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Diffstat (limited to 'gitlab/issues_text/target_i386/host_x86/accel_missing/1910')
| -rw-r--r-- | gitlab/issues_text/target_i386/host_x86/accel_missing/1910 | 62 |
1 files changed, 0 insertions, 62 deletions
diff --git a/gitlab/issues_text/target_i386/host_x86/accel_missing/1910 b/gitlab/issues_text/target_i386/host_x86/accel_missing/1910 deleted file mode 100644 index 6181dcd77..000000000 --- a/gitlab/issues_text/target_i386/host_x86/accel_missing/1910 +++ /dev/null @@ -1,62 +0,0 @@ -Signal handlers in x86_64 userspace have wrongly aligned stack -Description of problem: -Various applications crash in signal handlers due to `movaps` getting a misaligned stack address. For some reason this is reported as a NULL deref, but `gdb` clearly shows the true cause. - -```plaintext -> qemu-x86_64 /usr/bin/ruby -e '`true`' --e:1: [BUG] Segmentation fault at 0x0000000000000000 -ruby 3.2.2 (2023-03-30 revision e51014f9c0) [x86_64-linux-gnu] - --- Control frame information ----------------------------------------------- -c:0003 p:---- s:0011 e:000010 CFUNC :` -c:0002 p:0005 s:0006 e:000005 EVAL -e:1 [FINISH] -c:0001 p:0000 s:0003 E:0015b0 DUMMY [FINISH] - --- Ruby level backtrace information ---------------------------------------- --e:1:in `<main>' --e:1:in ``' - --- Machine register context ------------------------------------------------ - RIP: 0x00002aaaab50f98a RBP: 0x00002aaaabb136b8 RSP: 0x00002aaaab2a9c98 - RAX: 0x0000000000000000 RBX: 0x0000000000004946 RCX: 0x0000000000000000 - RDX: 0x00002aaaab2a9c98 RDI: 0x000000000caf0000 RSI: 0x0000000000000000 - R8: 0x00002aaaab2aaa50 R9: 0x0000000000000050 R10: 0x0000000000000008 - R11: 0x0000000000000000 R12: 0x0000000000000002 R13: 0x0000000000007310 - R14: 0x0000000000005e10 R15: 0x00002aaab0537f20 EFL: 0x0000000000000246 - --- C level backtrace information ------------------------------------------- -``` - -```plaintext -(gdb) x/i $pc -=> 0x2aaaab50f98a: movaps %xmm0,(%rsp) -(gdb) p/x $rsp -$3 = 0x2aaaab2a9998 -``` -Steps to reproduce: -1. ```qemu-x86_64 /usr/bin/ruby -e '`true`'``` -Additional information: -The x86_64 psABI says: - -> the value (%rsp − 8) is always a multiple of 16 when control is transferred to the function entry point. - -However, when QEMU jumps to the signal handler, $rsp is aligned to 16B, i.e. ends in `0x..0`. - -The relevant kernel code: - -https://elixir.bootlin.com/linux/v6.5.5/source/arch/x86/kernel/signal.c#L123 - -```plaintext - sp -= frame_size; - - if (ia32_frame) - /* - * Align the stack pointer according to the i386 ABI, - * i.e. so that on function entry ((sp + 4) & 15) == 0. - */ - sp = ((sp + 4) & -FRAME_ALIGNMENT) - 4; - else - sp = round_down(sp, FRAME_ALIGNMENT) - 8; -``` - -CC @lvivier @bonzini @rth7680 |