Syscalls based on the ASM templates have missing CFI for r31 and info for LR is innacurate. Example for kill: $ readelf -wF libc.so.6 | grep 0004b9d4.. -A 7 && objdump --disassemble=kill libc.so.6 00004a48 000000000000001c 00004a4c FDE cie=00000000 pc=000000000004b9d4..000000000004ba3c LOC CFA ra 000000000004b9d4 r1+0 u <------ Missing information for r31 000000000004b9e8 r1+48 u <------ Wrong LOC 000000000004b9fc r1+48 c+16 <------ Wrong offset, should be c-32 000000000004ba08 r1+48 000000000004ba1c r1+0 00004a68 000000000000001c 00004a6c FDE cie=00000000 pc=000000000004ba80..000000000004bb10 LOC CFA ra libc.so.6: file format elf64-powerpcle Disassembly of section .text: 000000000004b9d4 <kill>: 4b9d4: 1f 00 4c 3c addis r2,r12,31 4b9d8: 2c c3 42 38 addi r2,r2,-15572 4b9dc: 25 00 00 38 li r0,37 4b9e0: d1 ff 21 f8 stdu r1,-48(r1) 4b9e4: 20 00 e1 fb std r31,32(r1) 4b9e8: 98 8f ed eb ld r31,-28776(r13) 4b9ec: 10 00 ff 77 andis. r31,r31,16 4b9f0: 1c 00 82 41 beq 4ba0c <kill+0x38> 4b9f4: a6 02 28 7d mflr r9 4b9f8: 10 00 21 f9 std r9,16(r1) 4b9fc: 01 00 00 44 scv 0 4ba00: 10 00 21 e9 ld r9,16(r1) 4ba04: a6 03 28 7d mtlr r9 4ba08: 08 00 00 48 b 4ba10 <kill+0x3c> 4ba0c: 02 00 00 44 sc 4ba10: 00 00 bf 2e cmpdi cr5,r31,0 4ba14: 20 00 e1 eb ld r31,32(r1) 4ba18: 30 00 21 38 addi r1,r1,48 4ba1c: 18 00 96 41 beq cr5,4ba34 <kill+0x60> 4ba20: 01 f0 20 39 li r9,-4095 4ba24: 40 48 23 7c cmpld r3,r9 4ba28: 20 00 e0 4d bltlr+ 4ba2c: d0 00 63 7c neg r3,r3 4ba30: 08 00 00 48 b 4ba38 <kill+0x64> 4ba34: 20 00 e3 4c bnslr+ 4ba38: c8 32 fe 4b b 2ed00 <__syscall_error> ... 4ba44: 40 20 0c 00 .long 0xc2040 4ba48: 68 00 00 00 .long 0x68 4ba4c: 06 00 5f 5f rlwnm r31,r26,r0,0,3 4ba50: 6b 69 6c 6c xoris r12,r3,26987 Disassembly of section __libc_freeres_fn:
Shouldn't lr always be saved in the caller's frame?
> Shouldn't lr always be saved in the caller's frame? Yes, this and CFI info have been fixed by d120fb9941be1fb1934f0b50c6ad64e4c5e404fb
Unfortunately the fix caused some tests to fail only on powerpc64 (BE) FAIL: nptl/tst-mutexpi9 FAIL: nptl/tst-mutexpi5 FAIL: nptl/tst-mutexpi5a FAIL: io/tst-statx I'm investigating it.
New failing tests are now fixed by: commit ae91d3df24a4a1b1f264d101a71a298bff310d14 Author: Matheus Castanho <msc@linux.ibm.com> Date: Wed Dec 1 11:14:40 2021 -0300 powerpc64[le]: Allocate extra stack frame on syscall.S The syscall function does not allocate the extra stack frame for scv like other assembly syscalls using DO_CALL_SCV. So after commit d120fb9941 changed the offset that is used to save LR, syscall ended up using an invalid offset, causing regressions on powerpc64. So make sure the extra stack frame is allocated in syscall.S as well to make it consistent with other uses of DO_CALL_SCV and avoid similar issues in the future. Tested on powerpc, powerpc64, and powerpc64le (with and without scv) Reviewed-by: Raphael M Zinsly <rzinsly@linux.ibm.com>