+++ /dev/null
-From 6c95eccff5eb43c8c3ad865d3b1316b7952cc58e Mon Sep 17 00:00:00 2001
-Date: Fri, 28 May 2021 08:59:58 +0200
-Subject: [PATCH] powerpc: fix PIE/PIC builds with newer gcc/binutils which use
- secureplt by default
-
-This patch fixes segfault of all user space processes (including init, which caused a panic) on recent buildroot powerpc32 builds.
-
-The issue has been reported by Romain Naour in this thread: https://mailman.uclibc-ng.org/pipermail/devel/2021-May/002068.html
-
-Recent buildroot toolchain enables secure PLT in powerpc gcc.
-The latter will then supply -msecure-plt to gas invocations by default.
-Recent buildroot also enables PIE by default.
-
-For the secure PLT to work in PIC, the r30 register needs to point to the GOT.
-Old "bss plt" was just a one-instruction-wide PLT slot, pointed-to by a R_PPC_JMP_SLOT relocation, which was written on-the-fly to contain a branch instruction to the correct address. It therefore had to stay writable+executable, which you generally want to avoid for security reasons.
-New secure PLT only contains read-only code which loads the branch address from the writable GOT.
-
-Note: secure PLT without PIC does not need r30 to be set. Because offset between plt stub code and got is known at link-time. In this case the PLT entry looks like:
-1009b3e0 <__uClibc_main@plt>:
-1009b3e0: 3d 60 10 0e lis r11,4110
-1009b3e4: 81 6b 03 74 lwz r11,884(r11)
-1009b3e8: 7d 69 03 a6 mtctr r11
-1009b3ec: 4e 80 04 20 bctr
-
-Whereas secure PLT with PIC - offset between plt and got is unknown at link-time - looks like this:
-000af800 <00000000.plt_pic32.__uClibc_main>:
- af800: 81 7e 03 80 lwz r11,896(r30)
- af804: 7d 69 03 a6 mtctr r11
- af808: 4e 80 04 20 bctr
- af80c: 60 00 00 00 nop
-
-Upstream status: Pending:
-https://mailman.uclibc-ng.org/pipermail/devel/2021-May/002091.html
-
----
- Rules.mak | 3 ++-
- ldso/ldso/powerpc/dl-startup.h | 3 +++
- libc/sysdeps/linux/powerpc/crt1.S | 4 ++++
- 3 files changed, 9 insertions(+), 1 deletion(-)
-
-diff --git a/Rules.mak b/Rules.mak
-index 10f88b3de..60ac59b85 100644
---- a/Rules.mak
-+++ b/Rules.mak
-@@ -477,9 +477,10 @@ ifeq ($(TARGET_ARCH),powerpc)
- PICFLAG:=-fpic
- PIEFLAG_NAME:=-fpie
- PPC_HAS_REL16:=$(shell printf "\t.text\n\taddis 11,30,_GLOBAL_OFFSET_TABLE_-.@ha\n" | $(CC) -c -x assembler -o /dev/null - 2> /dev/null && echo -n y || echo -n n)
-+ PPC_HAS_SECUREPLT:=$(shell $(CC) --verbose 2>&1 | grep -- --enable-secureplt > /dev/null && echo -n y || echo -n n)
-+ CPU_CFLAGS-$(PPC_HAS_SECUREPLT) += -DPPC_HAS_SECUREPLT
- CPU_CFLAGS-$(PPC_HAS_REL16)+= -DHAVE_ASM_PPC_REL16
- CPU_CFLAGS-$(CONFIG_E500) += "-D__NO_MATH_INLINES"
--
- endif
-
- ifeq ($(TARGET_ARCH),bfin)
-diff --git a/ldso/ldso/powerpc/dl-startup.h b/ldso/ldso/powerpc/dl-startup.h
-index 8b2a517e2..7749395eb 100644
---- a/ldso/ldso/powerpc/dl-startup.h
-+++ b/ldso/ldso/powerpc/dl-startup.h
-@@ -25,6 +25,9 @@ __asm__(
- #else
- " bl _GLOBAL_OFFSET_TABLE_-4@local\n" /* Put our GOT pointer in r31, */
- " mflr 31\n"
-+#endif
-+#ifdef PPC_HAS_SECUREPLT
-+ " mr 30,31\n"
- #endif
- " addi 1,1,16\n" /* Restore SP */
- " lwz 7,_dl_skip_args@got(31)\n" /* load EA of _dl_skip_args */
-diff --git a/libc/sysdeps/linux/powerpc/crt1.S b/libc/sysdeps/linux/powerpc/crt1.S
-index 27bfc5a5a..3f5d056c0 100644
---- a/libc/sysdeps/linux/powerpc/crt1.S
-+++ b/libc/sysdeps/linux/powerpc/crt1.S
-@@ -56,6 +56,10 @@ _start:
- # else
- bl _GLOBAL_OFFSET_TABLE_-4@local
- mflr r31
-+# endif
-+ /* in PIC/PIE, plt stubs need r30 to point to the GOT if using secure-plt */
-+# ifdef PPC_HAS_SECUREPLT
-+ mr 30,31
- # endif
- #endif
- /* Set up the small data pointer in r13. */
---
-2.31.1
-