On 7/25/23 1:41 PM, Arnd Bergmann wrote:
From: Arnd Bergmann <arnd@xxxxxxxx>
bpf_probe_read_kernel() has a __weak definition in core.c and another
definition with an incompatible prototype in kernel/trace/bpf_trace.c,
when CONFIG_BPF_EVENTS is enabled.
Since the two are incompatible, there cannot be a shared declaration in
a header file, but the lack of a prototype causes a W=1 warning:
kernel/bpf/core.c:1638:12: error: no previous prototype for 'bpf_probe_read_kernel' [-Werror=missing-prototypes]
On 32-bit architectures, the local prototype
u64 __weak bpf_probe_read_kernel(void *dst, u32 size, const void *unsafe_ptr)
passes arguments in other registers as the one in bpf_trace.c
BPF_CALL_3(bpf_probe_read_kernel, void *, dst, u32, size,
const void *, unsafe_ptr)
which uses 64-bit arguments in pairs of registers.
As both versions of the function are fairly simple and only really
differ in one line, just move them into a header file as an inline
function that does not add any overhead for the bpf_trace.c callers
and actually avoids a function call for the other one.
Cc: stable@xxxxxxxxxxxxxxx
Link: https://lore.kernel.org/all/ac25cb0f-b804-1649-3afb-1dc6138c2716@xxxxxxxxxxxxx/
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
LGTM but there are some additional changes in kernel so you need to
rebase on top of master branch with the following additional change:
@@ -2082,7 +2076,7 @@ static u64 ___bpf_prog_run(u64 *regs, const struct
bpf_insn *insn)
DST = *(SIZE *)(unsigned long) (SRC + insn->off); \
CONT; \
LDX_PROBE_MEMSX_##SIZEOP: \
- bpf_probe_read_kernel(&DST, sizeof(SIZE), \
+ bpf_probe_read_kernel_common(&DST, sizeof(SIZE),
\
(const void *)(long) (SRC +
insn->off)); \
DST = *((SIZE *)&DST); \
CONT;
Thanks!
--
v4: rewrite again to use a shared inline helper
v3: clarify changelog text further.
v2: rewrite completely to fix the mismatch.
---
include/linux/bpf.h | 12 ++++++++++++
kernel/bpf/core.c | 10 ++--------
kernel/trace/bpf_trace.c | 11 -----------
3 files changed, 14 insertions(+), 19 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index ceaa8c23287fc..abe75063630b8 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2661,6 +2661,18 @@ static inline void bpf_dynptr_set_rdonly(struct bpf_dynptr_kern *ptr)
}
#endif /* CONFIG_BPF_SYSCALL */
+static __always_inline int
+bpf_probe_read_kernel_common(void *dst, u32 size, const void *unsafe_ptr)
+{
+ int ret = -EFAULT;
+
+ if (IS_ENABLED(CONFIG_BPF_EVENTS))
+ ret = copy_from_kernel_nofault(dst, unsafe_ptr, size);
+ if (unlikely(ret < 0))
+ memset(dst, 0, size);
+ return ret;
+}
+
void __bpf_free_used_btfs(struct bpf_prog_aux *aux,
struct btf_mod_pair *used_btfs, u32 len);
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index dd70c58c9d3a3..9cdf53bfb8bd3 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -1634,12 +1634,6 @@ bool bpf_opcode_in_insntable(u8 code)
}
#ifndef CONFIG_BPF_JIT_ALWAYS_ON
-u64 __weak bpf_probe_read_kernel(void *dst, u32 size, const void *unsafe_ptr)
-{
- memset(dst, 0, size);
- return -EFAULT;
-}
-
/**
* ___bpf_prog_run - run eBPF program on a given context
* @regs: is the array of MAX_BPF_EXT_REG eBPF pseudo-registers
@@ -1930,8 +1924,8 @@ static u64 ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn)
DST = *(SIZE *)(unsigned long) (SRC + insn->off); \
CONT; \
LDX_PROBE_MEM_##SIZEOP: \
- bpf_probe_read_kernel(&DST, sizeof(SIZE), \
- (const void *)(long) (SRC + insn->off)); \
+ bpf_probe_read_kernel_common(&DST, sizeof(SIZE), \
+ (const void *)(long) (SRC + insn->off)); \
DST = *((SIZE *)&DST); \
CONT;
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index c92eb8c6ff08d..83bde2475ae54 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -223,17 +223,6 @@ const struct bpf_func_proto bpf_probe_read_user_str_proto = {
.arg3_type = ARG_ANYTHING,
};
-static __always_inline int
-bpf_probe_read_kernel_common(void *dst, u32 size, const void *unsafe_ptr)
-{
- int ret;
-
- ret = copy_from_kernel_nofault(dst, unsafe_ptr, size);
- if (unlikely(ret < 0))
- memset(dst, 0, size);
- return ret;
-}
-
BPF_CALL_3(bpf_probe_read_kernel, void *, dst, u32, size,
const void *, unsafe_ptr)
{
