[PATCH v3 1/4] powerpc: Remove probe_user_read_inst()

[PATCH v3 1/4] powerpc: Remove probe_user_read_inst()

[Christophe Leroy]

Its name comes from former probe_user_read() function.
That function is now called copy_from_user_nofault().

probe_user_read_inst() uses copy_from_user_nofault() to read only
a few bytes. It is suboptimal.

It does the same as get_user_inst() but in addition disables
page faults.

But on the other hand, it is not used for the time being. So remove it
for now. If one day it is really needed, we can give it a new name
more in line with today's naming, and implement it using get_user_inst()

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/powerpc/include/asm/inst.h |  3 ---
 arch/powerpc/lib/inst.c         | 31 -------------------------------
 2 files changed, 34 deletions(-)

diff --git a/arch/powerpc/include/asm/inst.h b/arch/powerpc/include/asm/inst.h
index 19e18af2fac9..2902d4e6a363 100644
--- a/arch/powerpc/include/asm/inst.h
+++ b/arch/powerpc/include/asm/inst.h
@@ -175,9 +175,6 @@ static inline char *__ppc_inst_as_str(char str[PPC_INST_STR_LEN], struct ppc_ins
 	__str;				\
 })
 
-int probe_user_read_inst(struct ppc_inst *inst,
-			 struct ppc_inst __user *nip);
-
 int probe_kernel_read_inst(struct ppc_inst *inst,
 			   struct ppc_inst *src);
 
diff --git a/arch/powerpc/lib/inst.c b/arch/powerpc/lib/inst.c
index 9cc17eb62462..c57b3548de37 100644
--- a/arch/powerpc/lib/inst.c
+++ b/arch/powerpc/lib/inst.c
@@ -9,24 +9,6 @@
 #include <asm/ppc-opcode.h>
 
 #ifdef CONFIG_PPC64
-int probe_user_read_inst(struct ppc_inst *inst,
-			 struct ppc_inst __user *nip)
-{
-	unsigned int val, suffix;
-	int err;
-
-	err = copy_from_user_nofault(&val, nip, sizeof(val));
-	if (err)
-		return err;
-	if (get_op(val) == OP_PREFIX) {
-		err = copy_from_user_nofault(&suffix, (void __user *)nip + 4, 4);
-		*inst = ppc_inst_prefix(val, suffix);
-	} else {
-		*inst = ppc_inst(val);
-	}
-	return err;
-}
-
 int probe_kernel_read_inst(struct ppc_inst *inst,
 			   struct ppc_inst *src)
 {
@@ -45,19 +27,6 @@ int probe_kernel_read_inst(struct ppc_inst *inst,
 	return err;
 }
 #else /* !CONFIG_PPC64 */
-int probe_user_read_inst(struct ppc_inst *inst,
-			 struct ppc_inst __user *nip)
-{
-	unsigned int val;
-	int err;
-
-	err = copy_from_user_nofault(&val, nip, sizeof(val));
-	if (!err)
-		*inst = ppc_inst(val);
-
-	return err;
-}
-
 int probe_kernel_read_inst(struct ppc_inst *inst,
 			   struct ppc_inst *src)
 {
-- 
2.25.0

[PATCH v3 2/4] powerpc: Make probe_kernel_read_inst() common to PPC32 and PPC64

[Christophe Leroy]

We have two independant versions of probe_kernel_read_inst(), one for
PPC32 and one for PPC64.

The PPC32 is identical to the first part of the PPC64 version.
The remaining part of PPC64 version is not relevant for PPC32, but
not contradictory, so we can easily have a common function with
the PPC64 part opted out via a IS_ENABLED(CONFIG_PPC64).

The only need is to add a version of ppc_inst_prefix() for PPC32.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/powerpc/include/asm/inst.h |  2 ++
 arch/powerpc/lib/inst.c         | 17 +----------------
 2 files changed, 3 insertions(+), 16 deletions(-)

diff --git a/arch/powerpc/include/asm/inst.h b/arch/powerpc/include/asm/inst.h
index 2902d4e6a363..a40c3913a4a3 100644
--- a/arch/powerpc/include/asm/inst.h
+++ b/arch/powerpc/include/asm/inst.h
@@ -102,6 +102,8 @@ static inline bool ppc_inst_equal(struct ppc_inst x, struct ppc_inst y)
 
 #define ppc_inst(x) ((struct ppc_inst){ .val = x })
 
+#define ppc_inst_prefix(x, y) ppc_inst(x)
+
 static inline bool ppc_inst_prefixed(struct ppc_inst x)
 {
 	return false;
diff --git a/arch/powerpc/lib/inst.c b/arch/powerpc/lib/inst.c
index c57b3548de37..0dff3ac2d45f 100644
--- a/arch/powerpc/lib/inst.c
+++ b/arch/powerpc/lib/inst.c
@@ -8,7 +8,6 @@
 #include <asm/inst.h>
 #include <asm/ppc-opcode.h>
 
-#ifdef CONFIG_PPC64
 int probe_kernel_read_inst(struct ppc_inst *inst,
 			   struct ppc_inst *src)
 {
@@ -18,7 +17,7 @@ int probe_kernel_read_inst(struct ppc_inst *inst,
 	err = copy_from_kernel_nofault(&val, src, sizeof(val));
 	if (err)
 		return err;
-	if (get_op(val) == OP_PREFIX) {
+	if (IS_ENABLED(CONFIG_PPC64) && get_op(val) == OP_PREFIX) {
 		err = copy_from_kernel_nofault(&suffix, (void *)src + 4, 4);
 		*inst = ppc_inst_prefix(val, suffix);
 	} else {
@@ -26,17 +25,3 @@ int probe_kernel_read_inst(struct ppc_inst *inst,
 	}
 	return err;
 }
-#else /* !CONFIG_PPC64 */
-int probe_kernel_read_inst(struct ppc_inst *inst,
-			   struct ppc_inst *src)
-{
-	unsigned int val;
-	int err;
-
-	err = copy_from_kernel_nofault(&val, src, sizeof(val));
-	if (!err)
-		*inst = ppc_inst(val);
-
-	return err;
-}
-#endif /* CONFIG_PPC64 */
-- 
2.25.0

[PATCH v3 3/4] powerpc: Rename probe_kernel_read_inst()

[Christophe Leroy]

When probe_kernel_read_inst() was created, it was to mimic
probe_kernel_read() function.

Since then, probe_kernel_read() has been renamed
copy_from_kernel_nofault().

Rename probe_kernel_read_inst() into copy_inst_from_kernel_nofault().

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
v3: copy_inst_from_kernel_nofault() instead of copy_from_kernel_nofault_inst()
---
 arch/powerpc/include/asm/inst.h    |  3 +--
 arch/powerpc/kernel/align.c        |  2 +-
 arch/powerpc/kernel/trace/ftrace.c | 22 +++++++++++-----------
 arch/powerpc/lib/inst.c            |  3 +--
 4 files changed, 14 insertions(+), 16 deletions(-)

diff --git a/arch/powerpc/include/asm/inst.h b/arch/powerpc/include/asm/inst.h
index a40c3913a4a3..eaf5a6299034 100644
--- a/arch/powerpc/include/asm/inst.h
+++ b/arch/powerpc/include/asm/inst.h
@@ -177,7 +177,6 @@ static inline char *__ppc_inst_as_str(char str[PPC_INST_STR_LEN], struct ppc_ins
 	__str;				\
 })
 
-int probe_kernel_read_inst(struct ppc_inst *inst,
-			   struct ppc_inst *src);
+int copy_inst_from_kernel_nofault(struct ppc_inst *inst, struct ppc_inst *src);
 
 #endif /* _ASM_POWERPC_INST_H */
diff --git a/arch/powerpc/kernel/align.c b/arch/powerpc/kernel/align.c
index a97d5f1a3905..8f350d0478e6 100644
--- a/arch/powerpc/kernel/align.c
+++ b/arch/powerpc/kernel/align.c
@@ -311,7 +311,7 @@ int fix_alignment(struct pt_regs *regs)
 	CHECK_FULL_REGS(regs);
 
 	if (is_kernel_addr(regs->nip))
-		r = probe_kernel_read_inst(&instr, (void *)regs->nip);
+		r = copy_inst_from_kernel_nofault(&instr, (void *)regs->nip);
 	else
 		r = __get_user_instr(instr, (void __user *)regs->nip);
 
diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c
index 42761ebec9f7..ffe9537195aa 100644
--- a/arch/powerpc/kernel/trace/ftrace.c
+++ b/arch/powerpc/kernel/trace/ftrace.c
@@ -68,7 +68,7 @@ ftrace_modify_code(unsigned long ip, struct ppc_inst old, struct ppc_inst new)
 	 */
 
 	/* read the text we want to modify */
-	if (probe_kernel_read_inst(&replaced, (void *)ip))
+	if (copy_inst_from_kernel_nofault(&replaced, (void *)ip))
 		return -EFAULT;
 
 	/* Make sure it is what we expect it to be */
@@ -130,7 +130,7 @@ __ftrace_make_nop(struct module *mod,
 	struct ppc_inst op, pop;
 
 	/* read where this goes */
-	if (probe_kernel_read_inst(&op, (void *)ip)) {
+	if (copy_inst_from_kernel_nofault(&op, (void *)ip)) {
 		pr_err("Fetching opcode failed.\n");
 		return -EFAULT;
 	}
@@ -164,7 +164,7 @@ __ftrace_make_nop(struct module *mod,
 	/* When using -mkernel_profile there is no load to jump over */
 	pop = ppc_inst(PPC_INST_NOP);
 
-	if (probe_kernel_read_inst(&op, (void *)(ip - 4))) {
+	if (copy_inst_from_kernel_nofault(&op, (void *)(ip - 4))) {
 		pr_err("Fetching instruction at %lx failed.\n", ip - 4);
 		return -EFAULT;
 	}
@@ -197,7 +197,7 @@ __ftrace_make_nop(struct module *mod,
 	 * Check what is in the next instruction. We can see ld r2,40(r1), but
 	 * on first pass after boot we will see mflr r0.
 	 */
-	if (probe_kernel_read_inst(&op, (void *)(ip + 4))) {
+	if (copy_inst_from_kernel_nofault(&op, (void *)(ip + 4))) {
 		pr_err("Fetching op failed.\n");
 		return -EFAULT;
 	}
@@ -349,7 +349,7 @@ static int setup_mcount_compiler_tramp(unsigned long tramp)
 			return -1;
 
 	/* New trampoline -- read where this goes */
-	if (probe_kernel_read_inst(&op, (void *)tramp)) {
+	if (copy_inst_from_kernel_nofault(&op, (void *)tramp)) {
 		pr_debug("Fetching opcode failed.\n");
 		return -1;
 	}
@@ -399,7 +399,7 @@ static int __ftrace_make_nop_kernel(struct dyn_ftrace *rec, unsigned long addr)
 	struct ppc_inst op;
 
 	/* Read where this goes */
-	if (probe_kernel_read_inst(&op, (void *)ip)) {
+	if (copy_inst_from_kernel_nofault(&op, (void *)ip)) {
 		pr_err("Fetching opcode failed.\n");
 		return -EFAULT;
 	}
@@ -526,10 +526,10 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 	struct module *mod = rec->arch.mod;
 
 	/* read where this goes */
-	if (probe_kernel_read_inst(op, ip))
+	if (copy_inst_from_kernel_nofault(op, ip))
 		return -EFAULT;
 
-	if (probe_kernel_read_inst(op + 1, ip + 4))
+	if (copy_inst_from_kernel_nofault(op + 1, ip + 4))
 		return -EFAULT;
 
 	if (!expected_nop_sequence(ip, op[0], op[1])) {
@@ -592,7 +592,7 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 	unsigned long ip = rec->ip;
 
 	/* read where this goes */
-	if (probe_kernel_read_inst(&op, (void *)ip))
+	if (copy_inst_from_kernel_nofault(&op, (void *)ip))
 		return -EFAULT;
 
 	/* It should be pointing to a nop */
@@ -648,7 +648,7 @@ static int __ftrace_make_call_kernel(struct dyn_ftrace *rec, unsigned long addr)
 	}
 
 	/* Make sure we have a nop */
-	if (probe_kernel_read_inst(&op, ip)) {
+	if (copy_inst_from_kernel_nofault(&op, ip)) {
 		pr_err("Unable to read ftrace location %p\n", ip);
 		return -EFAULT;
 	}
@@ -726,7 +726,7 @@ __ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
 	}
 
 	/* read where this goes */
-	if (probe_kernel_read_inst(&op, (void *)ip)) {
+	if (copy_inst_from_kernel_nofault(&op, (void *)ip)) {
 		pr_err("Fetching opcode failed.\n");
 		return -EFAULT;
 	}
diff --git a/arch/powerpc/lib/inst.c b/arch/powerpc/lib/inst.c
index 0dff3ac2d45f..e554d1357f2f 100644
--- a/arch/powerpc/lib/inst.c
+++ b/arch/powerpc/lib/inst.c
@@ -8,8 +8,7 @@
 #include <asm/inst.h>
 #include <asm/ppc-opcode.h>
 
-int probe_kernel_read_inst(struct ppc_inst *inst,
-			   struct ppc_inst *src)
+int copy_inst_from_kernel_nofault(struct ppc_inst *inst, struct ppc_inst *src)
 {
 	unsigned int val, suffix;
 	int err;
-- 
2.25.0

[PATCH v3 4/4] powerpc: Move copy_from_kernel_nofault_inst()

[Christophe Leroy]

When probe_kernel_read_inst() was created, there was no good place to
put it, so a file called lib/inst.c was dedicated for it.

Since then, probe_kernel_read_inst() has been renamed
copy_from_kernel_nofault_inst(). And mm/maccess.h didn't exist at that
time. Today, mm/maccess.h is related to copy_from_kernel_nofault().

Move copy_from_kernel_nofault_inst() into mm/maccess.c

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
v2: Remove inst.o from Makefile
---
 arch/powerpc/lib/Makefile |  2 +-
 arch/powerpc/lib/inst.c   | 26 --------------------------
 arch/powerpc/mm/maccess.c | 21 +++++++++++++++++++++
 3 files changed, 22 insertions(+), 27 deletions(-)
 delete mode 100644 arch/powerpc/lib/inst.c

diff --git a/arch/powerpc/lib/Makefile b/arch/powerpc/lib/Makefile
index d4efc182662a..f2c690ee75d1 100644
--- a/arch/powerpc/lib/Makefile
+++ b/arch/powerpc/lib/Makefile
@@ -16,7 +16,7 @@ CFLAGS_code-patching.o += -DDISABLE_BRANCH_PROFILING
 CFLAGS_feature-fixups.o += -DDISABLE_BRANCH_PROFILING
 endif
 
-obj-y += alloc.o code-patching.o feature-fixups.o pmem.o inst.o test_code-patching.o
+obj-y += alloc.o code-patching.o feature-fixups.o pmem.o test_code-patching.o
 
 ifndef CONFIG_KASAN
 obj-y	+=	string.o memcmp_$(BITS).o
diff --git a/arch/powerpc/lib/inst.c b/arch/powerpc/lib/inst.c
deleted file mode 100644
index e554d1357f2f..000000000000
--- a/arch/powerpc/lib/inst.c
+++ /dev/null
@@ -1,26 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0-or-later
-/*
- *  Copyright 2020, IBM Corporation.
- */
-
-#include <linux/uaccess.h>
-#include <asm/disassemble.h>
-#include <asm/inst.h>
-#include <asm/ppc-opcode.h>
-
-int copy_inst_from_kernel_nofault(struct ppc_inst *inst, struct ppc_inst *src)
-{
-	unsigned int val, suffix;
-	int err;
-
-	err = copy_from_kernel_nofault(&val, src, sizeof(val));
-	if (err)
-		return err;
-	if (IS_ENABLED(CONFIG_PPC64) && get_op(val) == OP_PREFIX) {
-		err = copy_from_kernel_nofault(&suffix, (void *)src + 4, 4);
-		*inst = ppc_inst_prefix(val, suffix);
-	} else {
-		*inst = ppc_inst(val);
-	}
-	return err;
-}
diff --git a/arch/powerpc/mm/maccess.c b/arch/powerpc/mm/maccess.c
index fa9a7a718fc6..a3c30a884076 100644
--- a/arch/powerpc/mm/maccess.c
+++ b/arch/powerpc/mm/maccess.c
@@ -3,7 +3,28 @@
 #include <linux/uaccess.h>
 #include <linux/kernel.h>
 
+#include <asm/disassemble.h>
+#include <asm/inst.h>
+#include <asm/ppc-opcode.h>
+
 bool copy_from_kernel_nofault_allowed(const void *unsafe_src, size_t size)
 {
 	return is_kernel_addr((unsigned long)unsafe_src);
 }
+
+int copy_inst_from_kernel_nofault(struct ppc_inst *inst, struct ppc_inst *src)
+{
+	unsigned int val, suffix;
+	int err;
+
+	err = copy_from_kernel_nofault(&val, src, sizeof(val));
+	if (err)
+		return err;
+	if (IS_ENABLED(CONFIG_PPC64) && get_op(val) == OP_PREFIX) {
+		err = copy_from_kernel_nofault(&suffix, (void *)src + 4, 4);
+		*inst = ppc_inst_prefix(val, suffix);
+	} else {
+		*inst = ppc_inst(val);
+	}
+	return err;
+}
-- 
2.25.0

Re: [PATCH v3 1/4] powerpc: Remove probe_user_read_inst()

[Michael Ellerman]

On Wed, 14 Apr 2021 13:08:40 +0000 (UTC), Christophe Leroy wrote:
> Its name comes from former probe_user_read() function.
> That function is now called copy_from_user_nofault().
> 
> probe_user_read_inst() uses copy_from_user_nofault() to read only
> a few bytes. It is suboptimal.
> 
> It does the same as get_user_inst() but in addition disables
> page faults.
> 
> [...]

Applied to powerpc/next.

[1/4] powerpc: Remove probe_user_read_inst()
      https://git.kernel.org/powerpc/c/6ac7897f08e04b47df3955d7691652e9d12d4068
[2/4] powerpc: Make probe_kernel_read_inst() common to PPC32 and PPC64
      https://git.kernel.org/powerpc/c/6449078d50111c839bb7156c3b99b9def80eed42
[3/4] powerpc: Rename probe_kernel_read_inst()
      https://git.kernel.org/powerpc/c/41d6cf68b5f611934bcc6a7d4a1a2d9bfd04b420
[4/4] powerpc: Move copy_from_kernel_nofault_inst()
      https://git.kernel.org/powerpc/c/39352430aaa05fbe4ba710231c70b334513078f2

cheers