The branch main has been updated by markj: URL: https://cgit.FreeBSD.org/src/commit/?id=c874d312e78fc60e6731a043fc45b47165618370
commit c874d312e78fc60e6731a043fc45b47165618370 Author: Benjamin Jacobs <[email protected]> AuthorDate: 2026-09-03 13:52:21 +0000 Commit: Mark Johnston <[email protected]> CommitDate: 2026-09-03 15:05:03 +0000 dtrace/arm: Fix and de-pessimize dtrace_copy Use an unprivileged load to access user memory from dtrace_copy, which is running in SVC mode. Abort the loop if the load is trapped, as it is useless, hence wasteful, to keep faulting on successive addresses. I believe that this de-pessimization should also be done on aarch64 and riscv. PR: 298064 MFC after: 1 month Reviewed by: markj Differential Revision: https://reviews.freebsd.org/D59280 --- sys/cddl/dev/dtrace/arm/dtrace_asm.S | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/sys/cddl/dev/dtrace/arm/dtrace_asm.S b/sys/cddl/dev/dtrace/arm/dtrace_asm.S index b0eba6f1ed9f..d4730384b581 100644 --- a/sys/cddl/dev/dtrace/arm/dtrace_asm.S +++ b/sys/cddl/dev/dtrace/arm/dtrace_asm.S @@ -130,13 +130,14 @@ dtrace_copy(uintptr_t uaddr, uintptr_t kaddr, size_t size) ENTRY(dtrace_copy) stmfd sp!, {r4-r5} /* stack is 8 byte aligned */ teq r2, #0x00000000 - mov r5, #0x00000000 beq 2f -1: ldrb r4, [r0], #0x0001 - add r5, r5, #0x00000001 - strb r4, [r1], #0x0001 - teqne r5, r2 +1: mov r4, r0 + ldrbt r3, [r0], #1 + teq r0, r4 /* Check if the load was trapped */ + beq 2f /* Yes, quit now */ + strb r3, [r1], #1 + subs r2, r2, #1 bne 1b 2: ldmfd sp!, {r4-r5} /* stack is 8 byte aligned */
