linux_dsm_epyc7002/arch/s390/kernel/ftrace.c

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/*
* Dynamic function tracer architecture backend.
*
* Copyright IBM Corp. 2009,2014
*
* Author(s): Heiko Carstens <heiko.carstens@de.ibm.com>,
* Martin Schwidefsky <schwidefsky@de.ibm.com>
*/
#include <linux/hardirq.h>
#include <linux/uaccess.h>
#include <linux/ftrace.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/kprobes.h>
#include <trace/syscall.h>
#include <asm/asm-offsets.h>
#include "entry.h"
void mcount_replace_code(void);
void ftrace_disable_code(void);
void ftrace_enable_insn(void);
#ifdef CONFIG_64BIT
/*
* The 64-bit mcount code looks like this:
* stg %r14,8(%r15) # offset 0
* larl %r1,<&counter> # offset 6
* brasl %r14,_mcount # offset 12
* lg %r14,8(%r15) # offset 18
* Total length is 24 bytes. The complete mcount block initially gets replaced
* by ftrace_make_nop. Subsequent calls to ftrace_make_call / ftrace_make_nop
* only patch the jg/lg instruction within the block.
* Note: we do not patch the first instruction to an unconditional branch,
* since that would break kprobes/jprobes. It is easier to leave the larl
* instruction in and only modify the second instruction.
* The 64-bit enabled ftrace code block looks like this:
* larl %r0,.+24 # offset 0
* > lg %r1,__LC_FTRACE_FUNC # offset 6
* br %r1 # offset 12
* brcl 0,0 # offset 14
* brc 0,0 # offset 20
* The ftrace function gets called with a non-standard C function call ABI
* where r0 contains the return address. It is also expected that the called
* function only clobbers r0 and r1, but restores r2-r15.
* The return point of the ftrace function has offset 24, so execution
* continues behind the mcount block.
* larl %r0,.+24 # offset 0
* > jg .+18 # offset 6
* br %r1 # offset 12
* brcl 0,0 # offset 14
* brc 0,0 # offset 20
* The jg instruction branches to offset 24 to skip as many instructions
* as possible.
*/
asm(
" .align 4\n"
"mcount_replace_code:\n"
" larl %r0,0f\n"
"ftrace_disable_code:\n"
" jg 0f\n"
" br %r1\n"
" brcl 0,0\n"
" brc 0,0\n"
"0:\n"
" .align 4\n"
"ftrace_enable_insn:\n"
" lg %r1,"__stringify(__LC_FTRACE_FUNC)"\n");
#define MCOUNT_BLOCK_SIZE 24
#define MCOUNT_INSN_OFFSET 6
#define FTRACE_INSN_SIZE 6
#else /* CONFIG_64BIT */
/*
* The 31-bit mcount code looks like this:
* st %r14,4(%r15) # offset 0
* > bras %r1,0f # offset 4
* > .long _mcount # offset 8
* > .long <&counter> # offset 12
* > 0: l %r14,0(%r1) # offset 16
* > l %r1,4(%r1) # offset 20
* basr %r14,%r14 # offset 24
* l %r14,4(%r15) # offset 26
* Total length is 30 bytes. The twenty bytes starting from offset 4
* to offset 24 get overwritten by ftrace_make_nop / ftrace_make_call.
* The 31-bit enabled ftrace code block looks like this:
* st %r14,4(%r15) # offset 0
* > l %r14,__LC_FTRACE_FUNC # offset 4
* > j 0f # offset 8
* > .fill 12,1,0x07 # offset 12
* 0: basr %r14,%r14 # offset 24
* l %r14,4(%r14) # offset 26
* The return points of the mcount/ftrace function have the same offset 26.
* The 31-bit disabled ftrace code block looks like this:
* st %r14,4(%r15) # offset 0
* > j .+26 # offset 4
* > j 0f # offset 8
* > .fill 12,1,0x07 # offset 12
* 0: basr %r14,%r14 # offset 24
* l %r14,4(%r14) # offset 26
* The j instruction branches to offset 30 to skip as many instructions
* as possible.
*/
asm(
" .align 4\n"
"ftrace_disable_code:\n"
" j 1f\n"
" j 0f\n"
" .fill 12,1,0x07\n"
"0: basr %r14,%r14\n"
"1:\n"
" .align 4\n"
"ftrace_enable_insn:\n"
" l %r14,"__stringify(__LC_FTRACE_FUNC)"\n");
#define FTRACE_INSN_SIZE 4
#endif /* CONFIG_64BIT */
s390/ftrace: add HAVE_DYNAMIC_FTRACE_WITH_REGS support This code is based on a patch from Vojtech Pavlik. http://marc.info/?l=linux-s390&m=140438885114413&w=2 The actual implementation now differs significantly: Instead of adding a second function "ftrace_regs_caller" which would be nearly identical to the existing ftrace_caller function, the current ftrace_caller function is now an alias to ftrace_regs_caller and always passes the needed pt_regs structure and function_trace_op parameters unconditionally. Besides that also use asm offsets to correctly allocate and access the new struct pt_regs on the stack. While at it we can make use of new instruction to get rid of some indirect loads if compiled for new machines. The passed struct pt_regs can be changed by the called function and it's new contents will replace the current contents. Note: to change the return address the embedded psw member of the pt_regs structure must be changed. The psw member is right now incomplete, since the mask part is missing. For all current use cases this should be sufficent. Providing and restoring a sane mask would mean we need to add an epsw/lpswe pair to the mcount code. Only these two instruction would cost us ~120 cycles which currently seems not necessary. Cc: Vojtech Pavlik <vojtech@suse.cz> Cc: Jiri Kosina <jkosina@suse.cz> Cc: Jiri Slaby <jslaby@suse.cz> Cc: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2014-08-15 18:01:46 +07:00
#ifdef CONFIG_64BIT
int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
unsigned long addr)
{
return 0;
}
#endif
int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
unsigned long addr)
{
#ifdef CONFIG_64BIT
/* Initial replacement of the whole mcount block */
if (addr == MCOUNT_ADDR) {
if (probe_kernel_write((void *) rec->ip - MCOUNT_INSN_OFFSET,
mcount_replace_code,
MCOUNT_BLOCK_SIZE))
return -EPERM;
return 0;
}
#endif
if (probe_kernel_write((void *) rec->ip, ftrace_disable_code,
MCOUNT_INSN_SIZE))
return -EPERM;
return 0;
}
int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
if (probe_kernel_write((void *) rec->ip, ftrace_enable_insn,
FTRACE_INSN_SIZE))
return -EPERM;
return 0;
}
int ftrace_update_ftrace_func(ftrace_func_t func)
{
return 0;
}
int __init ftrace_dyn_arch_init(void)
{
return 0;
}
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
/*
* Hook the return address and push it in the stack of return addresses
* in current thread info.
*/
unsigned long __kprobes prepare_ftrace_return(unsigned long parent,
unsigned long ip)
{
struct ftrace_graph_ent trace;
if (unlikely(atomic_read(&current->tracing_graph_pause)))
goto out;
ip = (ip & PSW_ADDR_INSN) - MCOUNT_INSN_SIZE;
trace.func = ip;
trace.depth = current->curr_ret_stack + 1;
/* Only trace if the calling function expects to. */
if (!ftrace_graph_entry(&trace))
goto out;
if (ftrace_push_return_trace(parent, ip, &trace.depth, 0) == -EBUSY)
goto out;
parent = (unsigned long) return_to_handler;
out:
return parent;
}
/*
* Patch the kernel code at ftrace_graph_caller location. The instruction
* there is branch relative and save to prepare_ftrace_return. To disable
* the call to prepare_ftrace_return we patch the bras offset to point
* directly after the instructions. To enable the call we calculate
* the original offset to prepare_ftrace_return and put it back.
*/
#ifdef CONFIG_64BIT
int ftrace_enable_ftrace_graph_caller(void)
{
static unsigned short offset = 0x0002;
return probe_kernel_write((void *) ftrace_graph_caller + 2,
&offset, sizeof(offset));
}
int ftrace_disable_ftrace_graph_caller(void)
{
unsigned short offset;
offset = ((void *) &ftrace_graph_caller_end -
(void *) ftrace_graph_caller) / 2;
return probe_kernel_write((void *) ftrace_graph_caller + 2,
&offset, sizeof(offset));
}
#else /* CONFIG_64BIT */
int ftrace_enable_ftrace_graph_caller(void)
{
unsigned short offset;
offset = ((void *) prepare_ftrace_return -
(void *) ftrace_graph_caller) / 2;
return probe_kernel_write((void *) ftrace_graph_caller + 2,
&offset, sizeof(offset));
}
int ftrace_disable_ftrace_graph_caller(void)
{
static unsigned short offset = 0x0002;
return probe_kernel_write((void *) ftrace_graph_caller + 2,
&offset, sizeof(offset));
}
#endif /* CONFIG_64BIT */
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */