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Diffstat (limited to 'results/scraper/launchpad-without-comments/1699867')
| -rw-r--r-- | results/scraper/launchpad-without-comments/1699867 | 21 |
1 files changed, 21 insertions, 0 deletions
diff --git a/results/scraper/launchpad-without-comments/1699867 b/results/scraper/launchpad-without-comments/1699867 new file mode 100644 index 00000000..057eb1c7 --- /dev/null +++ b/results/scraper/launchpad-without-comments/1699867 @@ -0,0 +1,21 @@ +x86_64 qemu crashes at far call into long-mode + +I am experimenting with this OS https://github.com/phil-opp/blog_os and spotted a weird behavior with qemu. + +I am looking at code that does transition from 32bit mode to 64bit mode. Right now it does 'jmp $SELECTOR,64bitfunction'. https://github.com/phil-opp/blog_os/blob/557c6a58ea11e31685b9d014d307002d64df5c22/src/arch/x86_64/boot.asm#L32 + +This code works fine with qemu/kvm/vmware. + +To transition from 32 to 64 bit code it is possible to use 'call' operation. So I am trying to replace that code with 'call $SELECTOR,64bitfunction'. It works fine with kvm and wmware. But it fails with Qemu emulation. See the interrup debug log attached. qemu crashes at 10302c (far call mnemonic). + + + 103016: e8 18 00 00 00 callq 103033 <set_up_page_tables> + 10301b: e8 5c 00 00 00 callq 10307c <enable_paging> + 103020: e8 ec 00 00 00 callq 103111 <set_up_SSE> + 103025: 0f 01 15 28 00 10 00 lgdt 0x100028(%rip) # 203054 <GCC_except_table2+0xdb5f8> + 10302c: 9a (bad) + 10302d: 40 31 10 rex xor %edx,(%rax) + 103030: 00 08 add %cl,(%rax) + + +As the code works at hardware I expect it to work with qemu. Thus current qemu behavior looks like a bug. \ No newline at end of file |