Removing lib libraries for C that do not seem to be used

[iartemov-ledger]

Tested with app-starknet that was built and installed locally as:

docker run --rm -ti --name app-starknet  --net=host --privileged -v "/dev/bus/usb:/dev/bus/usb" -v "$(realpath .):/app" --publish 5001:5001 --publish 9999:9999 -v "/home/iartemov/git/LedgerHQ_apps/ledger-secure-sdk:/tmp/my-sdk" -v "/home/iartemov/git/LedgerHQ_apps/ledger-device-rust-sdk:/tmp/my-rust-sdk" -v "/tmp/.X11-unix:/tmp/.X11-unix" -e DISPLAY=$DISPLAY ghcr.io/ledgerhq/ledger-app-builder/ledger-app-dev-tools:latest

# In the container
    export LEDGER_SDK_PATH=/tmp/my-sdk/
    cd starknet
    rm -rf target
    cargo +$RUST_NIGHTLY update include_gif
    cargo +$RUST_NIGHTLY update ledger_secure_sdk_sys
    cargo +$RUST_NIGHTLY update ledger_device_sdk
    cargo ledger build flex
    ledgerctl install -f target/flex/release/app_flex.json

where:

• ledger-secure-sdk corresponds to ledger-secure-sdk@API_LEVEL_24 (case-1 - with arch sub-folder removed for the sake of test, case-2 - with all the files present)
• ledger-device-rust-sdk corresponds to ledger-device-rust-sdk@remove_libc (the present branch)
• local app-starknet case -1 was redirected to the local Rust SDK:

diff --git a/starknet/Cargo.toml b/starknet/Cargo.toml
index 66d85f2..2283586 100644
--- a/starknet/Cargo.toml
+++ b/starknet/Cargo.toml
@@ -5,8 +5,10 @@ edition = "2021"
 authors = ["Ledger"]
 
 [dependencies]
-ledger_device_sdk = {version = "1.22.11"}
-ledger_secure_sdk_sys = { version = "1.8.2", features = ["heap"]}
+#ledger_device_sdk = {version = "1.22.11"}
+ledger_device_sdk = { path = "/tmp/my-rust-sdk/ledger_device_sdk" }
+#ledger_secure_sdk_sys = { version = "1.8.2", features = ["heap"]}
+ledger_secure_sdk_sys = { path = "/tmp/my-rust-sdk/ledger_secure_sdk_sys"}
 include_gif = "1.2.0"
 hex = { version = "0.4", default-features = false, features = ["alloc"]}
 num-bigint = { version = "0.4", default-features = false }

and in case-2 that was without changes.

Then I compared the case-1 and case-2 result binaries.

Using readelf -S starknet/target/flex/release/starknet :

• case-1 (with the change):

Section Headers:
  [Nr] Name              Type            Addr     Off    Size   ES Flg Lk Inf Al
  [ 0]                   NULL            00000000 000000 000000 00      0   0  0
  [ 1] .text             PROGBITS        c0de0000 010000 011800 00  AX  0   0  4
  [ 2] .rel_flash        PROGBITS        c0df1800 021800 000618 00   A  0   0 512
  [ 3] .rodata           PROGBITS        c0df2000 022000 004800 00 AMS  0   0 512
  [ 4] .data             PROGBITS        da7a0000 026800 000000 00   A  0   0  4
  [ 5] .nvm_data         PROGBITS        c0df6800 026800 000400 00  WA  0   0 512
  [ 6] .bss              NOBITS          da7a0000 030000 002c6c 00  WA  0   0  4
  [ 7] ledger.target     PROGBITS        00000000 030000 000005 00      0   0  1
  [ 8] ledger.target_id  PROGBITS        00000000 030005 00000b 00      0   0  1
  [ 9] ledger.targe[...] PROGBITS        00000000 030010 00000c 00      0   0  1
  [10] ledger.api_level  PROGBITS        00000000 03001c 000003 00      0   0  1
  [11] ledger.sdk_v[...] PROGBITS        00000000 03001f 00001b 00      0   0  1
  [12] ledger.rust_[...] PROGBITS        00000000 03003a 000007 00      0   0  1
  [13] ledger.rust_[...] PROGBITS        00000000 030041 000016 00      0   0  1
  [14] ledger.sdk_name   PROGBITS        00000000 030057 000012 00      0   0  1
  [15] ledger.sdk_hash   PROGBITS        00000000 030069 00002f 00      0   0  1
  [16] ledger.sdk_g[...] PROGBITS        00000000 030098 000005 00      0   0  1
  [17] .rel.text         REL             00000000 0300a0 005e70 08   I 21   1  4
  [18] .rel.rodata       REL             00000000 035f10 000618 08   I 21   3  4
  [19] .comment          PROGBITS        00000000 036528 0000af 01  MS  0   0  1
  [20] .ARM.attributes   ARM_ATTRIBUTES  00000000 0365d7 000034 00      0   0  1
  [21] .symtab           SYMTAB          00000000 03660c 007ed0 10     23 1811  4
  [22] .shstrtab         STRTAB          00000000 03e4dc 000121 00      0   0  1
  [23] .strtab           STRTAB          00000000 03e5fd 00a342 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), y (purecode), p (processor specific)
readelf: Error: the PHDR segment must occur before any LOAD segment
readelf: Error: the PHDR segment is not covered by a LOAD segment

• case-2 (without changes):

Section Headers:
  [Nr] Name              Type            Addr     Off    Size   ES Flg Lk Inf Al
  [ 0]                   NULL            00000000 000000 000000 00      0   0  0
  [ 1] .text             PROGBITS        c0de0000 010000 011800 00  AX  0   0  4
  [ 2] .rel_flash        PROGBITS        c0df1800 021800 000618 00   A  0   0 512
  [ 3] .rodata           PROGBITS        c0df2000 022000 004800 00 AMS  0   0 512
  [ 4] .data             PROGBITS        da7a0000 026800 000000 00   A  0   0  4
  [ 5] .nvm_data         PROGBITS        c0df6800 026800 000400 00  WA  0   0 512
  [ 6] .bss              NOBITS          da7a0000 030000 002c6c 00  WA  0   0  4
  [ 7] ledger.target     PROGBITS        00000000 030000 000005 00      0   0  1
  [ 8] ledger.target_id  PROGBITS        00000000 030005 00000b 00      0   0  1
  [ 9] ledger.targe[...] PROGBITS        00000000 030010 00000c 00      0   0  1
  [10] ledger.api_level  PROGBITS        00000000 03001c 000003 00      0   0  1
  [11] ledger.sdk_v[...] PROGBITS        00000000 03001f 000015 00      0   0  1
  [12] ledger.rust_[...] PROGBITS        00000000 030034 000007 00      0   0  1
  [13] ledger.rust_[...] PROGBITS        00000000 03003b 000016 00      0   0  1
  [14] ledger.sdk_name   PROGBITS        00000000 030051 000012 00      0   0  1
  [15] ledger.sdk_hash   PROGBITS        00000000 030063 000029 00      0   0  1
  [16] ledger.sdk_g[...] PROGBITS        00000000 03008c 000005 00      0   0  1
  [17] .rel.text         REL             00000000 030094 005e70 08   I 21   1  4
  [18] .rel.rodata       REL             00000000 035f04 000618 08   I 21   3  4
  [19] .comment          PROGBITS        00000000 03651c 0000d5 01  MS  0   0  1
  [20] .ARM.attributes   ARM_ATTRIBUTES  00000000 0365f1 000034 00      0   0  1
  [21] .symtab           SYMTAB          00000000 036628 007ed0 10     23 1811  4
  [22] .shstrtab         STRTAB          00000000 03e4f8 000121 00      0   0  1
  [23] .strtab           STRTAB          00000000 03e619 00a342 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), y (purecode), p (processor specific)
readelf: Error: the PHDR segment must occur before any LOAD segment
readelf: Error: the PHDR segment is not covered by a LOAD segment

we can see that the sizes of sections almost did not change (as for .text section for example), only few sections changed slightly (as for example ledger.sdk_version one)

Then I compared few functions that make part of libc:

• memcmp():

c0df16a6 <memcmp>:
c0df16a6:	f7ff bfdd 	b.w	c0df1664 <_ZN17compiler_builtins3mem6memcmp17h0956d9528bdc24a9E>

...
c0df1664 <_ZN17compiler_builtins3mem6memcmp17h0956d9528bdc24a9E>:
c0df1664:	b5d0      	push	{r4, r6, r7, lr}
c0df1666:	af02      	add	r7, sp, #8
c0df1668:	b142      	cbz	r2, c0df167c <_ZN17compiler_builtins3mem6memcmp17h0956d9528bdc24a9E+0x18>
c0df166a:	f810 3b01 	ldrb.w	r3, [r0], #1
c0df166e:	3a01      	subs	r2, #1
c0df1670:	f811 4b01 	ldrb.w	r4, [r1], #1
c0df1674:	42a3      	cmp	r3, r4
c0df1676:	d0f7      	beq.n	c0df1668 <_ZN17compiler_builtins3mem6memcmp17h0956d9528bdc24a9E+0x4>
c0df1678:	1b18      	subs	r0, r3, r4
c0df167a:	bdd0      	pop	{r4, r6, r7, pc}
c0df167c:	2000      	movs	r0, #0
c0df167e:	bdd0      	pop	{r4, r6, r7, pc}

• strlen():

c0df13b0 <strlen>:
c0df13b0:	f000 b966 	b.w	c0df1680 <_ZN17compiler_builtins3mem6strlen17ha9b2bc55fe0aca04E>

...

c0df1680 <_ZN17compiler_builtins3mem6strlen17ha9b2bc55fe0aca04E>:
c0df1680:	4601      	mov	r1, r0
c0df1682:	2000      	movs	r0, #0
c0df1684:	5c0a      	ldrb	r2, [r1, r0]
c0df1686:	b10a      	cbz	r2, c0df168c <_ZN17compiler_builtins3mem6strlen17ha9b2bc55fe0aca04E+0xc>
c0df1688:	3001      	adds	r0, #1
c0df168a:	e7fb      	b.n	c0df1684 <_ZN17compiler_builtins3mem6strlen17ha9b2bc55fe0aca04E+0x4>
c0df168c:	4770      	bx	lr

We see that in the both cases a "compiler_builtins" is used behind, not a function from libc (that explains also why it builds).

Conclusion: the Rust application build does not require the libraries from C SDK.

Just in case I'm attaching the disassembles for the case-1 and case-2:
1.txt
2.txt

[yogh333]

Ok LGTM
Could you please bump versions for both crates ledger_secure_sdk_sys and ledger_device_sdk (which depends on ledger_secure_sdk_sys) ?
Thanks !