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fix(v4): the build refuses an Artemis cap its 32-bit block numbers cannot hold (#182)

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sk_v4_grow.c's dev_rw4k computes 1 KiB block numbers as (uint32_t)devblock * 4,
which wraps past 4 TiB; Artemis is capped at 256 GiB (STICK_ARTEMIS_CAP_GIB,
kernel/Makefile), so it is latent -- but nothing said so where the cast is. Now
a compile-time check there (the C99 negative-array pattern the tree uses): a
cap past 4 TiB stops the build, and a cap not defined at all is an #error, not
a skipped check. gpt.c's casts are bounded by the disk's own size, itself a
32-bit count of 1 KiB blocks, checked before each: each now says so.

kernel/tests' check_cap, seen to fail first (a 4096 GiB cap built); now 3
checks, 0 failures -- 256 GiB builds, 4096 GiB and none refused. Built for
amd64, aarch64, riscv64. The plan's increments 2 and 3 marked.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017RzZgrf7V7Zk2iczBXDRbm
This commit is contained in:
Claude
2026-11-12 18:07:23 +00:00
parent 41f8648dd9
commit 3c053f02a6
5 changed files with 36 additions and 6 deletions
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kernel/tests/Makefile
+15
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@@ -40,3 +40,18 @@ $(foreach t,$(TESTS),$(eval $(call TEST_RULE,$(t))))
.PHONY: test
test: $(addprefix run-,$(TESTS))
@echo "all kernel host tests passed"
# #182: sk_v4_grow.c's 32-bit block arithmetic holds while Artemis is capped below 4 TiB -- the build
# itself refuses a cap past that. Seen here: 256 GiB (the real cap) compiles, 4096 GiB must not.
.PHONY: run-check_cap
run-check_cap:
@echo "check_cap"
@$(CC) $(CFLAGS) -I$(ROOT)/v4/include -DSTICK_ARTEMIS_CAP_GIB=256ULL -c $(ROOT)/kernel/src/v4/sk_v4_grow.c -o /dev/null \
|| { echo "FAIL #182: sk_v4_grow.c does not build with the real cap, 256 GiB"; exit 1; }
@if $(CC) $(CFLAGS) -I$(ROOT)/v4/include -DSTICK_ARTEMIS_CAP_GIB=4096ULL -c $(ROOT)/kernel/src/v4/sk_v4_grow.c -o /dev/null 2>/dev/null; then \
echo "FAIL #182: a 4096 GiB cap builds -- its block numbers do not fit 32 bits, and nothing stops it"; exit 1; fi
@if $(CC) $(CFLAGS) -I$(ROOT)/v4/include -c $(ROOT)/kernel/src/v4/sk_v4_grow.c -o /dev/null 2>/dev/null; then \
echo "FAIL #182: no cap defined builds -- the check would be skipped, not failed"; exit 1; fi
@echo " 3 checks, 0 failures"
test: run-check_cap