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jump label: Make dynamic no-op selection available outside of ftrace 

Move Steve's code for finding the best 5-byte no-op from ftrace.c to
alternative.c. The idea is that other consumers (in this case jump label)
want to make use of that code.

Signed-off-by: Jason Baron <jbaron@redhat.com>
LKML-Reference: <96259ae74172dcac99c0020c249743c523a92e18.1284733808.git.jbaron@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Jason Baron 2010-09-17 11:08:51 -04:00 committed by Steven Rostedt
parent e9d2b06414
commit f49aa44856
4 changed files with 79 additions and 62 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
arch/x86/include/asm/alternative.h
View File

@ -180,4 +180,12 @@ static inline void apply_paravirt(struct paravirt_patch_site *start,
extern void *text_poke(void *addr, const void *opcode, size_t len);
extern void *text_poke_smp(void *addr, const void *opcode, size_t len);
#if defined(CONFIG_DYNAMIC_FTRACE)
#define IDEAL_NOP_SIZE_5 5
extern unsigned char ideal_nop5[IDEAL_NOP_SIZE_5];
extern void arch_init_ideal_nop5(void);
#else
static inline void arch_init_ideal_nop5(void) {}
#endif
#endif /* _ASM_X86_ALTERNATIVE_H */

64
arch/x86/kernel/alternative.c
View File

@ -641,3 +641,67 @@ void *__kprobes text_poke_smp(void *addr, const void *opcode, size_t len)
return addr;
}
#if defined(CONFIG_DYNAMIC_FTRACE)
unsigned char ideal_nop5[IDEAL_NOP_SIZE_5];
void __init arch_init_ideal_nop5(void)
{
extern const unsigned char ftrace_test_p6nop[];
extern const unsigned char ftrace_test_nop5[];
extern const unsigned char ftrace_test_jmp[];
int faulted = 0;
/*
* There is no good nop for all x86 archs.
* We will default to using the P6_NOP5, but first we
* will test to make sure that the nop will actually
* work on this CPU. If it faults, we will then
* go to a lesser efficient 5 byte nop. If that fails
* we then just use a jmp as our nop. This isn't the most
* efficient nop, but we can not use a multi part nop
* since we would then risk being preempted in the middle
* of that nop, and if we enabled tracing then, it might
* cause a system crash.
*
* TODO: check the cpuid to determine the best nop.
*/
asm volatile (
"ftrace_test_jmp:"
"jmp ftrace_test_p6nop\n"
"nop\n"
"nop\n"
"nop\n" /* 2 byte jmp + 3 bytes */
"ftrace_test_p6nop:"
P6_NOP5
"jmp 1f\n"
"ftrace_test_nop5:"
".byte 0x66,0x66,0x66,0x66,0x90\n"
"1:"
".section .fixup, \"ax\"\n"
"2: movl $1, %0\n"
" jmp ftrace_test_nop5\n"
"3: movl $2, %0\n"
" jmp 1b\n"
".previous\n"
_ASM_EXTABLE(ftrace_test_p6nop, 2b)
_ASM_EXTABLE(ftrace_test_nop5, 3b)
: "=r"(faulted) : "0" (faulted));
switch (faulted) {
case 0:
pr_info("converting mcount calls to 0f 1f 44 00 00\n");
memcpy(ideal_nop5, ftrace_test_p6nop, IDEAL_NOP_SIZE_5);
break;
case 1:
pr_info("converting mcount calls to 66 66 66 66 90\n");
memcpy(ideal_nop5, ftrace_test_nop5, IDEAL_NOP_SIZE_5);
break;
case 2:
pr_info("converting mcount calls to jmp . + 5\n");
memcpy(ideal_nop5, ftrace_test_jmp, IDEAL_NOP_SIZE_5);
break;
}
}
#endif

63
arch/x86/kernel/ftrace.c
View File

@ -257,14 +257,9 @@ do_ftrace_mod_code(unsigned long ip, void *new_code)
return mod_code_status;
}
static unsigned char ftrace_nop[MCOUNT_INSN_SIZE];
static unsigned char *ftrace_nop_replace(void)
{
return ftrace_nop;
return ideal_nop5;
}
static int
@ -338,62 +333,6 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
int __init ftrace_dyn_arch_init(void *data)
{
extern const unsigned char ftrace_test_p6nop[];
extern const unsigned char ftrace_test_nop5[];
extern const unsigned char ftrace_test_jmp[];
int faulted = 0;
/*
* There is no good nop for all x86 archs.
* We will default to using the P6_NOP5, but first we
* will test to make sure that the nop will actually
* work on this CPU. If it faults, we will then
* go to a lesser efficient 5 byte nop. If that fails
* we then just use a jmp as our nop. This isn't the most
* efficient nop, but we can not use a multi part nop
* since we would then risk being preempted in the middle
* of that nop, and if we enabled tracing then, it might
* cause a system crash.
*
* TODO: check the cpuid to determine the best nop.
*/
asm volatile (
"ftrace_test_jmp:"
"jmp ftrace_test_p6nop\n"
"nop\n"
"nop\n"
"nop\n" /* 2 byte jmp + 3 bytes */
"ftrace_test_p6nop:"
P6_NOP5
"jmp 1f\n"
"ftrace_test_nop5:"
".byte 0x66,0x66,0x66,0x66,0x90\n"
"1:"
".section .fixup, \"ax\"\n"
"2: movl $1, %0\n"
" jmp ftrace_test_nop5\n"
"3: movl $2, %0\n"
" jmp 1b\n"
".previous\n"
_ASM_EXTABLE(ftrace_test_p6nop, 2b)
_ASM_EXTABLE(ftrace_test_nop5, 3b)
: "=r"(faulted) : "0" (faulted));
switch (faulted) {
case 0:
pr_info("converting mcount calls to 0f 1f 44 00 00\n");
memcpy(ftrace_nop, ftrace_test_p6nop, MCOUNT_INSN_SIZE);
break;
case 1:
pr_info("converting mcount calls to 66 66 66 66 90\n");
memcpy(ftrace_nop, ftrace_test_nop5, MCOUNT_INSN_SIZE);
break;
case 2:
pr_info("converting mcount calls to jmp . + 5\n");
memcpy(ftrace_nop, ftrace_test_jmp, MCOUNT_INSN_SIZE);
break;
}
/* The return code is retured via data */
*(unsigned long *)data = 0;

6
arch/x86/kernel/setup.c
View File

@ -112,6 +112,7 @@
#include <asm/numa_64.h>
#endif
#include <asm/mce.h>
#include <asm/alternative.h>
/*
* end_pfn only includes RAM, while max_pfn_mapped includes all e820 entries.
@ -726,6 +727,7 @@ void __init setup_arch(char **cmdline_p)
{
int acpi = 0;
int k8 = 0;
unsigned long flags;
#ifdef CONFIG_X86_32
memcpy(&boot_cpu_data, &new_cpu_data, sizeof(new_cpu_data));
@ -1071,6 +1073,10 @@ void __init setup_arch(char **cmdline_p)
x86_init.oem.banner();
mcheck_init();
local_irq_save(flags);
arch_init_ideal_nop5();
local_irq_restore(flags);
}
#ifdef CONFIG_X86_32