From cad539baa48ff257b598000a90db2b7edd4b2dd5 Mon Sep 17 00:00:00 2001 From: Puranjay Mohan Date: Thu, 31 Aug 2023 13:12:28 +0000 Subject: riscv: implement a memset like function for text MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The BPF JIT needs to write invalid instructions to RX regions of memory to invalidate removed BPF programs. This needs a function like memset() that can work with RX memory. Implement patch_text_set_nosync() which is similar to text_poke_set() of x86. Signed-off-by: Puranjay Mohan Reviewed-by: Pu Lehui Acked-by: Björn Töpel Tested-by: Björn Töpel Acked-by: Daniel Borkmann Link: https://lore.kernel.org/r/20230831131229.497941-4-puranjay12@gmail.com Signed-off-by: Palmer Dabbelt --- arch/riscv/include/asm/patch.h | 1 + arch/riscv/kernel/patch.c | 77 ++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 78 insertions(+) (limited to 'arch/riscv') diff --git a/arch/riscv/include/asm/patch.h b/arch/riscv/include/asm/patch.h index 63c98833d510..e88b52d39eac 100644 --- a/arch/riscv/include/asm/patch.h +++ b/arch/riscv/include/asm/patch.h @@ -7,6 +7,7 @@ #define _ASM_RISCV_PATCH_H int patch_text_nosync(void *addr, const void *insns, size_t len); +int patch_text_set_nosync(void *addr, u8 c, size_t len); int patch_text(void *addr, u32 *insns, int ninsns); extern int riscv_patch_in_stop_machine; diff --git a/arch/riscv/kernel/patch.c b/arch/riscv/kernel/patch.c index 2c97e246f4dc..13ee7bf589a1 100644 --- a/arch/riscv/kernel/patch.c +++ b/arch/riscv/kernel/patch.c @@ -6,6 +6,7 @@ #include #include #include +#include #include #include #include @@ -53,6 +54,39 @@ static void patch_unmap(int fixmap) } NOKPROBE_SYMBOL(patch_unmap); +static int __patch_insn_set(void *addr, u8 c, size_t len) +{ + void *waddr = addr; + bool across_pages = (((uintptr_t)addr & ~PAGE_MASK) + len) > PAGE_SIZE; + + /* + * Only two pages can be mapped at a time for writing. + */ + if (len + offset_in_page(addr) > 2 * PAGE_SIZE) + return -EINVAL; + /* + * Before reaching here, it was expected to lock the text_mutex + * already, so we don't need to give another lock here and could + * ensure that it was safe between each cores. + */ + lockdep_assert_held(&text_mutex); + + if (across_pages) + patch_map(addr + PAGE_SIZE, FIX_TEXT_POKE1); + + waddr = patch_map(addr, FIX_TEXT_POKE0); + + memset(waddr, c, len); + + patch_unmap(FIX_TEXT_POKE0); + + if (across_pages) + patch_unmap(FIX_TEXT_POKE1); + + return 0; +} +NOKPROBE_SYMBOL(__patch_insn_set); + static int __patch_insn_write(void *addr, const void *insn, size_t len) { void *waddr = addr; @@ -95,6 +129,14 @@ static int __patch_insn_write(void *addr, const void *insn, size_t len) } NOKPROBE_SYMBOL(__patch_insn_write); #else +static int __patch_insn_set(void *addr, u8 c, size_t len) +{ + memset(addr, c, len); + + return 0; +} +NOKPROBE_SYMBOL(__patch_insn_set); + static int __patch_insn_write(void *addr, const void *insn, size_t len) { return copy_to_kernel_nofault(addr, insn, len); @@ -102,6 +144,41 @@ static int __patch_insn_write(void *addr, const void *insn, size_t len) NOKPROBE_SYMBOL(__patch_insn_write); #endif /* CONFIG_MMU */ +static int patch_insn_set(void *addr, u8 c, size_t len) +{ + size_t patched = 0; + size_t size; + int ret = 0; + + /* + * __patch_insn_set() can only work on 2 pages at a time so call it in a + * loop with len <= 2 * PAGE_SIZE. + */ + while (patched < len && !ret) { + size = min_t(size_t, PAGE_SIZE * 2 - offset_in_page(addr + patched), len - patched); + ret = __patch_insn_set(addr + patched, c, size); + + patched += size; + } + + return ret; +} +NOKPROBE_SYMBOL(patch_insn_set); + +int patch_text_set_nosync(void *addr, u8 c, size_t len) +{ + u32 *tp = addr; + int ret; + + ret = patch_insn_set(tp, c, len); + + if (!ret) + flush_icache_range((uintptr_t)tp, (uintptr_t)tp + len); + + return ret; +} +NOKPROBE_SYMBOL(patch_text_set_nosync); + static int patch_insn_write(void *addr, const void *insn, size_t len) { size_t patched = 0; -- cgit v1.2.3