Stefan Sperling has posted comments on this change. ( https://gerrit.osmocom.org/10028 )
Change subject: fix unaligned access in build_ipcp_pco() ...................................................................... Patch Set 1: (1 comment) https://gerrit.osmocom.org/#/c/10028/1/ggsn/ggsn.c File ggsn/ggsn.c: https://gerrit.osmocom.org/#/c/10028/1/ggsn/ggsn.c@514 PS1, Line 514: ipcp = (struct pco_ipcp_hdr *)pco_contains_proto(&pdp->pco_req, PCO_P_IPCP); > So we increased size of the struct prepending bytes, but we still pass same > pointer here and didn't […] The alignment problem occurs because of the + 3 addition to the pointer value in the old code. The pointer is 2-byte aligned before this addition, but is unaligned after + 3. The new code uses an aligned struct pointer only, and passes it on, whereas the old code manually created an unaligned struct pointer and passed it on. Accessing a struct through an unaligned pointer is a problem. Depending on the generated assembly and the platform, the consequences range from inefficiency to a fatal CPU trap exception. But accessing any element of the struct through an aligned struct pointer is OK, and the new code makes that happen. -- To view, visit https://gerrit.osmocom.org/10028 To unsubscribe, or for help writing mail filters, visit https://gerrit.osmocom.org/settings Gerrit-Project: osmo-ggsn Gerrit-Branch: master Gerrit-MessageType: comment Gerrit-Change-Id: Ia75ee0f64e660f6ff6d81d808f9c460b7cac93d2 Gerrit-Change-Number: 10028 Gerrit-PatchSet: 1 Gerrit-Owner: Stefan Sperling <[email protected]> Gerrit-Reviewer: Jenkins Builder Gerrit-Reviewer: Neels Hofmeyr <[email protected]> Gerrit-Reviewer: Pau Espin Pedrol <[email protected]> Gerrit-Reviewer: Stefan Sperling <[email protected]> Gerrit-Comment-Date: Thu, 19 Jul 2018 12:34:46 +0000 Gerrit-HasComments: Yes Gerrit-HasLabels: No
