140KB was high (not sure where I got it as a debug build is 160KB): $ readelf -lS kernel.elf There are 15 section headers, starting at offset 0x1a158:
Section Headers: [Nr] Name Type Addr Off Size ES Flg Lk Inf Al [ 0] NULL 00000000 000000 000000 00 0 0 0 [ 1] .boot.text PROGBITS ff800000 001000 001dfe 00 AX 0 0 2 [ 2] .boot.rodata PROGBITS ff801dfe 002dfe 0000ca 00 A 0 0 2 [ 3] .text PROGBITS ff802000 003000 00d19a 00 AX 0 0 64 [ 4] .sdata PROGBITS ff80f19c 01019c 000004 00 WA 0 0 4 [ 5] .srodata PROGBITS ff80f1a0 0101a0 000010 00 A 0 0 4 [ 6] .rodata PROGBITS ff80f1b0 0101b0 0063d6 00 A 0 0 4 [ 7] ._idle_thread PROGBITS ff815600 016600 000200 00 WA 0 0 256 [ 8] .boot.bss PROGBITS ff815800 016800 00025c 00 WA 0 0 64 [ 9] .bss NOBITS ff815a5c 016a5c 0075ac 00 WA 0 0 4 [10] .riscv.attributes RISCV_ATTRIBUTE 00000000 016a5c 00002f 00 0 0 1 [11] .comment PROGBITS 00000000 016a8b 000012 01 MS 0 0 1 [12] .symtab SYMTAB 00000000 016aa0 001b90 10 13 95 4 [13] .strtab STRTAB 00000000 018630 001ab2 00 0 0 1 [14] .shstrtab STRTAB 00000000 01a0e2 000076 00 0 0 1 Key to Flags: W (write), A (alloc), X (execute), M (merge), S (strings), I (info), L (link order), O (extra OS processing required), G (group), T (TLS), C (compressed), x (unknown), o (OS specific), E (exclude), D (mbind), p (processor specific) Elf file type is EXEC (Executable file) Entry point 0xff800000 There is 1 program header, starting at offset 52 Program Headers: Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align LOAD 0x001000 0xff800000 0x28000000 0x15a5c 0x1d008 RWE 0x1000 Section to Segment mapping: Segment Sections... 00 .boot.text .boot.rodata .text .sdata .srodata .rodata ._idle_thread .boot.bss .bss So a release build is 116KB at start and 108KB after boot completes (I wasn't considering the reclaiming of .boot sections). I built an image w/o CONFIG_PRINTING and got 84KB/76KB. As I noted before we have multiple kernel changes so this is likely in-line with your 56KB number. Regardless, these numbers are small compared to the rootserver. But thanks for making me look :) Why isn't .boot.bss reclaimed? Can you point me in the direction of the .boot section reclaiming? (didn't immediately see it) On Tue, Jul 12, 2022 at 4:39 PM Kent Mcleod <[email protected]> wrote: > >> It's unchanged because opentitan uses the kernel.elf headers to specify > where to load the kernel (prior to applying the PR the SBI reservation was > just ignored)--which took me a while to understand :(). > >>> > >>> > >>> What is the size of the kernel image footprint that you're observing? > >> > >> > >> Looks like ~130KB, likely because we have CONFIG_PRINTING + some > drivers. I haven't looked too closely at that # because the immediate goal > is to reclaim all the rootserver resources which will allow us to meet our > target platform constraints--and that looks doable. We likely have lots of > places we can trim fat (e.g. kernel config, user space optimizations, > removing devel facilities). > >>> > > Are you able to send a dump of the kernel.elf's section and program > headers? When I do a release build of the riscv32 kernel I get a > kernel footprint of 56KiB. (One interesting thing of note is the > .boot.bss section is in the wrong place and so won't be recovered when > switching to user level): > Program Header: > LOAD off 0x00001000 vaddr 0xff800000 paddr 0x84000000 align 2**12 > filesz 0x000098e8 memsz 0x0000e000 flags rwx > > Sections: > Idx Name Size VMA LMA File off Algn > 0 .boot.text 00001558 ff800000 84000000 00001000 2**1 > CONTENTS, ALLOC, LOAD, READONLY, CODE > 1 .boot.rodata 00000008 ff801558 84001558 00002558 2**2 > CONTENTS, ALLOC, LOAD, READONLY, DATA > 2 .text 00006b6a ff802000 84002000 00003000 2**6 > CONTENTS, ALLOC, LOAD, READONLY, CODE > 3 .small 000001f4 ff808b80 84008b80 00009b80 2**6 > CONTENTS, ALLOC, LOAD, DATA > 4 .rodata 000006b0 ff808d74 84008d74 00009d74 2**2 > CONTENTS, ALLOC, LOAD, READONLY, DATA > 5 ._idle_thread 00000200 ff809500 84009500 0000a500 2**8 > CONTENTS, ALLOC, LOAD, DATA > 6 .boot.bss 000001e8 ff809700 84009700 0000a700 2**2 > CONTENTS, ALLOC, LOAD, DATA > 7 .bss 00004718 ff8098e8 840098e8 0000a8e8 2**12 > ALLOC > 8 .riscv.attributes 0000002b 00000000 00000000 0000a8e8 2**0 > CONTENTS, READONLY > 9 .comment 0000000e 00000000 00000000 0000a913 2**0 > CONTENTS, READONLY > > > > >>> > >>> > >>> > -Sam > >>> > _______________________________________________ > >>> > Devel mailing list -- [email protected] > >>> > To unsubscribe send an email to [email protected] > _______________________________________________ Devel mailing list -- [email protected] To unsubscribe send an email to [email protected]
