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| author | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2019-05-10 12:05:46 -0400 |
|---|---|---|
| committer | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2019-05-10 12:33:03 -0400 |
| commit | 518049d9d3e25dcd7be6e3d728e86f292ad0c922 (patch) | |
| tree | fdc458e59447517e471a9113d8f32f11cb4d4a8d /arch/x86/kernel/ftrace_32.S | |
| parent | a15fd609ad53a631a927c6680e8fb606f42a712b (diff) | |
| download | linux-518049d9d3e25dcd7be6e3d728e86f292ad0c922.tar.bz2 | |
ftrace/x86_32: Remove support for non DYNAMIC_FTRACE
When DYNAMIC_FTRACE is enabled in the kernel, all the functions that can be
traced by the function tracer have a "nop" placeholder at the start of the
function. When function tracing is enabled, the nop is converted into a call
to the tracing infrastructure where the functions get traced. This also
allows for specifying specific functions to trace, and a lot of
infrastructure is built on top of this.
When DYNAMIC_FTRACE is not enabled, all the functions have a call to the
ftrace trampoline. A check is made to see if a function pointer is the
ftrace_stub or not, and if it is not, it calls the function pointer to trace
the code. This adds over 10% overhead to the kernel even when tracing is
disabled.
When an architecture supports DYNAMIC_FTRACE there really is no reason to
use the static tracing. I have kept non DYNAMIC_FTRACE available in x86 so
that the generic code for non DYNAMIC_FTRACE can be tested. There is no
reason to support non DYNAMIC_FTRACE for both x86_64 and x86_32. As the non
DYNAMIC_FTRACE for x86_32 does not even support fentry, and we want to
remove mcount completely, there's no reason to keep non DYNAMIC_FTRACE
around for x86_32.
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Diffstat (limited to 'arch/x86/kernel/ftrace_32.S')
| -rw-r--r-- | arch/x86/kernel/ftrace_32.S | 39 |
1 files changed, 0 insertions, 39 deletions
diff --git a/arch/x86/kernel/ftrace_32.S b/arch/x86/kernel/ftrace_32.S index 4c8440de3355..459e6b4a19bc 100644 --- a/arch/x86/kernel/ftrace_32.S +++ b/arch/x86/kernel/ftrace_32.S @@ -18,8 +18,6 @@ EXPORT_SYMBOL(__fentry__) EXPORT_SYMBOL(mcount) #endif -#ifdef CONFIG_DYNAMIC_FTRACE - /* mcount uses a frame pointer even if CONFIG_FRAME_POINTER is not set */ #if !defined(CC_USING_FENTRY) || defined(CONFIG_FRAME_POINTER) # define USING_FRAME_POINTER @@ -170,43 +168,6 @@ GLOBAL(ftrace_regs_call) lea 3*4(%esp), %esp /* Skip orig_ax, ip and cs */ jmp .Lftrace_ret -#else /* ! CONFIG_DYNAMIC_FTRACE */ - -ENTRY(function_hook) - cmpl $__PAGE_OFFSET, %esp - jb ftrace_stub /* Paging not enabled yet? */ - - cmpl $ftrace_stub, ftrace_trace_function - jnz .Ltrace -#ifdef CONFIG_FUNCTION_GRAPH_TRACER - cmpl $ftrace_stub, ftrace_graph_return - jnz ftrace_graph_caller - - cmpl $ftrace_graph_entry_stub, ftrace_graph_entry - jnz ftrace_graph_caller -#endif -.globl ftrace_stub -ftrace_stub: - ret - - /* taken from glibc */ -.Ltrace: - pushl %eax - pushl %ecx - pushl %edx - movl 0xc(%esp), %eax - movl 0x4(%ebp), %edx - subl $MCOUNT_INSN_SIZE, %eax - - movl ftrace_trace_function, %ecx - CALL_NOSPEC %ecx - - popl %edx - popl %ecx - popl %eax - jmp ftrace_stub -END(function_hook) -#endif /* CONFIG_DYNAMIC_FTRACE */ #ifdef CONFIG_FUNCTION_GRAPH_TRACER ENTRY(ftrace_graph_caller) |