From: Arnd Bergmann <[email protected]>
This function has no callers and no declaration when CONFIG_BPF_JIT_ALWAYS_ON
is enabled:
kernel/bpf/core.c:2075:6: error: no previous prototype for 'bpf_patch_call_args' [-Werror=missing-prototypes]
Hide the definition as well.
Signed-off-by: Arnd Bergmann <[email protected]>
---
kernel/bpf/core.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 7421487422d4..6f5ede31e471 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -2064,7 +2064,7 @@ EVAL4(PROG_NAME_LIST, 416, 448, 480, 512)
};
#undef PROG_NAME_LIST
#define PROG_NAME_LIST(stack_size) PROG_NAME_ARGS(stack_size),
-static u64 (*interpreters_args[])(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5,
+static __maybe_unused u64 (*interpreters_args[])(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5,
const struct bpf_insn *insn) = {
EVAL6(PROG_NAME_LIST, 32, 64, 96, 128, 160, 192)
EVAL6(PROG_NAME_LIST, 224, 256, 288, 320, 352, 384)
@@ -2072,6 +2072,7 @@ EVAL4(PROG_NAME_LIST, 416, 448, 480, 512)
};
#undef PROG_NAME_LIST
+#ifdef CONFIG_BPF_SYSCALL
void bpf_patch_call_args(struct bpf_insn *insn, u32 stack_depth)
{
stack_depth = max_t(u32, stack_depth, 1);
@@ -2080,6 +2081,7 @@ void bpf_patch_call_args(struct bpf_insn *insn, u32 stack_depth)
__bpf_call_base_args;
insn->code = BPF_JMP | BPF_CALL_ARGS;
}
+#endif
#else
static unsigned int __bpf_prog_ret0_warn(const void *ctx,
--
2.39.2
From: Arnd Bergmann <[email protected]>
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]
Add a prototype directly in front of the function instead to shut
up the warning. Also, to avoid having an incompatible function override
the __weak definition, use an #ifdef to ensure that only one of the
two is ever defined.
I'm not sure what can be done to make the two prototypes match.
Signed-off-by: Arnd Bergmann <[email protected]>
---
kernel/bpf/core.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 6f5ede31e471..38762a784b86 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -1635,11 +1635,14 @@ 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)
+u64 bpf_probe_read_kernel(void *dst, u32 size, const void *unsafe_ptr);
+#ifndef CONFIG_BPF_EVENTS
+u64 bpf_probe_read_kernel(void *dst, u32 size, const void *unsafe_ptr)
{
memset(dst, 0, size);
return -EFAULT;
}
+#endif
/**
* ___bpf_prog_run - run eBPF program on a given context
--
2.39.2
On 5/17/23 2:56 PM, Arnd Bergmann wrote:
> From: Arnd Bergmann <[email protected]>
>
> This function has no callers and no declaration when CONFIG_BPF_JIT_ALWAYS_ON
> is enabled:
>
> kernel/bpf/core.c:2075:6: error: no previous prototype for 'bpf_patch_call_args' [-Werror=missing-prototypes]
>
> Hide the definition as well.
>
> Signed-off-by: Arnd Bergmann <[email protected]>
> ---
> kernel/bpf/core.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
> index 7421487422d4..6f5ede31e471 100644
> --- a/kernel/bpf/core.c
> +++ b/kernel/bpf/core.c
> @@ -2064,7 +2064,7 @@ EVAL4(PROG_NAME_LIST, 416, 448, 480, 512)
> };
> #undef PROG_NAME_LIST
> #define PROG_NAME_LIST(stack_size) PROG_NAME_ARGS(stack_size),
> -static u64 (*interpreters_args[])(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5,
> +static __maybe_unused u64 (*interpreters_args[])(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5,
> const struct bpf_insn *insn) = {
Patch 2 lgtm, small nit above: could you fix up indent?
> EVAL6(PROG_NAME_LIST, 32, 64, 96, 128, 160, 192)
> EVAL6(PROG_NAME_LIST, 224, 256, 288, 320, 352, 384)
> @@ -2072,6 +2072,7 @@ EVAL4(PROG_NAME_LIST, 416, 448, 480, 512)
> };
> #undef PROG_NAME_LIST
>
> +#ifdef CONFIG_BPF_SYSCALL
> void bpf_patch_call_args(struct bpf_insn *insn, u32 stack_depth)
> {
> stack_depth = max_t(u32, stack_depth, 1);
> @@ -2080,6 +2081,7 @@ void bpf_patch_call_args(struct bpf_insn *insn, u32 stack_depth)
> __bpf_call_base_args;
> insn->code = BPF_JMP | BPF_CALL_ARGS;
> }
> +#endif
>
> #else
> static unsigned int __bpf_prog_ret0_warn(const void *ctx,
Thanks,
Daniel
On Wed, May 17, 2023 at 5:56 AM Arnd Bergmann <[email protected]> wrote:
>
> From: Arnd Bergmann <[email protected]>
>
> 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]
>
> Add a prototype directly in front of the function instead to shut
> up the warning. Also, to avoid having an incompatible function override
> the __weak definition, use an #ifdef to ensure that only one of the
> two is ever defined.
>
> I'm not sure what can be done to make the two prototypes match.
>
> Signed-off-by: Arnd Bergmann <[email protected]>
> ---
> kernel/bpf/core.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
> index 6f5ede31e471..38762a784b86 100644
> --- a/kernel/bpf/core.c
> +++ b/kernel/bpf/core.c
> @@ -1635,11 +1635,14 @@ 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)
> +u64 bpf_probe_read_kernel(void *dst, u32 size, const void *unsafe_ptr);
> +#ifndef CONFIG_BPF_EVENTS
> +u64 bpf_probe_read_kernel(void *dst, u32 size, const void *unsafe_ptr)
> {
> memset(dst, 0, size);
> return -EFAULT;
> }
This is not right, but you've spotted a bug.
bpf_probe_read_kernel
It should be BPF_CALL_3(bpf_probe_read_kernel, void *, dst, u32, size,
const void *, unsafe_ptr)
here in kernel/bpf/core.c as well otherwise bpf prog won't
pass the arguments correctly on 32-bit arches.
The kconfig without CONFIG_BPF_EVENTS and with BPF_SYSCALL is very odd.
I suspect the progs will likely refuse to load,
but still worth fixing it correctly at least to document the calling convention.
On Tue, May 23, 2023, at 03:05, Alexei Starovoitov wrote:
> On Wed, May 17, 2023 at 5:56 AM Arnd Bergmann <[email protected]> wrote:
>> @@ -1635,11 +1635,14 @@ 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)
>> +u64 bpf_probe_read_kernel(void *dst, u32 size, const void *unsafe_ptr);
>> +#ifndef CONFIG_BPF_EVENTS
>> +u64 bpf_probe_read_kernel(void *dst, u32 size, const void *unsafe_ptr)
>> {
>> memset(dst, 0, size);
>> return -EFAULT;
>> }
>
> This is not right, but you've spotted a bug.
> bpf_probe_read_kernel
> It should be BPF_CALL_3(bpf_probe_read_kernel, void *, dst, u32, size,
> const void *, unsafe_ptr)
> here in kernel/bpf/core.c as well otherwise bpf prog won't
> pass the arguments correctly on 32-bit arches.
I tried that before and again now, but could not figure out how
to do this correctly though.
With this patch on top:
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -1635,9 +1635,8 @@ bool bpf_opcode_in_insntable(u8 code)
}
#ifndef CONFIG_BPF_JIT_ALWAYS_ON
-u64 bpf_probe_read_kernel(void *dst, u32 size, const void *unsafe_ptr);
#ifndef CONFIG_BPF_EVENTS
-u64 bpf_probe_read_kernel(void *dst, u32 size, const void *unsafe_ptr)
+BPF_CALL_3(bpf_probe_read_kernel, void *, dst, u32, size, const void *, unsafe_ptr)
{
memset(dst, 0, size);
return -EFAULT;
I see a ton of other build failures, for every function calling
bpf_probe_read_kernel() from kernel/bpf:
kernel/bpf/core.c: In function '___bpf_prog_run':
kernel/bpf/core.c:1936:39: error: passing argument 1 of 'bpf_probe_read_kernel' makes integer from pointer without a cast [-Werror=int-conversion]
1936 | bpf_probe_read_kernel(&DST, sizeof(SIZE), \
| ^
| |
| u64 * {aka long long unsigned int *}
kernel/bpf/core.c:1937:39: error: passing argument 3 of 'bpf_probe_read_kernel' makes integer from pointer without a cast [-Werror=int-conversion
1937 | (const void *)(long) (SRC + insn->off)); \
Though the code from samples/bpf seems to be able to call this
without problems.
If you have a suggestion for how to do it correctly, can you send
that as a patch yourself? Let me know if you'd like me to run that
through my test builds.
> The kconfig without CONFIG_BPF_EVENTS and with BPF_SYSCALL is very odd.
> I suspect the progs will likely refuse to load, but still worth
> fixing it correctly at least to document the calling convention.
Do you think there should be a change to the Kconfig files as well then?
I see a lot of features depend on BPF_SYSCALL but not BPF_EVENTS:
HID_BPF, BPF_LIRC_MODE2, CGROUP_BPF, BPF_PRELOAD, DEBUG_INFO_BTF,
BPF_STREAM_PARSER, AF_KCM, XDP_SOCKETS and NETFILTER_BPF_LINK.
Right now, these can all be enabled when {KPROBE,UPROBE,PERF,BPF}_EVENTS
are disabled.
Arnd