Messages in this thread | ![/](/images/icornerl.gif) | | Date | Mon, 29 Jan 2024 09:02:10 +0800 | Subject | Re: [PATCH bpf-next v7 1/2] arm64: patching: implement text_poke API | From | Xu Kuohai <> |
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On 1/25/2024 9:31 PM, Puranjay Mohan wrote: > The text_poke API is used to implement functions like memcpy() and > memset() for instruction memory (RO+X). The implementation is similar to > the x86 version. > > This will be used by the BPF JIT to write and modify BPF programs. There > could be more users of this in the future. > > Signed-off-by: Puranjay Mohan <puranjay12@gmail.com> > --- > arch/arm64/include/asm/patching.h | 2 + > arch/arm64/kernel/patching.c | 80 +++++++++++++++++++++++++++++++ > 2 files changed, 82 insertions(+) > > diff --git a/arch/arm64/include/asm/patching.h b/arch/arm64/include/asm/patching.h > index 68908b82b168..587bdb91ab7a 100644 > --- a/arch/arm64/include/asm/patching.h > +++ b/arch/arm64/include/asm/patching.h > @@ -8,6 +8,8 @@ int aarch64_insn_read(void *addr, u32 *insnp); > int aarch64_insn_write(void *addr, u32 insn); > > int aarch64_insn_write_literal_u64(void *addr, u64 val); > +void *aarch64_insn_set(void *dst, u32 insn, size_t len); > +void *aarch64_insn_copy(void *dst, void *src, size_t len); > > int aarch64_insn_patch_text_nosync(void *addr, u32 insn); > int aarch64_insn_patch_text(void *addrs[], u32 insns[], int cnt); > diff --git a/arch/arm64/kernel/patching.c b/arch/arm64/kernel/patching.c > index b4835f6d594b..5c2d34d890cf 100644 > --- a/arch/arm64/kernel/patching.c > +++ b/arch/arm64/kernel/patching.c > @@ -105,6 +105,86 @@ noinstr int aarch64_insn_write_literal_u64(void *addr, u64 val) > return ret; > } > > +typedef void text_poke_f(void *dst, void *src, size_t patched, size_t len); > +
How about removing the argument 'patched' and passing 'src + patched' as the second argument?
> +static void *__text_poke(text_poke_f func, void *addr, void *src, size_t len) > +{ > + unsigned long flags; > + size_t patched = 0; > + size_t size; > + void *waddr; > + void *ptr; > + int ret; > + > + raw_spin_lock_irqsave(&patch_lock, flags); > + > + while (patched < len) { > + ptr = addr + patched; > + size = min_t(size_t, PAGE_SIZE - offset_in_page(ptr), > + len - patched); > + > + waddr = patch_map(ptr, FIX_TEXT_POKE0); > + func(waddr, src, patched, size); > + patch_unmap(FIX_TEXT_POKE0); > + > + if (ret < 0) {
Where is 'ret' assigned?
> + raw_spin_unlock_irqrestore(&patch_lock, flags); > + return NULL; > + } > + patched += size; > + } > + raw_spin_unlock_irqrestore(&patch_lock, flags); > + > + flush_icache_range((uintptr_t)addr, (uintptr_t)addr + len); > + > + return addr; > +} > + > +static void text_poke_memcpy(void *dst, void *src, size_t patched, size_t len) > +{ > + copy_to_kernel_nofault(dst, src + patched, len); > +} > + > +static void text_poke_memset(void *dst, void *src, size_t patched, size_t len) > +{ > + u32 c = *(u32 *)src; > + > + memset32(dst, c, len / 4); > +} > + > +/** > + * aarch64_insn_copy - Copy instructions into (an unused part of) RX memory > + * @dst: address to modify > + * @src: source of the copy > + * @len: length to copy > + * > + * Useful for JITs to dump new code blocks into unused regions of RX memory. > + */ > +noinstr void *aarch64_insn_copy(void *dst, void *src, size_t len) > +{ > + /* A64 instructions must be word aligned */ > + if ((uintptr_t)dst & 0x3) > + return NULL; > + > + return __text_poke(text_poke_memcpy, dst, src, len); > +} > + > +/** > + * aarch64_insn_set - memset for RX memory regions. > + * @dst: address to modify > + * @insn: value to set > + * @len: length of memory region. > + * > + * Useful for JITs to fill regions of RX memory with illegal instructions. > + */ > +noinstr void *aarch64_insn_set(void *dst, u32 insn, size_t len) > +{ > + if ((uintptr_t)dst & 0x3) > + return NULL; > + > + return __text_poke(text_poke_memset, dst, &insn, len); > +} > + > int __kprobes aarch64_insn_patch_text_nosync(void *addr, u32 insn) > { > u32 *tp = addr;
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