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ftrace/x86: Add separate function to save regs

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Add a way to have different functions calling different trampolines.
If a ftrace_ops wants regs saved on the return, then have only the
functions with ops registered to save regs. Functions registered by
other ops would not be affected, unless the functions overlap.

If one ftrace_ops registered functions A, B and C and another ops
registered fucntions to save regs on A, and D, then only functions
A and D would be saving regs. Function B and C would work as normal.
Although A is registered by both ops: normal and saves regs; this is fine
as saving the regs is needed to satisfy one of the ops that calls it
but the regs are ignored by the other ops function.

x86_64 implements the full regs saving, and i386 just passes a NULL
for regs to satisfy the ftrace_ops passing. Where an arch must supply
both regs and ftrace_ops parameters, even if regs is just NULL.

It is OK for an arch to pass NULL regs. All function trace users that
require regs passing must add the flag FTRACE_OPS_FL_SAVE_REGS when
registering the ftrace_ops. If the arch does not support saving regs
then the ftrace_ops will fail to register. The flag
FTRACE_OPS_FL_SAVE_REGS_IF_SUPPORTED may be set that will prevent the
ftrace_ops from failing to register. In this case, the handler may
either check if regs is not NULL or check if ARCH_SUPPORTS_FTRACE_SAVE_REGS.
If the arch supports passing regs it will set this macro and pass regs
for ops that request them. All other archs will just pass NULL.

Link: Link: http://lkml.kernel.org/r/20120711195745.107705970@goodmis.org

Cc: Alexander van Heukelum <heukelum@fastmail.fm>
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt
2012-04-30 16:20:23 -04:00
committed by Steven Rostedt
parent 28fb5dfa78
commit 08f6fba503
6 changed files with 373 additions and 47 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
arch/x86/kernel/entry_32.S
View File

@@ -1109,7 +1109,8 @@ ENTRY(ftrace_caller)
pushl %eax
pushl %ecx
pushl %edx
movl 0xc(%esp), %eax
pushl $0 /* Pass NULL as regs pointer */
movl 4*4(%esp), %eax
movl 0x4(%ebp), %edx
leal function_trace_op, %ecx
subl $MCOUNT_INSN_SIZE, %eax
@@ -1118,6 +1119,7 @@ ENTRY(ftrace_caller)
ftrace_call:
call ftrace_stub
addl $4,%esp /* skip NULL pointer */
popl %edx
popl %ecx
popl %eax

94
arch/x86/kernel/entry_64.S
View File

@@ -73,21 +73,34 @@ ENTRY(mcount)
retq
END(mcount)
/* skip is set if stack has been adjusted */
.macro ftrace_caller_setup skip=0
MCOUNT_SAVE_FRAME \skip
/* Load the ftrace_ops into the 3rd parameter */
leaq function_trace_op, %rdx
/* Load ip into the first parameter */
movq RIP(%rsp), %rdi
subq $MCOUNT_INSN_SIZE, %rdi
/* Load the parent_ip into the second parameter */
movq 8(%rbp), %rsi
.endm
ENTRY(ftrace_caller)
/* Check if tracing was disabled (quick check) */
cmpl $0, function_trace_stop
jne ftrace_stub
MCOUNT_SAVE_FRAME
leaq function_trace_op, %rdx
movq 0x38(%rsp), %rdi
movq 8(%rbp), %rsi
subq $MCOUNT_INSN_SIZE, %rdi
ftrace_caller_setup
/* regs go into 4th parameter (but make it NULL) */
movq $0, %rcx
GLOBAL(ftrace_call)
call ftrace_stub
MCOUNT_RESTORE_FRAME
ftrace_return:
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
GLOBAL(ftrace_graph_call)
@@ -98,6 +111,71 @@ GLOBAL(ftrace_stub)
retq
END(ftrace_caller)
ENTRY(ftrace_regs_caller)
/* Save the current flags before compare (in SS location)*/
pushfq
/* Check if tracing was disabled (quick check) */
cmpl $0, function_trace_stop
jne ftrace_restore_flags
/* skip=8 to skip flags saved in SS */
ftrace_caller_setup 8
/* Save the rest of pt_regs */
movq %r15, R15(%rsp)
movq %r14, R14(%rsp)
movq %r13, R13(%rsp)
movq %r12, R12(%rsp)
movq %r11, R11(%rsp)
movq %r10, R10(%rsp)
movq %rbp, RBP(%rsp)
movq %rbx, RBX(%rsp)
/* Copy saved flags */
movq SS(%rsp), %rcx
movq %rcx, EFLAGS(%rsp)
/* Kernel segments */
movq $__KERNEL_DS, %rcx
movq %rcx, SS(%rsp)
movq $__KERNEL_CS, %rcx
movq %rcx, CS(%rsp)
/* Stack - skipping return address */
leaq SS+16(%rsp), %rcx
movq %rcx, RSP(%rsp)
/* regs go into 4th parameter */
leaq (%rsp), %rcx
GLOBAL(ftrace_regs_call)
call ftrace_stub
/* Copy flags back to SS, to restore them */
movq EFLAGS(%rsp), %rax
movq %rax, SS(%rsp)
/* restore the rest of pt_regs */
movq R15(%rsp), %r15
movq R14(%rsp), %r14
movq R13(%rsp), %r13
movq R12(%rsp), %r12
movq R10(%rsp), %r10
movq RBP(%rsp), %rbp
movq RBX(%rsp), %rbx
/* skip=8 to skip flags saved in SS */
MCOUNT_RESTORE_FRAME 8
/* Restore flags */
popfq
jmp ftrace_return
ftrace_restore_flags:
popfq
jmp ftrace_stub
END(ftrace_regs_caller)
#else /* ! CONFIG_DYNAMIC_FTRACE */
ENTRY(mcount)
cmpl $0, function_trace_stop
@@ -120,7 +198,7 @@ GLOBAL(ftrace_stub)
trace:
MCOUNT_SAVE_FRAME
movq 0x38(%rsp), %rdi
movq RIP(%rsp), %rdi
movq 8(%rbp), %rsi
subq $MCOUNT_INSN_SIZE, %rdi
@@ -141,7 +219,7 @@ ENTRY(ftrace_graph_caller)
MCOUNT_SAVE_FRAME
leaq 8(%rbp), %rdi
movq 0x38(%rsp), %rsi
movq RIP(%rsp), %rsi
movq (%rbp), %rdx
subq $MCOUNT_INSN_SIZE, %rsi

77
arch/x86/kernel/ftrace.c
View File

@@ -206,6 +206,23 @@ static int
ftrace_modify_code(unsigned long ip, unsigned const char *old_code,
unsigned const char *new_code);
#ifdef ARCH_SUPPORTS_FTRACE_SAVE_REGS
/*
* Should never be called:
* As it is only called by __ftrace_replace_code() which is called by
* ftrace_replace_code() that x86 overrides, and by ftrace_update_code()
* which is called to turn mcount into nops or nops into function calls
* but not to convert a function from not using regs to one that uses
* regs, which ftrace_modify_call() is for.
*/
int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
unsigned long addr)
{
WARN_ON(1);
return -EINVAL;
}
#endif
int ftrace_update_ftrace_func(ftrace_func_t func)
{
unsigned long ip = (unsigned long)(&ftrace_call);
@@ -220,6 +237,16 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
ret = ftrace_modify_code(ip, old, new);
#ifdef ARCH_SUPPORTS_FTRACE_SAVE_REGS
/* Also update the regs callback function */
if (!ret) {
ip = (unsigned long)(&ftrace_regs_call);
memcpy(old, &ftrace_regs_call, MCOUNT_INSN_SIZE);
new = ftrace_call_replace(ip, (unsigned long)func);
ret = ftrace_modify_code(ip, old, new);
}
#endif
atomic_dec(&modifying_ftrace_code);
return ret;
@@ -299,6 +326,32 @@ static int add_brk_on_nop(struct dyn_ftrace *rec)
return add_break(rec->ip, old);
}
/*
* If the record has the FTRACE_FL_REGS set, that means that it
* wants to convert to a callback that saves all regs. If FTRACE_FL_REGS
* is not not set, then it wants to convert to the normal callback.
*/
static unsigned long get_ftrace_addr(struct dyn_ftrace *rec)
{
if (rec->flags & FTRACE_FL_REGS)
return (unsigned long)FTRACE_REGS_ADDR;
else
return (unsigned long)FTRACE_ADDR;
}
/*
* The FTRACE_FL_REGS_EN is set when the record already points to
* a function that saves all the regs. Basically the '_EN' version
* represents the current state of the function.
*/
static unsigned long get_ftrace_old_addr(struct dyn_ftrace *rec)
{
if (rec->flags & FTRACE_FL_REGS_EN)
return (unsigned long)FTRACE_REGS_ADDR;
else
return (unsigned long)FTRACE_ADDR;
}
static int add_breakpoints(struct dyn_ftrace *rec, int enable)
{
unsigned long ftrace_addr;
@@ -306,7 +359,7 @@ static int add_breakpoints(struct dyn_ftrace *rec, int enable)
ret = ftrace_test_record(rec, enable);
ftrace_addr = (unsigned long)FTRACE_ADDR;
ftrace_addr = get_ftrace_addr(rec);
switch (ret) {
case FTRACE_UPDATE_IGNORE:
@@ -316,6 +369,10 @@ static int add_breakpoints(struct dyn_ftrace *rec, int enable)
/* converting nop to call */
return add_brk_on_nop(rec);
case FTRACE_UPDATE_MODIFY_CALL_REGS:
case FTRACE_UPDATE_MODIFY_CALL:
ftrace_addr = get_ftrace_old_addr(rec);
/* fall through */
case FTRACE_UPDATE_MAKE_NOP:
/* converting a call to a nop */
return add_brk_on_call(rec, ftrace_addr);
@@ -360,13 +417,21 @@ static int remove_breakpoint(struct dyn_ftrace *rec)
* If not, don't touch the breakpoint, we make just create
* a disaster.
*/
ftrace_addr = (unsigned long)FTRACE_ADDR;
ftrace_addr = get_ftrace_addr(rec);
nop = ftrace_call_replace(ip, ftrace_addr);
if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) == 0)
goto update;
/* Check both ftrace_addr and ftrace_old_addr */
ftrace_addr = get_ftrace_old_addr(rec);
nop = ftrace_call_replace(ip, ftrace_addr);
if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) != 0)
return -EINVAL;
}
update:
return probe_kernel_write((void *)ip, &nop[0], 1);
}
@@ -405,12 +470,14 @@ static int add_update(struct dyn_ftrace *rec, int enable)
ret = ftrace_test_record(rec, enable);
ftrace_addr = (unsigned long)FTRACE_ADDR;
ftrace_addr = get_ftrace_addr(rec);
switch (ret) {
case FTRACE_UPDATE_IGNORE:
return 0;
case FTRACE_UPDATE_MODIFY_CALL_REGS:
case FTRACE_UPDATE_MODIFY_CALL:
case FTRACE_UPDATE_MAKE_CALL:
/* converting nop to call */
return add_update_call(rec, ftrace_addr);
@@ -455,12 +522,14 @@ static int finish_update(struct dyn_ftrace *rec, int enable)
ret = ftrace_update_record(rec, enable);
ftrace_addr = (unsigned long)FTRACE_ADDR;
ftrace_addr = get_ftrace_addr(rec);
switch (ret) {
case FTRACE_UPDATE_IGNORE:
return 0;
case FTRACE_UPDATE_MODIFY_CALL_REGS:
case FTRACE_UPDATE_MODIFY_CALL:
case FTRACE_UPDATE_MAKE_CALL:
/* converting nop to call */
return finish_update_call(rec, ftrace_addr);