];
+#ifdef CONFIG_KALLSYMS
const char *name;

sprint_symbol(str, address);
name = kretprobed(str);

- trace_seq_printf(s, fmt, name);
+ if (name && strlen(name)) {
+ trace_seq_printf(s, fmt, name);
+ return;
+ }
#endif
+ snprintf(str, KSYM_SYMBOL_LEN, "0x%08lx", address);
+ trace_seq_printf(s, fmt, str);
}

#ifndef CONFIG_64BIT
--
2.10.2

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