[PATCH 3/4] kprobes/treewide: Explicitly override alloc/free functions

From: Mark Rutland <mark.rutland@arm.com>
Date: 2024-03-26 16:36:44
Also in: lkml
Subsystem: arm64 port (aarch64 architecture), kprobes, linux for powerpc (32-bit and 64-bit), risc-v architecture, s390 architecture, the rest, x86 architecture (32-bit and 64-bit) · Maintainers: Catalin Marinas, Will Deacon, Naveen N Rao, "David S. Miller", Masami Hiramatsu, Madhavan Srinivasan, Michael Ellerman, Paul Walmsley, Palmer Dabbelt, Albert Ou, Heiko Carstens, Vasily Gorbik, Alexander Gordeev, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen

Currently architectures can override kprobes_alloc_insn_page(), but
kprobes_free_insn_page() is always implemented using module_memfree(),
which might not be what an architecture needs, especially as we'd like
to make it possible to use kprobes without requiring MODULES.

It would be nicer if architectures either:

(a) Used only the generic kprobes_alloc_insn_page() and
    kprobes_free_insn_page(), implicitly depending on MODULES.

(b) Provided their own implementation of both kprobes_alloc_insn_page()
    and kprobes_free_insn_page(), handling the relevant dependencies
    themselves.

This patch applies that split treewide:

(a) Architectures using the generic kprobes_free_insn_page() and
    kprobes_free_insn_page() are left as-is. The __weak annotation is
    removed from the generic implementations so that accidental
    overrides/misuse can be detected easily.

(b) Architectures which provide their own kprobes_free_insn_page() are
    given a matching implementation of kprobes_free_insn_page(), and
    select HAVE_KPROBES_ALLOC.

    This new Kconfig symbol will allow subsequent patches to relax the
    dependency on MODULES to (MODULES || HAVE_KPROBES_ALLOC) once other
    module dependencies in the core kprobes code are cleaned up.

    Architectures which use module_alloc() are given an implementation
    using module_memfree() along with an explicit dependency on MODULES.

    Architectures using __vmalloc_node_range() are given an
    implementation using vfree(). This loses the warning for
    in_interrupt(), but vfree() can handle this via vfree_atomic(), so
    the warning isn't necessary.

    On riscv, the allocator depends on !XIP_KERNEL, which is already a
    dependency for HAVE_KPROBES in arch/riscv/Kconfig.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Anil S Keshavamurthy <redacted>
Cc: David S. Miller <davem@davemloft.net>
Cc: Jarkko Sakkinen <jarkko@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Naveen N. Rao <redacted>
---
 arch/Kconfig                       | 3 +++
 arch/arm64/Kconfig                 | 1 +
 arch/arm64/kernel/probes/kprobes.c | 5 +++++
 arch/powerpc/Kconfig               | 3 ++-
 arch/powerpc/kernel/kprobes.c      | 5 +++++
 arch/riscv/Kconfig                 | 1 +
 arch/riscv/kernel/probes/kprobes.c | 5 +++++
 arch/s390/Kconfig                  | 3 ++-
 arch/s390/kernel/kprobes.c         | 5 +++++
 arch/x86/Kconfig                   | 3 ++-
 arch/x86/kernel/kprobes/core.c     | 5 +++++
 include/linux/kprobes.h            | 1 +
 kernel/kprobes.c                   | 6 ++++--
 13 files changed, 41 insertions(+), 5 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index 9f066785bb71d..85bb59f7b8c07 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig

@@ -206,6 +206,9 @@ config HAVE_IOREMAP_PROT
 config HAVE_KPROBES
 	bool
 
+config HAVE_KPROBES_ALLOC
+	bool
+
 config HAVE_KRETPROBES
 	bool

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 7b11c98b3e84b..bda7913d6c9b8 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig

@@ -233,6 +233,7 @@ config ARM64
 	select HAVE_STACKPROTECTOR
 	select HAVE_SYSCALL_TRACEPOINTS
 	select HAVE_KPROBES
+	select HAVE_KPROBES_ALLOC
 	select HAVE_KRETPROBES
 	select HAVE_GENERIC_VDSO
 	select HOTPLUG_CORE_SYNC_DEAD if HOTPLUG_CPU

diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c
index 4b6ab7b1fa211..69d19a390cd48 100644
--- a/arch/arm64/kernel/probes/kprobes.c
+++ b/arch/arm64/kernel/probes/kprobes.c

@@ -136,6 +136,11 @@ void *kprobes_alloc_insn_page(void)
 			NUMA_NO_NODE, __builtin_return_address(0));
 }
 
+void kprobes_free_insn_page(void *page)
+{
+	vfree(page);
+}
+
 /* arm kprobe: install breakpoint in text */
 void __kprobes arch_arm_kprobe(struct kprobe *p)
 {

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 1c4be33736860..13e0fc51dcdcf 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig

@@ -254,7 +254,8 @@ config PPC
 	select HAVE_KERNEL_LZMA			if DEFAULT_UIMAGE
 	select HAVE_KERNEL_LZO			if DEFAULT_UIMAGE
 	select HAVE_KERNEL_XZ			if PPC_BOOK3S || 44x
-	select HAVE_KPROBES
+	select HAVE_KPROBES			if MODULES
+	select HAVE_KPROBES_ALLOC
 	select HAVE_KPROBES_ON_FTRACE
 	select HAVE_KRETPROBES
 	select HAVE_LD_DEAD_CODE_DATA_ELIMINATION if HAVE_OBJTOOL_MCOUNT && (!ARCH_USING_PATCHABLE_FUNCTION_ENTRY || (!CC_IS_GCC || GCC_VERSION >= 110100))

diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index 0b297718d5de6..d0332aaebab09 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c

@@ -146,6 +146,11 @@ void *kprobes_alloc_insn_page(void)
 	return NULL;
 }
 
+void kprobes_free_insn_page(void *page)
+{
+	module_memfree(page);
+}
+
 int arch_prepare_kprobe(struct kprobe *p)
 {
 	int ret = 0;

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index be09c8836d56b..4e22549a522a5 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig

@@ -139,6 +139,7 @@ config RISCV
 	select HAVE_GENERIC_VDSO if MMU && 64BIT
 	select HAVE_IRQ_TIME_ACCOUNTING
 	select HAVE_KPROBES if !XIP_KERNEL
+	select HAVE_KPROBES_ALLOC
 	select HAVE_KPROBES_ON_FTRACE if !XIP_KERNEL
 	select HAVE_KRETPROBES if !XIP_KERNEL
 	# https://github.com/ClangBuiltLinux/linux/issues/1881

diff --git a/arch/riscv/kernel/probes/kprobes.c b/arch/riscv/kernel/probes/kprobes.c
index 75201ce721057..37fdfa952d999 100644
--- a/arch/riscv/kernel/probes/kprobes.c
+++ b/arch/riscv/kernel/probes/kprobes.c

@@ -112,6 +112,11 @@ void *kprobes_alloc_insn_page(void)
 				     VM_FLUSH_RESET_PERMS, NUMA_NO_NODE,
 				     __builtin_return_address(0));
 }
+
+void kprobes_free_insn_page(void *page)
+{
+	vfree(page);
+}
 #endif
 
 /* install breakpoint in text */

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 8f01ada6845e3..635eddc3fce80 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig

@@ -193,7 +193,8 @@ config S390
 	select HAVE_KERNEL_UNCOMPRESSED
 	select HAVE_KERNEL_XZ
 	select HAVE_KERNEL_ZSTD
-	select HAVE_KPROBES
+	select HAVE_KPROBES		if MODULES
+	select HAVE_KPROBES_ALLOC
 	select HAVE_KPROBES_ON_FTRACE
 	select HAVE_KRETPROBES
 	select HAVE_LIVEPATCH

diff --git a/arch/s390/kernel/kprobes.c b/arch/s390/kernel/kprobes.c
index 91ca4d501d4ef..a5b142b8eb0f7 100644
--- a/arch/s390/kernel/kprobes.c
+++ b/arch/s390/kernel/kprobes.c

@@ -45,6 +45,11 @@ void *kprobes_alloc_insn_page(void)
 	return page;
 }
 
+void kprobes_free_insn_page(void *page)
+{
+	module_memfree(page);
+}
+
 static void *alloc_s390_insn_page(void)
 {
 	if (xchg(&insn_page_in_use, 1) == 1)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 39886bab943a8..bdd327b0124e2 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig

@@ -240,7 +240,8 @@ config X86
 	select HAVE_KERNEL_LZO
 	select HAVE_KERNEL_XZ
 	select HAVE_KERNEL_ZSTD
-	select HAVE_KPROBES
+	select HAVE_KPROBES			if MODULES
+	select HAVE_KPROBES_ALLOC
 	select HAVE_KPROBES_ON_FTRACE
 	select HAVE_FUNCTION_ERROR_INJECTION
 	select HAVE_KRETPROBES

diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index 7f01bbbfa9e2a..5f093b94d9b40 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c

@@ -508,6 +508,11 @@ void *kprobes_alloc_insn_page(void)
 	return page;
 }
 
+void kprobes_free_insn_page(void *page)
+{
+	module_memfree(page);
+}
+
 /* Kprobe x86 instruction emulation - only regs->ip or IF flag modifiers */
 
 static void kprobe_emulate_ifmodifiers(struct kprobe *p, struct pt_regs *regs)

diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index ad4b561100f9e..651c807727bea 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h

@@ -431,6 +431,7 @@ int enable_kprobe(struct kprobe *kp);
 void dump_kprobe(struct kprobe *kp);
 
 void *kprobes_alloc_insn_page(void);
+void kprobes_free_insn_page(void *page);
 
 void *kprobes_alloc_optinsn_page(void);
 void kprobes_free_optinsn_page(void *page);

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 35adf56430c9b..fa2ee4e59eca2 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c

@@ -110,7 +110,8 @@ enum kprobe_slot_state {
 	SLOT_USED = 2,
 };
 
-void __weak *kprobes_alloc_insn_page(void)
+#ifndef CONFIG_HAVE_KPROBES_ALLOC
+void *kprobes_alloc_insn_page(void)
 {
 	/*
 	 * Use module_alloc() so this page is within +/- 2GB of where the

@@ -121,10 +122,11 @@ void __weak *kprobes_alloc_insn_page(void)
 	return module_alloc(PAGE_SIZE);
 }
 
-static void kprobes_free_insn_page(void *page)
+void kprobes_free_insn_page(void *page)
 {
 	module_memfree(page);
 }
+#endif
 
 struct kprobe_insn_cache kprobe_insn_slots = {
 	.mutex = __MUTEX_INITIALIZER(kprobe_insn_slots.mutex),

-- 
2.30.2


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