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riscv: implement a memset like function for text

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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 <puranjay12@gmail.com>
Reviewed-by: Pu Lehui <pulehui@huawei.com>
Acked-by: Björn Töpel <bjorn@kernel.org>
Tested-by: Björn Töpel <bjorn@rivosinc.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/r/20230831131229.497941-4-puranjay12@gmail.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
This commit is contained in:
Puranjay Mohan 2023-08-31 13:12:28 +00:00 committed by Palmer Dabbelt
parent 9721873c3c
commit cad539baa4
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GPG Key ID: 2E1319F35FBB1889
2 changed files with 78 additions and 0 deletions
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1
arch/riscv/include/asm/patch.h
View File

@ -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;

77
arch/riscv/kernel/patch.c
View File

@ -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;