7b050b366b
Although the original motivation given for the workaround[1] is correct,
nlr.o and nlrthumb.o are linked with a small enough distance that the
problem does not occur, and the workaround isn't necessary. The distance
between the b instruction and its target (nlr_push_tail) is just 64
bytes[2], well within the ±2046 byte range addressable by an
unconditional branch instruction in Thumb mode.
The workaround induces a relocation in the text section (textrel), which
isn't supported everywhere, notably not on musl-libc[3], where it causes
a crash on start-up. With the workaround removed, micropython works on an
ARMv5T Linux system built with musl-libc.
This commit changes nlrthumb.c to use a direct jump by default, but
leaves the long jump workaround as an option for those cases where it's
actually needed.
[1]: commit dd376a239d
Author: Damien George <damien.p.george@gmail.com>
Date: Fri Sep 1 15:25:29 2017 +1000
py/nlrthumb: Get working again on standard Thumb arch (ie not Thumb2).
"b" on Thumb might not be long enough for the jump to nlr_push_tail so
it must be done indirectly.
[2]: Excerpt from objdump -d micropython:
000095c4 <nlr_push_tail>:
95c4: b510 push {r4, lr}
95c6: 0004 movs r4, r0
95c8: f02d fd42 bl 37050 <mp_thread_get_state>
95cc: 6943 ldr r3, [r0, #20]
95ce: 6023 str r3, [r4, #0]
95d0: 6144 str r4, [r0, #20]
95d2: 2000 movs r0, #0
95d4: bd10 pop {r4, pc}
000095d6 <nlr_pop>:
95d6: b510 push {r4, lr}
95d8: f02d fd3a bl 37050 <mp_thread_get_state>
95dc: 6943 ldr r3, [r0, #20]
95de: 681b ldr r3, [r3, #0]
95e0: 6143 str r3, [r0, #20]
95e2: bd10 pop {r4, pc}
000095e4 <nlr_push>:
95e4: 60c4 str r4, [r0, #12]
95e6: 6105 str r5, [r0, #16]
95e8: 6146 str r6, [r0, #20]
95ea: 6187 str r7, [r0, #24]
95ec: 4641 mov r1, r8
95ee: 61c1 str r1, [r0, #28]
95f0: 4649 mov r1, r9
95f2: 6201 str r1, [r0, #32]
95f4: 4651 mov r1, sl
95f6: 6241 str r1, [r0, #36] @ 0x24
95f8: 4659 mov r1, fp
95fa: 6281 str r1, [r0, #40] @ 0x28
95fc: 4669 mov r1, sp
95fe: 62c1 str r1, [r0, #44] @ 0x2c
9600: 4671 mov r1, lr
9602: 6081 str r1, [r0, #8]
9604: e7de b.n 95c4 <nlr_push_tail>
[3]: https://www.openwall.com/lists/musl/2020/09/25/4
Signed-off-by: J. Neuschäfer <j.ne@posteo.net>
150 lines
6.3 KiB
C
150 lines
6.3 KiB
C
/*
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* This file is part of the MicroPython project, http://micropython.org/
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*
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* The MIT License (MIT)
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*
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* Copyright (c) 2013-2017 Damien P. George
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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#include "py/mpstate.h"
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#if MICROPY_NLR_THUMB
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#undef nlr_push
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// We only need the functions here if we are on arm/thumb, and we are not
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// using setjmp/longjmp.
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//
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// For reference, arm/thumb callee save regs are:
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// r4-r11, r13=sp
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__attribute__((naked)) unsigned int nlr_push(nlr_buf_t *nlr) {
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// If you get a linker error here, indicating that a relocation doesn't
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// fit, try the following (in that order):
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//
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// 1. Ensure that nlr.o nlrthumb.o are linked closely together, i.e.
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// there aren't too many other files between them in the linker list
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// (PY_CORE_O_BASENAME in py/py.mk)
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// 2. Set -DMICROPY_NLR_THUMB_USE_LONG_JUMP=1 during the build
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//
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__asm volatile (
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"str r4, [r0, #12] \n" // store r4 into nlr_buf
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"str r5, [r0, #16] \n" // store r5 into nlr_buf
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"str r6, [r0, #20] \n" // store r6 into nlr_buf
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"str r7, [r0, #24] \n" // store r7 into nlr_buf
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#if !defined(__thumb2__)
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"mov r1, r8 \n"
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"str r1, [r0, #28] \n" // store r8 into nlr_buf
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"mov r1, r9 \n"
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"str r1, [r0, #32] \n" // store r9 into nlr_buf
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"mov r1, r10 \n"
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"str r1, [r0, #36] \n" // store r10 into nlr_buf
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"mov r1, r11 \n"
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"str r1, [r0, #40] \n" // store r11 into nlr_buf
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"mov r1, r13 \n"
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"str r1, [r0, #44] \n" // store r13=sp into nlr_buf
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"mov r1, lr \n"
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"str r1, [r0, #8] \n" // store lr into nlr_buf
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#else
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"str r8, [r0, #28] \n" // store r8 into nlr_buf
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"str r9, [r0, #32] \n" // store r9 into nlr_buf
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"str r10, [r0, #36] \n" // store r10 into nlr_buf
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"str r11, [r0, #40] \n" // store r11 into nlr_buf
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"str r13, [r0, #44] \n" // store r13=sp into nlr_buf
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#if MICROPY_NLR_NUM_REGS == 16
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"vstr d8, [r0, #48] \n" // store s16-s17 into nlr_buf
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"vstr d9, [r0, #56] \n" // store s18-s19 into nlr_buf
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"vstr d10, [r0, #64] \n" // store s20-s21 into nlr_buf
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#endif
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"str lr, [r0, #8] \n" // store lr into nlr_buf
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#endif
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#if MICROPY_NLR_THUMB_USE_LONG_JUMP
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"ldr r1, nlr_push_tail_var \n"
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"bx r1 \n" // do the rest in C
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".align 2 \n"
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"nlr_push_tail_var: .word nlr_push_tail \n"
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#else
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#if defined(__APPLE__) || defined(__MACH__)
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"b _nlr_push_tail \n" // do the rest in C
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#else
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"b nlr_push_tail \n" // do the rest in C
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#endif
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#endif
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);
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#if !defined(__clang__) && defined(__GNUC__) && (__GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 8))
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// Older versions of gcc give an error when naked functions don't return a value
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// Additionally exclude Clang as it also defines __GNUC__ but doesn't need this statement
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return 0;
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#endif
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}
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NORETURN void nlr_jump(void *val) {
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MP_NLR_JUMP_HEAD(val, top)
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__asm volatile (
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"mov r0, %0 \n" // r0 points to nlr_buf
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"ldr r4, [r0, #12] \n" // load r4 from nlr_buf
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"ldr r5, [r0, #16] \n" // load r5 from nlr_buf
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"ldr r6, [r0, #20] \n" // load r6 from nlr_buf
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"ldr r7, [r0, #24] \n" // load r7 from nlr_buf
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#if !defined(__thumb2__)
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"ldr r1, [r0, #28] \n" // load r8 from nlr_buf
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"mov r8, r1 \n"
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"ldr r1, [r0, #32] \n" // load r9 from nlr_buf
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"mov r9, r1 \n"
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"ldr r1, [r0, #36] \n" // load r10 from nlr_buf
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"mov r10, r1 \n"
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"ldr r1, [r0, #40] \n" // load r11 from nlr_buf
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"mov r11, r1 \n"
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"ldr r1, [r0, #44] \n" // load r13=sp from nlr_buf
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"mov r13, r1 \n"
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"ldr r1, [r0, #8] \n" // load lr from nlr_buf
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"mov lr, r1 \n"
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#else
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"ldr r8, [r0, #28] \n" // load r8 from nlr_buf
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"ldr r9, [r0, #32] \n" // load r9 from nlr_buf
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"ldr r10, [r0, #36] \n" // load r10 from nlr_buf
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"ldr r11, [r0, #40] \n" // load r11 from nlr_buf
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"ldr r13, [r0, #44] \n" // load r13=sp from nlr_buf
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#if MICROPY_NLR_NUM_REGS == 16
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"vldr d8, [r0, #48] \n" // load s16-s17 from nlr_buf
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"vldr d9, [r0, #56] \n" // load s18-s19 from nlr_buf
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"vldr d10, [r0, #64] \n" // load s20-s21 from nlr_buf
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#endif
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"ldr lr, [r0, #8] \n" // load lr from nlr_buf
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#endif
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"movs r0, #1 \n" // return 1, non-local return
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"bx lr \n" // return
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: // output operands
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: "r" (top) // input operands
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: "memory" // clobbered registers
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);
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MP_UNREACHABLE
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}
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#endif // MICROPY_NLR_THUMB
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