Patchwork [02/40] ftrace syscalls: Make arch_syscall_addr weak

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Submitter Ian Munsie
Date June 23, 2010, 10:02 a.m.
Message ID <>
Download mbox | patch
Permalink /patch/56628/
State Not Applicable
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Ian Munsie - June 23, 2010, 10:02 a.m.
From: Ian Munsie <>

Some architectures use non-trivial system call tables and will not work
with the generic arch_syscall_addr code. For example, PowerPC64 uses a
table of twin long longs.

This patch makes the generic arch_syscall_addr weak to allow
architectures with non-trivial system call tables to override it.

Signed-off-by: Ian Munsie <>
 Documentation/trace/ftrace-design.txt |    3 +++
 kernel/trace/trace_syscalls.c         |    2 +-
 2 files changed, 4 insertions(+), 1 deletions(-)


diff --git a/Documentation/trace/ftrace-design.txt b/Documentation/trace/ftrace-design.txt
index f1f81af..8369a1c 100644
--- a/Documentation/trace/ftrace-design.txt
+++ b/Documentation/trace/ftrace-design.txt
@@ -244,6 +244,9 @@  You need very few things to get the syscalls tracing in an arch.
 - Support the TIF_SYSCALL_TRACEPOINT thread flags.
 - Put the trace_sys_enter() and trace_sys_exit() tracepoints calls from ptrace
   in the ptrace syscalls tracing path.
+- If the system call table on this arch is more complicated than a simple array
+  of addresses of the system calls, implement an arch_syscall_addr to return
+  the address of a given system call.
diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index 82246ce..e2b657e 100644
--- a/kernel/trace/trace_syscalls.c
+++ b/kernel/trace/trace_syscalls.c
@@ -453,7 +453,7 @@  int init_syscall_trace(struct ftrace_event_call *call)
 	return id;
-unsigned long __init arch_syscall_addr(int nr)
+unsigned long __init __weak arch_syscall_addr(int nr)
 	return (unsigned long)sys_call_table[nr];