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bpf: Revert ("Fix dispatcher patchable function entry to 5 bytes nop")

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Because __attribute__((patchable_function_entry)) is only available
since GCC-8 this solution fails to build on the minimum required GCC
version.

Undo these changes so we might try again -- without cluttering up the
patches with too many changes.

This is an almost complete revert of:

  dbe69b2998 ("bpf: Fix dispatcher patchable function entry to 5 bytes nop")
  ceea991a01 ("bpf: Move bpf_dispatcher function out of ftrace locations")

(notably the arch/x86/Kconfig hunk is kept).

Reported-by: David Laight <David.Laight@aculab.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: Björn Töpel <bjorn@kernel.org>
Tested-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Björn Töpel <bjorn@kernel.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lkml.kernel.org/r/439d8dc735bb4858875377df67f1b29a@AcuMS.aculab.com
Link: https://lore.kernel.org/bpf/20221103120647.728830733@infradead.org
This commit is contained in:
Peter Zijlstra 2022-11-03 13:00:13 +01:00 committed by Daniel Borkmann
parent d3fd203f36
commit 18acb7fac2
3 changed files with 1 additions and 39 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

13
arch/x86/net/bpf_jit_comp.c
View file

@ -11,7 +11,6 @@
#include <linux/bpf.h>
#include <linux/memory.h>
#include <linux/sort.h>
#include <linux/init.h>
#include <asm/extable.h>
#include <asm/set_memory.h>
#include <asm/nospec-branch.h>
@ -389,18 +388,6 @@ static int __bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
return ret;
}
int __init bpf_arch_init_dispatcher_early(void *ip)
{
const u8 *nop_insn = x86_nops[5];
if (is_endbr(*(u32 *)ip))
ip += ENDBR_INSN_SIZE;
if (memcmp(ip, nop_insn, X86_PATCH_SIZE))
text_poke_early(ip, nop_insn, X86_PATCH_SIZE);
return 0;
}
int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
void *old_addr, void *new_addr)
{

21
include/linux/bpf.h
View file

@ -27,7 +27,6 @@
#include <linux/bpfptr.h>
#include <linux/btf.h>
#include <linux/rcupdate_trace.h>
#include <linux/init.h>
struct bpf_verifier_env;
struct bpf_verifier_log;
@ -971,8 +970,6 @@ struct bpf_trampoline *bpf_trampoline_get(u64 key,
struct bpf_attach_target_info *tgt_info);
void bpf_trampoline_put(struct bpf_trampoline *tr);
int arch_prepare_bpf_dispatcher(void *image, void *buf, s64 *funcs, int num_funcs);
int __init bpf_arch_init_dispatcher_early(void *ip);
#define BPF_DISPATCHER_INIT(_name) { \
.mutex = __MUTEX_INITIALIZER(_name.mutex), \
.func = &_name##_func, \
@ -986,21 +983,7 @@ int __init bpf_arch_init_dispatcher_early(void *ip);
}, \
}
#define BPF_DISPATCHER_INIT_CALL(_name) \
static int __init _name##_init(void) \
{ \
return bpf_arch_init_dispatcher_early(_name##_func); \
} \
early_initcall(_name##_init)
#ifdef CONFIG_X86_64
#define BPF_DISPATCHER_ATTRIBUTES __attribute__((patchable_function_entry(5)))
#else
#define BPF_DISPATCHER_ATTRIBUTES
#endif
#define DEFINE_BPF_DISPATCHER(name) \
notrace BPF_DISPATCHER_ATTRIBUTES \
noinline __nocfi unsigned int bpf_dispatcher_##name##_func( \
const void *ctx, \
const struct bpf_insn *insnsi, \
@ -1010,9 +993,7 @@ int __init bpf_arch_init_dispatcher_early(void *ip);
} \
EXPORT_SYMBOL(bpf_dispatcher_##name##_func); \
struct bpf_dispatcher bpf_dispatcher_##name = \
BPF_DISPATCHER_INIT(bpf_dispatcher_##name); \
BPF_DISPATCHER_INIT_CALL(bpf_dispatcher_##name);
BPF_DISPATCHER_INIT(bpf_dispatcher_##name);
#define DECLARE_BPF_DISPATCHER(name) \
unsigned int bpf_dispatcher_##name##_func( \
const void *ctx, \

6
kernel/bpf/dispatcher.c
View file

@ -4,7 +4,6 @@
#include <linux/hash.h>
#include <linux/bpf.h>
#include <linux/filter.h>
#include <linux/init.h>
/* The BPF dispatcher is a multiway branch code generator. The
* dispatcher is a mechanism to avoid the performance penalty of an
@ -91,11 +90,6 @@ int __weak arch_prepare_bpf_dispatcher(void *image, void *buf, s64 *funcs, int n
return -ENOTSUPP;
}
int __weak __init bpf_arch_init_dispatcher_early(void *ip)
{
return -ENOTSUPP;
}
static int bpf_dispatcher_prepare(struct bpf_dispatcher *d, void *image, void *buf)
{
s64 ips[BPF_DISPATCHER_MAX] = {}, *ipsp = &ips[0];