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Differential D2784

Various changes to the registers displayed in DDB for x86.
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Authored by jhb on Jun 11 2015, 7:36 PM.
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rS285783: Various changes to the registers displayed in DDB for x86.
Summary

Various changes to the registers displayed in DDB for x86.

  • Fix segment registers to only display the low 16 bits.
  • Remove unused handlers and entries for the debug registers.
  • Display xcr0 (if valid) in 'show sysregs'.
  • Add '0x' prefix to MSR values to match other values in 'show sysregs'.
  • MFamd64: Display various MSRs in 'show sysregs'.
  • Add a 'show dbregs' to display the value of debug registers.
  • Dynamically size the column width for register values to properly align columns on 64-bit platforms.
  • Display %gs for i386 in 'show registers'.
Test Plan
  • Check 'show registers' in DDB before and after on amd64 and i386.
  • Check 'show sysreg' and 'show dbreg' as well.

Diff Detail

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rS FreeBSD src repository - subversion
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jhb updated this revision to Diff 6115.Jun 11 2015, 7:36 PM
jhb retitled this revision from to Various changes to the registers displayed in DDB for x86..
jhb updated this object.
jhb edited the test plan for this revision. (Show Details)
jhb added a reviewer: kib.
Herald added a subscriber: imp. · View Herald TranscriptJun 11 2015, 7:36 PM
kib edited edge metadata.Jun 11 2015, 8:01 PM

There is 'show sysregs' which now duplicates partially the functionality. I think crX display should be removed from 'show sysregs' ?

sys/amd64/amd64/db_trace.c
169

CR4_OSXSAVE must be tested as well. If either CR4_XSAVE or CR4_OSXSAVE bits is cleared, xgetbv results in #UD.

jhb updated this revision to Diff 6150.Jun 12 2015, 9:17 PM
jhb edited edge metadata.

Rebase.

jhb added a comment.Jun 12 2015, 9:23 PM
In D2784#53324, @kib wrote:

There is 'show sysregs' which now duplicates partially the functionality. I think crX display should be removed from 'show sysregs' ?

Ugh, somehow I didn't find that earlier. Do you prefer having crX in 'show sysregs' or in 'show registers'? I don't mind either way but would probably place drX and xcr0 next to crX in whichever place.

sys/amd64/amd64/db_trace.c
169

%cr4 just has the XSAVE bit. cpuid features has XSAVE and OSXSAVE.

kib added a comment.Jun 12 2015, 9:50 PM
In D2784#53600, @jhb wrote:

Ugh, somehow I didn't find that earlier. Do you prefer having crX in 'show sysregs' or in 'show registers'? I don't mind either way but would probably place drX and xcr0 next to crX in whichever place.

I do not have a strong opinion there. I usually find it convenient to see the whole command output on single terminal screen without scrolling. From this PoV, it would be natural to 'show regs' to only show general-purpose registers, 'show sysregs' to show system controls, and might be 'show dbregs' for dbX.

sys/amd64/amd64/db_trace.c
169

Oh, yes, I was confused. But, the reason for the confusion is that SDM recommends to test CPUID flags (because code is supposed to run both in user and kernel space). Might be, cpuid feature bit test is more correct, I am not sure.

jhb updated this revision to Diff 6185.Jun 14 2015, 6:33 AM
  • Move control regs into special DDB commands.
  • Just make db_gs explicit instead of a one-use macro.
kib added inline comments.Jun 14 2015, 7:01 AM
sys/amd64/amd64/machdep.c
897

Note that accessing dr4 and dr5 is not safe, generally. See SDM Vol. 3A 17.2.2 Debug Registers DR4 and DR5:

Debug registers DR4 and DR5 are reserved when debug extensions are enabled (when the DE flag in control
register CR4 is set) and attempts to reference the DR4 and DR5 registers cause invalid-opcode exceptions (#UD).
When debug extensions are not enabled (when the DE flag is clear), these registers are aliased to debug registers
DR6 and DR7.

jhb added a reviewer: markj.Jul 21 2015, 5:07 AM

I have some followup fixes I've tested that I will upload once I've rebuilt arcanist on my laptop.

jhb updated this revision to Diff 7148.Jul 21 2015, 5:44 PM
  • Don't display dr4/dr5.
  • Add more MSRs to i386 system regs.
  • Add 0x prefixes for MSRs to match other registers.
jhb updated this object.Jul 21 2015, 5:50 PM
jhb edited the test plan for this revision. (Show Details)
jhb set the repository for this revision to rS FreeBSD src repository - subversion.
kib accepted this revision.Jul 21 2015, 6:30 PM
kib edited edge metadata.
This revision is now accepted and ready to land.Jul 21 2015, 6:30 PM
markj accepted this revision.Jul 21 2015, 6:58 PM
markj edited edge metadata.
jhb updated this revision to Diff 7160.Jul 22 2015, 12:35 AM
jhb edited edge metadata.

Rebase after db_ss and get_rsp removal in HEAD.

This revision now requires review to proceed.Jul 22 2015, 12:35 AM
Closed by commit rS285783: Various changes to the registers displayed in DDB for x86. (authored by jhb). · Explain WhyJul 22 2015, 1:09 AM
This revision was automatically updated to reflect the committed changes.

Revision Contents
Changeset List

PathSize
sys/
amd64/
amd64/
69 lines
15 lines
ddb/
3 lines
i386/
i386/
80 lines
18 lines

Diff 6185

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sys/amd64/amd64/db_trace.c

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sys/amd64/amd64/machdep.c

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sys/ddb/db_print.c

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sys/i386/i386/db_trace.c

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sys/i386/i386/machdep.c

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