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Subject[tip: core/kprobes] x86/ftrace: Use text_gen_insn()
The following commit has been merged into the core/kprobes branch of tip:

Commit-ID: a02273c89f76df917b49694a7f836b2d61c0ff87
Gitweb: https://git.kernel.org/tip/a02273c89f76df917b49694a7f836b2d61c0ff87
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Wed, 09 Oct 2019 12:44:14 +02:00
Committer: Ingo Molnar <mingo@kernel.org>
CommitterDate: Fri, 15 Nov 2019 09:07:43 +01:00

x86/ftrace: Use text_gen_insn()

Replace the ftrace_code_union with the generic text_gen_insn() helper,
which does exactly this.

Tested-by: Alexei Starovoitov <ast@kernel.org>
Tested-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20191111132457.932808000@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/include/asm/text-patching.h | 30 ++++++++++++++++++++++++-
arch/x86/kernel/alternative.c | 26 +----------------------
arch/x86/kernel/ftrace.c | 32 +++++----------------------
3 files changed, 36 insertions(+), 52 deletions(-)

diff --git a/arch/x86/include/asm/text-patching.h b/arch/x86/include/asm/text-patching.h
index 93e4266..ad8f9f4 100644
--- a/arch/x86/include/asm/text-patching.h
+++ b/arch/x86/include/asm/text-patching.h
@@ -80,7 +80,35 @@ static inline int text_opcode_size(u8 opcode)
return size;
}

-extern void *text_gen_insn(u8 opcode, const void *addr, const void *dest);
+union text_poke_insn {
+ u8 text[POKE_MAX_OPCODE_SIZE];
+ struct {
+ u8 opcode;
+ s32 disp;
+ } __attribute__((packed));
+};
+
+static __always_inline
+void *text_gen_insn(u8 opcode, const void *addr, const void *dest)
+{
+ static union text_poke_insn insn; /* per instance */
+ int size = text_opcode_size(opcode);
+
+ insn.opcode = opcode;
+
+ if (size > 1) {
+ insn.disp = (long)dest - (long)(addr + size);
+ if (size == 2) {
+ /*
+ * Ensure that for JMP9 the displacement
+ * actually fits the signed byte.
+ */
+ BUG_ON((insn.disp >> 31) != (insn.disp >> 7));
+ }
+ }
+
+ return &insn.text;
+}

extern int after_bootmem;
extern __ro_after_init struct mm_struct *poking_mm;
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index f8f34f9..cfcfadf 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -1247,29 +1247,3 @@ void __ref text_poke_bp(void *addr, const void *opcode, size_t len, const void *
text_poke_loc_init(&tp, addr, opcode, len, emulate);
text_poke_bp_batch(&tp, 1);
}
-
-union text_poke_insn {
- u8 text[POKE_MAX_OPCODE_SIZE];
- struct {
- u8 opcode;
- s32 disp;
- } __attribute__((packed));
-};
-
-void *text_gen_insn(u8 opcode, const void *addr, const void *dest)
-{
- static union text_poke_insn insn; /* text_mutex */
- int size = text_opcode_size(opcode);
-
- lockdep_assert_held(&text_mutex);
-
- insn.opcode = opcode;
-
- if (size > 1) {
- insn.disp = (long)dest - (long)(addr + size);
- if (size == 2)
- BUG_ON((insn.disp >> 31) != (insn.disp >> 7));
- }
-
- return &insn.text;
-}
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 3d8adeb..2a179fb 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -63,24 +63,6 @@ int ftrace_arch_code_modify_post_process(void)
return 0;
}

-union ftrace_code_union {
- char code[MCOUNT_INSN_SIZE];
- struct {
- char op;
- int offset;
- } __attribute__((packed));
-};
-
-static const char *ftrace_text_replace(char op, unsigned long ip, unsigned long addr)
-{
- static union ftrace_code_union calc;
-
- calc.op = op;
- calc.offset = (int)(addr - (ip + MCOUNT_INSN_SIZE));
-
- return calc.code;
-}
-
static const char *ftrace_nop_replace(void)
{
return ideal_nops[NOP_ATOMIC5];
@@ -88,7 +70,7 @@ static const char *ftrace_nop_replace(void)

static const char *ftrace_call_replace(unsigned long ip, unsigned long addr)
{
- return ftrace_text_replace(CALL_INSN_OPCODE, ip, addr);
+ return text_gen_insn(CALL_INSN_OPCODE, (void *)ip, (void *)addr);
}

static int ftrace_verify_code(unsigned long ip, const char *old_code)
@@ -480,20 +462,20 @@ void arch_ftrace_update_trampoline(struct ftrace_ops *ops)
/* Return the address of the function the trampoline calls */
static void *addr_from_call(void *ptr)
{
- union ftrace_code_union calc;
+ union text_poke_insn call;
int ret;

- ret = probe_kernel_read(&calc, ptr, MCOUNT_INSN_SIZE);
+ ret = probe_kernel_read(&call, ptr, CALL_INSN_SIZE);
if (WARN_ON_ONCE(ret < 0))
return NULL;

/* Make sure this is a call */
- if (WARN_ON_ONCE(calc.op != 0xe8)) {
- pr_warn("Expected e8, got %x\n", calc.op);
+ if (WARN_ON_ONCE(call.opcode != CALL_INSN_OPCODE)) {
+ pr_warn("Expected E8, got %x\n", call.opcode);
return NULL;
}

- return ptr + MCOUNT_INSN_SIZE + calc.offset;
+ return ptr + CALL_INSN_SIZE + call.disp;
}

void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent,
@@ -562,7 +544,7 @@ extern void ftrace_graph_call(void);

static const char *ftrace_jmp_replace(unsigned long ip, unsigned long addr)
{
- return ftrace_text_replace(JMP32_INSN_OPCODE, ip, addr);
+ return text_gen_insn(JMP32_INSN_OPCODE, (void *)ip, (void *)addr);
}

static int ftrace_mod_jmp(unsigned long ip, void *func)
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