[PATCH 01/10] jump label v11: make dynamic no-op selection available outside of ftrace

Jason Baron
2010-09-17T15:09:35Z

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>
---
arch/x86/include/asm/alternative.h | 8 ++++
arch/x86/kernel/alternative.c | 64 ++++++++++++++++++++++++++++++++++++
arch/x86/kernel/ftrace.c | 63 +----------------------------------
arch/x86/kernel/setup.c | 6 +++
4 files changed, 79 insertions(+), 62 deletions(-)

diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index bc6abb7..27a35b6 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -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 */
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index f65ab8b..1849d80 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -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
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index cd37469..3afb33f 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -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;

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 1427c36..fb37842 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -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.
@@ -689,6 +690,7 @@ 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));
@@ -1036,6 +1038,10 @@ 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
--
1.7.1