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a=openpgp; fpr=D818ACDD385CAE92D4BAC01A6269794D24791D21 X-Endpoint-Received: by B4 Relay for chenlinxuan@uniontech.com/default with auth_id=380 X-Original-From: Chen Linxuan Reply-To: chenlinxuan@uniontech.com X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 0C4E214000B X-Stat-Signature: nfu7wazb85mabcfhdjhm9pqpndg5su16 X-Rspam-User: X-HE-Tag: 1744796701-201989 X-HE-Meta: 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 Y8vU+634 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Chen Linxuan From: Winston Wen Presume that kernel is compiled for x86_64 with gcc version 13.3.0: make defconfig ./scripts/kconfig/merge_config.sh .config <( echo CONFIG_TCG_TPM=y echo CONFIG_HW_RANDOM=m ) make KCFLAGS="-fno-inline-small-functions -fno-inline-functions-called-once" This results a link error: ld: vmlinux.o: in function `tpm_add_hwrng': tpm-chip.c:(.text+0x6c5924): undefined reference to `hwrng_register' ld: vmlinux.o: in function `tpm_chip_unregister': (.text+0x6c5bc9): undefined reference to `hwrng_unregister' ld: vmlinux.o: in function `tpm_chip_register': (.text+0x6c5c9b): undefined reference to `hwrng_unregister' With `CONFIG_TCG_TPM=y` and `CONFIG_HW_RANDOM=m`, the functions `tpm_add_hwrng`, `tpm_chip_unregister`, and `tpm_chip_register` are compiled into `vmlinux.o` and reference the symbols `hwrng_register` and `hwrng_unregister`. These symbols, however, are compiled into `rng-core.ko`, which results in the linking error. I am not sure but I think this weird linking error only arises when auto inlining is disabled because of some dead code elimination. `CONFIG_TCG_TPM=y` and `CONFIG_HW_RANDOM=m` set `CONFIG_HW_RANDOM_TPM=n`. This causes the function `tpm_is_hwrng_enabled` to always return `false`, as shown below: static bool tpm_is_hwrng_enabled(struct tpm_chip *chip) { if (!IS_ENABLED(CONFIG_HW_RANDOM_TPM)) return false; if (tpm_is_firmware_upgrade(chip)) return false; if (chip->flags & TPM_CHIP_FLAG_HWRNG_DISABLED) return false; return true; } When `tpm_is_hwrng_enabled` is inlined, dead code elimination optimizations are applied and the reference to the `hwrng_*` functions will been removed. For instance, in the `tpm_chip_unregister` function: void tpm_chip_unregister(struct tpm_chip *chip) { #ifdef CONFIG_TCG_TPM2_HMAC int rc; rc = tpm_try_get_ops(chip); if (!rc) { tpm2_end_auth_session(chip); tpm_put_ops(chip); } #endif tpm_del_legacy_sysfs(chip); if (tpm_is_hwrng_enabled(chip)) hwrng_unregister(&chip->hwrng); tpm_bios_log_teardown(chip); if (chip->flags & TPM_CHIP_FLAG_TPM2 && !tpm_is_firmware_upgrade(chip)) tpm_devs_remove(chip); tpm_del_char_device(chip); } When `tpm_is_hwrng_enabled` is inlined and always returns `false`, the call to `hwrng_unregister` is effectively part of a `if (false)` block, which I guess that will be then optimized out. However, when the `-fno-inline-small-functions` and `-fno-inline-functions-called-once` flags are used, tpm_is_hwrng_enabled is not inline. And this optimization some how cannot occur, leading to the undefined reference errors during linking. Adding the `__always_inline` attribute ensures that `tpm_is_hwrng_enabled` is inlined regardless of the compiler flags. This allows the dead code elimination to proceed as expected, resolving the linking issue. Co-developed-by: Chen Linxuan Signed-off-by: Chen Linxuan Signed-off-by: Winston Wen Reviewed-by: Jarkko Sakkinen --- drivers/char/tpm/tpm-chip.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c index e25daf2396d37bcaeae8a96267764df0861ad1be..48cc74d84247e258a39f2118e03aa10d0cbb066a 100644 --- a/drivers/char/tpm/tpm-chip.c +++ b/drivers/char/tpm/tpm-chip.c @@ -534,7 +534,7 @@ static int tpm_hwrng_read(struct hwrng *rng, void *data, size_t max, bool wait) return tpm_get_random(chip, data, max); } -static bool tpm_is_hwrng_enabled(struct tpm_chip *chip) +static __always_inline bool tpm_is_hwrng_enabled(struct tpm_chip *chip) { if (!IS_ENABLED(CONFIG_HW_RANDOM_TPM)) return false;