| Message ID | 20230523194930.2116181-2-arnd@kernel.org (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | BPF |
| Headers | show |
| Series | [1/2,v2] bpf: hide unused bpf_patch_call_args | expand |
On 5/23/23 12:43 PM, Arnd Bergmann wrote: > From: Arnd Bergmann <arnd@arndb.de> > > 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] > > Change the core.c file to only reference the inner > bpf_probe_read_kernel_common() helper and provide a prototype for that. > > Aside from the warning, this addresses a bug on 32-bit architectures > from incorrect argument passing with the mismatched prototype. Could you explain what is this '32-bit architectures ... incorrect argument passing' thing? > > Cc: stable@vger.kernel.org > Signed-off-by: Arnd Bergmann <arnd@arndb.de> > -- > v2: rewrite completely to fix the mismatch. > --- > include/linux/bpf.h | 2 ++ > kernel/bpf/core.c | 9 ++++++--- > kernel/trace/bpf_trace.c | 3 +-- > 3 files changed, 9 insertions(+), 5 deletions(-) > > diff --git a/include/linux/bpf.h b/include/linux/bpf.h > index 36e4b2d8cca2..6a231ec61a87 100644 > --- a/include/linux/bpf.h > +++ b/include/linux/bpf.h > @@ -2619,6 +2619,8 @@ static inline void bpf_dynptr_set_rdonly(struct bpf_dynptr_kern *ptr) > } > #endif /* CONFIG_BPF_SYSCALL */ > > +int bpf_probe_read_kernel_common(void *dst, u32 size, const void *unsafe_ptr); > + > 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 0926714641eb..e7f0d5f146fa 100644 > --- a/kernel/bpf/core.c > +++ b/kernel/bpf/core.c > @@ -35,6 +35,7 @@ > #include <linux/bpf_verifier.h> > #include <linux/nodemask.h> > #include <linux/nospec.h> > +#include <linux/bpf.h> > #include <linux/bpf_mem_alloc.h> > #include <linux/memcontrol.h> > > @@ -1635,11 +1636,13 @@ 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) > +#ifndef CONFIG_BPF_EVENTS > +int bpf_probe_read_kernel_common(void * dst, u32 size, const void *unsafe_ptr) void * dst => void *dst > { > memset(dst, 0, size); > return -EFAULT; > } > +#endif > > /** > * ___bpf_prog_run - run eBPF program on a given context > @@ -1931,8 +1934,8 @@ 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 2bc41e6ac9fe..290fdce2ce53 100644 > --- a/kernel/trace/bpf_trace.c > +++ b/kernel/trace/bpf_trace.c > @@ -223,8 +223,7 @@ 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 bpf_probe_read_kernel_common(void *dst, u32 size, const void *unsafe_ptr) > { > int ret; >
On Wed, May 24, 2023, at 05:12, Yonghong Song wrote: > On 5/23/23 12:43 PM, Arnd Bergmann wrote: >> Aside from the warning, this addresses a bug on 32-bit architectures >> from incorrect argument passing with the mismatched prototype. > > Could you explain what is this '32-bit architectures ... incorrect > argument passing' thing? I've expanded that paragraph now: | Aside from the warning, this addresses a bug on 32-bit architectures | from incorrect argument passing with the mismatched prototype: | BPF_CALL_x() functions use 64-bit arguments that are passed in | pairs of register or on the stack on 32-bit architectures, while the | normal function uses one register per argument. Let me know if you think I should put more details in there. >> @@ -1635,11 +1636,13 @@ 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) >> +#ifndef CONFIG_BPF_EVENTS >> +int bpf_probe_read_kernel_common(void * dst, u32 size, const void *unsafe_ptr) > > void * dst => void *dst > Fixed now. Thanks, Arnd
On 5/24/23 6:28 AM, Arnd Bergmann wrote: > On Wed, May 24, 2023, at 05:12, Yonghong Song wrote: >> On 5/23/23 12:43 PM, Arnd Bergmann wrote: > >>> Aside from the warning, this addresses a bug on 32-bit architectures >>> from incorrect argument passing with the mismatched prototype. >> >> Could you explain what is this '32-bit architectures ... incorrect >> argument passing' thing? > > I've expanded that paragraph now: > > | Aside from the warning, this addresses a bug on 32-bit architectures > | from incorrect argument passing with the mismatched prototype: > | BPF_CALL_x() functions use 64-bit arguments that are passed in > | pairs of register or on the stack on 32-bit architectures, while the > | normal function uses one register per argument. > > Let me know if you think I should put more details in there. Please mention the function you try to address for the bug on 32-bit architecture is: u64 __weak bpf_probe_read_kernel(void *dst, u32 size, const void *unsafe_ptr) which will be incompatible with BPF_CALL_3(bpf_probe_read_kernel, void *, dst, u32, size, const void *, unsafe_ptr) in bpf_trace.c. So you fixed this bug by using internal function bpf_probe_read_kernel_common() instead. Thanks. > >>> @@ -1635,11 +1636,13 @@ 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) >>> +#ifndef CONFIG_BPF_EVENTS >>> +int bpf_probe_read_kernel_common(void * dst, u32 size, const void *unsafe_ptr) >> >> void * dst => void *dst >> > > Fixed now. > > Thanks, > > Arnd
diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 36e4b2d8cca2..6a231ec61a87 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -2619,6 +2619,8 @@ static inline void bpf_dynptr_set_rdonly(struct bpf_dynptr_kern *ptr) } #endif /* CONFIG_BPF_SYSCALL */ +int bpf_probe_read_kernel_common(void *dst, u32 size, const void *unsafe_ptr); + 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 0926714641eb..e7f0d5f146fa 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -35,6 +35,7 @@ #include <linux/bpf_verifier.h> #include <linux/nodemask.h> #include <linux/nospec.h> +#include <linux/bpf.h> #include <linux/bpf_mem_alloc.h> #include <linux/memcontrol.h> @@ -1635,11 +1636,13 @@ 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) +#ifndef CONFIG_BPF_EVENTS +int bpf_probe_read_kernel_common(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 @@ -1931,8 +1934,8 @@ 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 2bc41e6ac9fe..290fdce2ce53 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -223,8 +223,7 @@ 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 bpf_probe_read_kernel_common(void *dst, u32 size, const void *unsafe_ptr) { int ret;