Prev: [PATCH 8/9] jump label: initialize workqueue tracepoints *before* they are registered
Next: uio_pci_generic: extensions to allow access for?non-privileged processes
From: Jason Baron on 9 Apr 2010 16:00
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. I've created a global: 'char ideal_nop[5]', that is setup during
setup_arch that can be used.

Signed-off-by: Jason Baron <jbaron(a)redhat.com>
---
arch/x86/include/asm/alternative.h | 14 +++++++
arch/x86/include/asm/jump_label.h | 10 ++----
arch/x86/kernel/alternative.c | 71 +++++++++++++++++++++++++++++++++++-
arch/x86/kernel/ftrace.c | 70 +-----------------------------------
arch/x86/kernel/jump_label.c | 15 +-------
arch/x86/kernel/module.c | 3 ++
arch/x86/kernel/setup.c | 2 +
include/linux/jump_label.h | 9 +++++
kernel/jump_label.c | 33 +++++++++++++++++
kernel/trace/ftrace.c | 13 +------
10 files changed, 137 insertions(+), 103 deletions(-)

diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index b09ec55..0218dbd 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -5,6 +5,7 @@
#include <linux/stddef.h>
#include <linux/stringify.h>
#include <asm/asm.h>
+#include <asm/jump_label.h>

/*
* Alternative inline assembly for SMP.
@@ -153,6 +154,8 @@ static inline void apply_paravirt(struct paravirt_patch_site *start,
#define __parainstructions_end NULL
#endif

+extern void *text_poke_early(void *addr, const void *opcode, size_t len);
+
/*
* Clear and restore the kernel write-protection flag on the local CPU.
* Allows the kernel to edit read-only pages.
@@ -173,4 +176,15 @@ 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) || defined(__HAVE_ARCH_JUMP_LABEL)
+#define IDEAL_NOP_SIZE_5 5
+extern unsigned char ideal_nop5[IDEAL_NOP_SIZE_5];
+extern int arch_init_ideal_nop5(void);
+#else
+static inline arch_init_ideal_nop5(void)
+{
+ return 0;
+}
+#endif
+
#endif /* _ASM_X86_ALTERNATIVE_H */
diff --git a/arch/x86/include/asm/jump_label.h b/arch/x86/include/asm/jump_label.h
index b8ebdc8..e3af6ca 100644
--- a/arch/x86/include/asm/jump_label.h
+++ b/arch/x86/include/asm/jump_label.h
@@ -9,23 +9,19 @@

#ifdef __HAVE_ARCH_JUMP_LABEL

-# ifdef CONFIG_X86_64
-# define JUMP_LABEL_NOP P6_NOP5
-# else
-# define JUMP_LABEL_NOP ".byte 0xe9 \n\t .long 0\n\t"
-# endif
+# define JUMP_LABEL_INITIAL_NOP ".byte 0xe9 \n\t .long 0\n\t"

# define JUMP_LABEL(tag, label, cond) \
do { \
extern const char __jlstrtab_##tag[]; \
asm goto("1:" \
- JUMP_LABEL_NOP \
+ JUMP_LABEL_INITIAL_NOP \
".pushsection __jump_table, \"a\" \n\t"\
_ASM_PTR "1b, %l[" #label "], %c0 \n\t" \
".popsection \n\t" \
: : "i" (__jlstrtab_##tag) : : label);\
} while (0)

-# endif
+#endif

#endif
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index 3a4bf35..083ce9d 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -194,7 +194,6 @@ static void __init_or_module add_nops(void *insns, unsigned int len)

extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
extern u8 *__smp_locks[], *__smp_locks_end[];
-static void *text_poke_early(void *addr, const void *opcode, size_t len);

/* Replace instructions with better alternatives for this CPU type.
This runs before SMP is initialized to avoid SMP problems with
@@ -513,7 +512,7 @@ void __init alternative_instructions(void)
* instructions. And on the local CPU you need to be protected again NMI or MCE
* handlers seeing an inconsistent instruction while you patch.
*/
-static void *__init_or_module text_poke_early(void *addr, const void *opcode,
+void *__init_or_module text_poke_early(void *addr, const void *opcode,
size_t len)
{
unsigned long flags;
@@ -632,3 +631,71 @@ void *__kprobes text_poke_smp(void *addr, const void *opcode, size_t len)
return addr;
}

+#if defined(CONFIG_DYNAMIC_FTRACE) || defined(__HAVE_ARCH_JUMP_LABEL)
+
+unsigned char ideal_nop5[IDEAL_NOP_SIZE_5];
+
+int __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;
+ unsigned long flags;
+
+ local_irq_save(flags);
+ /*
+ * 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;
+ }
+
+ local_irq_restore(flags);
+ return 0;
+}
+#endif
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index cd37469..ba2e0d9 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
@@ -336,69 +331,6 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
return ret;
}

-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;
-
- return 0;
-}
#endif

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c
index 7fc4f84..8eca1b8 100644
--- a/arch/x86/kernel/jump_label.c
+++ b/arch/x86/kernel/jump_label.c
@@ -30,19 +30,8 @@ void arch_jump_label_transform(struct jump_entry *entry, enum jump_label_type ty
if (type == JUMP_LABEL_ENABLE) {
code.jump = 0xe9;
code.offset = entry->target - (entry->code + RELATIVEJUMP_SIZE);
- } else {
-#ifdef CONFIG_X86_64
- /* opcode for P6_NOP5 */
- code.code[0] = 0x0f;
- code.code[1] = 0x1f;
- code.code[2] = 0x44;
- code.code[3] = 0x00;
- code.code[4] = 0x00;
-#else
- code.jump = 0xe9;
- code.offset = 0;
-#endif
- }
+ } else
+ memcpy(&code, ideal_nop5, 5);
get_online_cpus();
mutex_lock(&text_mutex);
text_poke_smp((void *)entry->code, &code, RELATIVEJUMP_SIZE);
diff --git a/arch/x86/kernel/module.c b/arch/x86/kernel/module.c
index 89f386f..e47fe49 100644
--- a/arch/x86/kernel/module.c
+++ b/arch/x86/kernel/module.c
@@ -238,6 +238,9 @@ int module_finalize(const Elf_Ehdr *hdr,
apply_paravirt(pseg, pseg + para->sh_size);
}

+ /* make jump label nops */
+ apply_jump_label_nops(me);
+
return module_bug_finalize(hdr, sechdrs, me);
}

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 5d7ba1a..7a4577a 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1040,6 +1040,8 @@ void __init setup_arch(char **cmdline_p)
x86_init.oem.banner();

mcheck_init();
+
+ arch_init_ideal_nop5();
}

#ifdef CONFIG_X86_32
diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h
index e0f968d..9868c43 100644
--- a/include/linux/jump_label.h
+++ b/include/linux/jump_label.h
@@ -14,6 +14,8 @@ enum jump_label_type {
JUMP_LABEL_DISABLE
};

+struct module;
+
#ifdef __HAVE_ARCH_JUMP_LABEL

extern struct jump_entry __start___jump_table[];
@@ -29,6 +31,8 @@ extern void arch_jump_label_transform(struct jump_entry *entry,

extern void jump_label_update(const char *name, enum jump_label_type type);

+extern void apply_jump_label_nops(struct module *mod);
+
#define enable_jump_label(name) \
jump_label_update(name, JUMP_LABEL_ENABLE);

@@ -55,6 +59,11 @@ static inline int disable_jump_label(const char *name)
return 0;
}

+static inline int apply_jump_label_nops(struct module *mod)
+{
+ return 0;
+}
+
#endif

#endif
diff --git a/kernel/jump_label.c b/kernel/jump_label.c
index 0714c20..7e7458b 100644
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -182,10 +182,19 @@ void jump_label_update(const char *name, enum jump_label_type type)
static int init_jump_label(void)
{
int ret;
+ struct jump_entry *iter_start = __start___jump_table;
+ struct jump_entry *iter_stop = __start___jump_table;
+ struct jump_entry *iter;

mutex_lock(&jump_label_mutex);
ret = build_jump_label_hashtable(__start___jump_table,
__stop___jump_table);
+ /* update with ideal nop */
+ iter = iter_start;
+ while (iter < iter_stop) {
+ text_poke_early((void *)iter->code, ideal_nop5, IDEAL_NOP_SIZE_5);
+ iter++;
+ }
mutex_unlock(&jump_label_mutex);
return ret;
}
@@ -296,6 +305,30 @@ static int jump_label_module_notify(struct notifier_block *self, unsigned long v
return ret;
}

+/***
+ * apply_jump_label_nops - patch module jump labels with ideal_nop5
+ * @mod: module to patch
+ *
+ * When a module is intially loaded the code has 'jump 5' instructions
+ * as nops. These are not the most optimal nops, so before the module
+ * loads patch these with the 'ideal_nop5', which was determined boot
+ * time.
+ */
+void apply_jump_label_nops(struct module *mod)
+{
+ struct jump_entry *iter;
+
+ /* if the module doesn't have jump label entries, just return */
+ if (!mod->num_jump_entries)
+ return;
+
+ iter = mod->jump_entries;
+ while (iter < mod->jump_entries + mod->num_jump_entries) {
+ text_poke_early((void *)iter->code, ideal_nop5, IDEAL_NOP_SIZE_5);
+ iter++;
+ }
+}
+
struct notifier_block jump_label_module_nb = {
.notifier_call = jump_label_module_notify,
.priority = 0,
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 8378357..abe6eaf 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2725,20 +2725,9 @@ extern unsigned long __stop_mcount_loc[];

void __init ftrace_init(void)
{
- unsigned long count, addr, flags;
+ unsigned long count;
int ret;

- /* Keep the ftrace pointer to the stub */
- addr = (unsigned long)ftrace_stub;
-
- local_irq_save(flags);
- ftrace_dyn_arch_init(&addr);
- local_irq_restore(flags);
-
- /* ftrace_dyn_arch_init places the return code in addr */
- if (addr)
- goto failed;
-
count = __stop_mcount_loc - __start_mcount_loc;

ret = ftrace_dyn_table_alloc(count);
--
1.7.0.1

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo(a)vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
 | 
Pages: 1
Prev: [PATCH 8/9] jump label: initialize workqueue tracepoints *before* they are registered
Next: uio_pci_generic: extensions to allow access for?non-privileged processes