[RFC PATCH 2/5] fprobe: rethook: Use fprobe_regs in fprobe exit handler and rethook

Masami Hiramatsu (Google)
2023-08-05T14:58:28Z

Change the fprobe exit handler and rethook to use ftrace_regs data structure
instead of pt_regs. This also introduce HAVE_FTRACE_REGS_COMPATIBLE_WITH_PT_REGS
which means the ftrace_regs is equal to the pt_regs so that those are
compatible. 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@kernel.org>
---
arch/Kconfig | 1 +
arch/loongarch/Kconfig | 1 +
arch/s390/Kconfig | 1 +
arch/x86/Kconfig | 1 +
arch/x86/kernel/rethook.c | 9 ++++++---
include/linux/fprobe.h | 2 +-
include/linux/rethook.h | 11 ++++++-----
kernel/kprobes.c | 9 +++++++--
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 +-
15 files changed, 56 insertions(+), 28 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index aff2746c8af2..e321bdb8b22b 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_COMPAT_FTRACE_REGS || !HAVE_DYNAMIC_FTRACE_WITH_ARGS
select RETHOOK

config USER_RETURN_NOTIFIER
diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index e55511af4c77..93a4336b0a94 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -102,6 +102,7 @@ config LOONGARCH
select HAVE_DMA_CONTIGUOUS
select HAVE_DYNAMIC_FTRACE
select HAVE_DYNAMIC_FTRACE_WITH_ARGS
+ select HAVE_PT_REGS_COMPAT_FTRACE_REGS
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..299ba17d3316 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_COMPAT_FTRACE_REGS
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 7422db409770..df1b7a2791e8 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_COMPAT_FTRACE_REGS 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..79a52bfde562 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()
@@ -104,9 +105,10 @@ 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)
{
+ struct pt_regs *regs = ftrace_get_regs(fregs);
unsigned long *frame_pointer = (void *)(regs + 1);

/* Replace fake return address with real one. */
@@ -114,8 +116,9 @@ void arch_rethook_fixup_return(struct pt_regs *regs,
}
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)
{
+ struct pt_regs *regs = ftrace_get_regs(fregs);
unsigned long *stack = (unsigned long *)regs->sp;

rh->ret_addr = stack[0];
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/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 1fc6095d502d..ccbe41c961c3 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -2120,7 +2120,7 @@ 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));
+ rethook_hook(rhn, (struct ftrace_regs *)regs, kprobe_ftrace(p));

return 0;
}
@@ -2128,12 +2128,17 @@ 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;
+ struct pt_regs *regs = ftrace_get_regs(fregs);
struct kretprobe_instance *ri;
struct kprobe_ctlblk *kcb;

+ /* This is bug because this depends on HAVE_PT_REGS_COMPAT_FTRACE_REGS */
+ if (WARN_ON_ONCE(!regs))
+ return;
+
/* The data must NOT be null. This means rethook data structure is broken. */
if (WARN_ON_ONCE(!data) || !rp->handler)
return;
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 976fd594b446..7d6abb5bd861 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_COMPAT_FTRACE_REGS
+ bool
+ help
+ If this is set, the ftrace_regs data structure is compatible
+ with the pt_regs. So it is possible to be converted by
+ ftrace_get_regs().
+
config HAVE_DYNAMIC_FTRACE_NO_PATCHABLE
bool
help
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 51573eaa04c4..99c5f95360f9 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -2668,10 +2668,14 @@ 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 15a2aef92733..70b9c493e52d 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, &current->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 4d3ae79f036e..f440c97e050f 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;