From cc08d6f5d1a152279c340f56539a43d932ea0b0d Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?J=2E=20Neusch=C3=A4fer?= Date: Wed, 29 May 2024 20:22:57 +0200 Subject: [PATCH] micropython: Add patch to avoid textrel on arm/thumb MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Signed-off-by: J. Neuschäfer Signed-off-by: Yann E. MORIN --- ...-non-Thumb2-long-jump-workaround-opt.patch | 130 ++++++++++++++++++ 1 file changed, 130 insertions(+) create mode 100644 package/micropython/0001-py-nlrthumb-Make-non-Thumb2-long-jump-workaround-opt.patch diff --git a/package/micropython/0001-py-nlrthumb-Make-non-Thumb2-long-jump-workaround-opt.patch b/package/micropython/0001-py-nlrthumb-Make-non-Thumb2-long-jump-workaround-opt.patch new file mode 100644 index 0000000000..b05791045e --- /dev/null +++ b/package/micropython/0001-py-nlrthumb-Make-non-Thumb2-long-jump-workaround-opt.patch @@ -0,0 +1,130 @@ +From 7b050b366b7dacfb43779c51702a892d8f1873d0 Mon Sep 17 00:00:00 2001 +From: =?UTF-8?q?J=2E=20Neusch=C3=A4fer?= +Date: Sun, 2 Apr 2023 19:58:42 +0200 +Subject: [PATCH] py/nlrthumb: Make non-Thumb2 long-jump workaround opt-in. +MIME-Version: 1.0 +Content-Type: text/plain; charset=UTF-8 +Content-Transfer-Encoding: 8bit + +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 dd376a239dc4f47b0ee7866810fcda151f3cf6dd + +Author: Damien George +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 : + 95c4: b510 push {r4, lr} + 95c6: 0004 movs r4, r0 + 95c8: f02d fd42 bl 37050 + 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 : + 95d6: b510 push {r4, lr} + 95d8: f02d fd3a bl 37050 + 95dc: 6943 ldr r3, [r0, #20] + 95de: 681b ldr r3, [r3, #0] + 95e0: 6143 str r3, [r0, #20] + 95e2: bd10 pop {r4, pc} + +000095e4 : + 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 + +[3]: https://www.openwall.com/lists/musl/2020/09/25/4 + +Signed-off-by: J. Neuschäfer +Upstream: https://github.com/micropython/micropython/commit/7b050b366b7dacfb43779c51702a892d8f1873d0 +--- + py/mpconfig.h | 6 ++++++ + py/nlrthumb.c | 10 +++++++++- + 2 files changed, 15 insertions(+), 1 deletion(-) + +diff --git a/py/mpconfig.h b/py/mpconfig.h +index af2480266..1aa3e0699 100644 +--- a/py/mpconfig.h ++++ b/py/mpconfig.h +@@ -587,6 +587,12 @@ + /*****************************************************************************/ + /* Python internal features */ + ++// Use a special long jump in nlrthumb.c, which may be necessary if nlr.o and ++// nlrthumb.o are linked far apart from each other. ++#ifndef MICROPY_NLR_THUMB_USE_LONG_JUMP ++#define MICROPY_NLR_THUMB_USE_LONG_JUMP (0) ++#endif ++ + // Whether to enable import of external modules + // When disabled, only importing of built-in modules is supported + // When enabled, a port must implement mp_import_stat (among other things) +diff --git a/py/nlrthumb.c b/py/nlrthumb.c +index a22c5df5b..e7b24f242 100644 +--- a/py/nlrthumb.c ++++ b/py/nlrthumb.c +@@ -38,6 +38,14 @@ + + __attribute__((naked)) unsigned int nlr_push(nlr_buf_t *nlr) { + ++ // If you get a linker error here, indicating that a relocation doesn't ++ // fit, try the following (in that order): ++ // ++ // 1. Ensure that nlr.o nlrthumb.o are linked closely together, i.e. ++ // there aren't too many other files between them in the linker list ++ // (PY_CORE_O_BASENAME in py/py.mk) ++ // 2. Set -DMICROPY_NLR_THUMB_USE_LONG_JUMP=1 during the build ++ // + __asm volatile ( + "str r4, [r0, #12] \n" // store r4 into nlr_buf + "str r5, [r0, #16] \n" // store r5 into nlr_buf +@@ -71,7 +79,7 @@ __attribute__((naked)) unsigned int nlr_push(nlr_buf_t *nlr) { + "str lr, [r0, #8] \n" // store lr into nlr_buf + #endif + +- #if !defined(__thumb2__) ++ #if MICROPY_NLR_THUMB_USE_LONG_JUMP + "ldr r1, nlr_push_tail_var \n" + "bx r1 \n" // do the rest in C + ".align 2 \n" +-- +2.43.0 +