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| /freebsd-11.0-release/sys/cddl/dev/dtrace/ | ||
| H A D | dtrace_cddl.h | diff 264434 Mon Apr 14 00:33:32 MDT 2014 markj DTrace's pid provider works by inserting breakpoint instructions at probe sites and installing a hook at the kernel's trap handler. The fasttrap code will emulate the overwritten instruction in some common cases, but otherwise copies it out into some scratch space in the traced process' address space and ensures that it's executed after returning from the trap. In Solaris and illumos, this (per-thread) scratch space comes from some reserved space in TLS, accessible via the fs segment register. This approach is somewhat unappealing on FreeBSD since it would require some modifications to rtld and jemalloc (for static TLS) to ensure that TLS is executable, and would thus introduce dependencies on their implementation details. I think it would also be impossible to safely trace static binaries compiled without these modifications. This change implements the functionality in a different way, by having fasttrap map pages into the target process' address space on demand. Each page is divided into 64-byte chunks for use by individual threads, and fasttrap's process descriptor struct has been extended to keep track of any scratch space allocated for the corresponding process. With this change it's possible to trace all libc functions in a program, e.g. with pid$target:libc.so.*::entry {@[probefunc] = count();} Previously this would generally cause the victim process to crash, as tracing memcpy on amd64 requires the functionality described above. Tested by: Prashanth Kumar <pra_udupi@yahoo.co.in> (earlier version) MFC after: 6 weeks |
| /freebsd-11.0-release/sys/cddl/contrib/opensolaris/uts/common/sys/ | ||
| H A D | fasttrap_impl.h | diff 264434 Mon Apr 14 00:33:32 MDT 2014 markj DTrace's pid provider works by inserting breakpoint instructions at probe sites and installing a hook at the kernel's trap handler. The fasttrap code will emulate the overwritten instruction in some common cases, but otherwise copies it out into some scratch space in the traced process' address space and ensures that it's executed after returning from the trap. In Solaris and illumos, this (per-thread) scratch space comes from some reserved space in TLS, accessible via the fs segment register. This approach is somewhat unappealing on FreeBSD since it would require some modifications to rtld and jemalloc (for static TLS) to ensure that TLS is executable, and would thus introduce dependencies on their implementation details. I think it would also be impossible to safely trace static binaries compiled without these modifications. This change implements the functionality in a different way, by having fasttrap map pages into the target process' address space on demand. Each page is divided into 64-byte chunks for use by individual threads, and fasttrap's process descriptor struct has been extended to keep track of any scratch space allocated for the corresponding process. With this change it's possible to trace all libc functions in a program, e.g. with pid$target:libc.so.*::entry {@[probefunc] = count();} Previously this would generally cause the victim process to crash, as tracing memcpy on amd64 requires the functionality described above. Tested by: Prashanth Kumar <pra_udupi@yahoo.co.in> (earlier version) MFC after: 6 weeks |
| /freebsd-11.0-release/sys/cddl/contrib/opensolaris/uts/intel/dtrace/ | ||
| H A D | fasttrap_isa.c | diff 264434 Mon Apr 14 00:33:32 MDT 2014 markj DTrace's pid provider works by inserting breakpoint instructions at probe sites and installing a hook at the kernel's trap handler. The fasttrap code will emulate the overwritten instruction in some common cases, but otherwise copies it out into some scratch space in the traced process' address space and ensures that it's executed after returning from the trap. In Solaris and illumos, this (per-thread) scratch space comes from some reserved space in TLS, accessible via the fs segment register. This approach is somewhat unappealing on FreeBSD since it would require some modifications to rtld and jemalloc (for static TLS) to ensure that TLS is executable, and would thus introduce dependencies on their implementation details. I think it would also be impossible to safely trace static binaries compiled without these modifications. This change implements the functionality in a different way, by having fasttrap map pages into the target process' address space on demand. Each page is divided into 64-byte chunks for use by individual threads, and fasttrap's process descriptor struct has been extended to keep track of any scratch space allocated for the corresponding process. With this change it's possible to trace all libc functions in a program, e.g. with pid$target:libc.so.*::entry {@[probefunc] = count();} Previously this would generally cause the victim process to crash, as tracing memcpy on amd64 requires the functionality described above. Tested by: Prashanth Kumar <pra_udupi@yahoo.co.in> (earlier version) MFC after: 6 weeks |
| /freebsd-11.0-release/sys/cddl/contrib/opensolaris/uts/common/dtrace/ | ||
| H A D | fasttrap.c | diff 264434 Mon Apr 14 00:33:32 MDT 2014 markj DTrace's pid provider works by inserting breakpoint instructions at probe sites and installing a hook at the kernel's trap handler. The fasttrap code will emulate the overwritten instruction in some common cases, but otherwise copies it out into some scratch space in the traced process' address space and ensures that it's executed after returning from the trap. In Solaris and illumos, this (per-thread) scratch space comes from some reserved space in TLS, accessible via the fs segment register. This approach is somewhat unappealing on FreeBSD since it would require some modifications to rtld and jemalloc (for static TLS) to ensure that TLS is executable, and would thus introduce dependencies on their implementation details. I think it would also be impossible to safely trace static binaries compiled without these modifications. This change implements the functionality in a different way, by having fasttrap map pages into the target process' address space on demand. Each page is divided into 64-byte chunks for use by individual threads, and fasttrap's process descriptor struct has been extended to keep track of any scratch space allocated for the corresponding process. With this change it's possible to trace all libc functions in a program, e.g. with pid$target:libc.so.*::entry {@[probefunc] = count();} Previously this would generally cause the victim process to crash, as tracing memcpy on amd64 requires the functionality described above. Tested by: Prashanth Kumar <pra_udupi@yahoo.co.in> (earlier version) MFC after: 6 weeks |
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