Unverified Commit 9721873c authored by Puranjay Mohan's avatar Puranjay Mohan Committed by Palmer Dabbelt
Browse files

riscv: extend patch_text_nosync() for multiple pages 



The patch_insn_write() function currently doesn't work for multiple pages
of instructions, therefore patch_text_nosync() will fail with a page fault
if called with lengths spanning multiple pages.

This commit extends the patch_insn_write() function to support multiple
pages by copying at max 2 pages at a time in a loop. This implementation
is similar to text_poke_copy() function of x86.

Signed-off-by: default avatarPuranjay Mohan <puranjay12@gmail.com>
Reviewed-by: default avatarPu Lehui <pulehui@huawei.com>
Reviewed-by: default avatarBjörn Töpel <bjorn@rivosinc.com>
Tested-by: default avatarBjörn Töpel <bjorn@rivosinc.com>
Acked-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/r/20230831131229.497941-3-puranjay12@gmail.com


Signed-off-by: default avatarPalmer Dabbelt <palmer@rivosinc.com>
parent 20e490ad

arch/riscv/kernel/patch.c

+32 −5
Original line number Diff line number Diff line
@@ -53,12 +53,18 @@ static void patch_unmap(int fixmap) 
}

NOKPROBE_SYMBOL(patch_unmap);



static int patch_insn_write(void *addr, const void *insn, size_t len)

static int __patch_insn_write(void *addr, const void *insn, size_t len)

{

	void *waddr = addr;

	bool across_pages = (((uintptr_t) addr & ~PAGE_MASK) + len) > PAGE_SIZE;

	int ret;



	/*

	 * 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
@@ -74,7 +80,7 @@ static int patch_insn_write(void *addr, const void *insn, size_t len) 
		lockdep_assert_held(&text_mutex);



	if (across_pages)

		patch_map(addr + len, FIX_TEXT_POKE1);

		patch_map(addr + PAGE_SIZE, FIX_TEXT_POKE1);



	waddr = patch_map(addr, FIX_TEXT_POKE0);
@@ -87,15 +93,36 @@ static int patch_insn_write(void *addr, const void *insn, size_t len) 


	return ret;

}

NOKPROBE_SYMBOL(patch_insn_write);

NOKPROBE_SYMBOL(__patch_insn_write);

#else

static int patch_insn_write(void *addr, const void *insn, size_t len)

static int __patch_insn_write(void *addr, const void *insn, size_t len)

{

	return copy_to_kernel_nofault(addr, insn, len);

}

NOKPROBE_SYMBOL(patch_insn_write);

NOKPROBE_SYMBOL(__patch_insn_write);

#endif /* CONFIG_MMU */



static int patch_insn_write(void *addr, const void *insn, size_t len)

{

	size_t patched = 0;

	size_t size;

	int ret = 0;



	/*

	 * Copy the instructions to the destination address, two pages at a time

	 * because __patch_insn_write() can only handle 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_write(addr + patched, insn + patched, size);



		patched += size;

	}



	return ret;

}

NOKPROBE_SYMBOL(patch_insn_write);



int patch_text_nosync(void *addr, const void *insns, size_t len)

{

	u32 *tp = addr;