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charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Spamd-Bar: --- X-Spamd-Result: default: False [-4.00 / 15.00]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_MEDIUM(-1.00)[-1.000]; NEURAL_HAM_SHORT(-1.00)[-0.999]; DMARC_POLICY_ALLOW(-0.50)[gmail.com,none]; R_DKIM_ALLOW(-0.20)[gmail.com:s=20230601]; R_SPF_ALLOW(-0.20)[+ip6:2a00:1450:4000::/36]; MIME_GOOD(-0.10)[text/plain]; FREEMAIL_FROM(0.00)[gmail.com]; RCVD_TLS_LAST(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; TO_DN_SOME(0.00)[]; DWL_DNSWL_NONE(0.00)[gmail.com:dkim]; MIME_TRACE(0.00)[0:+]; ARC_NA(0.00)[]; DKIM_TRACE(0.00)[gmail.com:+]; FROM_HAS_DN(0.00)[]; RCVD_IN_DNSWL_NONE(0.00)[2a00:1450:4864:20::22f:from]; MLMMJ_DEST(0.00)[dev-commits-src-all@freebsd.org,dev-commits-src-main@freebsd.org]; MID_RHS_MATCH_FROMTLD(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; RCPT_COUNT_THREE(0.00)[4]; ASN(0.00)[asn:15169, ipnet:2a00:1450::/32, country:US]; FREEFALL_USER(0.00)[rlibby]; RCVD_COUNT_ONE(0.00)[1]; MISSING_XM_UA(0.00)[]; FREEMAIL_ENVFROM(0.00)[gmail.com] X-Rspamd-Queue-Id: 4W7Bsd0cLtz4J0V On Wed, Jun 19, 2024 at 1:58=E2=80=AFPM Mark Johnston w= rote: > > The branch main has been updated by markj: > > URL: https://cgit.FreeBSD.org/src/commit/?id=3Dddf0ed09bd8f83677407db3682= 8aca2c10f419c9 > > commit ddf0ed09bd8f83677407db36828aca2c10f419c9 > Author: Mark Johnston > AuthorDate: 2024-06-19 20:57:09 +0000 > Commit: Mark Johnston > CommitDate: 2024-06-19 20:57:41 +0000 > > sdt: Implement SDT probes using hot-patching > > The idea here is to avoid a memory access and conditional branch per > probe site. Instead, the probe is represented by an "unreachable" > unconditional function call. asm goto is used to store the address o= f > the probe site (represented by a no-op sled) and the address of the > function call into a tracepoint record. Each SDT probe carries a lis= t > of tracepoints. Questions out of curiosity and maybe ignorance: How does this work with relocations? Something must be adjusting these addresses? > +/* > + * Work around an apparent clang bug or limitation which prevents the us= e of the > + * "i" (immediate) constraint with the probe structure. > + */ > +#define _SDT_ASM_PROBE_CONSTRAINT "Ws" > +#define _SDT_ASM_PROBE_OPERAND "p" Is it because i386 kmods are built with -fPIC? By the way, it seems gcc13 (latest in ports) doesn't support the "Ws" constraint. It seems to have been added to gcc 14. I know i386 is tier 2 these days, and gcc is a second consideration anyway. Trying to test out a patch for i386 gcc, I found that it doesn't build currently and this is one of a few reasons. Ryan