From 82fd7314c7df8c5555dce027df6f2c98ca5a927f Mon Sep 17 00:00:00 2001 From: Adhemerval Zanella Date: Fri, 12 Feb 2021 19:20:27 +0300 Subject: [PATCH] powerpc: Remove backtrace implementation The powerpc optimization to provide a fast stacktrace requires some ad-hoc code to handle Linux signal frames and the change is fragile once the kernel decides to slight change its execution sequence [1]. The generic implementation work as-is and it should be future proof since the kernel provides the expected CFI directives in vDSO shared page. Checked on powerpc-linux-gnu, powerpc64le-linux-gnu, and powerpc64-linux-gnu. [1] https://sourceware.org/pipermail/libc-alpha/2021-January/122027.html --- sysdeps/powerpc/powerpc32/backtrace.c | 133 ------------------------------- sysdeps/powerpc/powerpc64/backtrace.c | 117 --------------------------- sysdeps/unix/sysv/linux/dl-vdso-setup.c | 11 --- sysdeps/unix/sysv/linux/dl-vdso-setup.h | 9 --- sysdeps/unix/sysv/linux/powerpc/sysdep.h | 7 -- 5 files changed, 277 deletions(-) delete mode 100644 sysdeps/powerpc/powerpc32/backtrace.c delete mode 100644 sysdeps/powerpc/powerpc64/backtrace.c diff --git a/sysdeps/powerpc/powerpc32/backtrace.c b/sysdeps/powerpc/powerpc32/backtrace.c deleted file mode 100644 index 6031477..0000000 --- a/sysdeps/powerpc/powerpc32/backtrace.c +++ /dev/null @@ -1,133 +0,0 @@ -/* Return backtrace of current program state. - Copyright (C) 1998-2021 Free Software Foundation, Inc. - This file is part of the GNU C Library. - - The GNU C Library is free software; you can redistribute it and/or - modify it under the terms of the GNU Lesser General Public - License as published by the Free Software Foundation; either - version 2.1 of the License, or (at your option) any later version. - - The GNU C Library is distributed in the hope that it will be useful, - but WITHOUT ANY WARRANTY; without even the implied warranty of - MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU - Lesser General Public License for more details. - - You should have received a copy of the GNU Lesser General Public - License along with the GNU C Library; if not, see - . */ - -#include -#include -#include -#include -#include - -/* This is the stack layout we see with every stack frame. - Note that every routine is required by the ABI to lay out the stack - like this. - - +----------------+ +-----------------+ - %r1 -> | %r1 last frame--------> | %r1 last frame--->... --> NULL - | | | | - | (unused) | | return address | - +----------------+ +-----------------+ -*/ -struct layout -{ - struct layout *next; - void *return_address; -}; - -#define SIGNAL_FRAMESIZE 64 - -/* Since the signal handler is just like any other function it needs to - save/restore its LR and it will save it into callers stack frame. - Since a signal handler doesn't have a caller, the kernel creates a - dummy frame to make it look like it has a caller. */ -struct signal_frame_32 { - char dummy[SIGNAL_FRAMESIZE]; - struct sigcontext sctx; - mcontext_t mctx; - /* We don't care about the rest, since IP value is at 'mctx' field. */ -}; - -static inline bool -is_sigtramp_address (void *nip) -{ -#ifdef HAVE_SIGTRAMP_RT32 - if (nip == GLRO (dl_vdso_sigtramp_32)) - return true; -#endif - return false; -} - -struct rt_signal_frame_32 { - char dummy[SIGNAL_FRAMESIZE + 16]; - siginfo_t info; - ucontext_t uc; - /* We don't care about the rest, since IP value is at 'uc' field. */ -}; - -static inline bool -is_sigtramp_address_rt (void * nip) -{ -#ifdef HAVE_SIGTRAMP_32 - if (nip == GLRO (dl_vdso_sigtramp_rt32)) - return true; -#endif - return false; -} - -int -__backtrace (void **array, int size) -{ - struct layout *current; - int count; - - /* Force gcc to spill LR. */ - asm volatile ("" : "=l"(current)); - - /* Get the address on top-of-stack. */ - asm volatile ("lwz %0,0(1)" : "=r"(current)); - - for ( count = 0; - current != NULL && count < size; - current = current->next, count++) - { - gregset_t *gregset = NULL; - - array[count] = current->return_address; - - /* Check if the symbol is the signal trampoline and get the interrupted - * symbol address from the trampoline saved area. */ - if (is_sigtramp_address (current->return_address)) - { - struct signal_frame_32 *sigframe = - (struct signal_frame_32*) current; - gregset = &sigframe->mctx.gregs; - } - else if (is_sigtramp_address_rt (current->return_address)) - { - struct rt_signal_frame_32 *sigframe = - (struct rt_signal_frame_32*) current; - gregset = &sigframe->uc.uc_mcontext.uc_regs->gregs; - } - if (gregset) - { - if (count + 1 == size) - break; - array[++count] = (void*)((*gregset)[PT_NIP]); - current = (void*)((*gregset)[PT_R1]); - } - } - - /* It's possible the second-last stack frame can't return - (that is, it's __libc_start_main), in which case - the CRT startup code will have set its LR to 'NULL'. */ - if (count > 0 && array[count-1] == NULL) - count--; - - return count; -} -weak_alias (__backtrace, backtrace) -libc_hidden_def (__backtrace) diff --git a/sysdeps/powerpc/powerpc64/backtrace.c b/sysdeps/powerpc/powerpc64/backtrace.c deleted file mode 100644 index 37de9b5..0000000 --- a/sysdeps/powerpc/powerpc64/backtrace.c +++ /dev/null @@ -1,117 +0,0 @@ -/* Return backtrace of current program state. - Copyright (C) 1998-2021 Free Software Foundation, Inc. - This file is part of the GNU C Library. - - The GNU C Library is free software; you can redistribute it and/or - modify it under the terms of the GNU Library General Public License as - published by the Free Software Foundation; either version 2 of the - License, or (at your option) any later version. - - The GNU C Library is distributed in the hope that it will be useful, - but WITHOUT ANY WARRANTY; without even the implied warranty of - MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU - Library General Public License for more details. - - You should have received a copy of the GNU Library General Public - License along with the GNU C Library; see the file COPYING.LIB. If - not, see . */ - -#include -#include -#include -#include - -#include -#include - -/* This is the stack layout we see with every stack frame. - Note that every routine is required by the ABI to lay out the stack - like this. - - +----------------+ +-----------------+ - %r1 -> | %r1 last frame--------> | %r1 last frame--->... --> NULL - | | | | - | cr save | | cr save | - | | | | - | (unused) | | return address | - +----------------+ +-----------------+ -*/ -struct layout -{ - struct layout *next; - long int condition_register; - void *return_address; -}; - -/* Since the signal handler is just like any other function it needs to - save/restore its LR and it will save it into callers stack frame. - Since a signal handler doesn't have a caller, the kernel creates a - dummy frame to make it look like it has a caller. */ -struct signal_frame_64 { -#define SIGNAL_FRAMESIZE 128 - char dummy[SIGNAL_FRAMESIZE]; - ucontext_t uc; - /* We don't care about the rest, since the IP value is at 'uc' field. */ -}; - -/* Test if the address match to the inside the trampoline code. - Up to and including kernel 5.8, returning from an interrupt or syscall to a - signal handler starts execution directly at the handler's entry point, with - LR set to address of the sigreturn trampoline (the vDSO symbol). - Newer kernels will branch to signal handler from the trampoline instead, so - checking the stacktrace against the vDSO entrypoint does not work in such - case. - The vDSO branches with a 'bctrl' instruction, so checking either the - vDSO address itself and the next instruction should cover all kernel - versions. */ -static inline bool -is_sigtramp_address (void *nip) -{ -#ifdef HAVE_SIGTRAMP_RT64 - if (nip == GLRO (dl_vdso_sigtramp_rt64) || - nip == GLRO (dl_vdso_sigtramp_rt64) + 4) - return true; -#endif - return false; -} - -int -__backtrace (void **array, int size) -{ - struct layout *current; - int count; - - /* Force gcc to spill LR. */ - asm volatile ("" : "=l"(current)); - - /* Get the address on top-of-stack. */ - asm volatile ("ld %0,0(1)" : "=r"(current)); - - for ( count = 0; - current != NULL && count < size; - current = current->next, count++) - { - array[count] = current->return_address; - - /* Check if the symbol is the signal trampoline and get the interrupted - * symbol address from the trampoline saved area. */ - if (is_sigtramp_address (current->return_address)) - { - struct signal_frame_64 *sigframe = (struct signal_frame_64*) current; - if (count + 1 == size) - break; - array[++count] = (void*) sigframe->uc.uc_mcontext.gp_regs[PT_NIP]; - current = (void*) sigframe->uc.uc_mcontext.gp_regs[PT_R1]; - } - } - - /* It's possible the second-last stack frame can't return - (that is, it's __libc_start_main), in which case - the CRT startup code will have set its LR to 'NULL'. */ - if (count > 0 && array[count-1] == NULL) - count--; - - return count; -} -weak_alias (__backtrace, backtrace) -libc_hidden_def (__backtrace) diff --git a/sysdeps/unix/sysv/linux/dl-vdso-setup.c b/sysdeps/unix/sysv/linux/dl-vdso-setup.c index 037a277..b42b9df 100644 --- a/sysdeps/unix/sysv/linux/dl-vdso-setup.c +++ b/sysdeps/unix/sysv/linux/dl-vdso-setup.c @@ -71,17 +71,6 @@ PROCINFO_CLASS int (*_dl_vdso_clock_getres_time64) (clockid_t, # ifdef HAVE_GET_TBFREQ PROCINFO_CLASS uint64_t (*_dl_vdso_get_tbfreq)(void) RELRO; # endif -/* The sigtramp are used on powerpc backtrace without using - INLINE_VSYSCALL, so there is no need to set their type. */ -# ifdef HAVE_SIGTRAMP_RT64 -PROCINFO_CLASS void *_dl_vdso_sigtramp_rt64 RELRO; -# endif -# ifdef HAVE_SIGTRAMP_RT32 -PROCINFO_CLASS void *_dl_vdso_sigtramp_rt32 RELRO; -# endif -# ifdef HAVE_SIGTRAMP_32 -PROCINFO_CLASS void *_dl_vdso_sigtramp_32 RELRO; -# endif #endif #undef RELRO diff --git a/sysdeps/unix/sysv/linux/dl-vdso-setup.h b/sysdeps/unix/sysv/linux/dl-vdso-setup.h index daf9873..75b00a0 100644 --- a/sysdeps/unix/sysv/linux/dl-vdso-setup.h +++ b/sysdeps/unix/sysv/linux/dl-vdso-setup.h @@ -47,15 +47,6 @@ setup_vdso_pointers (void) #ifdef HAVE_GET_TBFREQ GLRO(dl_vdso_get_tbfreq) = dl_vdso_vsym (HAVE_GET_TBFREQ); #endif -#ifdef HAVE_SIGTRAMP_RT64 - GLRO(dl_vdso_sigtramp_rt64) = dl_vdso_vsym (HAVE_SIGTRAMP_RT64); -#endif -#ifdef HAVE_SIGTRAMP_RT32 - GLRO(dl_vdso_sigtramp_rt32) = dl_vdso_vsym (HAVE_SIGTRAMP_RT32); -#endif -#ifdef HAVE_SIGTRAMP_32 - GLRO(dl_vdso_sigtramp_32) = dl_vdso_vsym (HAVE_SIGTRAMP_32); -#endif } #endif diff --git a/sysdeps/unix/sysv/linux/powerpc/sysdep.h b/sysdeps/unix/sysv/linux/powerpc/sysdep.h index 4b9d43c..ff9644d 100644 --- a/sysdeps/unix/sysv/linux/powerpc/sysdep.h +++ b/sysdeps/unix/sysv/linux/powerpc/sysdep.h @@ -255,11 +255,4 @@ #define HAVE_GETTIMEOFDAY_VSYSCALL "__kernel_gettimeofday" #define HAVE_GET_TBFREQ "__kernel_get_tbfreq" -#if defined(__PPC64__) || defined(__powerpc64__) -# define HAVE_SIGTRAMP_RT64 "__kernel_sigtramp_rt64" -#else -# define HAVE_SIGTRAMP_32 "__kernel_sigtramp32" -# define HAVE_SIGTRAMP_RT32 "__kernel_sigtramp_rt32" -#endif - #endif /* _LINUX_POWERPC_SYSDEP_H */ -- 2.7.4