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Improve /proc/self/exe substitution on Android
* exec/configure.ac (USER_SWORD): New macro. * exec/exec.c (format_pid): Export this function. * exec/exec.h: * exec/trace.c (canon_path): New function. (handle_readlinkat, handle_openat): Test complete file name against /proc/self/exe, and further check for /proc/pid/exe.
This commit is contained in:
Po Lu
parent
db5c8bda63
commit
30bc867aec
4 changed files with 121 additions and 11 deletions
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@ -122,6 +122,7 @@ AH_TEMPLATE([SYSCALL_RET_REG], [Define to register holding value of system calls
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AH_TEMPLATE([STACK_POINTER], [Define to register holding the stack pointer.])
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AH_TEMPLATE([EXEC_SYSCALL], [Define to number of the `exec' system call.])
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AH_TEMPLATE([USER_WORD], [Define to word type used by tracees.])
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AH_TEMPLATE([USER_SWORD], [Define to signed word type used by tracees.])
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AH_TEMPLATE([EXEC_64], [Define to 1 if the system utilizes 64-bit ELF.])
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AH_TEMPLATE([STACK_GROWS_DOWNWARDS], [Define to 1 if the stack grows downwards.])
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AH_TEMPLATE([ABI_RED_ZONE], [Define to number of reserved bytes past the stack frame.])
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@ -251,6 +252,7 @@ AS_CASE([$host], [x86_64-*linux*],
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AC_DEFINE([STACK_POINTER], [rsp])
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AC_DEFINE([EXEC_SYSCALL], [__NR_execve])
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AC_DEFINE([USER_WORD], [uintptr_t])
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AC_DEFINE([USER_SWORD], [intptr_t])
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AC_DEFINE([EXEC_64], [1])
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AC_DEFINE([ABI_RED_ZONE], [128])
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AC_DEFINE([EXECUTABLE_BASE], [0x555555554000])
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@ -283,6 +285,7 @@ AS_CASE([$host], [x86_64-*linux*],
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AC_DEFINE([STACK_POINTER], [esp])
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AC_DEFINE([EXEC_SYSCALL], [__NR_execve])
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AC_DEFINE([USER_WORD], [uintptr_t])
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AC_DEFINE([USER_SWORD], [intptr_t])
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AC_DEFINE([EXECUTABLE_BASE], [0x0f000000])
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AC_DEFINE([INTERPRETER_BASE], [0xaf000000])
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AC_DEFINE([STACK_GROWS_DOWNWARDS], [1])
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@ -313,6 +316,7 @@ AS_CASE([$host], [x86_64-*linux*],
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AC_DEFINE([STACK_POINTER], [sp])
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AC_DEFINE([EXEC_SYSCALL], [__NR_execve])
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AC_DEFINE([USER_WORD], [uintptr_t])
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AC_DEFINE([USER_SWORD], [intptr_t])
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AC_DEFINE([EXEC_64], [1])
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AC_DEFINE([EXECUTABLE_BASE], [0x3000000000])
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AC_DEFINE([INTERPRETER_BASE], [0x3f00000000])
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@ -344,6 +348,7 @@ AS_CASE([$host], [x86_64-*linux*],
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AC_DEFINE([STACK_POINTER], [[uregs[13]]])
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AC_DEFINE([EXEC_SYSCALL], [__NR_execve])
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AC_DEFINE([USER_WORD], [uintptr_t])
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AC_DEFINE([USER_SWORD], [intptr_t])
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AC_DEFINE([EXECUTABLE_BASE], [0x0f000000])
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AC_DEFINE([INTERPRETER_BASE], [0x1f000000])
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AC_DEFINE([STACK_GROWS_DOWNWARDS], [1])
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@ -368,6 +373,7 @@ AS_CASE([$host], [x86_64-*linux*],
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AC_DEFINE([STACK_POINTER], [[uregs[13]]])
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AC_DEFINE([EXEC_SYSCALL], [__NR_execve])
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AC_DEFINE([USER_WORD], [uintptr_t])
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AC_DEFINE([USER_SWORD], [intptr_t])
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AC_DEFINE([EXECUTABLE_BASE], [0x0f000000])
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AC_DEFINE([INTERPRETER_BASE], [0x1f000000])
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AC_DEFINE([STACK_GROWS_DOWNWARDS], [1])
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@ -398,6 +404,7 @@ AS_CASE([$host], [x86_64-*linux*],
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AC_DEFINE([STACK_POINTER], [[gregs[29]]]) # sp
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AC_DEFINE([EXEC_SYSCALL], [__NR_execve])
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AC_DEFINE([USER_WORD], [uintptr_t])
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AC_DEFINE([USER_SWORD], [intptr_t])
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AC_DEFINE([EXECUTABLE_BASE], [0x0f000000])
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AC_DEFINE([INTERPRETER_BASE], [0x1f000000])
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AC_DEFINE([STACK_GROWS_DOWNWARDS], [1])
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@ -427,6 +434,7 @@ AS_CASE([$host], [x86_64-*linux*],
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AC_DEFINE([STACK_POINTER], [[gregs[29]]]) # sp
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AC_DEFINE([EXEC_SYSCALL], [__NR_execve])
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AC_DEFINE([USER_WORD], [uintptr_t])
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AC_DEFINE([USER_SWORD], [intptr_t])
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AC_DEFINE([EXEC_64], [1])
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AC_DEFINE([EXECUTABLE_BASE], [0x400000])
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AC_DEFINE([INTERPRETER_BASE], [0x3f00000000])
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@ -865,7 +865,7 @@ insert_args (struct exec_tracee *tracee, USER_REGS_STRUCT *regs,
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result in *IN, and return a pointer to the byte after the
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result. REM should be NULL. */
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static char *
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char *
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format_pid (char *in, unsigned int pid)
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{
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unsigned int digits[32], *fill;
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@ -180,6 +180,7 @@ extern int aarch64_set_regs (pid_t, USER_REGS_STRUCT *, bool);
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extern char *format_pid (char *, unsigned int);
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extern USER_WORD user_alloca (struct exec_tracee *, USER_REGS_STRUCT *,
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USER_REGS_STRUCT *, USER_WORD);
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extern int user_copy (struct exec_tracee *, const unsigned char *,
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121
exec/trace.c
121
exec/trace.c
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@ -31,6 +31,7 @@ along with GNU Emacs. If not, see <https://www.gnu.org/licenses/>. */
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#include <unistd.h>
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#include <stdlib.h>
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#include <errno.h>
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#include <fcntl.h>
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#include "exec.h"
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@ -894,6 +895,68 @@ handle_exec (struct exec_tracee *tracee, USER_REGS_STRUCT *regs)
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return 3;
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}
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/* Modify BUFFER, of size SIZE, so that it holds the absolute name of
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the file identified by BUFFER, relative to the current working
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directory of TRACEE if FD be AT_FDCWD, or the file referenced by FD
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otherwise.
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Value is 1 if this information is unavailable (of which there are
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variety of causes), and 0 on success. */
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static int
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canon_path (struct exec_tracee *tracee, int fd, char *buffer,
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ptrdiff_t size)
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{
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char link[sizeof "/proc//fd/" + 48], *p; /* Or /proc/pid/cwd. */
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char target[PATH_MAX];
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ssize_t rc, length;
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if (buffer[0] == '/')
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/* Absolute file name; return immediately. */
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return 0;
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else if (fd == AT_FDCWD)
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{
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p = stpcpy (link, "/proc/");
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p = format_pid (p, tracee->pid);
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stpcpy (p, "/cwd");
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}
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else if (fd < 0)
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/* Invalid file descriptor. */
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return 1;
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else
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{
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p = stpcpy (link, "/proc/");
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p = format_pid (p, tracee->pid);
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p = stpcpy (p, "/fd/");
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format_pid (p, fd);
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}
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/* Read LINK's target, and should it be oversized, punt. */
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rc = readlink (link, target, PATH_MAX);
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if (rc < 0 || rc >= PATH_MAX)
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return 1;
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/* Consider the amount by which BUFFER's existing contents should be
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displaced. */
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length = strlen (buffer) + 1;
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if ((length + rc + (target[rc - 1] != '/')) > size)
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/* Punt if this would overflow. */
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return 1;
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memmove ((buffer + rc + (target[rc - 1] != '/')),
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buffer, length);
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/* Copy the new file name into BUFFER. */
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memcpy (buffer, target, rc);
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/* Insert separator in between if need be. */
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if (target[rc - 1] != '/')
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buffer[rc] = '/';
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return 0;
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}
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/* Handle a `readlink' or `readlinkat' system call.
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CALLNO is the system call number, and REGS are the current user
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@ -924,22 +987,26 @@ handle_readlinkat (USER_WORD callno, USER_REGS_STRUCT *regs,
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char buffer[PATH_MAX + 1];
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USER_WORD address, return_buffer, size;
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size_t length;
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char proc_pid_exe[sizeof "/proc//exe" + 24], *p;
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int dirfd;
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/* Read the file name. */
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#ifdef READLINK_SYSCALL
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if (callno == READLINK_SYSCALL)
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{
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address = regs->SYSCALL_ARG_REG;
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dirfd = AT_FDCWD;
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address = regs->SYSCALL_ARG_REG;
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return_buffer = regs->SYSCALL_ARG1_REG;
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size = regs->SYSCALL_ARG2_REG;
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size = regs->SYSCALL_ARG2_REG;
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}
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else
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#endif /* READLINK_SYSCALL */
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{
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address = regs->SYSCALL_ARG1_REG;
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dirfd = (USER_SWORD) regs->SYSCALL_ARG_REG;
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address = regs->SYSCALL_ARG1_REG;
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return_buffer = regs->SYSCALL_ARG2_REG;
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size = regs->SYSCALL_ARG3_REG;
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size = regs->SYSCALL_ARG3_REG;
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}
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read_memory (tracee, buffer, PATH_MAX, address);
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@ -952,12 +1019,25 @@ handle_readlinkat (USER_WORD callno, USER_REGS_STRUCT *regs,
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return 1;
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}
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/* Now check if the caller is looking for /proc/self/exe.
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/* Expand BUFFER into an absolute file name. TODO:
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AT_SYMLINK_FOLLOW? */
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if (canon_path (tracee, dirfd, buffer, sizeof buffer))
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return 0;
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/* Now check if the caller is looking for /proc/self/exe or its
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equivalent with the PID made explicit.
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dirfd can be ignored, as for now only absolute file names are
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handled. FIXME. */
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if (strcmp (buffer, "/proc/self/exe") || !tracee->exec_file)
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p = stpcpy (proc_pid_exe, "/proc/");
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p = format_pid (p, tracee->pid);
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stpcpy (p, "/exe");
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if ((strcmp (buffer, "/proc/self/exe")
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&& strcmp (buffer, proc_pid_exe))
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|| !tracee->exec_file)
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return 0;
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/* Copy over tracee->exec_file. Truncate it to PATH_MAX, length, or
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@ -1004,15 +1084,23 @@ handle_openat (USER_WORD callno, USER_REGS_STRUCT *regs,
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USER_WORD address;
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size_t length;
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USER_REGS_STRUCT original;
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char proc_pid_exe[sizeof "/proc//exe" + 24], *p;
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int dirfd;
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/* Read the file name. */
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#ifdef OPEN_SYSCALL
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if (callno == OPEN_SYSCALL)
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address = regs->SYSCALL_ARG_REG;
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{
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dirfd = AT_FDCWD;
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address = regs->SYSCALL_ARG_REG;
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}
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else
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#endif /* OPEN_SYSCALL */
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address = regs->SYSCALL_ARG1_REG;
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{
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dirfd = (USER_SWORD) regs->SYSCALL_ARG_REG;
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address = regs->SYSCALL_ARG1_REG;
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}
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/* Read the file name into the buffer and verify that it is NULL
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terminated. */
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@ -1024,12 +1112,25 @@ handle_openat (USER_WORD callno, USER_REGS_STRUCT *regs,
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return 1;
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}
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/* Now check if the caller is looking for /proc/self/exe.
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/* Expand BUFFER into an absolute file name. TODO:
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AT_SYMLINK_FOLLOW? */
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if (canon_path (tracee, dirfd, buffer, sizeof buffer))
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return 0;
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/* Now check if the caller is looking for /proc/self/exe or its
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equivalent with the PID made explicit.
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dirfd can be ignored, as for now only absolute file names are
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handled. FIXME. */
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if (strcmp (buffer, "/proc/self/exe") || !tracee->exec_file)
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p = stpcpy (proc_pid_exe, "/proc/");
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p = format_pid (p, tracee->pid);
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stpcpy (p, "/exe");
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if ((strcmp (buffer, "/proc/self/exe")
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&& strcmp (buffer, proc_pid_exe))
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|| !tracee->exec_file)
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return 0;
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/* Copy over tracee->exec_file. This doesn't correctly handle the
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