| Message ID | 20211215060102.3793196-6-song@kernel.org (mailing list archive) |
|---|---|
| State | Changes Requested |
| Delegated to: | BPF |
| Headers | show |
| Series | bpf_prog_pack allocator | expand |
On Tue, Dec 14, 2021 at 10:01:00PM -0800, Song Liu wrote:
> This will be used by BPF jit compiler to dump JITed binary to a RWX huge
RWX *must* not happen, ever. If you still rely on that full NAK.
On Tue, Dec 14, 2021 at 10:01:00PM -0800, Song Liu wrote: > This will be used by BPF jit compiler to dump JITed binary to a RWX huge OK, I read the actually allocator you use and the relevant code for this patch and the above is a typo, you meant: RX. Those pages are most definitely not writable. > +void *text_poke_jit(void *addr, const void *opcode, size_t len) > +{ > + unsigned long start = (unsigned long)addr; > + size_t patched = 0; > + > + if (WARN_ON_ONCE(core_kernel_text(start))) > + return NULL; > + > + while (patched < len) { > + unsigned long ptr = start + patched; > + size_t s; > + > + s = min_t(size_t, PAGE_SIZE * 2 - offset_in_page(ptr), len - patched); Cute, should work. > + > + __text_poke((void *)ptr, opcode + patched, s); > + patched += s; > + } > + return addr; > +}
> On Dec 15, 2021, at 1:17 AM, Peter Zijlstra <peterz@infradead.org> wrote: > > On Tue, Dec 14, 2021 at 10:01:00PM -0800, Song Liu wrote: >> This will be used by BPF jit compiler to dump JITed binary to a RWX huge > > OK, I read the actually allocator you use and the relevant code for this > patch and the above is a typo, you meant: RX. Those pages are most > definitely not writable. Yeah, it was a typo. I meant to say ROX. Thanks, Song > > >> +void *text_poke_jit(void *addr, const void *opcode, size_t len) >> +{ >> + unsigned long start = (unsigned long)addr; >> + size_t patched = 0; >> + >> + if (WARN_ON_ONCE(core_kernel_text(start))) >> + return NULL; >> + >> + while (patched < len) { >> + unsigned long ptr = start + patched; >> + size_t s; >> + >> + s = min_t(size_t, PAGE_SIZE * 2 - offset_in_page(ptr), len - patched); > > Cute, should work. > >> + >> + __text_poke((void *)ptr, opcode + patched, s); >> + patched += s; >> + } >> + return addr; >> +}
diff --git a/arch/x86/include/asm/text-patching.h b/arch/x86/include/asm/text-patching.h index b7421780e4e9..991058c9b4b1 100644 --- a/arch/x86/include/asm/text-patching.h +++ b/arch/x86/include/asm/text-patching.h @@ -44,6 +44,7 @@ extern void text_poke_early(void *addr, const void *opcode, size_t len); extern void *text_poke(void *addr, const void *opcode, size_t len); extern void text_poke_sync(void); extern void *text_poke_kgdb(void *addr, const void *opcode, size_t len); +extern void *text_poke_jit(void *addr, const void *opcode, size_t len); extern int poke_int3_handler(struct pt_regs *regs); extern void text_poke_bp(void *addr, const void *opcode, size_t len, const void *emulate); diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index 23fb4d51a5da..02c35725cc62 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -1102,6 +1102,34 @@ void *text_poke_kgdb(void *addr, const void *opcode, size_t len) return __text_poke(addr, opcode, len); } +/** + * text_poke_jit - Update instructions on a live kernel by jit engine + * @addr: address to modify + * @opcode: source of the copy + * @len: length to copy, could be more than 2x PAGE_SIZE + * + * Only module memory taking jit text (e.g. for bpf) should be patched. + */ +void *text_poke_jit(void *addr, const void *opcode, size_t len) +{ + unsigned long start = (unsigned long)addr; + size_t patched = 0; + + if (WARN_ON_ONCE(core_kernel_text(start))) + return NULL; + + while (patched < len) { + unsigned long ptr = start + patched; + size_t s; + + s = min_t(size_t, PAGE_SIZE * 2 - offset_in_page(ptr), len - patched); + + __text_poke((void *)ptr, opcode + patched, s); + patched += s; + } + return addr; +} + static void do_sync_core(void *info) { sync_core();
This will be used by BPF jit compiler to dump JITed binary to a RWX huge page, and thus allow multiple BPF programs sharing the a huge (2MB) page. Signed-off-by: Song Liu <song@kernel.org> --- arch/x86/include/asm/text-patching.h | 1 + arch/x86/kernel/alternative.c | 28 ++++++++++++++++++++++++++++ 2 files changed, 29 insertions(+)