[PW_SID:1148379] riscv: kprobes: simulate nop and c.nop instructions - #2496
[PW_SID:1148379] riscv: kprobes: simulate nop and c.nop instructions#2496linux-riscv-bot wants to merge 5 commits into
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…_RWX When CONFIG_STRICT_MODULE_RWX is not set, execmem cannot create temporary writable mappings for read-only executable pages. In this case, the execmem ranges must already have writable permissions. Currently EXECMEM_KPROBES unconditionally uses PAGE_KERNEL_READ_EXEC, which causes kprobe instruction slot writes to trigger page faults on systems where CONFIG_STRICT_MODULE_RWX is not enabled. Fix this by using PAGE_KERNEL_EXEC when CONFIG_STRICT_MODULE_RWX is not available. Signed-off-by: Xiaofeng Yuan <xiaofengmian@163.com> Tested-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com> Reviewed-by: Nam Cao <namcao@linutronix.de> Link: https://patch.msgid.link/20260814082742.148403-2-xiaofengmian@163.com Signed-off-by: Paul Walmsley <pjw@kernel.org>
patch_map() always creates a temporary writable mapping via fixmap for kernel text addresses, even when CONFIG_STRICT_KERNEL_RWX is disabled and the kernel text is already mapped with _PAGE_WRITE. This is unnecessary overhead at best, and on minimal configurations it can cause page faults. Skip the fixmap path for kernel text when CONFIG_STRICT_KERNEL_RWX is not enabled, since the text pages are already writable in that case. The module text path is already gated on CONFIG_STRICT_MODULE_RWX and is kept unchanged. Reported-by: Klara Modin <klara@kasm.eu> Closes: https://lore.kernel.org/all/ant_8TaBbov_GS4i@soda.int.kasm.eu/ Reported-by: Lad Prabhakar <prabhakar.csengg@gmail.com> Closes: https://lore.kernel.org/all/CA+V-a8tQK8rih9SGGTyqrEBGpNkx4H0eX2YccCRrgkVAPr+EBg@mail.gmail.com/ Tested-by: Klara Modin <klarasmodin@gmail.com> Tested-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com> Link: https://patch.msgid.link/20260814082742.148403-3-xiaofengmian@163.com Signed-off-by: Paul Walmsley <pjw@kernel.org>
nop and c.nop have no architectural effect, so allocating an out-of-line instruction slot and single-stepping through them is pure overhead. Simulate them directly in the breakpoint handler by advancing the program counter, following the approach already used on arm64. This avoids slot allocation, text patching, IRQ flag save/restore and the single-step exception for these instructions. Compile tested on RISC-V, and verified with the RISC-V kprobes KUnit test which now covers nop and c.nop. Signed-off-by: Xiaofeng Yuan <yuanxiaofeng@eswincomputing.com> Signed-off-by: Linux RISC-V bot <linux.riscv.bot@gmail.com>
Extend the RISC-V kprobes KUnit test with test_kprobes_nop and test_kprobes_c_nop, covering both the 32-bit nop and the compressed c.nop simulation paths. Signed-off-by: Xiaofeng Yuan <yuanxiaofeng@eswincomputing.com> Signed-off-by: Linux RISC-V bot <linux.riscv.bot@gmail.com>
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Patch 1: "[1/2] riscv: kprobes: simulate nop and c.nop instructions" |
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Patch 1: "[1/2] riscv: kprobes: simulate nop and c.nop instructions" |
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Patch 1: "[1/2] riscv: kprobes: simulate nop and c.nop instructions" |
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Patch 1: "[1/2] riscv: kprobes: simulate nop and c.nop instructions" |
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Patch 1: "[1/2] riscv: kprobes: simulate nop and c.nop instructions" |
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Patch 1: "[1/2] riscv: kprobes: simulate nop and c.nop instructions" |
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Patch 1: "[1/2] riscv: kprobes: simulate nop and c.nop instructions" |
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Patch 1: "[1/2] riscv: kprobes: simulate nop and c.nop instructions" |
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Patch 1: "[1/2] riscv: kprobes: simulate nop and c.nop instructions" |
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Patch 1: "[1/2] riscv: kprobes: simulate nop and c.nop instructions" |
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Patch 1: "[1/2] riscv: kprobes: simulate nop and c.nop instructions" |
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Patch 1: "[1/2] riscv: kprobes: simulate nop and c.nop instructions" |
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Patch 2: "[2/2] riscv: kprobes: add nop and c.nop to the KUnit test" |
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Patch 2: "[2/2] riscv: kprobes: add nop and c.nop to the KUnit test" |
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Patch 2: "[2/2] riscv: kprobes: add nop and c.nop to the KUnit test" |
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Patch 2: "[2/2] riscv: kprobes: add nop and c.nop to the KUnit test" |
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Patch 2: "[2/2] riscv: kprobes: add nop and c.nop to the KUnit test" |
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Patch 2: "[2/2] riscv: kprobes: add nop and c.nop to the KUnit test" |
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Patch 2: "[2/2] riscv: kprobes: add nop and c.nop to the KUnit test" |
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Patch 2: "[2/2] riscv: kprobes: add nop and c.nop to the KUnit test" |
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Patch 2: "[2/2] riscv: kprobes: add nop and c.nop to the KUnit test" |
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Patch 2: "[2/2] riscv: kprobes: add nop and c.nop to the KUnit test" |
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Patch 2: "[2/2] riscv: kprobes: add nop and c.nop to the KUnit test" |
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Patch 2: "[2/2] riscv: kprobes: add nop and c.nop to the KUnit test" |
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3 participants
PR for series 1148379 applied to workflow__riscv__fixes
Name: riscv: kprobes: simulate nop and c.nop instructions
URL: https://patchwork.kernel.org/project/linux-riscv/list/?series=1148379
Version: 1