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ARM: 8678/1: ftrace: Adds support for CONFIG_DYNAMIC_FTRACE_WITH_REGS

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The DYNAMIC_FTRACE_WITH_REGS configuration makes it possible for a
ftrace operation to specify if registers need to saved/restored by
the ftrace handler. This is needed by kgraft and possibly other
ftrace-based tools, and the ARM architecture is currently lacking
this feature. It would also be the first step to support the
"Kprobes-on-ftrace" optimization on ARM.

This patch introduces a new ftrace handler that stores the registers
on the stack before calling the next stage. The registers are restored
from the stack before going back to the instrumented function.

A side-effect of this patch is to activate the support for
ftrace_modify_call() as it defines ARCH_SUPPORTS_FTRACE_OPS for the
ARM architecture.

Signed-off-by: Abel Vesa <abelvesa@linux.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
This commit is contained in:
Abel Vesa
2017-05-26 21:49:47 +01:00
committed by Russell King
parent 1515b186c2
commit 620176f335
4 changed files with 142 additions and 0 deletions
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37
arch/arm/kernel/ftrace.c
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@@ -141,6 +141,15 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
ret = ftrace_modify_code(pc, 0, new, false);
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
if (!ret) {
pc = (unsigned long)&ftrace_regs_call;
new = ftrace_call_replace(pc, (unsigned long)func);
ret = ftrace_modify_code(pc, 0, new, false);
}
#endif
#ifdef CONFIG_OLD_MCOUNT
if (!ret) {
pc = (unsigned long)&ftrace_call_old;
@@ -159,11 +168,29 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
unsigned long ip = rec->ip;
old = ftrace_nop_replace(rec);
new = ftrace_call_replace(ip, adjust_address(rec, addr));
return ftrace_modify_code(rec->ip, old, new, true);
}
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
unsigned long addr)
{
unsigned long new, old;
unsigned long ip = rec->ip;
old = ftrace_call_replace(ip, adjust_address(rec, old_addr));
new = ftrace_call_replace(ip, adjust_address(rec, addr));
return ftrace_modify_code(rec->ip, old, new, true);
}
#endif
int ftrace_make_nop(struct module *mod,
struct dyn_ftrace *rec, unsigned long addr)
{
@@ -231,6 +258,8 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
extern unsigned long ftrace_graph_call;
extern unsigned long ftrace_graph_call_old;
extern void ftrace_graph_caller_old(void);
extern unsigned long ftrace_graph_regs_call;
extern void ftrace_graph_regs_caller(void);
static int __ftrace_modify_caller(unsigned long *callsite,
void (*func) (void), bool enable)
@@ -253,6 +282,14 @@ static int ftrace_modify_graph_caller(bool enable)
ftrace_graph_caller,
enable);
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
if (!ret)
ret = __ftrace_modify_caller(&ftrace_graph_regs_call,
ftrace_graph_regs_caller,
enable);
#endif
#ifdef CONFIG_OLD_MCOUNT
if (!ret)
ret = __ftrace_modify_caller(&ftrace_graph_call_old,