On Wednesday, June 17, 2020 10:25:05 AM CEST Ard Biesheuvel wrote: > On architectures that implement KASLR using the ELF native RELA relocation > format (such as arm64), every absolute reference in the code incurs an > overhead of 24 bytes in the .rela section. So storing a 41 element array > of 4 character signature strings using an array of pointer-to-char incurs > an 8x overhead (32 bytes per entry => ~1500 bytes), and given the fixed > length of the entries, and the fact that the array is only used locally, > it is much better to use an array of arrays here, which gets rid of the > overhead entirely. > > While at it, make it __initconst, as it is never referenced except from > __init code. > > Signed-off-by: Ard Biesheuvel <[email protected]> > --- > drivers/acpi/tables.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/drivers/acpi/tables.c b/drivers/acpi/tables.c > index 0e905c3d1645..ada36bc40c2b 100644 > --- a/drivers/acpi/tables.c > +++ b/drivers/acpi/tables.c > @@ -490,7 +490,7 @@ static u8 __init acpi_table_checksum(u8 *buffer, u32 > length) > } > > /* All but ACPI_SIG_RSDP and ACPI_SIG_FACS: */ > -static const char * const table_sigs[] = { > +static const char table_sigs[][ACPI_NAMESEG_SIZE] __initconst = { > ACPI_SIG_BERT, ACPI_SIG_BGRT, ACPI_SIG_CPEP, ACPI_SIG_ECDT, > ACPI_SIG_EINJ, ACPI_SIG_ERST, ACPI_SIG_HEST, ACPI_SIG_MADT, > ACPI_SIG_MSCT, ACPI_SIG_SBST, ACPI_SIG_SLIT, ACPI_SIG_SRAT, > @@ -501,7 +501,7 @@ static const char * const table_sigs[] = { > ACPI_SIG_WDDT, ACPI_SIG_WDRT, ACPI_SIG_DSDT, ACPI_SIG_FADT, > ACPI_SIG_PSDT, ACPI_SIG_RSDT, ACPI_SIG_XSDT, ACPI_SIG_SSDT, > ACPI_SIG_IORT, ACPI_SIG_NFIT, ACPI_SIG_HMAT, ACPI_SIG_PPTT, > - ACPI_SIG_NHLT, NULL }; > + ACPI_SIG_NHLT }; > > #define ACPI_HEADER_SIZE sizeof(struct acpi_table_header) > > @@ -548,11 +548,11 @@ void __init acpi_table_upgrade(void) > > table = file.data; > > - for (sig = 0; table_sigs[sig]; sig++) > + for (sig = 0; sig < ARRAY_SIZE(table_sigs); sig++) > if (!memcmp(table->signature, table_sigs[sig], 4)) > break; > > - if (!table_sigs[sig]) { > + if (sig >= ARRAY_SIZE(table_sigs)) { > pr_err("ACPI OVERRIDE: Unknown signature [%s%s]\n", > cpio_path, file.name); > continue; >
Applied as 5.9 material, thanks!
