X-Git-Url: http://drtracing.org/?a=blobdiff_plain;f=gdb%2Famd64-linux-nat.c;h=f98d992070a340d0c37d249f0a8c10a3c5d71aa9;hb=06a6207a1ab458521656f293bb1ca8fd013d6f7c;hp=5a39fa87741e8649cfb63b4e670e4e95d47630c9;hpb=34a79281e4bd5d1a7f1d22a5a5be1ac2db56a3fc;p=deliverable%2Fbinutils-gdb.git diff --git a/gdb/amd64-linux-nat.c b/gdb/amd64-linux-nat.c index 5a39fa8774..f98d992070 100644 --- a/gdb/amd64-linux-nat.c +++ b/gdb/amd64-linux-nat.c @@ -1,6 +1,6 @@ /* Native-dependent code for GNU/Linux x86-64. - Copyright (C) 2001-2018 Free Software Foundation, Inc. + Copyright (C) 2001-2020 Free Software Foundation, Inc. Contributed by Jiri Smid, SuSE Labs. This file is part of GDB. @@ -33,7 +33,7 @@ #include "amd64-tdep.h" #include "amd64-linux-tdep.h" #include "i386-linux-tdep.h" -#include "x86-xstate.h" +#include "gdbsupport/x86-xstate.h" #include "x86-linux-nat.h" #include "nat/linux-ptrace.h" @@ -92,6 +92,71 @@ static int amd64_linux_gregset32_reg_offset[] = /* Transfering the general-purpose registers between GDB, inferiors and core files. */ +/* See amd64_collect_native_gregset. This linux specific version handles + issues with negative EAX values not being restored correctly upon syscall + return when debugging 32-bit targets. It has no effect on 64-bit + targets. */ + +static void +amd64_linux_collect_native_gregset (const struct regcache *regcache, + void *gregs, int regnum) +{ + amd64_collect_native_gregset (regcache, gregs, regnum); + + struct gdbarch *gdbarch = regcache->arch (); + if (gdbarch_bfd_arch_info (gdbarch)->bits_per_word == 32) + { + /* Sign extend EAX value to avoid potential syscall restart + problems. + + On Linux, when a syscall is interrupted by a signal, the + (kernel function implementing the) syscall may return + -ERESTARTSYS when a signal occurs. Doing so indicates that + the syscall is restartable. Then, depending on settings + associated with the signal handler, and after the signal + handler is called, the kernel can then either return -EINTR + or it can cause the syscall to be restarted. We are + concerned with the latter case here. + + On (32-bit) i386, the status (-ERESTARTSYS) is placed in the + EAX register. When debugging a 32-bit process from a 64-bit + (amd64) GDB, the debugger fetches 64-bit registers even + though the process being debugged is only 32-bit. The + register cache is only 32 bits wide though; GDB discards the + high 32 bits when placing 64-bit values in the 32-bit + regcache. Normally, this is not a problem since the 32-bit + process should only care about the lower 32-bit portions of + these registers. That said, it can happen that the 64-bit + value being restored will be different from the 64-bit value + that was originally retrieved from the kernel. The one place + (that we know of) where it does matter is in the kernel's + syscall restart code. The kernel's code for restarting a + syscall after a signal expects to see a negative value + (specifically -ERESTARTSYS) in the 64-bit RAX register in + order to correctly cause a syscall to be restarted. + + The call to amd64_collect_native_gregset, above, is setting + the high 32 bits of RAX (and other registers too) to 0. For + syscall restart, we need to sign extend EAX so that RAX will + appear as a negative value when EAX is set to -ERESTARTSYS. + This in turn will cause the signal handling code in the + kernel to recognize -ERESTARTSYS which will in turn cause the + syscall to be restarted. + + The test case gdb.base/interrupt.exp tests for this problem. + Without this sign extension code in place, it'll show + a number of failures when testing against unix/-m32. */ + + if (regnum == -1 || regnum == I386_EAX_REGNUM) + { + void *ptr = ((gdb_byte *) gregs + + amd64_linux_gregset32_reg_offset[I386_EAX_REGNUM]); + + *(int64_t *) ptr = *(int32_t *) ptr; + } + } +} + /* Fill GDB's register cache with the general-purpose register values in *GREGSETP. */ @@ -109,7 +174,7 @@ void fill_gregset (const struct regcache *regcache, elf_gregset_t *gregsetp, int regnum) { - amd64_collect_native_gregset (regcache, gregsetp, regnum); + amd64_linux_collect_native_gregset (regcache, gregsetp, regnum); } /* Transfering floating-point registers between GDB, inferiors and cores. */ @@ -148,9 +213,9 @@ amd64_linux_nat_target::fetch_registers (struct regcache *regcache, int regnum) int tid; /* GNU/Linux LWP ID's are process ID's. */ - tid = ptid_get_lwp (regcache->ptid ()); + tid = regcache->ptid ().lwp (); if (tid == 0) - tid = ptid_get_pid (regcache->ptid ()); /* Not a threaded program. */ + tid = regcache->ptid ().pid (); /* Not a threaded program. */ if (regnum == -1 || amd64_native_gregset_supplies_p (gdbarch, regnum)) { @@ -173,6 +238,12 @@ amd64_linux_nat_target::fetch_registers (struct regcache *regcache, int regnum) char xstateregs[X86_XSTATE_MAX_SIZE]; struct iovec iov; + /* Pre-4.14 kernels have a bug (fixed by commit 0852b374173b + "x86/fpu: Add FPU state copying quirk to handle XRSTOR failure on + Intel Skylake CPUs") that sometimes causes the mxcsr location in + xstateregs not to be copied by PTRACE_GETREGSET. Make sure that + the location is at least initialized with a defined value. */ + memset (xstateregs, 0, sizeof (xstateregs)); iov.iov_base = xstateregs; iov.iov_len = sizeof (xstateregs); if (ptrace (PTRACE_GETREGSET, tid, @@ -226,9 +297,9 @@ amd64_linux_nat_target::store_registers (struct regcache *regcache, int regnum) int tid; /* GNU/Linux LWP ID's are process ID's. */ - tid = ptid_get_lwp (regcache->ptid ()); + tid = regcache->ptid ().lwp (); if (tid == 0) - tid = ptid_get_pid (regcache->ptid ()); /* Not a threaded program. */ + tid = regcache->ptid ().pid (); /* Not a threaded program. */ if (regnum == -1 || amd64_native_gregset_supplies_p (gdbarch, regnum)) { @@ -237,7 +308,7 @@ amd64_linux_nat_target::store_registers (struct regcache *regcache, int regnum) if (ptrace (PTRACE_GETREGS, tid, 0, (long) ®s) < 0) perror_with_name (_("Couldn't get registers")); - amd64_collect_native_gregset (regcache, ®s, regnum); + amd64_linux_collect_native_gregset (regcache, ®s, regnum); if (ptrace (PTRACE_SETREGS, tid, 0, (long) ®s) < 0) perror_with_name (_("Couldn't write registers"));