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author
Alexei Starovoitov
committed
Merge branch 'bpf-reduce-verifier-stack-frame-size'
Yonghong Song says: ==================== bpf: Reduce verifier stack frame size Arnd Bergmann reported an issue ([1]) where clang compiler (less than llvm18) may trigger an error where the stack frame size exceeds the limit. I can reproduce the error like below: kernel/bpf/verifier.c:24491:5: error: stack frame size (2552) exceeds limit (1280) in 'bpf_check' [-Werror,-Wframe-larger-than] kernel/bpf/verifier.c:19921:12: error: stack frame size (1368) exceeds limit (1280) in 'do_check' [-Werror,-Wframe-larger-than] This patch series fixed the above two errors by reducing stack size. See each individual patches for details. [1] https://lore.kernel.org/bpf/[email protected]/ Changelogs: v2 -> v3: - v2: https://lore.kernel.org/bpf/[email protected]/ - Rename env->callchain to env->callchain_buf so it is clear that - env->callchain_buf is used for a temp buf. v1 -> v2: - v1: https://lore.kernel.org/bpf/[email protected]/ - Simplify assignment to struct bpf_insn pointer in do_misc_fixups(). - Restore original implementation in opt_hard_wire_dead_code_branches() as only one insn on the stack. - Avoid unnecessary insns for 64bit modulo (mod 0/-1) operations. ==================== Link: https://patch.msgid.link/[email protected] Signed-off-by: Alexei Starovoitov <[email protected]>
2 parents 0325472 + 82bc4ab commit 03fe01d

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-118
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2 files changed

+113
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lines changed

‎include/linux/bpf_verifier.h

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -841,6 +841,7 @@ struct bpf_verifier_env {
841841
char tmp_str_buf[TMP_STR_BUF_LEN];
842842
struct bpf_insn insn_buf[INSN_BUF_SIZE];
843843
struct bpf_insn epilogue_buf[INSN_BUF_SIZE];
844+
struct bpf_scc_callchain callchain_buf;
844845
/* array of pointers to bpf_scc_info indexed by SCC id */
845846
struct bpf_scc_info **scc_info;
846847
u32 scc_cnt;

‎kernel/bpf/verifier.c

Lines changed: 112 additions & 118 deletions
Original file line numberDiff line numberDiff line change
@@ -1914,19 +1914,19 @@ static char *format_callchain(struct bpf_verifier_env *env, struct bpf_scc_callc
19141914
*/
19151915
static int maybe_enter_scc(struct bpf_verifier_env *env, struct bpf_verifier_state *st)
19161916
{
1917-
struct bpf_scc_callchain callchain;
1917+
struct bpf_scc_callchain *callchain = &env->callchain_buf;
19181918
struct bpf_scc_visit *visit;
19191919

1920-
if (!compute_scc_callchain(env, st, &callchain))
1920+
if (!compute_scc_callchain(env, st, callchain))
19211921
return 0;
1922-
visit = scc_visit_lookup(env, &callchain);
1923-
visit = visit ?: scc_visit_alloc(env, &callchain);
1922+
visit = scc_visit_lookup(env, callchain);
1923+
visit = visit ?: scc_visit_alloc(env, callchain);
19241924
if (!visit)
19251925
return -ENOMEM;
19261926
if (!visit->entry_state) {
19271927
visit->entry_state = st;
19281928
if (env->log.level & BPF_LOG_LEVEL2)
1929-
verbose(env, "SCC enter %s\n", format_callchain(env, &callchain));
1929+
verbose(env, "SCC enter %s\n", format_callchain(env, callchain));
19301930
}
19311931
return 0;
19321932
}
@@ -1939,21 +1939,21 @@ static int propagate_backedges(struct bpf_verifier_env *env, struct bpf_scc_visi
19391939
*/
19401940
static int maybe_exit_scc(struct bpf_verifier_env *env, struct bpf_verifier_state *st)
19411941
{
1942-
struct bpf_scc_callchain callchain;
1942+
struct bpf_scc_callchain *callchain = &env->callchain_buf;
19431943
struct bpf_scc_visit *visit;
19441944

1945-
if (!compute_scc_callchain(env, st, &callchain))
1945+
if (!compute_scc_callchain(env, st, callchain))
19461946
return 0;
1947-
visit = scc_visit_lookup(env, &callchain);
1947+
visit = scc_visit_lookup(env, callchain);
19481948
if (!visit) {
19491949
verifier_bug(env, "scc exit: no visit info for call chain %s",
1950-
format_callchain(env, &callchain));
1950+
format_callchain(env, callchain));
19511951
return -EFAULT;
19521952
}
19531953
if (visit->entry_state != st)
19541954
return 0;
19551955
if (env->log.level & BPF_LOG_LEVEL2)
1956-
verbose(env, "SCC exit %s\n", format_callchain(env, &callchain));
1956+
verbose(env, "SCC exit %s\n", format_callchain(env, callchain));
19571957
visit->entry_state = NULL;
19581958
env->num_backedges -= visit->num_backedges;
19591959
visit->num_backedges = 0;
@@ -1968,22 +1968,22 @@ static int add_scc_backedge(struct bpf_verifier_env *env,
19681968
struct bpf_verifier_state *st,
19691969
struct bpf_scc_backedge *backedge)
19701970
{
1971-
struct bpf_scc_callchain callchain;
1971+
struct bpf_scc_callchain *callchain = &env->callchain_buf;
19721972
struct bpf_scc_visit *visit;
19731973

1974-
if (!compute_scc_callchain(env, st, &callchain)) {
1974+
if (!compute_scc_callchain(env, st, callchain)) {
19751975
verifier_bug(env, "add backedge: no SCC in verification path, insn_idx %d",
19761976
st->insn_idx);
19771977
return -EFAULT;
19781978
}
1979-
visit = scc_visit_lookup(env, &callchain);
1979+
visit = scc_visit_lookup(env, callchain);
19801980
if (!visit) {
19811981
verifier_bug(env, "add backedge: no visit info for call chain %s",
1982-
format_callchain(env, &callchain));
1982+
format_callchain(env, callchain));
19831983
return -EFAULT;
19841984
}
19851985
if (env->log.level & BPF_LOG_LEVEL2)
1986-
verbose(env, "SCC backedge %s\n", format_callchain(env, &callchain));
1986+
verbose(env, "SCC backedge %s\n", format_callchain(env, callchain));
19871987
backedge->next = visit->backedges;
19881988
visit->backedges = backedge;
19891989
visit->num_backedges++;
@@ -1999,12 +1999,12 @@ static int add_scc_backedge(struct bpf_verifier_env *env,
19991999
static bool incomplete_read_marks(struct bpf_verifier_env *env,
20002000
struct bpf_verifier_state *st)
20012001
{
2002-
struct bpf_scc_callchain callchain;
2002+
struct bpf_scc_callchain *callchain = &env->callchain_buf;
20032003
struct bpf_scc_visit *visit;
20042004

2005-
if (!compute_scc_callchain(env, st, &callchain))
2005+
if (!compute_scc_callchain(env, st, callchain))
20062006
return false;
2007-
visit = scc_visit_lookup(env, &callchain);
2007+
visit = scc_visit_lookup(env, callchain);
20082008
if (!visit)
20092009
return false;
20102010
return !!visit->backedges;
@@ -21011,7 +21011,10 @@ static int opt_remove_nops(struct bpf_verifier_env *env)
2101121011
static int opt_subreg_zext_lo32_rnd_hi32(struct bpf_verifier_env *env,
2101221012
const union bpf_attr *attr)
2101321013
{
21014-
struct bpf_insn *patch, zext_patch[2], rnd_hi32_patch[4];
21014+
struct bpf_insn *patch;
21015+
/* use env->insn_buf as two independent buffers */
21016+
struct bpf_insn *zext_patch = env->insn_buf;
21017+
struct bpf_insn *rnd_hi32_patch = &env->insn_buf[2];
2101521018
struct bpf_insn_aux_data *aux = env->insn_aux_data;
2101621019
int i, patch_len, delta = 0, len = env->prog->len;
2101721020
struct bpf_insn *insns = env->prog->insnsi;
@@ -21189,13 +21192,12 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env)
2118921192

2119021193
if (env->insn_aux_data[i + delta].nospec) {
2119121194
WARN_ON_ONCE(env->insn_aux_data[i + delta].alu_state);
21192-
struct bpf_insn patch[] = {
21193-
BPF_ST_NOSPEC(),
21194-
*insn,
21195-
};
21195+
struct bpf_insn *patch = insn_buf;
2119621196

21197-
cnt = ARRAY_SIZE(patch);
21198-
new_prog = bpf_patch_insn_data(env, i + delta, patch, cnt);
21197+
*patch++ = BPF_ST_NOSPEC();
21198+
*patch++ = *insn;
21199+
cnt = patch - insn_buf;
21200+
new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt);
2119921201
if (!new_prog)
2120021202
return -ENOMEM;
2120121203

@@ -21263,13 +21265,12 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env)
2126321265
/* nospec_result is only used to mitigate Spectre v4 and
2126421266
* to limit verification-time for Spectre v1.
2126521267
*/
21266-
struct bpf_insn patch[] = {
21267-
*insn,
21268-
BPF_ST_NOSPEC(),
21269-
};
21268+
struct bpf_insn *patch = insn_buf;
2127021269

21271-
cnt = ARRAY_SIZE(patch);
21272-
new_prog = bpf_patch_insn_data(env, i + delta, patch, cnt);
21270+
*patch++ = *insn;
21271+
*patch++ = BPF_ST_NOSPEC();
21272+
cnt = patch - insn_buf;
21273+
new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt);
2127321274
if (!new_prog)
2127421275
return -ENOMEM;
2127521276

@@ -21939,13 +21940,12 @@ static int do_misc_fixups(struct bpf_verifier_env *env)
2193921940
u16 stack_depth_extra = 0;
2194021941

2194121942
if (env->seen_exception && !env->exception_callback_subprog) {
21942-
struct bpf_insn patch[] = {
21943-
env->prog->insnsi[insn_cnt - 1],
21944-
BPF_MOV64_REG(BPF_REG_0, BPF_REG_1),
21945-
BPF_EXIT_INSN(),
21946-
};
21943+
struct bpf_insn *patch = insn_buf;
2194721944

21948-
ret = add_hidden_subprog(env, patch, ARRAY_SIZE(patch));
21945+
*patch++ = env->prog->insnsi[insn_cnt - 1];
21946+
*patch++ = BPF_MOV64_REG(BPF_REG_0, BPF_REG_1);
21947+
*patch++ = BPF_EXIT_INSN();
21948+
ret = add_hidden_subprog(env, insn_buf, patch - insn_buf);
2194921949
if (ret < 0)
2195021950
return ret;
2195121951
prog = env->prog;
@@ -21981,20 +21981,18 @@ static int do_misc_fixups(struct bpf_verifier_env *env)
2198121981
insn->off == 1 && insn->imm == -1) {
2198221982
bool is64 = BPF_CLASS(insn->code) == BPF_ALU64;
2198321983
bool isdiv = BPF_OP(insn->code) == BPF_DIV;
21984-
struct bpf_insn *patchlet;
21985-
struct bpf_insn chk_and_sdiv[] = {
21986-
BPF_RAW_INSN((is64 ? BPF_ALU64 : BPF_ALU) |
21987-
BPF_NEG | BPF_K, insn->dst_reg,
21988-
0, 0, 0),
21989-
};
21990-
struct bpf_insn chk_and_smod[] = {
21991-
BPF_MOV32_IMM(insn->dst_reg, 0),
21992-
};
21984+
struct bpf_insn *patch = insn_buf;
21985+
21986+
if (isdiv)
21987+
*patch++ = BPF_RAW_INSN((is64 ? BPF_ALU64 : BPF_ALU) |
21988+
BPF_NEG | BPF_K, insn->dst_reg,
21989+
0, 0, 0);
21990+
else
21991+
*patch++ = BPF_MOV32_IMM(insn->dst_reg, 0);
2199321992

21994-
patchlet = isdiv ? chk_and_sdiv : chk_and_smod;
21995-
cnt = isdiv ? ARRAY_SIZE(chk_and_sdiv) : ARRAY_SIZE(chk_and_smod);
21993+
cnt = patch - insn_buf;
2199621994

21997-
new_prog = bpf_patch_insn_data(env, i + delta, patchlet, cnt);
21995+
new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt);
2199821996
if (!new_prog)
2199921997
return -ENOMEM;
2200021998

@@ -22013,83 +22011,79 @@ static int do_misc_fixups(struct bpf_verifier_env *env)
2201322011
bool isdiv = BPF_OP(insn->code) == BPF_DIV;
2201422012
bool is_sdiv = isdiv && insn->off == 1;
2201522013
bool is_smod = !isdiv && insn->off == 1;
22016-
struct bpf_insn *patchlet;
22017-
struct bpf_insn chk_and_div[] = {
22018-
/* [R,W]x div 0 -> 0 */
22019-
BPF_RAW_INSN((is64 ? BPF_JMP : BPF_JMP32) |
22020-
BPF_JNE | BPF_K, insn->src_reg,
22021-
0, 2, 0),
22022-
BPF_ALU32_REG(BPF_XOR, insn->dst_reg, insn->dst_reg),
22023-
BPF_JMP_IMM(BPF_JA, 0, 0, 1),
22024-
*insn,
22025-
};
22026-
struct bpf_insn chk_and_mod[] = {
22027-
/* [R,W]x mod 0 -> [R,W]x */
22028-
BPF_RAW_INSN((is64 ? BPF_JMP : BPF_JMP32) |
22029-
BPF_JEQ | BPF_K, insn->src_reg,
22030-
0, 1 + (is64 ? 0 : 1), 0),
22031-
*insn,
22032-
BPF_JMP_IMM(BPF_JA, 0, 0, 1),
22033-
BPF_MOV32_REG(insn->dst_reg, insn->dst_reg),
22034-
};
22035-
struct bpf_insn chk_and_sdiv[] = {
22014+
struct bpf_insn *patch = insn_buf;
22015+
22016+
if (is_sdiv) {
2203622017
/* [R,W]x sdiv 0 -> 0
2203722018
* LLONG_MIN sdiv -1 -> LLONG_MIN
2203822019
* INT_MIN sdiv -1 -> INT_MIN
2203922020
*/
22040-
BPF_MOV64_REG(BPF_REG_AX, insn->src_reg),
22041-
BPF_RAW_INSN((is64 ? BPF_ALU64 : BPF_ALU) |
22042-
BPF_ADD | BPF_K, BPF_REG_AX,
22043-
0, 0, 1),
22044-
BPF_RAW_INSN((is64 ? BPF_JMP : BPF_JMP32) |
22045-
BPF_JGT | BPF_K, BPF_REG_AX,
22046-
0, 4, 1),
22047-
BPF_RAW_INSN((is64 ? BPF_JMP : BPF_JMP32) |
22048-
BPF_JEQ | BPF_K, BPF_REG_AX,
22049-
0, 1, 0),
22050-
BPF_RAW_INSN((is64 ? BPF_ALU64 : BPF_ALU) |
22051-
BPF_MOV | BPF_K, insn->dst_reg,
22052-
0, 0, 0),
22021+
*patch++ = BPF_MOV64_REG(BPF_REG_AX, insn->src_reg);
22022+
*patch++ = BPF_RAW_INSN((is64 ? BPF_ALU64 : BPF_ALU) |
22023+
BPF_ADD | BPF_K, BPF_REG_AX,
22024+
0, 0, 1);
22025+
*patch++ = BPF_RAW_INSN((is64 ? BPF_JMP : BPF_JMP32) |
22026+
BPF_JGT | BPF_K, BPF_REG_AX,
22027+
0, 4, 1);
22028+
*patch++ = BPF_RAW_INSN((is64 ? BPF_JMP : BPF_JMP32) |
22029+
BPF_JEQ | BPF_K, BPF_REG_AX,
22030+
0, 1, 0);
22031+
*patch++ = BPF_RAW_INSN((is64 ? BPF_ALU64 : BPF_ALU) |
22032+
BPF_MOV | BPF_K, insn->dst_reg,
22033+
0, 0, 0);
2205322034
/* BPF_NEG(LLONG_MIN) == -LLONG_MIN == LLONG_MIN */
22054-
BPF_RAW_INSN((is64 ? BPF_ALU64 : BPF_ALU) |
22055-
BPF_NEG | BPF_K, insn->dst_reg,
22056-
0, 0, 0),
22057-
BPF_JMP_IMM(BPF_JA, 0, 0, 1),
22058-
*insn,
22059-
};
22060-
struct bpf_insn chk_and_smod[] = {
22035+
*patch++ = BPF_RAW_INSN((is64 ? BPF_ALU64 : BPF_ALU) |
22036+
BPF_NEG | BPF_K, insn->dst_reg,
22037+
0, 0, 0);
22038+
*patch++ = BPF_JMP_IMM(BPF_JA, 0, 0, 1);
22039+
*patch++ = *insn;
22040+
cnt = patch - insn_buf;
22041+
} else if (is_smod) {
2206122042
/* [R,W]x mod 0 -> [R,W]x */
2206222043
/* [R,W]x mod -1 -> 0 */
22063-
BPF_MOV64_REG(BPF_REG_AX, insn->src_reg),
22064-
BPF_RAW_INSN((is64 ? BPF_ALU64 : BPF_ALU) |
22065-
BPF_ADD | BPF_K, BPF_REG_AX,
22066-
0, 0, 1),
22067-
BPF_RAW_INSN((is64 ? BPF_JMP : BPF_JMP32) |
22068-
BPF_JGT | BPF_K, BPF_REG_AX,
22069-
0, 3, 1),
22070-
BPF_RAW_INSN((is64 ? BPF_JMP : BPF_JMP32) |
22071-
BPF_JEQ | BPF_K, BPF_REG_AX,
22072-
0, 3 + (is64 ? 0 : 1), 1),
22073-
BPF_MOV32_IMM(insn->dst_reg, 0),
22074-
BPF_JMP_IMM(BPF_JA, 0, 0, 1),
22075-
*insn,
22076-
BPF_JMP_IMM(BPF_JA, 0, 0, 1),
22077-
BPF_MOV32_REG(insn->dst_reg, insn->dst_reg),
22078-
};
22079-
22080-
if (is_sdiv) {
22081-
patchlet = chk_and_sdiv;
22082-
cnt = ARRAY_SIZE(chk_and_sdiv);
22083-
} else if (is_smod) {
22084-
patchlet = chk_and_smod;
22085-
cnt = ARRAY_SIZE(chk_and_smod) - (is64 ? 2 : 0);
22044+
*patch++ = BPF_MOV64_REG(BPF_REG_AX, insn->src_reg);
22045+
*patch++ = BPF_RAW_INSN((is64 ? BPF_ALU64 : BPF_ALU) |
22046+
BPF_ADD | BPF_K, BPF_REG_AX,
22047+
0, 0, 1);
22048+
*patch++ = BPF_RAW_INSN((is64 ? BPF_JMP : BPF_JMP32) |
22049+
BPF_JGT | BPF_K, BPF_REG_AX,
22050+
0, 3, 1);
22051+
*patch++ = BPF_RAW_INSN((is64 ? BPF_JMP : BPF_JMP32) |
22052+
BPF_JEQ | BPF_K, BPF_REG_AX,
22053+
0, 3 + (is64 ? 0 : 1), 1);
22054+
*patch++ = BPF_MOV32_IMM(insn->dst_reg, 0);
22055+
*patch++ = BPF_JMP_IMM(BPF_JA, 0, 0, 1);
22056+
*patch++ = *insn;
22057+
22058+
if (!is64) {
22059+
*patch++ = BPF_JMP_IMM(BPF_JA, 0, 0, 1);
22060+
*patch++ = BPF_MOV32_REG(insn->dst_reg, insn->dst_reg);
22061+
}
22062+
cnt = patch - insn_buf;
22063+
} else if (isdiv) {
22064+
/* [R,W]x div 0 -> 0 */
22065+
*patch++ = BPF_RAW_INSN((is64 ? BPF_JMP : BPF_JMP32) |
22066+
BPF_JNE | BPF_K, insn->src_reg,
22067+
0, 2, 0);
22068+
*patch++ = BPF_ALU32_REG(BPF_XOR, insn->dst_reg, insn->dst_reg);
22069+
*patch++ = BPF_JMP_IMM(BPF_JA, 0, 0, 1);
22070+
*patch++ = *insn;
22071+
cnt = patch - insn_buf;
2208622072
} else {
22087-
patchlet = isdiv ? chk_and_div : chk_and_mod;
22088-
cnt = isdiv ? ARRAY_SIZE(chk_and_div) :
22089-
ARRAY_SIZE(chk_and_mod) - (is64 ? 2 : 0);
22073+
/* [R,W]x mod 0 -> [R,W]x */
22074+
*patch++ = BPF_RAW_INSN((is64 ? BPF_JMP : BPF_JMP32) |
22075+
BPF_JEQ | BPF_K, insn->src_reg,
22076+
0, 1 + (is64 ? 0 : 1), 0);
22077+
*patch++ = *insn;
22078+
22079+
if (!is64) {
22080+
*patch++ = BPF_JMP_IMM(BPF_JA, 0, 0, 1);
22081+
*patch++ = BPF_MOV32_REG(insn->dst_reg, insn->dst_reg);
22082+
}
22083+
cnt = patch - insn_buf;
2209022084
}
2209122085

22092-
new_prog = bpf_patch_insn_data(env, i + delta, patchlet, cnt);
22086+
new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt);
2209322087
if (!new_prog)
2209422088
return -ENOMEM;
2209522089

@@ -22103,7 +22097,7 @@ static int do_misc_fixups(struct bpf_verifier_env *env)
2210322097
if (BPF_CLASS(insn->code) == BPF_LDX &&
2210422098
(BPF_MODE(insn->code) == BPF_PROBE_MEM ||
2210522099
BPF_MODE(insn->code) == BPF_PROBE_MEMSX)) {
22106-
struct bpf_insn *patch = &insn_buf[0];
22100+
struct bpf_insn *patch = insn_buf;
2210722101
u64 uaddress_limit = bpf_arch_uaddress_limit();
2210822102

2210922103
if (!uaddress_limit)
@@ -22154,7 +22148,7 @@ static int do_misc_fixups(struct bpf_verifier_env *env)
2215422148
insn->code == (BPF_ALU64 | BPF_SUB | BPF_X)) {
2215522149
const u8 code_add = BPF_ALU64 | BPF_ADD | BPF_X;
2215622150
const u8 code_sub = BPF_ALU64 | BPF_SUB | BPF_X;
22157-
struct bpf_insn *patch = &insn_buf[0];
22151+
struct bpf_insn *patch = insn_buf;
2215822152
bool issrc, isneg, isimm;
2215922153
u32 off_reg;
2216022154

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