Hello Yann, Thanks for the help!
Le 24/05/2021 à 21:02, y...@sionneau.net a écrit : > From: Yann Sionneau <y...@sionneau.net> > > This patch fixes segfault of all user space processes (including init, which > caused a panic) on recent buildroot powerpc32 builds. Indeed, recent Buildroot enable by default BR2_PIC_PIE option. > > Recent buildroot toolchain enables secure PLT in powerpc gcc. > The latter will then supply -msecure-plt to gas invocations by default. I guess the problem is using secure PLT and PIC/PIE at the same time. By disabling BR2_PIC_PIE the issue is gone. Maybe you can keep in the commit log the link to the initial report: https://mailman.uclibc-ng.org/pipermail/devel/2021-May/002068.html > > For the secure PLT to work, 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. > New secure PLT only contains read-only code which loads the branch address > from the writable GOT. With this patch applied, the init program still crash during boot: transfering control to application @ 0x690a40 init[1]: segfault (11) at 378 nip 695e80 lr 0 code 1 in busybox[5e0000+e1000] init[1]: code: 817e97a4 7d6903a6 4e800420 60000000 817ebedc 7d6903a6 4e800420 60000000 init[1]: code: 817ed9b8 7d6903a6 4e800420 60000000 <817e0378> 7d6903a6 4e800420 60000000 Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b It's due to the PPC_HAS_SECUREPLT test where the '\' charactere is still present in the generated source file: printf '\#include <stdio.h>\nint main(void) ^ There is no need to escape the '#'. With that fixed the system boot correctly: Tested-by: Romain Naour <romain.na...@gmail.com> Best regards, Romain > > Signed-off-by: Yann Sionneau <y...@sionneau.net> > --- > Rules.mak | 4 +++- > ldso/ldso/powerpc/dl-startup.h | 3 +++ > libc/sysdeps/linux/powerpc/crt1.S | 5 ++++- > 3 files changed, 10 insertions(+), 2 deletions(-) > > diff --git a/Rules.mak b/Rules.mak > index 1fa09be23..0ab41e800 100644 > --- a/Rules.mak > +++ b/Rules.mak > @@ -58,6 +58,7 @@ LD = $(CROSS_COMPILE)ld > NM = $(CROSS_COMPILE)nm > OBJDUMP = $(CROSS_COMPILE)objdump > STRIPTOOL = $(CROSS_COMPILE)strip > +READELF = $(CROSS_COMPILE)readelf > > INSTALL = install > LN = ln > @@ -483,9 +484,10 @@ ifeq ($(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 tmpfile=$$(mktemp); printf '\#include > <stdio.h>\nint main(void) { puts("hello"); return 0;}' > $${tmpfile}.c; $(CC) > -x c $${tmpfile}.c -o $${tmpfile}; $(READELF) -d $${tmpfile} | grep PPC_GOT > > /dev/null && echo -n y || echo -n n; rm $${tmpfile}.c $${tmpfile}) > + 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..78b946ad6 100644 > --- a/libc/sysdeps/linux/powerpc/crt1.S > +++ b/libc/sysdeps/linux/powerpc/crt1.S > @@ -47,7 +47,7 @@ > _start: > mr r9,r1 /* Save the stack pointer and pass it to __uClibc_main > */ > clrrwi r1,r1,4 /* Align stack ptr to 16 bytes */ > -#ifdef __PIC__ > +#if defined(__PIC__) || defined(PPC_HAS_SECUREPLT) > # ifdef HAVE_ASM_PPC_REL16 > bcl 20,31,1f > 1: mflr r31 > @@ -57,6 +57,9 @@ _start: > bl _GLOBAL_OFFSET_TABLE_-4@local > mflr r31 > # endif > +#endif > +#ifdef PPC_HAS_SECUREPLT > + mr 30,31 > #endif > /* Set up the small data pointer in r13. */ > #ifdef __PIC__ > _______________________________________________ devel mailing list devel@uclibc-ng.org https://mailman.uclibc-ng.org/cgi-bin/mailman/listinfo/devel
