Messages in this thread Patch in this message | | | From | Chen Guokai <> | Subject | [PATCH v6 02/13] riscv/kprobe: Allocate detour buffer from module region | Date | Fri, 27 Jan 2023 21:05:30 +0800 |
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From: Liao Chang <liaochang1@huawei.com>
To address the limitation of PC-relative branch instruction on riscv architecture, detour buffer slot used for optprobes has to be allocated at virtual address that can access from kernel and modules text via AUIPC/JALR.
For the time being, the vmalloc region is far from kernel/modules text, the distance between them is half of kernel address space [1], which can't transfer control to 32-bit pc-relative address, hence it needs to override the alloc_optinsn_page() to allocate detour buffer from module region.
[1] Documentation/riscv/vm-layout.rst
Signed-off-by: Liao Chang <liaochang1@huawei.com> Co-developed-by: Chen Guokai <chenguokai17@mails.ucas.ac.cn> Signed-off-by: Chen Guokai <chenguokai17@mails.ucas.ac.cn> --- arch/riscv/kernel/probes/kprobes.c | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+)
diff --git a/arch/riscv/kernel/probes/kprobes.c b/arch/riscv/kernel/probes/kprobes.c index f21592d20306..e1856b04db04 100644 --- a/arch/riscv/kernel/probes/kprobes.c +++ b/arch/riscv/kernel/probes/kprobes.c @@ -6,6 +6,7 @@ #include <linux/extable.h> #include <linux/slab.h> #include <linux/stop_machine.h> +#include <linux/set_memory.h> #include <asm/ptrace.h> #include <linux/uaccess.h> #include <asm/sections.h> @@ -84,6 +85,29 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p) } #ifdef CONFIG_MMU +#if defined(CONFIG_OPTPROBES) && defined(CONFIG_64BIT) +void *alloc_optinsn_page(void) +{ + void *page; + + page = __vmalloc_node_range(PAGE_SIZE, 1, MODULES_VADDR, + MODULES_END, GFP_KERNEL, + PAGE_KERNEL, 0, NUMA_NO_NODE, + __builtin_return_address(0)); + if (!page) + return NULL; + + set_vm_flush_reset_perms(page); + /* + * First make the page read-only, and only then make it executable to + * prevent it from being W+X in between. + */ + set_memory_rox((unsigned long)page, 1); + + return page; +} +#endif + void *alloc_insn_page(void) { return __vmalloc_node_range(PAGE_SIZE, 1, VMALLOC_START, VMALLOC_END, -- 2.34.1
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