From mboxrd@z Thu Jan 1 00:00:00 1970 From: rostedt@goodmis.org (Steven Rostedt) Date: Mon, 27 Feb 2017 17:09:11 -0500 Subject: [PATCH] jump_label: align jump_entry table to at least 4-bytes In-Reply-To: <6db89a8d-6053-51d1-5fd4-bae0179a5ebd@caviumnetworks.com> References: <1488221364-13905-1-git-send-email-jbaron@akamai.com> <93219edf-0f6d-5cc7-309c-c998f16fe7ac@akamai.com> <20170227160601.5b79a1fe@gandalf.local.home> <6db89a8d-6053-51d1-5fd4-bae0179a5ebd@caviumnetworks.com> Message-ID: <20170227170911.2280ca3e@gandalf.local.home> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Mon, 27 Feb 2017 13:41:13 -0800 David Daney wrote: > On 02/27/2017 01:06 PM, Steven Rostedt wrote: > > On Mon, 27 Feb 2017 11:59:50 -0800 > > David Daney wrote: > > > >> For me the size is not the important issue, it is the alignment of the > >> struct jump_entry entries in the table. I don't understand how your > >> patch helps, and I cannot Acked-by unless I understand what is being > >> done and can see that it is both correct and necessary. > > > > You brought up a very good point and I'm glad that I had Jason Cc all > > the arch maintainers in one patch. > > > > I think jump_labels may be much more broken than we think, and Jason's > > fix doesn't fix anything. We had this same issues with tracepoints. > > > > I'm looking at jump_label_init, and how we iterate over an array of > > struct jump_entry's that was put together by the linker. The problem is > > that jump_entry is not a power of 2 in size. > > > > ELF sections may have an ENTSIZE property exactly for arrays. Since > each jump_entry will have a unique value they cannot be merged, but we > can tell the assembler they are an array and get them properly packed. > Perhaps something like (untested): > > .pushsection __jump_table, \"awM\", at progbits,24 > FOO > .popsection > And the linker will honor this too? -- Steve