Exception 'Load access fault' mepc=0x42050260, mtval=0x09ccdd7c when trying to connect to ESP32-C3

[ChocolateLoverRaj]

Device: Pixel 2 XL
OS: LineageOS Android 13

When I try to connect to the device I get an error. Here is the full output:

I (43) boot: ESP-IDF v5.1-beta1-378-gea5e0ff298-dirt 2nd stage bootloader
I (43) boot: compile time Jun  7 2023 07:59:10
I (44) boot: chip revision: v0.4
I (48) boot.esp32c3: SPI Speed      : 40MHz
I (53) boot.esp32c3: SPI Mode       : DIO
I (57) boot.esp32c3: SPI Flash Size : 4MB
I (62) boot: Enabling RNG early entropy source...
I (68) boot: Partition Table:
I (71) boot: ## Label            Usage          Type ST Offset   Length
I (78) boot:  0 nvs              WiFi data        01 02 00009000 00006000
I (86) boot:  1 phy_init         RF data          01 01 0000f000 00001000
I (93) boot:  2 factory          factory app      00 00 00010000 003f0000
I (101) boot: End of partition table
I (105) esp_image: segment 0: paddr=00010020 vaddr=3c100020 size=223d8h (140248) map
I (144) esp_image: segment 1: paddr=00032400 vaddr=3fc86808 size=00fd0h (  4048) load
I (146) esp_image: segment 2: paddr=000333d8 vaddr=3fca1a18 size=001a4h (   420) load
I (150) esp_image: segment 3: paddr=00033584 vaddr=40380000 size=06804h ( 26628) load
I (165) esp_image: segment 4: paddr=00039d90 vaddr=00000000 size=06288h ( 25224) 
I (172) esp_image: segment 5: paddr=00040020 vaddr=42000020 size=f5930h (1005872) map
I (397) boot: Loaded app from partition at offset 0x10000
I (397) boot: Disabling RNG early entropy source...
Connector created
Ok(CommandComplete { num_packets: 5, opcode: 3075, data: [0] })
Ok(CommandComplete { num_packets: 5, opcode: 8198, data: [0] })
Ok(CommandComplete { num_packets: 5, opcode: 8200, data: [0] })
Ok(CommandComplete { num_packets: 5, opcode: 8202, data: [0] })
started advertising
Exception 'Load access fault' mepc=0x42050260, mtval=0x09ccdd7c
0x42050260 - esp_hal_common::interrupt::riscv::handle_exception
    at /var/home/rajas/.cargo/registry/src/index.crates.io-6f17d22bba15001f/esp-hal-common-0.13.1/src/interrupt/riscv.rs:466
0x09ccdd7c - ??
    at ??:??
TrapFrame
PC=0x42050260         RA/x1=0x40380202      SP/x2=0x00000000      GP/x3=0x3fc8c1b0      TP/x4=0x00000000
0x42050260 - esp_hal_common::interrupt::riscv::handle_exception
    at /var/home/rajas/.cargo/registry/src/index.crates.io-6f17d22bba15001f/esp-hal-common-0.13.1/src/interrupt/riscv.rs:466
0x40380202 - _start_trap_rust_hal
    at /var/home/rajas/.cargo/registry/src/index.crates.io-6f17d22bba15001f/esp-hal-common-0.13.1/src/interrupt/riscv.rs:412
0x00000000 - hmac_md5_vector
    at /home/bjoern/esp/esp-idf/components/wpa_supplicant/src/crypto/md5.c:107
0x3fc8c1b0 - _ZN8esp_wifi7preempt10TASK_STACK17hd5096faab3453f50E
    at ??:??
0x00000000 - hmac_md5_vector
    at /home/bjoern/esp/esp-idf/components/wpa_supplicant/src/crypto/md5.c:107
T0/x5=0x00000000      T1/x6=0x09ccdd7c      T2/x7=0x00000000      S0/FP/x8=0x3fc8c2a0   S1/x9=0x3fca1000
0x00000000 - hmac_md5_vector
    at /home/bjoern/esp/esp-idf/components/wpa_supplicant/src/crypto/md5.c:107
0x09ccdd7c - ??
    at ??:??
0x00000000 - hmac_md5_vector
    at /home/bjoern/esp/esp-idf/components/wpa_supplicant/src/crypto/md5.c:107
0x3fc8c2a0 - _ZN8esp_wifi7preempt10TASK_STACK17hd5096faab3453f50E
    at ??:??
0x3fca1000 - phy_version_str
    at ??:??
A0/x10=0x09ccdd7c     A1/x11=0x3fc8c2d0     A2/x12=0x00000000     A3/x13=0x00000c80     A4/x14=0x0000dbf3
0x09ccdd7c - ??
    at ??:??
0x3fc8c2d0 - _ZN8esp_wifi7preempt10TASK_STACK17hd5096faab3453f50E
    at ??:??
0x00000000 - hmac_md5_vector
    at /home/bjoern/esp/esp-idf/components/wpa_supplicant/src/crypto/md5.c:107
0x00000c80 - libm::math::lgammaf_r::lgammaf_r
    at /var/home/rajas/.cargo/registry/src/index.crates.io-6f17d22bba15001f/libm-0.2.8/src/math/lgammaf_r.rs:205
0x0000dbf3 - ??
    at ??:??
A5/x15=0x09ccdd7d     A6/x16=0x00000000     A7/x17=0x00000000     S2/x18=0x00000002     S3/x19=0x3fce0000
0x09ccdd7d - ??
    at ??:??
0x00000000 - hmac_md5_vector
    at /home/bjoern/esp/esp-idf/components/wpa_supplicant/src/crypto/md5.c:107
0x00000000 - hmac_md5_vector
    at /home/bjoern/esp/esp-idf/components/wpa_supplicant/src/crypto/md5.c:107
0x00000002 - hmac_md5_vector
    at /home/bjoern/esp/esp-idf/components/wpa_supplicant/src/crypto/md5.c:107
0x3fce0000 - bars
    at ??:??
S4/x20=0x3c11aca4     S5/x21=0x3fce0000     S6/x22=0x3fce0000     S7/x23=0x00000001     S8/x24=0x3fce0000
0x3c11aca4 - .L__unnamed_68
    at ??:??
0x3fce0000 - bars
    at ??:??
0x3fce0000 - bars
    at ??:??
0x00000001 - hmac_md5_vector
    at /home/bjoern/esp/esp-idf/components/wpa_supplicant/src/crypto/md5.c:107
0x3fce0000 - bars
    at ??:??
S9/x25=0x00000000     S10/x26=0x00000000    S11/x27=0x00000000    T3/x28=0x00000000     T4/x29=0x00000000
0x00000000 - hmac_md5_vector
    at /home/bjoern/esp/esp-idf/components/wpa_supplicant/src/crypto/md5.c:107
0x00000000 - hmac_md5_vector
    at /home/bjoern/esp/esp-idf/components/wpa_supplicant/src/crypto/md5.c:107
0x00000000 - hmac_md5_vector
    at /home/bjoern/esp/esp-idf/components/wpa_supplicant/src/crypto/md5.c:107
0x00000000 - hmac_md5_vector
    at /home/bjoern/esp/esp-idf/components/wpa_supplicant/src/crypto/md5.c:107
0x00000000 - hmac_md5_vector
    at /home/bjoern/esp/esp-idf/components/wpa_supplicant/src/crypto/md5.c:107
T5/x30=0x00000000     T6/x31=0x00000000
0x00000000 - hmac_md5_vector
    at /home/bjoern/esp/esp-idf/components/wpa_supplicant/src/crypto/md5.c:107
0x00000000 - hmac_md5_vector
    at /home/bjoern/esp/esp-idf/components/wpa_supplicant/src/crypto/md5.c:107

MSTATUS=0x00001801
0x00001801 - libm::math::rem_pio2_large::rem_pio2_large
    at /var/home/rajas/.cargo/registry/src/index.crates.io-6f17d22bba15001f/libm-0.2.8/src/math/rem_pio2_large.rs:388
MCAUSE=0x00000005
0x00000005 - hmac_md5_vector
    at /home/bjoern/esp/esp-idf/components/wpa_supplicant/src/crypto/md5.c:107
MTVAL=0x09ccdd7c
0x09ccdd7c - ??
    at ??:??
        
0x40380202
0x40380202 - _start_trap_rust_hal
    at /var/home/rajas/.cargo/registry/src/index.crates.io-6f17d22bba15001f/esp-hal-common-0.13.1/src/interrupt/riscv.rs:412
0x40380060
0x40380060 - bars
    at ??:??
0x420b51da
0x420b51da - rw_schedule
    at ??:??

[ChocolateLoverRaj]

Seems like this is the error but idk what is causing it: https://docs.espressif.com/projects/esp-idf/en/latest/esp32c3/api-guides/fatal-errors.html?highlight=load%20access%20fault#instruction-access-fault-load-access-fault-store-access-fault

[bjoernQ]

Looks like a stack corruption (e.g. SP/x2=0x00000000 doesn't look good). You probably run the code in non-release mode. When doing that it will allocate a lot more memory on the stack (more than possible) and crash. Try cargo run --release

I can also reproduce your crash in debug mode - I guess this will solve the issue

[ChocolateLoverRaj]

Could it be that this error is a bug with a dependency? Is this PR and it's associated issue related to this? esp-rs/esp-wifi-sys#266

[ChocolateLoverRaj]

I ran it with --release and it worked on Android. On Fedora 39 I was able to connect but pressing the button did not type anything.

[bjoernQ]

Good to hear it's working so far.

It's also not yet working with a Windows host - I haven't tried too hard to make it work since this is more like a proof-of-concept / experiment I cannot put too much time into this. However, I think I will continue working on this some day

[ChocolateLoverRaj]

It's fine, I don't want / need it to work on Windows and Linux either, I was just looking for an example of using an ESP32-C3 as a BLE peripheral, and this is a good example.