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| author | Luc Van Oostenryck <luc.vanoostenryck@gmail.com> | 2020-06-20 23:52:14 +0200 |
|---|---|---|
| committer | Luc Van Oostenryck <luc.vanoostenryck@gmail.com> | 2020-08-06 18:30:44 +0200 |
| commit | 9aa1c8656be5fee7394cb242a80d7ea8eed32385 (patch) | |
| tree | 499fd2c3b3154ac371873dae541798cab2e021c0 /linearize.c | |
| parent | c2a5bd264187f42564b7055bce4cf72a7985cbc5 (diff) | |
| download | sparse-dev-9aa1c8656be5fee7394cb242a80d7ea8eed32385.tar.gz | |
bad-shift: wait dead code elimination to warn about bad shifts
Sparse complains when a shift amount is too big for the size
of its operand or if it's negative.
However, it does this even for expressions that are never evaluated.
It's especially annoying in the kernel for type generic macros,
for example the ones in arch/*/include/asm/cmpxchg.h
So, remove all warnings done at expansion time and avoid any
simplifications of such expressions. Same, at linearization
and optimization time but in this case mark the instructions as
'tainted' to inhibit any further simplifications. Finally, at the
end of the optimization phase, warn for the tainted instructions.
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Diffstat (limited to 'linearize.c')
| -rw-r--r-- | linearize.c | 44 |
1 files changed, 44 insertions, 0 deletions
diff --git a/linearize.c b/linearize.c index 49274681..5a8e7497 100644 --- a/linearize.c +++ b/linearize.c @@ -2468,6 +2468,49 @@ static pseudo_t linearize_statement(struct entrypoint *ep, struct statement *stm return VOID; } +static void check_tainted_insn(struct instruction *insn) +{ + unsigned long long uval; + long long sval; + pseudo_t src2; + + switch (insn->opcode) { + case OP_DIVU: case OP_DIVS: + case OP_MODU: case OP_MODS: + if (insn->src2 == value_pseudo(0)) + warning(insn->pos, "divide by zero"); + break; + case OP_SHL: case OP_LSR: case OP_ASR: + src2 = insn->src2; + if (src2->type != PSEUDO_VAL) + break; + uval = src2->value; + if (uval < insn->size) + break; + sval = sign_extend(uval, insn->size); + if (Wshift_count_negative && sval < 0) + warning(insn->pos, "shift count is negative (%lld)", sval); + else if (Wshift_count_overflow) + warning(insn->pos, "shift too big (%llu) for type %s", uval, show_typename(insn->type)); + } +} + +/// +// issue warnings after all possible DCE +static void late_warnings(struct entrypoint *ep) +{ + struct basic_block *bb; + FOR_EACH_PTR(ep->bbs, bb) { + struct instruction *insn; + FOR_EACH_PTR(bb->insns, insn) { + if (!insn->bb) + continue; + if (insn->tainted) + check_tainted_insn(insn); + } END_FOR_EACH_PTR(insn); + } END_FOR_EACH_PTR(bb); +} + static struct entrypoint *linearize_fn(struct symbol *sym, struct symbol *base_type) { struct statement *stmt = base_type->stmt; @@ -2514,6 +2557,7 @@ static struct entrypoint *linearize_fn(struct symbol *sym, struct symbol *base_t add_one_insn(ep, ret); optimize(ep); + late_warnings(ep); return ep; } |