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Differential D15123

Simplify the code to allocate stack for auxv, argv[], and environment vectors.
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Authored by jhb on Apr 17 2018, 10:58 PM.

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rS332782: Simplify the code to allocate stack for auxv, argv[], and environment vectors.

Summary

Remove auxarg_size as it was only used once right after a confusing
assignment in each of the variants of exec_copyout_strings().

Test Plan

booted a patched FreeBSD/amd64 kernel and was able to run FreeBSD/amd64, FreeBSD/i386, and Linux/x86-64 binaries.

Diff Detail

Repository

rS FreeBSD src repository - subversion

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Tests Not Applicable

Event Timeline

jhb created this revision.Apr 17 2018, 10:58 PM

Harbormaster completed remote builds in B16204: Diff 41603.Apr 17 2018, 10:58 PM

emaste accepted this revision.Apr 18 2018, 7:44 PM

emaste added inline comments.

sys/amd64/linux/linux_sysvec.c
344 ↗	(On Diff #41603)	Maybe capital-A Auxargs follows from struct Elf64_Auxargs?
347–348 ↗	(On Diff #41603)	Perhaps a `_Static_assert` that `sizeof(Elf_Auxinfo)` is some multiple of `sizeof (char *)`?
355 ↗	(On Diff #41603)	Thanks, I think this comment is much improved.

This revision is now accepted and ready to land.Apr 18 2018, 7:44 PM

jhb added inline comments.Apr 19 2018, 12:03 AM

sys/amd64/linux/linux_sysvec.c
347–348 ↗	(On Diff #41603)	I started down that path and then tried an alternate approach of decrementing vectp directly using howmany(). This doesn't require the casts and is shorter and looks more like the math to handle the argv and env vectors. Will update after some more testing. This also needs to use Elf64_Auxinfo.
sys/amd64/linux32/linux32_sysvec.c
830 ↗	(On Diff #41603)	Just noticed these roundup/rounddown's are probably wrong (just need to be aligned to uint32_t) but it doesn't hurt beyond a few bytes of wasted space.

Use howmany() and pointer subtraction for auxargs.

This revision now requires review to proceed.Apr 19 2018, 2:58 AM

Harbormaster completed remote builds in B16219: Diff 41644.Apr 19 2018, 2:58 AM

emaste accepted this revision.Apr 19 2018, 1:57 PM

This revision is now accepted and ready to land.Apr 19 2018, 1:57 PM

Closed by commit rS332782: Simplify the code to allocate stack for auxv, argv[], and environment vectors. (authored by jhb). · Explain WhyApr 19 2018, 4:00 PM

This revision was automatically updated to reflect the committed changes.

Herald added a subscriber: imp. · View Herald TranscriptApr 19 2018, 4:00 PM

Revision Contents
Changeset List

Path

Size

head/

sys/

amd64/

linux/

32 lines

linux32/

linux32_sysvec.c

32 lines

compat/

freebsd32/

freebsd32_misc.c

34 lines

i386/

linux/

30 lines

kern/

34 lines

sys/

1 line

Diff 41657

head/sys/amd64/linux/linux_sysvec.c

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head/sys/amd64/linux32/linux32_sysvec.c

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head/sys/compat/freebsd32/freebsd32_misc.c

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head/sys/i386/linux/linux_sysvec.c

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head/sys/kern/kern_exec.c

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head/sys/sys/imgact.h

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