When building for LoongArch with clang 18.0.0, the stack usage of probe() is larger than the allowed 2048 bytes:
drivers/media/dvb-frontends/mxl5xx.c:1698:12: warning: stack frame size (2368) exceeds limit (2048) in 'probe' [-Wframe-larger-than] 1698 | static int probe(struct mxl *state, struct mxl5xx_cfg *cfg) | ^ 1 warning generated.
This is the result of the linked LLVM commit, which changes how the arrays of structures in config_ts() get handled with CONFIG_INIT_STACK_ZERO and CONFIG_INIT_STACK_PATTERN, which causes the above warning in combination with inlining, as config_ts() gets inlined into probe().
This warning can be easily fixed by moving the array of structures off of the stackvia 'static const', which is a better location for these variables anyways because they are static data that is only ever read from, never modified, so allocating the stack space is wasteful.
This drops the stack usage from 2368 bytes to 256 bytes with the same compiler and configuration.
Cc: stable@vger.kernel.org Closes: https://github.com/ClangBuiltLinux/linux/issues/1977 Link: https://github.com/llvm/llvm-project/commit/afe8b93ffdfef5d8879e1894b9d7dda4... Signed-off-by: Nathan Chancellor nathan@kernel.org --- drivers/media/dvb-frontends/mxl5xx.c | 22 +++++++++++----------- 1 file changed, 11 insertions(+), 11 deletions(-)
diff --git a/drivers/media/dvb-frontends/mxl5xx.c b/drivers/media/dvb-frontends/mxl5xx.c index 4ebbcf05cc09..91e9c378397c 100644 --- a/drivers/media/dvb-frontends/mxl5xx.c +++ b/drivers/media/dvb-frontends/mxl5xx.c @@ -1381,57 +1381,57 @@ static int config_ts(struct mxl *state, enum MXL_HYDRA_DEMOD_ID_E demod_id, u32 nco_count_min = 0; u32 clk_type = 0;
- struct MXL_REG_FIELD_T xpt_sync_polarity[MXL_HYDRA_DEMOD_MAX] = { + static const struct MXL_REG_FIELD_T xpt_sync_polarity[MXL_HYDRA_DEMOD_MAX] = { {0x90700010, 8, 1}, {0x90700010, 9, 1}, {0x90700010, 10, 1}, {0x90700010, 11, 1}, {0x90700010, 12, 1}, {0x90700010, 13, 1}, {0x90700010, 14, 1}, {0x90700010, 15, 1} }; - struct MXL_REG_FIELD_T xpt_clock_polarity[MXL_HYDRA_DEMOD_MAX] = { + static const struct MXL_REG_FIELD_T xpt_clock_polarity[MXL_HYDRA_DEMOD_MAX] = { {0x90700010, 16, 1}, {0x90700010, 17, 1}, {0x90700010, 18, 1}, {0x90700010, 19, 1}, {0x90700010, 20, 1}, {0x90700010, 21, 1}, {0x90700010, 22, 1}, {0x90700010, 23, 1} }; - struct MXL_REG_FIELD_T xpt_valid_polarity[MXL_HYDRA_DEMOD_MAX] = { + static const struct MXL_REG_FIELD_T xpt_valid_polarity[MXL_HYDRA_DEMOD_MAX] = { {0x90700014, 0, 1}, {0x90700014, 1, 1}, {0x90700014, 2, 1}, {0x90700014, 3, 1}, {0x90700014, 4, 1}, {0x90700014, 5, 1}, {0x90700014, 6, 1}, {0x90700014, 7, 1} }; - struct MXL_REG_FIELD_T xpt_ts_clock_phase[MXL_HYDRA_DEMOD_MAX] = { + static const struct MXL_REG_FIELD_T xpt_ts_clock_phase[MXL_HYDRA_DEMOD_MAX] = { {0x90700018, 0, 3}, {0x90700018, 4, 3}, {0x90700018, 8, 3}, {0x90700018, 12, 3}, {0x90700018, 16, 3}, {0x90700018, 20, 3}, {0x90700018, 24, 3}, {0x90700018, 28, 3} }; - struct MXL_REG_FIELD_T xpt_lsb_first[MXL_HYDRA_DEMOD_MAX] = { + static const struct MXL_REG_FIELD_T xpt_lsb_first[MXL_HYDRA_DEMOD_MAX] = { {0x9070000C, 16, 1}, {0x9070000C, 17, 1}, {0x9070000C, 18, 1}, {0x9070000C, 19, 1}, {0x9070000C, 20, 1}, {0x9070000C, 21, 1}, {0x9070000C, 22, 1}, {0x9070000C, 23, 1} }; - struct MXL_REG_FIELD_T xpt_sync_byte[MXL_HYDRA_DEMOD_MAX] = { + static const struct MXL_REG_FIELD_T xpt_sync_byte[MXL_HYDRA_DEMOD_MAX] = { {0x90700010, 0, 1}, {0x90700010, 1, 1}, {0x90700010, 2, 1}, {0x90700010, 3, 1}, {0x90700010, 4, 1}, {0x90700010, 5, 1}, {0x90700010, 6, 1}, {0x90700010, 7, 1} }; - struct MXL_REG_FIELD_T xpt_enable_output[MXL_HYDRA_DEMOD_MAX] = { + static const struct MXL_REG_FIELD_T xpt_enable_output[MXL_HYDRA_DEMOD_MAX] = { {0x9070000C, 0, 1}, {0x9070000C, 1, 1}, {0x9070000C, 2, 1}, {0x9070000C, 3, 1}, {0x9070000C, 4, 1}, {0x9070000C, 5, 1}, {0x9070000C, 6, 1}, {0x9070000C, 7, 1} }; - struct MXL_REG_FIELD_T xpt_err_replace_sync[MXL_HYDRA_DEMOD_MAX] = { + static const struct MXL_REG_FIELD_T xpt_err_replace_sync[MXL_HYDRA_DEMOD_MAX] = { {0x9070000C, 24, 1}, {0x9070000C, 25, 1}, {0x9070000C, 26, 1}, {0x9070000C, 27, 1}, {0x9070000C, 28, 1}, {0x9070000C, 29, 1}, {0x9070000C, 30, 1}, {0x9070000C, 31, 1} }; - struct MXL_REG_FIELD_T xpt_err_replace_valid[MXL_HYDRA_DEMOD_MAX] = { + static const struct MXL_REG_FIELD_T xpt_err_replace_valid[MXL_HYDRA_DEMOD_MAX] = { {0x90700014, 8, 1}, {0x90700014, 9, 1}, {0x90700014, 10, 1}, {0x90700014, 11, 1}, {0x90700014, 12, 1}, {0x90700014, 13, 1}, {0x90700014, 14, 1}, {0x90700014, 15, 1} }; - struct MXL_REG_FIELD_T xpt_continuous_clock[MXL_HYDRA_DEMOD_MAX] = { + static const struct MXL_REG_FIELD_T xpt_continuous_clock[MXL_HYDRA_DEMOD_MAX] = { {0x907001D4, 0, 1}, {0x907001D4, 1, 1}, {0x907001D4, 2, 1}, {0x907001D4, 3, 1}, {0x907001D4, 4, 1}, {0x907001D4, 5, 1}, {0x907001D4, 6, 1}, {0x907001D4, 7, 1} }; - struct MXL_REG_FIELD_T xpt_nco_clock_rate[MXL_HYDRA_DEMOD_MAX] = { + static const struct MXL_REG_FIELD_T xpt_nco_clock_rate[MXL_HYDRA_DEMOD_MAX] = { {0x90700044, 16, 80}, {0x90700044, 16, 81}, {0x90700044, 16, 82}, {0x90700044, 16, 83}, {0x90700044, 16, 84}, {0x90700044, 16, 85},
--- base-commit: 02d4e62ae2452c83e4a3e279b8e4cb4dcbad4b31 change-id: 20240111-dvb-mxl5xx-move-structs-off-stack-e12172b1ef02
Best regards,
On Thu, 11 Jan 2024 17:40:36 -0700 Nathan Chancellor nathan@kernel.org wrote:
Closes: https://github.com/ClangBuiltLinux/linux/issues/1977
The next one: 1978 :)
of the stackvia 'static const', which is a better location for these
Nit: space.
Built-tested for loongarch64:
Reviewed-by: Miguel Ojeda ojeda@kernel.org Tested-by: Miguel Ojeda ojeda@kernel.org
With this applied, I have a `WERROR`-clean `defconfig` build with a Rust-enabled kernel using LLVM 18 (using LLVM-provided apt pre-releases).
Thanks Nathan!
Cheers, Miguel
On Sat, Feb 10, 2024 at 05:26:04PM +0100, Miguel Ojeda wrote:
On Thu, 11 Jan 2024 17:40:36 -0700 Nathan Chancellor nathan@kernel.org wrote:
Closes: https://github.com/ClangBuiltLinux/linux/issues/1977
The next one: 1978 :)
This is probably the third link I have messed up in the past couple of weeks :/ Mauro, do you want a v2 for these two minor issues or can you fix them up during application?
of the stackvia 'static const', which is a better location for these
Nit: space.
Built-tested for loongarch64:
Reviewed-by: Miguel Ojeda ojeda@kernel.org Tested-by: Miguel Ojeda ojeda@kernel.org
With this applied, I have a `WERROR`-clean `defconfig` build with a Rust-enabled kernel using LLVM 18 (using LLVM-provided apt pre-releases).
Thanks for taking a look, this is great to hear!
Cheers, Nathan
On Tue, Feb 13, 2024 at 12:28 AM Nathan Chancellor nathan@kernel.org wrote:
Thanks for taking a look, this is great to hear!
My pleasure!
I am happy to report that it also worked with the new toolchain you just uploaded (i.e. the one that included `libclang.so` :)
Cheers, Miguel
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