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| author | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2020-10-27 10:55:55 -0400 |
|---|---|---|
| committer | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2020-11-13 12:14:59 -0500 |
| commit | 02a474ca266a47ea8f4d5a11f4ffa120f83730ad (patch) | |
| tree | 60f4ae7249955f386d0d5d30a673d726ae4b9df8 /arch/x86/kernel/ftrace_64.S | |
| parent | d19ad0775dcd64b49eecf4fa79c17959ebfbd26b (diff) | |
| download | linux-02a474ca266a47ea8f4d5a11f4ffa120f83730ad.tar.gz linux-02a474ca266a47ea8f4d5a11f4ffa120f83730ad.tar.bz2 linux-02a474ca266a47ea8f4d5a11f4ffa120f83730ad.zip | |
ftrace/x86: Allow for arguments to be passed in to ftrace_regs by default
Currently, the only way to get access to the registers of a function via a
ftrace callback is to set the "FL_SAVE_REGS" bit in the ftrace_ops. But as this
saves all regs as if a breakpoint were to trigger (for use with kprobes), it
is expensive.
The regs are already saved on the stack for the default ftrace callbacks, as
that is required otherwise a function being traced will get the wrong
arguments and possibly crash. And on x86, the arguments are already stored
where they would be on a pt_regs structure to use that code for both the
regs version of a callback, it makes sense to pass that information always
to all functions.
If an architecture does this (as x86_64 now does), it is to set
HAVE_DYNAMIC_FTRACE_WITH_ARGS, and this will let the generic code that it
could have access to arguments without having to set the flags.
This also includes having the stack pointer being saved, which could be used
for accessing arguments on the stack, as well as having the function graph
tracer not require its own trampoline!
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Diffstat (limited to 'arch/x86/kernel/ftrace_64.S')
| -rw-r--r-- | arch/x86/kernel/ftrace_64.S | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/arch/x86/kernel/ftrace_64.S b/arch/x86/kernel/ftrace_64.S index ac3d5f22fe64..60e3b64f5ea6 100644 --- a/arch/x86/kernel/ftrace_64.S +++ b/arch/x86/kernel/ftrace_64.S @@ -140,12 +140,19 @@ SYM_FUNC_START(ftrace_caller) /* save_mcount_regs fills in first two parameters */ save_mcount_regs + /* Stack - skipping return address of ftrace_caller */ + leaq MCOUNT_REG_SIZE+8(%rsp), %rcx + movq %rcx, RSP(%rsp) + SYM_INNER_LABEL(ftrace_caller_op_ptr, SYM_L_GLOBAL) /* Load the ftrace_ops into the 3rd parameter */ movq function_trace_op(%rip), %rdx - /* regs go into 4th parameter (but make it NULL) */ - movq $0, %rcx + /* regs go into 4th parameter */ + leaq (%rsp), %rcx + + /* Only ops with REGS flag set should have CS register set */ + movq $0, CS(%rsp) SYM_INNER_LABEL(ftrace_call, SYM_L_GLOBAL) call ftrace_stub |