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x86/ftrace: Make non direct case the default in ftrace_regs_caller 

If a direct function is hooked along with one of the ftrace registered
functions, then the ftrace_regs_caller is attached to the function that
shares the direct hook as well as the ftrace hook. The ftrace_regs_caller
will call ftrace_ops_list_func() that iterates through all the registered
ftrace callbacks, and if there's a direct callback attached to that
function, the direct ftrace_ops callback is called to notify that
ftrace_regs_caller to return to the direct caller instead of going back to
the function that called it.

But this is a very uncommon case. Currently, the code has it as the default
case. Modify ftrace_regs_caller to make the default case (the non jump) to
just return normally, and have the jump to the handling of the direct
caller.

Link: http://lkml.kernel.org/r/20200422162750.350373278@goodmis.org

Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (VMware) 2020-04-22 12:25:40 -04:00
parent c791cc4b1f
commit 0b4f8ddc0c
1 changed files with 15 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

31
arch/x86/kernel/ftrace_64.S
View File

@ -241,22 +241,9 @@ SYM_INNER_LABEL(ftrace_regs_call, SYM_L_GLOBAL)
*/
movq ORIG_RAX(%rsp), %rax
testq %rax, %rax
jz 1f
jnz 1f
/* Swap the flags with orig_rax */
movq MCOUNT_REG_SIZE(%rsp), %rdi
movq %rdi, MCOUNT_REG_SIZE-8(%rsp)
movq %rax, MCOUNT_REG_SIZE(%rsp)
restore_mcount_regs 8
/* Restore flags */
popfq
SYM_INNER_LABEL(ftrace_regs_caller_ret, SYM_L_GLOBAL);
UNWIND_HINT_RET_OFFSET
jmp ftrace_epilogue
1: restore_mcount_regs
restore_mcount_regs
/* Restore flags */
popfq
@ -266,9 +253,21 @@ SYM_INNER_LABEL(ftrace_regs_caller_ret, SYM_L_GLOBAL);
* The trampoline will add the code to jump
* to the return.
*/
SYM_INNER_LABEL(ftrace_regs_caller_end, SYM_L_GLOBAL)
SYM_INNER_LABEL(ftrace_regs_caller_ret, SYM_L_GLOBAL)
jmp ftrace_epilogue
/* Swap the flags with orig_rax */
1: movq MCOUNT_REG_SIZE(%rsp), %rdi
movq %rdi, MCOUNT_REG_SIZE-8(%rsp)
movq %rax, MCOUNT_REG_SIZE(%rsp)
restore_mcount_regs 8
/* Restore flags */
popfq
SYM_INNER_LABEL(ftrace_regs_caller_end, SYM_L_GLOBAL)
UNWIND_HINT_RET_OFFSET
jmp ftrace_epilogue
SYM_FUNC_END(ftrace_regs_caller)