forked from Minki/linux
mainlining shenanigans
f4483f2cc1
When a tail call fails, it is documented that the tail call should
continue execution at the following instruction. An example tail call
sequence is:
12: (85) call bpf_tail_call#12
13: (b7) r0 = 0
14: (95) exit
The ARM assembler for the tail call in this case ends up branching to
instruction 14 instead of instruction 13, resulting in the BPF filter
returning a non-zero value:
178: ldr r8, [sp, #588] ; insn 12
17c: ldr r6, [r8, r6]
180: ldr r8, [sp, #580]
184: cmp r8, r6
188: bcs 0x1e8
18c: ldr r6, [sp, #524]
190: ldr r7, [sp, #528]
194: cmp r7, #0
198: cmpeq r6, #32
19c: bhi 0x1e8
1a0: adds r6, r6, #1
1a4: adc r7, r7, #0
1a8: str r6, [sp, #524]
1ac: str r7, [sp, #528]
1b0: mov r6, #104
1b4: ldr r8, [sp, #588]
1b8: add r6, r8, r6
1bc: ldr r8, [sp, #580]
1c0: lsl r7, r8, #2
1c4: ldr r6, [r6, r7]
1c8: cmp r6, #0
1cc: beq 0x1e8
1d0: mov r8, #32
1d4: ldr r6, [r6, r8]
1d8: add r6, r6, #44
1dc: bx r6
1e0: mov r0, #0 ; insn 13
1e4: mov r1, #0
1e8: add sp, sp, #596 ; insn 14
1ec: pop {r4, r5, r6, r7, r8, sl, pc}
For other sequences, the tail call could end up branching midway through
the following BPF instructions, or maybe off the end of the function,
leading to unknown behaviours.
Fixes:
|
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| firmware | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.