kernel/bpf/verifier.c:3959:12: warning: stack frame size (1152) exceeds limit (1024) in '__mark_chain_precision'

From: kernel test robot
Date: Sat Jul 22 2023 - 06:17:26 EST

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Hi Eduard,

FYI, the error/warning still remains.

tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head: d192f5382581d972c4ae1b4d72e0b59b34cadeb9
commit: 904e6ddf4133c52fdb9654c2cd2ad90f320d48b9 bpf: Use scalar ids in mark_chain_precision()
date: 6 weeks ago
config: riscv-randconfig-r022-20230722 (https://download.01.org/0day-ci/archive/20230722/202307221821.As1rdRHs-lkp@xxxxxxxxx/config)
compiler: clang version 14.0.6 (https://github.com/llvm/llvm-project.git f28c006a5895fc0e329fe15fead81e37457cb1d1)
reproduce: (https://download.01.org/0day-ci/archive/20230722/202307221821.As1rdRHs-lkp@xxxxxxxxx/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@xxxxxxxxx>
| Closes: https://lore.kernel.org/oe-kbuild-all/202307221821.As1rdRHs-lkp@xxxxxxxxx/

All warnings (new ones prefixed by >>):

In file included from include/linux/io.h:13:
In file included from arch/riscv/include/asm/io.h:136:
include/asm-generic/io.h:751:2: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
insw(addr, buffer, count);
^~~~~~~~~~~~~~~~~~~~~~~~~
arch/riscv/include/asm/io.h:105:53: note: expanded from macro 'insw'
#define insw(addr, buffer, count) __insw(PCI_IOBASE + (addr), buffer, count)
~~~~~~~~~~ ^
In file included from kernel/bpf/verifier.c:7:
In file included from include/linux/bpf-cgroup.h:5:
In file included from include/linux/bpf.h:31:
In file included from include/linux/memcontrol.h:13:
In file included from include/linux/cgroup.h:26:
In file included from include/linux/kernel_stat.h:9:
In file included from include/linux/interrupt.h:11:
In file included from include/linux/hardirq.h:11:
In file included from ./arch/riscv/include/generated/asm/hardirq.h:1:
In file included from include/asm-generic/hardirq.h:17:
In file included from include/linux/irq.h:20:
In file included from include/linux/io.h:13:
In file included from arch/riscv/include/asm/io.h:136:
include/asm-generic/io.h:759:2: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
insl(addr, buffer, count);
^~~~~~~~~~~~~~~~~~~~~~~~~
arch/riscv/include/asm/io.h:106:53: note: expanded from macro 'insl'
#define insl(addr, buffer, count) __insl(PCI_IOBASE + (addr), buffer, count)
~~~~~~~~~~ ^
In file included from kernel/bpf/verifier.c:7:
In file included from include/linux/bpf-cgroup.h:5:
In file included from include/linux/bpf.h:31:
In file included from include/linux/memcontrol.h:13:
In file included from include/linux/cgroup.h:26:
In file included from include/linux/kernel_stat.h:9:
In file included from include/linux/interrupt.h:11:
In file included from include/linux/hardirq.h:11:
In file included from ./arch/riscv/include/generated/asm/hardirq.h:1:
In file included from include/asm-generic/hardirq.h:17:
In file included from include/linux/irq.h:20:
In file included from include/linux/io.h:13:
In file included from arch/riscv/include/asm/io.h:136:
include/asm-generic/io.h:768:2: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
outsb(addr, buffer, count);
^~~~~~~~~~~~~~~~~~~~~~~~~~
arch/riscv/include/asm/io.h:118:55: note: expanded from macro 'outsb'
#define outsb(addr, buffer, count) __outsb(PCI_IOBASE + (addr), buffer, count)
~~~~~~~~~~ ^
In file included from kernel/bpf/verifier.c:7:
In file included from include/linux/bpf-cgroup.h:5:
In file included from include/linux/bpf.h:31:
In file included from include/linux/memcontrol.h:13:
In file included from include/linux/cgroup.h:26:
In file included from include/linux/kernel_stat.h:9:
In file included from include/linux/interrupt.h:11:
In file included from include/linux/hardirq.h:11:
In file included from ./arch/riscv/include/generated/asm/hardirq.h:1:
In file included from include/asm-generic/hardirq.h:17:
In file included from include/linux/irq.h:20:
In file included from include/linux/io.h:13:
In file included from arch/riscv/include/asm/io.h:136:
include/asm-generic/io.h:777:2: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
outsw(addr, buffer, count);
^~~~~~~~~~~~~~~~~~~~~~~~~~
arch/riscv/include/asm/io.h:119:55: note: expanded from macro 'outsw'
#define outsw(addr, buffer, count) __outsw(PCI_IOBASE + (addr), buffer, count)
~~~~~~~~~~ ^
In file included from kernel/bpf/verifier.c:7:
In file included from include/linux/bpf-cgroup.h:5:
In file included from include/linux/bpf.h:31:
In file included from include/linux/memcontrol.h:13:
In file included from include/linux/cgroup.h:26:
In file included from include/linux/kernel_stat.h:9:
In file included from include/linux/interrupt.h:11:
In file included from include/linux/hardirq.h:11:
In file included from ./arch/riscv/include/generated/asm/hardirq.h:1:
In file included from include/asm-generic/hardirq.h:17:
In file included from include/linux/irq.h:20:
In file included from include/linux/io.h:13:
In file included from arch/riscv/include/asm/io.h:136:
include/asm-generic/io.h:786:2: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
outsl(addr, buffer, count);
^~~~~~~~~~~~~~~~~~~~~~~~~~
arch/riscv/include/asm/io.h:120:55: note: expanded from macro 'outsl'
#define outsl(addr, buffer, count) __outsl(PCI_IOBASE + (addr), buffer, count)
~~~~~~~~~~ ^
In file included from kernel/bpf/verifier.c:7:
In file included from include/linux/bpf-cgroup.h:5:
In file included from include/linux/bpf.h:31:
In file included from include/linux/memcontrol.h:13:
In file included from include/linux/cgroup.h:26:
In file included from include/linux/kernel_stat.h:9:
In file included from include/linux/interrupt.h:11:
In file included from include/linux/hardirq.h:11:
In file included from ./arch/riscv/include/generated/asm/hardirq.h:1:
In file included from include/asm-generic/hardirq.h:17:
In file included from include/linux/irq.h:20:
In file included from include/linux/io.h:13:
In file included from arch/riscv/include/asm/io.h:136:
include/asm-generic/io.h:1134:55: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
return (port > MMIO_UPPER_LIMIT) ? NULL : PCI_IOBASE + port;
~~~~~~~~~~ ^
>> kernel/bpf/verifier.c:3959:12: warning: stack frame size (1152) exceeds limit (1024) in '__mark_chain_precision' [-Wframe-larger-than]
static int __mark_chain_precision(struct bpf_verifier_env *env, int regno)
^
kernel/bpf/verifier.c:17989:12: warning: stack frame size (1328) exceeds limit (1024) in 'do_misc_fixups' [-Wframe-larger-than]
static int do_misc_fixups(struct bpf_verifier_env *env)
^
kernel/bpf/verifier.c:16126:12: warning: stack frame size (1776) exceeds limit (1024) in 'do_check' [-Wframe-larger-than]
static int do_check(struct bpf_verifier_env *env)
^
kernel/bpf/verifier.c:10638:12: warning: stack frame size (2080) exceeds limit (1024) in 'check_kfunc_args' [-Wframe-larger-than]
static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_arg_meta *meta,
^
error: A dwo section may not contain relocations
error: A dwo section may not contain relocations
error: A dwo section may not contain relocations
error: A dwo section may not contain relocations
error: A dwo section may not contain relocations
error: A dwo section may not contain relocations
error: A dwo section may not contain relocations
error: A dwo section may not contain relocations
error: A dwo section may not contain relocations
error: A dwo section may not contain relocations
error: A dwo section may not contain relocations
error: A dwo section may not contain relocations
error: A dwo section may not contain relocations
error: A dwo section may not contain relocations
error: A dwo section may not contain relocations
error: A dwo section may not contain relocations
error: A dwo section may not contain relocations
error: A dwo section may not contain relocations
error: A dwo section may not contain relocations
fatal error: too many errors emitted, stopping now [-ferror-limit=]
17 warnings and 20 errors generated.

vim +/__mark_chain_precision +3959 kernel/bpf/verifier.c

904e6ddf4133c5 Eduard Zingerman 2023-06-13 3871
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3872 /*
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3873 * __mark_chain_precision() backtracks BPF program instruction sequence and
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3874 * chain of verifier states making sure that register *regno* (if regno >= 0)
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3875 * and/or stack slot *spi* (if spi >= 0) are marked as precisely tracked
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3876 * SCALARS, as well as any other registers and slots that contribute to
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3877 * a tracked state of given registers/stack slots, depending on specific BPF
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3878 * assembly instructions (see backtrack_insns() for exact instruction handling
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3879 * logic). This backtracking relies on recorded jmp_history and is able to
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3880 * traverse entire chain of parent states. This process ends only when all the
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3881 * necessary registers/slots and their transitive dependencies are marked as
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3882 * precise.
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3883 *
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3884 * One important and subtle aspect is that precise marks *do not matter* in
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3885 * the currently verified state (current state). It is important to understand
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3886 * why this is the case.
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3887 *
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3888 * First, note that current state is the state that is not yet "checkpointed",
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3889 * i.e., it is not yet put into env->explored_states, and it has no children
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3890 * states as well. It's ephemeral, and can end up either a) being discarded if
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3891 * compatible explored state is found at some point or BPF_EXIT instruction is
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3892 * reached or b) checkpointed and put into env->explored_states, branching out
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3893 * into one or more children states.
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3894 *
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3895 * In the former case, precise markings in current state are completely
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3896 * ignored by state comparison code (see regsafe() for details). Only
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3897 * checkpointed ("old") state precise markings are important, and if old
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3898 * state's register/slot is precise, regsafe() assumes current state's
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3899 * register/slot as precise and checks value ranges exactly and precisely. If
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3900 * states turn out to be compatible, current state's necessary precise
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3901 * markings and any required parent states' precise markings are enforced
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3902 * after the fact with propagate_precision() logic, after the fact. But it's
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3903 * important to realize that in this case, even after marking current state
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3904 * registers/slots as precise, we immediately discard current state. So what
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3905 * actually matters is any of the precise markings propagated into current
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3906 * state's parent states, which are always checkpointed (due to b) case above).
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3907 * As such, for scenario a) it doesn't matter if current state has precise
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3908 * markings set or not.
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3909 *
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3910 * Now, for the scenario b), checkpointing and forking into child(ren)
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3911 * state(s). Note that before current state gets to checkpointing step, any
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3912 * processed instruction always assumes precise SCALAR register/slot
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3913 * knowledge: if precise value or range is useful to prune jump branch, BPF
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3914 * verifier takes this opportunity enthusiastically. Similarly, when
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3915 * register's value is used to calculate offset or memory address, exact
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3916 * knowledge of SCALAR range is assumed, checked, and enforced. So, similar to
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3917 * what we mentioned above about state comparison ignoring precise markings
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3918 * during state comparison, BPF verifier ignores and also assumes precise
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3919 * markings *at will* during instruction verification process. But as verifier
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3920 * assumes precision, it also propagates any precision dependencies across
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3921 * parent states, which are not yet finalized, so can be further restricted
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3922 * based on new knowledge gained from restrictions enforced by their children
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3923 * states. This is so that once those parent states are finalized, i.e., when
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3924 * they have no more active children state, state comparison logic in
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3925 * is_state_visited() would enforce strict and precise SCALAR ranges, if
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3926 * required for correctness.
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3927 *
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3928 * To build a bit more intuition, note also that once a state is checkpointed,
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3929 * the path we took to get to that state is not important. This is crucial
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3930 * property for state pruning. When state is checkpointed and finalized at
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3931 * some instruction index, it can be correctly and safely used to "short
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3932 * circuit" any *compatible* state that reaches exactly the same instruction
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3933 * index. I.e., if we jumped to that instruction from a completely different
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3934 * code path than original finalized state was derived from, it doesn't
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3935 * matter, current state can be discarded because from that instruction
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3936 * forward having a compatible state will ensure we will safely reach the
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3937 * exit. States describe preconditions for further exploration, but completely
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3938 * forget the history of how we got here.
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3939 *
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3940 * This also means that even if we needed precise SCALAR range to get to
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3941 * finalized state, but from that point forward *that same* SCALAR register is
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3942 * never used in a precise context (i.e., it's precise value is not needed for
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3943 * correctness), it's correct and safe to mark such register as "imprecise"
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3944 * (i.e., precise marking set to false). This is what we rely on when we do
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3945 * not set precise marking in current state. If no child state requires
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3946 * precision for any given SCALAR register, it's safe to dictate that it can
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3947 * be imprecise. If any child state does require this register to be precise,
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3948 * we'll mark it precise later retroactively during precise markings
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3949 * propagation from child state to parent states.
7a830b53c17bba Andrii Nakryiko 2022-11-04 3950 *
7a830b53c17bba Andrii Nakryiko 2022-11-04 3951 * Skipping precise marking setting in current state is a mild version of
7a830b53c17bba Andrii Nakryiko 2022-11-04 3952 * relying on the above observation. But we can utilize this property even
7a830b53c17bba Andrii Nakryiko 2022-11-04 3953 * more aggressively by proactively forgetting any precise marking in the
7a830b53c17bba Andrii Nakryiko 2022-11-04 3954 * current state (which we inherited from the parent state), right before we
7a830b53c17bba Andrii Nakryiko 2022-11-04 3955 * checkpoint it and branch off into new child state. This is done by
7a830b53c17bba Andrii Nakryiko 2022-11-04 3956 * mark_all_scalars_imprecise() to hopefully get more permissive and generic
7a830b53c17bba Andrii Nakryiko 2022-11-04 3957 * finalized states which help in short circuiting more future states.
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3958 */
f655badf2a8fc0 Andrii Nakryiko 2023-05-04 @3959 static int __mark_chain_precision(struct bpf_verifier_env *env, int regno)
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 3960 {
407958a0e980b9 Andrii Nakryiko 2023-05-04 3961 struct backtrack_state *bt = &env->bt;
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 3962 struct bpf_verifier_state *st = env->cur_state;
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 3963 int first_idx = st->first_insn_idx;
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 3964 int last_idx = env->insn_idx;
d84b1a6708eec0 Andrii Nakryiko 2023-05-15 3965 int subseq_idx = -1;
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 3966 struct bpf_func_state *func;
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 3967 struct bpf_reg_state *reg;
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 3968 bool skip_first = true;
d84b1a6708eec0 Andrii Nakryiko 2023-05-15 3969 int i, fr, err;
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 3970
2c78ee898d8f10 Alexei Starovoitov 2020-05-13 3971 if (!env->bpf_capable)
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 3972 return 0;
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 3973
407958a0e980b9 Andrii Nakryiko 2023-05-04 3974 /* set frame number from which we are starting to backtrack */
f655badf2a8fc0 Andrii Nakryiko 2023-05-04 3975 bt_init(bt, env->cur_state->curframe);
407958a0e980b9 Andrii Nakryiko 2023-05-04 3976
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3977 /* Do sanity checks against current state of register and/or stack
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3978 * slot, but don't set precise flag in current state, as precision
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3979 * tracking in the current state is unnecessary.
f63181b6ae79fd Andrii Nakryiko 2022-11-04 3980 */
f655badf2a8fc0 Andrii Nakryiko 2023-05-04 3981 func = st->frame[bt->frame];
a3ce685dd01a78 Alexei Starovoitov 2019-06-28 3982 if (regno >= 0) {
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 3983 reg = &func->regs[regno];
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 3984 if (reg->type != SCALAR_VALUE) {
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 3985 WARN_ONCE(1, "backtracing misuse");
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 3986 return -EFAULT;
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 3987 }
407958a0e980b9 Andrii Nakryiko 2023-05-04 3988 bt_set_reg(bt, regno);
a3ce685dd01a78 Alexei Starovoitov 2019-06-28 3989 }
a3ce685dd01a78 Alexei Starovoitov 2019-06-28 3990
407958a0e980b9 Andrii Nakryiko 2023-05-04 3991 if (bt_empty(bt))
a3ce685dd01a78 Alexei Starovoitov 2019-06-28 3992 return 0;
be2ef8161572ec Andrii Nakryiko 2022-11-04 3993
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 3994 for (;;) {
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 3995 DECLARE_BITMAP(mask, 64);
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 3996 u32 history = st->jmp_history_cnt;
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 3997
d9439c21a9e476 Andrii Nakryiko 2023-05-04 3998 if (env->log.level & BPF_LOG_LEVEL2) {
d84b1a6708eec0 Andrii Nakryiko 2023-05-15 3999 verbose(env, "mark_precise: frame%d: last_idx %d first_idx %d subseq_idx %d \n",
d84b1a6708eec0 Andrii Nakryiko 2023-05-15 4000 bt->frame, last_idx, first_idx, subseq_idx);
d9439c21a9e476 Andrii Nakryiko 2023-05-04 4001 }
be2ef8161572ec Andrii Nakryiko 2022-11-04 4002
904e6ddf4133c5 Eduard Zingerman 2023-06-13 4003 /* If some register with scalar ID is marked as precise,
904e6ddf4133c5 Eduard Zingerman 2023-06-13 4004 * make sure that all registers sharing this ID are also precise.
904e6ddf4133c5 Eduard Zingerman 2023-06-13 4005 * This is needed to estimate effect of find_equal_scalars().
904e6ddf4133c5 Eduard Zingerman 2023-06-13 4006 * Do this at the last instruction of each state,
904e6ddf4133c5 Eduard Zingerman 2023-06-13 4007 * bpf_reg_state::id fields are valid for these instructions.
904e6ddf4133c5 Eduard Zingerman 2023-06-13 4008 *
904e6ddf4133c5 Eduard Zingerman 2023-06-13 4009 * Allows to track precision in situation like below:
904e6ddf4133c5 Eduard Zingerman 2023-06-13 4010 *
904e6ddf4133c5 Eduard Zingerman 2023-06-13 4011 * r2 = unknown value
904e6ddf4133c5 Eduard Zingerman 2023-06-13 4012 * ...
904e6ddf4133c5 Eduard Zingerman 2023-06-13 4013 * --- state #0 ---
904e6ddf4133c5 Eduard Zingerman 2023-06-13 4014 * ...
904e6ddf4133c5 Eduard Zingerman 2023-06-13 4015 * r1 = r2 // r1 and r2 now share the same ID
904e6ddf4133c5 Eduard Zingerman 2023-06-13 4016 * ...
904e6ddf4133c5 Eduard Zingerman 2023-06-13 4017 * --- state #1 {r1.id = A, r2.id = A} ---
904e6ddf4133c5 Eduard Zingerman 2023-06-13 4018 * ...
904e6ddf4133c5 Eduard Zingerman 2023-06-13 4019 * if (r2 > 10) goto exit; // find_equal_scalars() assigns range to r1
904e6ddf4133c5 Eduard Zingerman 2023-06-13 4020 * ...
904e6ddf4133c5 Eduard Zingerman 2023-06-13 4021 * --- state #2 {r1.id = A, r2.id = A} ---
904e6ddf4133c5 Eduard Zingerman 2023-06-13 4022 * r3 = r10
904e6ddf4133c5 Eduard Zingerman 2023-06-13 4023 * r3 += r1 // need to mark both r1 and r2
904e6ddf4133c5 Eduard Zingerman 2023-06-13 4024 */
904e6ddf4133c5 Eduard Zingerman 2023-06-13 4025 if (mark_precise_scalar_ids(env, st))
904e6ddf4133c5 Eduard Zingerman 2023-06-13 4026 return -EFAULT;
904e6ddf4133c5 Eduard Zingerman 2023-06-13 4027
be2ef8161572ec Andrii Nakryiko 2022-11-04 4028 if (last_idx < 0) {
be2ef8161572ec Andrii Nakryiko 2022-11-04 4029 /* we are at the entry into subprog, which
be2ef8161572ec Andrii Nakryiko 2022-11-04 4030 * is expected for global funcs, but only if
be2ef8161572ec Andrii Nakryiko 2022-11-04 4031 * requested precise registers are R1-R5
be2ef8161572ec Andrii Nakryiko 2022-11-04 4032 * (which are global func's input arguments)
be2ef8161572ec Andrii Nakryiko 2022-11-04 4033 */
be2ef8161572ec Andrii Nakryiko 2022-11-04 4034 if (st->curframe == 0 &&
be2ef8161572ec Andrii Nakryiko 2022-11-04 4035 st->frame[0]->subprogno > 0 &&
be2ef8161572ec Andrii Nakryiko 2022-11-04 4036 st->frame[0]->callsite == BPF_MAIN_FUNC &&
407958a0e980b9 Andrii Nakryiko 2023-05-04 4037 bt_stack_mask(bt) == 0 &&
407958a0e980b9 Andrii Nakryiko 2023-05-04 4038 (bt_reg_mask(bt) & ~BPF_REGMASK_ARGS) == 0) {
407958a0e980b9 Andrii Nakryiko 2023-05-04 4039 bitmap_from_u64(mask, bt_reg_mask(bt));
be2ef8161572ec Andrii Nakryiko 2022-11-04 4040 for_each_set_bit(i, mask, 32) {
be2ef8161572ec Andrii Nakryiko 2022-11-04 4041 reg = &st->frame[0]->regs[i];
be2ef8161572ec Andrii Nakryiko 2022-11-04 4042 if (reg->type != SCALAR_VALUE) {
407958a0e980b9 Andrii Nakryiko 2023-05-04 4043 bt_clear_reg(bt, i);
be2ef8161572ec Andrii Nakryiko 2022-11-04 4044 continue;
be2ef8161572ec Andrii Nakryiko 2022-11-04 4045 }
be2ef8161572ec Andrii Nakryiko 2022-11-04 4046 reg->precise = true;
be2ef8161572ec Andrii Nakryiko 2022-11-04 4047 }
be2ef8161572ec Andrii Nakryiko 2022-11-04 4048 return 0;
be2ef8161572ec Andrii Nakryiko 2022-11-04 4049 }
be2ef8161572ec Andrii Nakryiko 2022-11-04 4050
407958a0e980b9 Andrii Nakryiko 2023-05-04 4051 verbose(env, "BUG backtracking func entry subprog %d reg_mask %x stack_mask %llx\n",
407958a0e980b9 Andrii Nakryiko 2023-05-04 4052 st->frame[0]->subprogno, bt_reg_mask(bt), bt_stack_mask(bt));
be2ef8161572ec Andrii Nakryiko 2022-11-04 4053 WARN_ONCE(1, "verifier backtracking bug");
be2ef8161572ec Andrii Nakryiko 2022-11-04 4054 return -EFAULT;
be2ef8161572ec Andrii Nakryiko 2022-11-04 4055 }
be2ef8161572ec Andrii Nakryiko 2022-11-04 4056
d84b1a6708eec0 Andrii Nakryiko 2023-05-15 4057 for (i = last_idx;;) {
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4058 if (skip_first) {
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4059 err = 0;
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4060 skip_first = false;
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4061 } else {
d84b1a6708eec0 Andrii Nakryiko 2023-05-15 4062 err = backtrack_insn(env, i, subseq_idx, bt);
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4063 }
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4064 if (err == -ENOTSUPP) {
c50c0b57a51582 Andrii Nakryiko 2023-05-04 4065 mark_all_scalars_precise(env, env->cur_state);
407958a0e980b9 Andrii Nakryiko 2023-05-04 4066 bt_reset(bt);
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4067 return 0;
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4068 } else if (err) {
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4069 return err;
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4070 }
407958a0e980b9 Andrii Nakryiko 2023-05-04 4071 if (bt_empty(bt))
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4072 /* Found assignment(s) into tracked register in this state.
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4073 * Since this state is already marked, just return.
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4074 * Nothing to be tracked further in the parent state.
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4075 */
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4076 return 0;
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4077 if (i == first_idx)
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4078 break;
d84b1a6708eec0 Andrii Nakryiko 2023-05-15 4079 subseq_idx = i;
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4080 i = get_prev_insn_idx(st, i, &history);
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4081 if (i >= env->prog->len) {
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4082 /* This can happen if backtracking reached insn 0
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4083 * and there are still reg_mask or stack_mask
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4084 * to backtrack.
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4085 * It means the backtracking missed the spot where
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4086 * particular register was initialized with a constant.
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4087 */
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4088 verbose(env, "BUG backtracking idx %d\n", i);
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4089 WARN_ONCE(1, "verifier backtracking bug");
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4090 return -EFAULT;
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4091 }
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4092 }
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4093 st = st->parent;
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4094 if (!st)
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4095 break;
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4096
1ef22b6865a73a Andrii Nakryiko 2023-05-04 4097 for (fr = bt->frame; fr >= 0; fr--) {
1ef22b6865a73a Andrii Nakryiko 2023-05-04 4098 func = st->frame[fr];
1ef22b6865a73a Andrii Nakryiko 2023-05-04 4099 bitmap_from_u64(mask, bt_frame_reg_mask(bt, fr));
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4100 for_each_set_bit(i, mask, 32) {
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4101 reg = &func->regs[i];
a3ce685dd01a78 Alexei Starovoitov 2019-06-28 4102 if (reg->type != SCALAR_VALUE) {
1ef22b6865a73a Andrii Nakryiko 2023-05-04 4103 bt_clear_frame_reg(bt, fr, i);
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4104 continue;
a3ce685dd01a78 Alexei Starovoitov 2019-06-28 4105 }
407958a0e980b9 Andrii Nakryiko 2023-05-04 4106 if (reg->precise)
1ef22b6865a73a Andrii Nakryiko 2023-05-04 4107 bt_clear_frame_reg(bt, fr, i);
407958a0e980b9 Andrii Nakryiko 2023-05-04 4108 else
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4109 reg->precise = true;
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4110 }
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4111
1ef22b6865a73a Andrii Nakryiko 2023-05-04 4112 bitmap_from_u64(mask, bt_frame_stack_mask(bt, fr));
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4113 for_each_set_bit(i, mask, 64) {
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4114 if (i >= func->allocated_stack / BPF_REG_SIZE) {
2339cd6cd0b540 Alexei Starovoitov 2019-09-03 4115 /* the sequence of instructions:
2339cd6cd0b540 Alexei Starovoitov 2019-09-03 4116 * 2: (bf) r3 = r10
2339cd6cd0b540 Alexei Starovoitov 2019-09-03 4117 * 3: (7b) *(u64 *)(r3 -8) = r0
2339cd6cd0b540 Alexei Starovoitov 2019-09-03 4118 * 4: (79) r4 = *(u64 *)(r10 -8)
2339cd6cd0b540 Alexei Starovoitov 2019-09-03 4119 * doesn't contain jmps. It's backtracked
2339cd6cd0b540 Alexei Starovoitov 2019-09-03 4120 * as a single block.
2339cd6cd0b540 Alexei Starovoitov 2019-09-03 4121 * During backtracking insn 3 is not recognized as
2339cd6cd0b540 Alexei Starovoitov 2019-09-03 4122 * stack access, so at the end of backtracking
2339cd6cd0b540 Alexei Starovoitov 2019-09-03 4123 * stack slot fp-8 is still marked in stack_mask.
2339cd6cd0b540 Alexei Starovoitov 2019-09-03 4124 * However the parent state may not have accessed
2339cd6cd0b540 Alexei Starovoitov 2019-09-03 4125 * fp-8 and it's "unallocated" stack space.
2339cd6cd0b540 Alexei Starovoitov 2019-09-03 4126 * In such case fallback to conservative.
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4127 */
c50c0b57a51582 Andrii Nakryiko 2023-05-04 4128 mark_all_scalars_precise(env, env->cur_state);
407958a0e980b9 Andrii Nakryiko 2023-05-04 4129 bt_reset(bt);
2339cd6cd0b540 Alexei Starovoitov 2019-09-03 4130 return 0;
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4131 }
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4132
407958a0e980b9 Andrii Nakryiko 2023-05-04 4133 if (!is_spilled_scalar_reg(&func->stack[i])) {
1ef22b6865a73a Andrii Nakryiko 2023-05-04 4134 bt_clear_frame_slot(bt, fr, i);
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4135 continue;
a3ce685dd01a78 Alexei Starovoitov 2019-06-28 4136 }
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4137 reg = &func->stack[i].spilled_ptr;
407958a0e980b9 Andrii Nakryiko 2023-05-04 4138 if (reg->precise)
1ef22b6865a73a Andrii Nakryiko 2023-05-04 4139 bt_clear_frame_slot(bt, fr, i);
407958a0e980b9 Andrii Nakryiko 2023-05-04 4140 else
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4141 reg->precise = true;
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4142 }
496f3324048b6c Christy Lee 2021-12-16 4143 if (env->log.level & BPF_LOG_LEVEL2) {
1ef22b6865a73a Andrii Nakryiko 2023-05-04 4144 fmt_reg_mask(env->tmp_str_buf, TMP_STR_BUF_LEN,
1ef22b6865a73a Andrii Nakryiko 2023-05-04 4145 bt_frame_reg_mask(bt, fr));
1ef22b6865a73a Andrii Nakryiko 2023-05-04 4146 verbose(env, "mark_precise: frame%d: parent state regs=%s ",
1ef22b6865a73a Andrii Nakryiko 2023-05-04 4147 fr, env->tmp_str_buf);
1ef22b6865a73a Andrii Nakryiko 2023-05-04 4148 fmt_stack_mask(env->tmp_str_buf, TMP_STR_BUF_LEN,
1ef22b6865a73a Andrii Nakryiko 2023-05-04 4149 bt_frame_stack_mask(bt, fr));
1ef22b6865a73a Andrii Nakryiko 2023-05-04 4150 verbose(env, "stack=%s: ", env->tmp_str_buf);
2e5766483c8c5c Christy Lee 2021-12-16 4151 print_verifier_state(env, func, true);
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4152 }
1ef22b6865a73a Andrii Nakryiko 2023-05-04 4153 }
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4154
407958a0e980b9 Andrii Nakryiko 2023-05-04 4155 if (bt_empty(bt))
c50c0b57a51582 Andrii Nakryiko 2023-05-04 4156 return 0;
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4157
d84b1a6708eec0 Andrii Nakryiko 2023-05-15 4158 subseq_idx = first_idx;
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4159 last_idx = st->last_insn_idx;
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4160 first_idx = st->first_insn_idx;
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4161 }
c50c0b57a51582 Andrii Nakryiko 2023-05-04 4162
c50c0b57a51582 Andrii Nakryiko 2023-05-04 4163 /* if we still have requested precise regs or slots, we missed
c50c0b57a51582 Andrii Nakryiko 2023-05-04 4164 * something (e.g., stack access through non-r10 register), so
c50c0b57a51582 Andrii Nakryiko 2023-05-04 4165 * fallback to marking all precise
c50c0b57a51582 Andrii Nakryiko 2023-05-04 4166 */
c50c0b57a51582 Andrii Nakryiko 2023-05-04 4167 if (!bt_empty(bt)) {
c50c0b57a51582 Andrii Nakryiko 2023-05-04 4168 mark_all_scalars_precise(env, env->cur_state);
c50c0b57a51582 Andrii Nakryiko 2023-05-04 4169 bt_reset(bt);
c50c0b57a51582 Andrii Nakryiko 2023-05-04 4170 }
c50c0b57a51582 Andrii Nakryiko 2023-05-04 4171
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4172 return 0;
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4173 }
b5dc0163d8fd78 Alexei Starovoitov 2019-06-15 4174

:::::: The code at line 3959 was first introduced by commit
:::::: f655badf2a8fc028433d9583bf86a6b473721f09 bpf: fix propagate_precision() logic for inner frames

:::::: TO: Andrii Nakryiko <andrii@xxxxxxxxxx>
:::::: CC: Alexei Starovoitov <ast@xxxxxxxxxx>

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