What passages describe or discuss any of the attributes of chivalry in Sir Gawain and the Green Knight?

There are a number of characteristics attributed to
chivalric behavior found in Sir Gawain and the Green
Knight.

A knight was to adhere to certain rules.
Wikipedia.com notes that these included:

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...[d]uties to countrymen and fellow Christians:
this contains virtues such as mercy, courage, valor, fairness, protection of the weak
and the poor, and in the servant-hood of the knight to his
lord.

Mitchell's website on
chivalry provides more specific details:

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Honor:

Always keep
one's word

Always maintain one's
principles

Never betray a confidence or
comrade

...and...

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Courtesy:

Exhibit
manners

Practice the rules of
decorum

Be respectful of host, authority and
women

When Gawain travels to
meet the Green Knight, in answer to his original challenge issued the year before in
Arthur's court, the young knight shows his honor in keeping his word to show up, even
though he believes that when he faces the mystical Green Knight, he will surely
die.

When Gawain arrives early, near the chapel—the
appointed meeting place—he is invited to spend the holidays with Bertilak and his wife
at Bertilak's nearby castle. Unknown to Gawain, Bertilak is actually the Green Knight,
who tests Gawain each day to know if he is a true and honorable knight. The tests come
at the hands of the wife of Gawain's host, as she does her best to woo him with kisses,
romantic advances, and gifts.

Gawain adheres to the rules
of courtesy, never giving in to the wife's overtures. Gawain, fearing for his life,
however, does not divulge to his host the gift of a magic belt, given by Bertilak's
wife, to protect him from death in his upcoming confrontation with the Green Knight.
This is a betrayal of his code of honor, but when the Green Knight and Gawain finally
meet, Bertilak exposes his real identity, revealing his knowledge that his wife gave
Gawain the Green Knight's magic belt.

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'That belt you're wearing: it's mine, my wife
/

Gave it to you—I know it all
knight...

...But you failed a little, lost good
faith...

...For love of your life. I can hardly blame you.'
*

Bertilak forgives Gawain
for wanting to save his own life, noting that in all other ways, the young knight did
his best to be faithful to the chivalric vows he had pledged in becoming King Arthur's
man.

'You
stand confessed so clean, you took /

Such plain penance at
the point of my ax, /

That I hold you cleansed, as pure in
heart /

As if rom your birth to this day you'd
never'

Sinned.'
*

In Gawain's second meeting
with the Green Knight (in the person of Bertilak), we see how the young knight does his
best to adhere to two of the characteristics of chivalry: honor and
courtesy.

*Translation by Burton Raffel; printed
in Adventures in English Literature. Orlando: Harcourt Brace
Jovanovich, Publishers: 1985.