[PATCH v4 4/9] fprobe: rethook: Use ftrace_regs in fprobe exit handler and rethook
From: Masami Hiramatsu (Google)
Date: Wed Aug 23 2023 - 11:17:44 EST
From: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
Change the fprobe exit handler and rethook to use ftrace_regs data structure
instead of pt_regs. This also introduce HAVE_PT_REGS_TO_FTRACE_REGS_CAST
which means the ftrace_regs's memory layout is equal to the pt_regs so
that those are able to cast. Only if it is enabled, kretprobe will use
rethook since kretprobe requires pt_regs for backward compatibility.
This means the archs which currently implement rethook for kretprobes needs to
set that flag and it must ensure struct ftrace_regs is same as pt_regs.
If not, it must be either disabling kretprobe or implementing kretprobe
trampoline separately from rethook trampoline.
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
---
Changes in v3:
- Config rename to HAVE_PT_REGS_TO_FTRACE_REGS_CAST
- Use ftrace_regs_* APIs instead of ftrace_get_regs().
Changes in v4:
- Add static_assert() to ensure at least the size of pt_regs
and ftrace_regs are same if HAVE_PT_REGS_TO_FTRACE_REGS_CAST=y.
---
arch/Kconfig | 1 +
arch/loongarch/Kconfig | 1 +
arch/s390/Kconfig | 1 +
arch/x86/Kconfig | 1 +
arch/x86/kernel/rethook.c | 13 +++++++------
include/linux/fprobe.h | 2 +-
include/linux/ftrace.h | 6 ++++++
include/linux/rethook.h | 11 ++++++-----
kernel/kprobes.c | 10 ++++++++--
kernel/trace/Kconfig | 7 +++++++
kernel/trace/bpf_trace.c | 6 +++++-
kernel/trace/fprobe.c | 6 +++---
kernel/trace/rethook.c | 16 ++++++++--------
kernel/trace/trace_fprobe.c | 6 +++++-
lib/test_fprobe.c | 6 +++---
samples/fprobe/fprobe_example.c | 2 +-
16 files changed, 64 insertions(+), 31 deletions(-)
diff --git a/arch/Kconfig b/arch/Kconfig
index aff2746c8af2..e41a270c30bb 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -201,6 +201,7 @@ config KRETPROBE_ON_RETHOOK
def_bool y
depends on HAVE_RETHOOK
depends on KRETPROBES
+ depends on HAVE_PT_REGS_TO_FTRACE_REGS_CAST || !HAVE_DYNAMIC_FTRACE_WITH_ARGS
select RETHOOK
config USER_RETURN_NOTIFIER
diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index e71d5bf2cee0..33c3a4598ae0 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -103,6 +103,7 @@ config LOONGARCH
select HAVE_DMA_CONTIGUOUS
select HAVE_DYNAMIC_FTRACE
select HAVE_DYNAMIC_FTRACE_WITH_ARGS
+ select HAVE_PT_REGS_TO_FTRACE_REGS_CAST
select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
select HAVE_DYNAMIC_FTRACE_WITH_REGS
select HAVE_EBPF_JIT
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 5b39918b7042..ef06c3c2b06d 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -165,6 +165,7 @@ config S390
select HAVE_DMA_CONTIGUOUS
select HAVE_DYNAMIC_FTRACE
select HAVE_DYNAMIC_FTRACE_WITH_ARGS
+ select HAVE_PT_REGS_TO_FTRACE_REGS_CAST
select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
select HAVE_DYNAMIC_FTRACE_WITH_REGS
select HAVE_EBPF_JIT if HAVE_MARCH_Z196_FEATURES
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index e36261b4ea14..7c1f3194e209 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -207,6 +207,7 @@ config X86
select HAVE_DYNAMIC_FTRACE
select HAVE_DYNAMIC_FTRACE_WITH_REGS
select HAVE_DYNAMIC_FTRACE_WITH_ARGS if X86_64
+ select HAVE_PT_REGS_TO_FTRACE_REGS_CAST if X86_64
select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
select HAVE_SAMPLE_FTRACE_DIRECT if X86_64
select HAVE_SAMPLE_FTRACE_DIRECT_MULTI if X86_64
diff --git a/arch/x86/kernel/rethook.c b/arch/x86/kernel/rethook.c
index 8a1c0111ae79..d714d0276c93 100644
--- a/arch/x86/kernel/rethook.c
+++ b/arch/x86/kernel/rethook.c
@@ -83,7 +83,8 @@ __used __visible void arch_rethook_trampoline_callback(struct pt_regs *regs)
* arch_rethook_fixup_return() which called from this
* rethook_trampoline_handler().
*/
- rethook_trampoline_handler(regs, (unsigned long)frame_pointer);
+ rethook_trampoline_handler((struct ftrace_regs *)regs,
+ (unsigned long)frame_pointer);
/*
* Copy FLAGS to 'pt_regs::ss' so that arch_rethook_trapmoline()
@@ -104,22 +105,22 @@ NOKPROBE_SYMBOL(arch_rethook_trampoline_callback);
STACK_FRAME_NON_STANDARD_FP(arch_rethook_trampoline);
/* This is called from rethook_trampoline_handler(). */
-void arch_rethook_fixup_return(struct pt_regs *regs,
+void arch_rethook_fixup_return(struct ftrace_regs *fregs,
unsigned long correct_ret_addr)
{
- unsigned long *frame_pointer = (void *)(regs + 1);
+ unsigned long *frame_pointer = (void *)(fregs + 1);
/* Replace fake return address with real one. */
*frame_pointer = correct_ret_addr;
}
NOKPROBE_SYMBOL(arch_rethook_fixup_return);
-void arch_rethook_prepare(struct rethook_node *rh, struct pt_regs *regs, bool mcount)
+void arch_rethook_prepare(struct rethook_node *rh, struct ftrace_regs *fregs, bool mcount)
{
- unsigned long *stack = (unsigned long *)regs->sp;
+ unsigned long *stack = (unsigned long *)ftrace_regs_get_stack_pointer(fregs);
rh->ret_addr = stack[0];
- rh->frame = regs->sp;
+ rh->frame = (unsigned long)stack;
/* Replace the return addr with trampoline addr */
stack[0] = (unsigned long) arch_rethook_trampoline;
diff --git a/include/linux/fprobe.h b/include/linux/fprobe.h
index 36c0595f7b93..b9c0c216dedb 100644
--- a/include/linux/fprobe.h
+++ b/include/linux/fprobe.h
@@ -38,7 +38,7 @@ struct fprobe {
unsigned long ret_ip, struct ftrace_regs *regs,
void *entry_data);
void (*exit_handler)(struct fprobe *fp, unsigned long entry_ip,
- unsigned long ret_ip, struct pt_regs *regs,
+ unsigned long ret_ip, struct ftrace_regs *regs,
void *entry_data);
};
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index fe335d861f08..c0a42d0860b8 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -151,6 +151,12 @@ struct ftrace_regs {
#endif /* !CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS || !CONFIG_FUNCTION_TRACER */
+#ifdef CONFIG_HAVE_PT_REGS_TO_FTRACE_REGS_CAST
+
+static_assert(sizeof(struct pt_regs) == sizeof(struct ftrace_regs));
+
+#endif /* CONFIG_HAVE_PT_REGS_TO_FTRACE_REGS_CAST */
+
static __always_inline struct pt_regs *ftrace_get_regs(struct ftrace_regs *fregs)
{
if (!fregs)
diff --git a/include/linux/rethook.h b/include/linux/rethook.h
index 26b6f3c81a76..138d64c8b67b 100644
--- a/include/linux/rethook.h
+++ b/include/linux/rethook.h
@@ -7,6 +7,7 @@
#include <linux/compiler.h>
#include <linux/freelist.h>
+#include <linux/ftrace.h>
#include <linux/kallsyms.h>
#include <linux/llist.h>
#include <linux/rcupdate.h>
@@ -14,7 +15,7 @@
struct rethook_node;
-typedef void (*rethook_handler_t) (struct rethook_node *, void *, unsigned long, struct pt_regs *);
+typedef void (*rethook_handler_t) (struct rethook_node *, void *, unsigned long, struct ftrace_regs *);
/**
* struct rethook - The rethook management data structure.
@@ -64,12 +65,12 @@ void rethook_free(struct rethook *rh);
void rethook_add_node(struct rethook *rh, struct rethook_node *node);
struct rethook_node *rethook_try_get(struct rethook *rh);
void rethook_recycle(struct rethook_node *node);
-void rethook_hook(struct rethook_node *node, struct pt_regs *regs, bool mcount);
+void rethook_hook(struct rethook_node *node, struct ftrace_regs *regs, bool mcount);
unsigned long rethook_find_ret_addr(struct task_struct *tsk, unsigned long frame,
struct llist_node **cur);
/* Arch dependent code must implement arch_* and trampoline code */
-void arch_rethook_prepare(struct rethook_node *node, struct pt_regs *regs, bool mcount);
+void arch_rethook_prepare(struct rethook_node *node, struct ftrace_regs *regs, bool mcount);
void arch_rethook_trampoline(void);
/**
@@ -84,11 +85,11 @@ static inline bool is_rethook_trampoline(unsigned long addr)
}
/* If the architecture needs to fixup the return address, implement it. */
-void arch_rethook_fixup_return(struct pt_regs *regs,
+void arch_rethook_fixup_return(struct ftrace_regs *regs,
unsigned long correct_ret_addr);
/* Generic trampoline handler, arch code must prepare asm stub */
-unsigned long rethook_trampoline_handler(struct pt_regs *regs,
+unsigned long rethook_trampoline_handler(struct ftrace_regs *regs,
unsigned long frame);
#ifdef CONFIG_RETHOOK
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 0c6185aefaef..821dff656149 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -2132,7 +2132,11 @@ static int pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs)
if (rp->entry_handler && rp->entry_handler(ri, regs))
rethook_recycle(rhn);
else
- rethook_hook(rhn, regs, kprobe_ftrace(p));
+ /*
+ * We can cast pt_regs to ftrace_regs because this depends on
+ * HAVE_PT_REGS_TO_FTRACE_REGS_CAST.
+ */
+ rethook_hook(rhn, (struct ftrace_regs *)regs, kprobe_ftrace(p));
return 0;
}
@@ -2140,9 +2144,11 @@ NOKPROBE_SYMBOL(pre_handler_kretprobe);
static void kretprobe_rethook_handler(struct rethook_node *rh, void *data,
unsigned long ret_addr,
- struct pt_regs *regs)
+ struct ftrace_regs *fregs)
{
struct kretprobe *rp = (struct kretprobe *)data;
+ /* Ditto, this depends on HAVE_PT_REGS_TO_FTRACE_REGS_CAST. */
+ struct pt_regs *regs = (struct pt_regs *)fregs;
struct kretprobe_instance *ri;
struct kprobe_ctlblk *kcb;
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 976fd594b446..d56304276318 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -57,6 +57,13 @@ config HAVE_DYNAMIC_FTRACE_WITH_ARGS
This allows for use of ftrace_regs_get_argument() and
ftrace_regs_get_stack_pointer().
+config HAVE_PT_REGS_TO_FTRACE_REGS_CAST
+ bool
+ help
+ If this is set, the memory layout of the ftrace_regs data structure
+ is the same as the pt_regs. So the pt_regs is possible to be casted
+ to ftrace_regs.
+
config HAVE_DYNAMIC_FTRACE_NO_PATCHABLE
bool
help
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 22d00c817f1a..c4d57c7cdc7c 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -2675,10 +2675,14 @@ kprobe_multi_link_handler(struct fprobe *fp, unsigned long fentry_ip,
static void
kprobe_multi_link_exit_handler(struct fprobe *fp, unsigned long fentry_ip,
- unsigned long ret_ip, struct pt_regs *regs,
+ unsigned long ret_ip, struct ftrace_regs *fregs,
void *data)
{
struct bpf_kprobe_multi_link *link;
+ struct pt_regs *regs = ftrace_get_regs(fregs);
+
+ if (!regs)
+ return;
link = container_of(fp, struct bpf_kprobe_multi_link, fp);
kprobe_multi_link_prog_run(link, get_entry_ip(fentry_ip), regs);
diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c
index 07deb52df44a..dfddc7e8424e 100644
--- a/kernel/trace/fprobe.c
+++ b/kernel/trace/fprobe.c
@@ -53,7 +53,7 @@ static inline void __fprobe_handler(unsigned long ip, unsigned long parent_ip,
if (ret)
rethook_recycle(rh);
else
- rethook_hook(rh, ftrace_get_regs(fregs), true);
+ rethook_hook(rh, fregs, true);
}
}
@@ -120,7 +120,7 @@ static void fprobe_kprobe_handler(unsigned long ip, unsigned long parent_ip,
}
static void fprobe_exit_handler(struct rethook_node *rh, void *data,
- unsigned long ret_ip, struct pt_regs *regs)
+ unsigned long ret_ip, struct ftrace_regs *fregs)
{
struct fprobe *fp = (struct fprobe *)data;
struct fprobe_rethook_node *fpr;
@@ -141,7 +141,7 @@ static void fprobe_exit_handler(struct rethook_node *rh, void *data,
return;
}
- fp->exit_handler(fp, fpr->entry_ip, ret_ip, regs,
+ fp->exit_handler(fp, fpr->entry_ip, ret_ip, fregs,
fp->entry_data_size ? (void *)fpr->data : NULL);
ftrace_test_recursion_unlock(bit);
}
diff --git a/kernel/trace/rethook.c b/kernel/trace/rethook.c
index 5eb9b598f4e9..7c5cf9d5910c 100644
--- a/kernel/trace/rethook.c
+++ b/kernel/trace/rethook.c
@@ -189,7 +189,7 @@ NOKPROBE_SYMBOL(rethook_try_get);
/**
* rethook_hook() - Hook the current function return.
* @node: The struct rethook node to hook the function return.
- * @regs: The struct pt_regs for the function entry.
+ * @fregs: The struct ftrace_regs for the function entry.
* @mcount: True if this is called from mcount(ftrace) context.
*
* Hook the current running function return. This must be called when the
@@ -199,9 +199,9 @@ NOKPROBE_SYMBOL(rethook_try_get);
* from the real function entry (e.g. kprobes) @mcount must be set false.
* This is because the way to hook the function return depends on the context.
*/
-void rethook_hook(struct rethook_node *node, struct pt_regs *regs, bool mcount)
+void rethook_hook(struct rethook_node *node, struct ftrace_regs *fregs, bool mcount)
{
- arch_rethook_prepare(node, regs, mcount);
+ arch_rethook_prepare(node, fregs, mcount);
__llist_add(&node->llist, ¤t->rethooks);
}
NOKPROBE_SYMBOL(rethook_hook);
@@ -269,7 +269,7 @@ unsigned long rethook_find_ret_addr(struct task_struct *tsk, unsigned long frame
}
NOKPROBE_SYMBOL(rethook_find_ret_addr);
-void __weak arch_rethook_fixup_return(struct pt_regs *regs,
+void __weak arch_rethook_fixup_return(struct ftrace_regs *fregs,
unsigned long correct_ret_addr)
{
/*
@@ -281,7 +281,7 @@ void __weak arch_rethook_fixup_return(struct pt_regs *regs,
}
/* This function will be called from each arch-defined trampoline. */
-unsigned long rethook_trampoline_handler(struct pt_regs *regs,
+unsigned long rethook_trampoline_handler(struct ftrace_regs *fregs,
unsigned long frame)
{
struct llist_node *first, *node = NULL;
@@ -295,7 +295,7 @@ unsigned long rethook_trampoline_handler(struct pt_regs *regs,
BUG_ON(1);
}
- instruction_pointer_set(regs, correct_ret_addr);
+ ftrace_regs_set_instruction_pointer(fregs, correct_ret_addr);
/*
* These loops must be protected from rethook_free_rcu() because those
@@ -315,7 +315,7 @@ unsigned long rethook_trampoline_handler(struct pt_regs *regs,
handler = READ_ONCE(rhn->rethook->handler);
if (handler)
handler(rhn, rhn->rethook->data,
- correct_ret_addr, regs);
+ correct_ret_addr, fregs);
if (first == node)
break;
@@ -323,7 +323,7 @@ unsigned long rethook_trampoline_handler(struct pt_regs *regs,
}
/* Fixup registers for returning to correct address. */
- arch_rethook_fixup_return(regs, correct_ret_addr);
+ arch_rethook_fixup_return(fregs, correct_ret_addr);
/* Unlink used shadow stack */
first = current->rethooks.first;
diff --git a/kernel/trace/trace_fprobe.c b/kernel/trace/trace_fprobe.c
index 71bf38d698f1..c60d0d9f1a95 100644
--- a/kernel/trace/trace_fprobe.c
+++ b/kernel/trace/trace_fprobe.c
@@ -341,10 +341,14 @@ static int fentry_dispatcher(struct fprobe *fp, unsigned long entry_ip,
NOKPROBE_SYMBOL(fentry_dispatcher);
static void fexit_dispatcher(struct fprobe *fp, unsigned long entry_ip,
- unsigned long ret_ip, struct pt_regs *regs,
+ unsigned long ret_ip, struct ftrace_regs *fregs,
void *entry_data)
{
struct trace_fprobe *tf = container_of(fp, struct trace_fprobe, fp);
+ struct pt_regs *regs = ftrace_get_regs(fregs);
+
+ if (!regs)
+ return;
if (trace_probe_test_flag(&tf->tp, TP_FLAG_TRACE))
fexit_trace_func(tf, entry_ip, ret_ip, regs);
diff --git a/lib/test_fprobe.c b/lib/test_fprobe.c
index ff607babba18..d1e80653bf0c 100644
--- a/lib/test_fprobe.c
+++ b/lib/test_fprobe.c
@@ -59,9 +59,9 @@ static notrace int fp_entry_handler(struct fprobe *fp, unsigned long ip,
static notrace void fp_exit_handler(struct fprobe *fp, unsigned long ip,
unsigned long ret_ip,
- struct pt_regs *regs, void *data)
+ struct ftrace_regs *fregs, void *data)
{
- unsigned long ret = regs_return_value(regs);
+ unsigned long ret = ftrace_regs_return_value(fregs);
KUNIT_EXPECT_FALSE(current_test, preemptible());
if (ip != target_ip) {
@@ -89,7 +89,7 @@ static notrace int nest_entry_handler(struct fprobe *fp, unsigned long ip,
static notrace void nest_exit_handler(struct fprobe *fp, unsigned long ip,
unsigned long ret_ip,
- struct pt_regs *regs, void *data)
+ struct ftrace_regs *fregs, void *data)
{
KUNIT_EXPECT_FALSE(current_test, preemptible());
KUNIT_EXPECT_EQ(current_test, ip, target_nest_ip);
diff --git a/samples/fprobe/fprobe_example.c b/samples/fprobe/fprobe_example.c
index 1545a1aac616..d476d1f07538 100644
--- a/samples/fprobe/fprobe_example.c
+++ b/samples/fprobe/fprobe_example.c
@@ -67,7 +67,7 @@ static int sample_entry_handler(struct fprobe *fp, unsigned long ip,
}
static void sample_exit_handler(struct fprobe *fp, unsigned long ip,
- unsigned long ret_ip, struct pt_regs *regs,
+ unsigned long ret_ip, struct ftrace_regs *regs,
void *data)
{
unsigned long rip = ret_ip;