1453220 - Rustc doesn't generate EHABI infomation on Android/arm

Status: RESOLVED WORKSFORME

(Firefox Build System :: General, defect)

Description

[Makoto Kato [:m_kato]]

Since crash reporter and gecko profiler cannot walk stack well, I am investigating why both cannot walk stack.

When dumping EHABI unwind information for generated code, object code by rustc doesn't generate EHABI information even if with --enable-debug.

arm-linux-androideabi-readelf -u toolkit/library/armv7-linux-androideabi/debug/incremental/nsstring-144mjr7phvqur/s-f00c36s0ex-doh3gy-1nfagmul8x179/2kjrmm4fe2aha78f.o

Unwind section '.ARM.exidx.text._ZN38_$LT$core..option..Option$LT$T$GT$$GT$3map1
7h593b3637e6548adcE' at offset 0x6c contains 1 entry:

0x0: 0x1 [cantunwind]


Unwind section '.ARM.exidx.text._ZN38_$LT$core..option..Option$LT$T$GT$$GT$3map1
7h7dfe6c3ba31b5218E' at offset 0xac contains 1 entry:

0x0: 0x1 [cantunwind]

...


Of course, "rustc --target armv7-linux-androideabi -O --emit obj main.rs" can generate EHABI information well.

Comment 1

[Mike Hommey [:glandium]]

Here is the problem:

$ rustc --target armv7-linux-androideabi -O --emit obj test.rs -C panic=abort
$ readelf -u test.rs
Unwind section '.ARM.exidx.text._ZN3std2rt10lang_start17h3bf68317e5768cf5E' at offset 0x50 contains 1 entry:

0x0: 0x1 [cantunwind]

(snip)

IOW, -C panic=abort makes the compiler stop emitting those, because it doesn't need them for panic.

Comment 2

[Mike Hommey [:glandium]]

IOW, this is a rustc issue. Please file upstream.

Comment 3

[Makoto Kato [:m_kato]]

(In reply to Mike Hommey [:glandium] from comment #2)
> IOW, this is a rustc issue. Please file upstream.

Oh, thanks, I filed it as https://github.com/rust-lang/rust/issues/49867

Comment 4

[Brian Birtles (:birtles)]

It looks like the corresponding rustc issue has been resolved. Where are we up to with this now? Just waiting for the fix to reach rust stable so we can use it?

Comment 5

[Makoto Kato [:m_kato]]

When I test on Rust 1.27, I cannot sometimes get current stack on rust code.  (C++ seems to be OK).  I need to investigate this again....

Comment 6

[Markus Stange [:mstange]]

Profiler stack walking in rust code on Android seems to be working fine these days. 32 bit example: https://perfht.ml/396JhCL