| 5b701ed1 | 19-Jul-2023 |
Christos Margiolis <[email protected]> |
kinst: start moving towards per-probe trampolines
Using per-CPU and per-thread trampolines is expensive and error-prone,
since we're rewriting the same memory blocks constantly. Per-probe
trampoline
kinst: start moving towards per-probe trampolines
Using per-CPU and per-thread trampolines is expensive and error-prone,
since we're rewriting the same memory blocks constantly. Per-probe
trampolines solve this problem by giving each probe its own block of
executable memory, which more or less remains the same after the initial
write.
What this patch does, is get rid of the initialization code which
allocates a trampoline for each thread, and instead let each port of
kinst allocate a trampoline for each new probe created. It also sets up
the infrastructure needed to support the new trampoline scheme.
This change is not currently supported on amd64, as the amd64 port needs
further changes to work, so this is a temporary/gradual patch to fix the
riscv and arm64 ports.
Reviewed by: markj
Approved by: markj (mentor)
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D40962
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| ea89133d | 19-Jul-2023 |
Christos Margiolis <[email protected]> |
kinst: check for 'push %rbp' anywhere in the function
Currently kinst checks if only the first instruction is 'push %rbp',
essentially excluding functions that do push RBP, but not in the first
inst
kinst: check for 'push %rbp' anywhere in the function
Currently kinst checks if only the first instruction is 'push %rbp',
essentially excluding functions that do push RBP, but not in the first
instruction. This patch modifies kinst to check for 'push %rbp', as
well, as a following 'pop %rbp', anywhere in the function. This behavior
also matches that of FBT.
Reviewed by: markj
Approved by: markj (mentor)
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D40283
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| 1aa48621 | 13-Jun-2023 |
Christos Margiolis <[email protected]> |
kinst: rename t_kinst to t_kinst_tramp
The forthcoming RISC-V and ARM64 ports of kinst introduce a new field
named "t_kinst_curprobe", so "t_kinst" (which points to a trampoline)
becomes a misleadin
kinst: rename t_kinst to t_kinst_tramp
The forthcoming RISC-V and ARM64 ports of kinst introduce a new field
named "t_kinst_curprobe", so "t_kinst" (which points to a trampoline)
becomes a misleading name.
No functional change intended.
Reviewed by: markj
Approved by: markj (mentor)
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D40507
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| 5c134fba | 26-May-2023 |
Christos Margiolis <[email protected]> |
kinst: fix memcpy() tracing crash
Tracing memcpy() would crash the kernel, because we'd also trace the
memcpy() calls from kinst_invop(). To fix this, introduce kinst_memcpy()
whose arguments are 'v
kinst: fix memcpy() tracing crash
Tracing memcpy() would crash the kernel, because we'd also trace the
memcpy() calls from kinst_invop(). To fix this, introduce kinst_memcpy()
whose arguments are 'volatile', so that we avoid having the compiler
replace it with a regular memcpy().
Reviewed by: markj
Approved by: markj (mentor)
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D40284
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| 84d7fe4a | 08-Dec-2022 |
Mark Johnston <[email protected]> |
kinst: Add per-CPU interrupt trampolines
In the common case, kinst emulates a traced instruction by copying it to
a trampoline, where it is followed by a jump back to the original code,
and pointing
kinst: Add per-CPU interrupt trampolines
In the common case, kinst emulates a traced instruction by copying it to
a trampoline, where it is followed by a jump back to the original code,
and pointing the interrupted thread's %rip at the trampoline. In
particular, the trampoline is executed with the same CPU context as the
original instruction, so if interrupts are enabled at the point where
the probe fires, they will be enabled when the trampoline is
subsequently executed.
It can happen that an interrupt is raised while a thread is executing a
kinst trampoline. In that case, it is possible that the interrupt
handler will trigger a kinst probe, so we must ensure that the thread
does not recurse and overwrite its trampoline before it is finished
executing the original contents, otherwise an attempt to trace code
called from interrupt handlers can crash the kernel.
To that end, add a per-CPU trampoline, used when the probe fired with
interrupts disabled. Note that this is not quite complete since it does
not handle the possibility of kinst probes firing while executing an NMI
handler.
Also ensure that we do not trace instructions which set IF, since in
that case it is not clear which trampoline (the per-thread trampoline or
the per-CPU trampoline) we should use, and since such instructions are
rare.
Reported and tested by: Domagoj Stolfa
Reviewed by: christos
Fixes: f0bc4ed144fc ("kinst: Initial revision")
Differential Revision: https://reviews.freebsd.org/D37619
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