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bpf: Simplify __bpf_arch_text_poke poke type handling

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Given that we have BPF_MOD_NOP_TO_{CALL,JUMP}, BPF_MOD_{CALL,JUMP}_TO_NOP
and BPF_MOD_{CALL,JUMP}_TO_{CALL,JUMP} poke types and that we also pass in
old_addr as well as new_addr, it's a bit redundant and unnecessarily
complicates __bpf_arch_text_poke() itself since we can derive the same from
the *_addr that were passed in. Hence simplify and use BPF_MOD_{CALL,JUMP}
as types which also allows to clean up call-sites.

In addition to that, __bpf_arch_text_poke() currently verifies that text
matches expected old_insn before we invoke text_poke_bp(). Also add a check
on new_insn and skip rewrite if it already matches. Reason why this is rather
useful is that it avoids making any special casing in prog_array_map_poke_run()
when old and new prog were NULL and has the benefit that also for this case
we perform a check on text whether it really matches our expectations.

Suggested-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/fcb00a2b0b288d6c73de4ef58116a821c8fe8f2f.1574555798.git.daniel@iogearbox.net
This commit is contained in:
Daniel Borkmann
2019-11-24 01:39:42 +01:00
committed by Alexei Starovoitov
parent f9a7cf6eb1
commit b553a6ec57
4 changed files with 32 additions and 83 deletions
Download Patch File Download Diff File Expand all files Collapse all files

85
arch/x86/net/bpf_jit_comp.c
View File

@@ -269,76 +269,42 @@ static int __bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
void *old_addr, void *new_addr,
const bool text_live)
{
int (*emit_patch_fn)(u8 **pprog, void *func, void *ip);
const u8 *nop_insn = ideal_nops[NOP_ATOMIC5];
u8 old_insn[X86_PATCH_SIZE] = {};
u8 new_insn[X86_PATCH_SIZE] = {};
u8 old_insn[X86_PATCH_SIZE];
u8 new_insn[X86_PATCH_SIZE];
u8 *prog;
int ret;
switch (t) {
case BPF_MOD_NOP_TO_CALL ... BPF_MOD_CALL_TO_NOP:
emit_patch_fn = emit_call;
break;
case BPF_MOD_NOP_TO_JUMP ... BPF_MOD_JUMP_TO_NOP:
emit_patch_fn = emit_jump;
break;
default:
return -ENOTSUPP;
memcpy(old_insn, nop_insn, X86_PATCH_SIZE);
if (old_addr) {
prog = old_insn;
ret = t == BPF_MOD_CALL ?
emit_call(&prog, old_addr, ip) :
emit_jump(&prog, old_addr, ip);
if (ret)
return ret;
}
switch (t) {
case BPF_MOD_NOP_TO_CALL:
case BPF_MOD_NOP_TO_JUMP:
if (!old_addr && new_addr) {
memcpy(old_insn, nop_insn, X86_PATCH_SIZE);
prog = new_insn;
ret = emit_patch_fn(&prog, new_addr, ip);
if (ret)
return ret;
break;
}
return -ENXIO;
case BPF_MOD_CALL_TO_CALL:
case BPF_MOD_JUMP_TO_JUMP:
if (old_addr && new_addr) {
prog = old_insn;
ret = emit_patch_fn(&prog, old_addr, ip);
if (ret)
return ret;
prog = new_insn;
ret = emit_patch_fn(&prog, new_addr, ip);
if (ret)
return ret;
break;
}
return -ENXIO;
case BPF_MOD_CALL_TO_NOP:
case BPF_MOD_JUMP_TO_NOP:
if (old_addr && !new_addr) {
memcpy(new_insn, nop_insn, X86_PATCH_SIZE);
prog = old_insn;
ret = emit_patch_fn(&prog, old_addr, ip);
if (ret)
return ret;
break;
}
return -ENXIO;
default:
return -ENOTSUPP;
memcpy(new_insn, nop_insn, X86_PATCH_SIZE);
if (new_addr) {
prog = new_insn;
ret = t == BPF_MOD_CALL ?
emit_call(&prog, new_addr, ip) :
emit_jump(&prog, new_addr, ip);
if (ret)
return ret;
}
ret = -EBUSY;
mutex_lock(&text_mutex);
if (memcmp(ip, old_insn, X86_PATCH_SIZE))
goto out;
if (text_live)
text_poke_bp(ip, new_insn, X86_PATCH_SIZE, NULL);
else
memcpy(ip, new_insn, X86_PATCH_SIZE);
if (memcmp(ip, new_insn, X86_PATCH_SIZE)) {
if (text_live)
text_poke_bp(ip, new_insn, X86_PATCH_SIZE, NULL);
else
memcpy(ip, new_insn, X86_PATCH_SIZE);
}
ret = 0;
out:
mutex_unlock(&text_mutex);
@@ -465,7 +431,6 @@ static void emit_bpf_tail_call_direct(struct bpf_jit_poke_descriptor *poke,
static void bpf_tail_call_direct_fixup(struct bpf_prog *prog)
{
static const enum bpf_text_poke_type type = BPF_MOD_NOP_TO_JUMP;
struct bpf_jit_poke_descriptor *poke;
struct bpf_array *array;
struct bpf_prog *target;
@@ -490,7 +455,7 @@ static void bpf_tail_call_direct_fixup(struct bpf_prog *prog)
* read-only. Both modifications on the given image
* are under text_mutex to avoid interference.
*/
ret = __bpf_arch_text_poke(poke->ip, type, NULL,
ret = __bpf_arch_text_poke(poke->ip, BPF_MOD_JUMP, NULL,
(u8 *)target->bpf_func +
poke->adj_off, false);
BUG_ON(ret < 0);