Unverified Commit cad539ba authored by Puranjay Mohan's avatar Puranjay Mohan Committed by Palmer Dabbelt
Browse files

riscv: implement a memset like function for text 



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: default avatarPuranjay Mohan <puranjay12@gmail.com>
Reviewed-by: default avatarPu Lehui <pulehui@huawei.com>
Acked-by: default avatarBjörn Töpel <bjorn@kernel.org>
Tested-by: default avatarBjörn Töpel <bjorn@rivosinc.com>
Acked-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/r/20230831131229.497941-4-puranjay12@gmail.com


Signed-off-by: default avatarPalmer Dabbelt <palmer@rivosinc.com>
parent 9721873c

arch/riscv/include/asm/patch.h

+1 −0
Original line number Diff line number Diff line
@@ -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;

arch/riscv/kernel/patch.c

+77 −0
Original line number Diff line number Diff line
@@ -6,6 +6,7 @@ 
#include <linux/spinlock.h>

#include <linux/mm.h>

#include <linux/memory.h>

#include <linux/string.h>

#include <linux/uaccess.h>

#include <linux/stop_machine.h>

#include <asm/kprobes.h>
@@ -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;