X-Git-Url: http://drtracing.org/?a=blobdiff_plain;f=gdb%2Fi386-linux-nat.c;h=2bfac295efe35688effb8c27882224a3c164a534;hb=a6abb2c0e922bf08b1713f7b9f17a00bd61a11ce;hp=bf5e821a27936e9a22f882006b1b0f702d4eac61;hpb=17f9defb0b0670c472e58af60cfa96ba4c3eaafb;p=deliverable%2Fbinutils-gdb.git diff --git a/gdb/i386-linux-nat.c b/gdb/i386-linux-nat.c index bf5e821a27..2bfac295ef 100644 --- a/gdb/i386-linux-nat.c +++ b/gdb/i386-linux-nat.c @@ -1,4 +1,5 @@ /* Native-dependent code for Linux running on i386's, for GDB. + Copyright (C) 1999, 2000 Free Software Foundation, Inc. This file is part of GDB. @@ -23,7 +24,6 @@ /* For i386_linux_skip_solib_resolver. */ #include "symtab.h" -#include "frame.h" #include "symfile.h" #include "objfiles.h" @@ -950,6 +950,91 @@ fetch_core_registers (char *core_reg_sect, unsigned core_reg_size, } } + +/* The instruction for a Linux system call is: + int $0x80 + or 0xcd 0x80. */ + +static const unsigned char linux_syscall[] = { 0xcd, 0x80 }; + +#define LINUX_SYSCALL_LEN (sizeof linux_syscall) + +/* The system call number is stored in the %eax register. */ +#define LINUX_SYSCALL_REGNUM 0 /* %eax */ + +/* We are specifically interested in the sigreturn and rt_sigreturn + system calls. */ + +#ifndef SYS_sigreturn +#define SYS_sigreturn 0x77 +#endif +#ifndef SYS_rt_sigreturn +#define SYS_rt_sigreturn 0xad +#endif + +/* Offset to saved processor flags, from . */ +#define LINUX_SIGCONTEXT_EFLAGS_OFFSET (64) + +/* Resume execution of the inferior process. + If STEP is nonzero, single-step it. + If SIGNAL is nonzero, give it that signal. */ + +void +child_resume (int pid, int step, enum target_signal signal) +{ + int request = PTRACE_CONT; + + if (pid == -1) + /* Resume all threads. */ + /* I think this only gets used in the non-threaded case, where "resume + all threads" and "resume inferior_pid" are the same. */ + pid = inferior_pid; + + if (step) + { + CORE_ADDR pc = read_pc_pid (pid); + unsigned char buf[LINUX_SYSCALL_LEN]; + + request = PTRACE_SINGLESTEP; + + /* Returning from a signal trampoline is done by calling a + special system call (sigreturn or rt_sigreturn, see + i386-linux-tdep.c for more information). This system call + restores the registers that were saved when the signal was + raised, including %eflags. That means that single-stepping + won't work. Instead, we'll have to modify the signal context + that's about to be restored, and set the trace flag there. */ + + /* First check if PC is at a system call. */ + if (read_memory_nobpt (pc, (char *) buf, LINUX_SYSCALL_LEN) == 0 + && memcmp (buf, linux_syscall, LINUX_SYSCALL_LEN) == 0) + { + int syscall = read_register_pid (LINUX_SYSCALL_REGNUM, pid); + + /* Then check the system call number. */ + if (syscall == SYS_sigreturn || syscall == SYS_rt_sigreturn) + { + CORE_ADDR sp = read_register (SP_REGNUM); + CORE_ADDR addr = sp; + unsigned long int eflags; + + if (syscall == SYS_rt_sigreturn) + addr = read_memory_integer (sp + 8, 4) + 20; + + /* Set the trace flag in the context that's about to be + restored. */ + addr += LINUX_SIGCONTEXT_EFLAGS_OFFSET; + read_memory (addr, (char *) &eflags, 4); + eflags |= 0x0100; + write_memory (addr, (char *) &eflags, 4); + } + } + } + + if (ptrace (request, pid, 0, target_signal_to_host (signal)) == -1) + perror_with_name ("ptrace"); +} + /* Calling functions in shared libraries. */ /* FIXME: kettenis/2000-03-05: Doesn't this belong in a @@ -1043,263 +1128,6 @@ i386_linux_skip_solib_resolver (CORE_ADDR pc) return 0; } - -/* Recognizing signal handler frames. */ - -/* Linux has two flavors of signals. Normal signal handlers, and - "realtime" (RT) signals. The RT signals can provide additional - information to the signal handler if the SA_SIGINFO flag is set - when establishing a signal handler using `sigaction'. It is not - unlikely that future versions of Linux will support SA_SIGINFO for - normal signals too. */ - -/* When the i386 Linux kernel calls a signal handler and the - SA_RESTORER flag isn't set, the return address points to a bit of - code on the stack. This function returns whether the PC appears to - be within this bit of code. - - The instruction sequence for normal signals is - pop %eax - mov $0x77,%eax - int $0x80 - or 0x58 0xb8 0x77 0x00 0x00 0x00 0xcd 0x80. - - Checking for the code sequence should be somewhat reliable, because - the effect is to call the system call sigreturn. This is unlikely - to occur anywhere other than a signal trampoline. - - It kind of sucks that we have to read memory from the process in - order to identify a signal trampoline, but there doesn't seem to be - any other way. The IN_SIGTRAMP macro in tm-linux.h arranges to - only call us if no function name could be identified, which should - be the case since the code is on the stack. - - Detection of signal trampolines for handlers that set the - SA_RESTORER flag is in general not possible. Unfortunately this is - what the GNU C Library has been doing for quite some time now. - However, as of version 2.1.2, the GNU C Library uses signal - trampolines (named __restore and __restore_rt) that are identical - to the ones used by the kernel. Therefore, these trampolines are - supported too. */ - -#define LINUX_SIGTRAMP_INSN0 (0x58) /* pop %eax */ -#define LINUX_SIGTRAMP_OFFSET0 (0) -#define LINUX_SIGTRAMP_INSN1 (0xb8) /* mov $NNNN,%eax */ -#define LINUX_SIGTRAMP_OFFSET1 (1) -#define LINUX_SIGTRAMP_INSN2 (0xcd) /* int */ -#define LINUX_SIGTRAMP_OFFSET2 (6) - -static const unsigned char linux_sigtramp_code[] = -{ - LINUX_SIGTRAMP_INSN0, /* pop %eax */ - LINUX_SIGTRAMP_INSN1, 0x77, 0x00, 0x00, 0x00, /* mov $0x77,%eax */ - LINUX_SIGTRAMP_INSN2, 0x80 /* int $0x80 */ -}; - -#define LINUX_SIGTRAMP_LEN (sizeof linux_sigtramp_code) - -/* If PC is in a sigtramp routine, return the address of the start of - the routine. Otherwise, return 0. */ - -static CORE_ADDR -i386_linux_sigtramp_start (CORE_ADDR pc) -{ - unsigned char buf[LINUX_SIGTRAMP_LEN]; - - /* We only recognize a signal trampoline if PC is at the start of - one of the three instructions. We optimize for finding the PC at - the start, as will be the case when the trampoline is not the - first frame on the stack. We assume that in the case where the - PC is not at the start of the instruction sequence, there will be - a few trailing readable bytes on the stack. */ - - if (read_memory_nobpt (pc, (char *) buf, LINUX_SIGTRAMP_LEN) != 0) - return 0; - - if (buf[0] != LINUX_SIGTRAMP_INSN0) - { - int adjust; - - switch (buf[0]) - { - case LINUX_SIGTRAMP_INSN1: - adjust = LINUX_SIGTRAMP_OFFSET1; - break; - case LINUX_SIGTRAMP_INSN2: - adjust = LINUX_SIGTRAMP_OFFSET2; - break; - default: - return 0; - } - - pc -= adjust; - - if (read_memory_nobpt (pc, (char *) buf, LINUX_SIGTRAMP_LEN) != 0) - return 0; - } - - if (memcmp (buf, linux_sigtramp_code, LINUX_SIGTRAMP_LEN) != 0) - return 0; - - return pc; -} - -/* This function does the same for RT signals. Here the instruction - sequence is - mov $0xad,%eax - int $0x80 - or 0xb8 0xad 0x00 0x00 0x00 0xcd 0x80. - - The effect is to call the system call rt_sigreturn. */ - -#define LINUX_RT_SIGTRAMP_INSN0 (0xb8) /* mov $NNNN,%eax */ -#define LINUX_RT_SIGTRAMP_OFFSET0 (0) -#define LINUX_RT_SIGTRAMP_INSN1 (0xcd) /* int */ -#define LINUX_RT_SIGTRAMP_OFFSET1 (5) - -static const unsigned char linux_rt_sigtramp_code[] = -{ - LINUX_RT_SIGTRAMP_INSN0, 0xad, 0x00, 0x00, 0x00, /* mov $0xad,%eax */ - LINUX_RT_SIGTRAMP_INSN1, 0x80 /* int $0x80 */ -}; - -#define LINUX_RT_SIGTRAMP_LEN (sizeof linux_rt_sigtramp_code) - -/* If PC is in a RT sigtramp routine, return the address of the start - of the routine. Otherwise, return 0. */ - -static CORE_ADDR -i386_linux_rt_sigtramp_start (CORE_ADDR pc) -{ - unsigned char buf[LINUX_RT_SIGTRAMP_LEN]; - - /* We only recognize a signal trampoline if PC is at the start of - one of the two instructions. We optimize for finding the PC at - the start, as will be the case when the trampoline is not the - first frame on the stack. We assume that in the case where the - PC is not at the start of the instruction sequence, there will be - a few trailing readable bytes on the stack. */ - - if (read_memory_nobpt (pc, (char *) buf, LINUX_RT_SIGTRAMP_LEN) != 0) - return 0; - - if (buf[0] != LINUX_RT_SIGTRAMP_INSN0) - { - if (buf[0] != LINUX_RT_SIGTRAMP_INSN1) - return 0; - - pc -= LINUX_RT_SIGTRAMP_OFFSET1; - - if (read_memory_nobpt (pc, (char *) buf, LINUX_RT_SIGTRAMP_LEN) != 0) - return 0; - } - - if (memcmp (buf, linux_rt_sigtramp_code, LINUX_RT_SIGTRAMP_LEN) != 0) - return 0; - - return pc; -} - -/* Return whether PC is in a Linux sigtramp routine. */ - -int -i386_linux_in_sigtramp (CORE_ADDR pc, char *name) -{ - if (name) - return STREQ ("__restore", name) || STREQ ("__restore_rt", name); - - return (i386_linux_sigtramp_start (pc) != 0 - || i386_linux_rt_sigtramp_start (pc) != 0); -} - -/* Assuming FRAME is for a Linux sigtramp routine, return the address - of the associated sigcontext structure. */ - -CORE_ADDR -i386_linux_sigcontext_addr (struct frame_info *frame) -{ - CORE_ADDR pc; - - pc = i386_linux_sigtramp_start (frame->pc); - if (pc) - { - CORE_ADDR sp; - - if (frame->next) - /* If this isn't the top frame, the next frame must be for the - signal handler itself. The sigcontext structure lives on - the stack, right after the signum argument. */ - return frame->next->frame + 12; - - /* This is the top frame. We'll have to find the address of the - sigcontext structure by looking at the stack pointer. Keep - in mind that the first instruction of the sigtramp code is - "pop %eax". If the PC is at this instruction, adjust the - returned value accordingly. */ - sp = read_register (SP_REGNUM); - if (pc == frame->pc) - return sp + 4; - return sp; - } - - pc = i386_linux_rt_sigtramp_start (frame->pc); - if (pc) - { - if (frame->next) - /* If this isn't the top frame, the next frame must be for the - signal handler itself. The sigcontext structure is part of - the user context. A pointer to the user context is passed - as the third argument to the signal handler. */ - return read_memory_integer (frame->next->frame + 16, 4) + 20; - - /* This is the top frame. Again, use the stack pointer to find - the address of the sigcontext structure. */ - return read_memory_integer (read_register (SP_REGNUM) + 8, 4) + 20; - } - - error ("Couldn't recognize signal trampoline."); - return 0; -} - -/* Offset to saved PC in sigcontext, from . */ -#define LINUX_SIGCONTEXT_PC_OFFSET (56) - -/* Assuming FRAME is for a Linux sigtramp routine, return the saved - program counter. */ - -CORE_ADDR -i386_linux_sigtramp_saved_pc (struct frame_info *frame) -{ - CORE_ADDR addr; - addr = i386_linux_sigcontext_addr (frame); - return read_memory_integer (addr + LINUX_SIGCONTEXT_PC_OFFSET, 4); -} - -/* Offset to saved SP in sigcontext, from . */ -#define LINUX_SIGCONTEXT_SP_OFFSET (28) - -/* Assuming FRAME is for a Linux sigtramp routine, return the saved - stack pointer. */ - -CORE_ADDR -i386_linux_sigtramp_saved_sp (struct frame_info *frame) -{ - CORE_ADDR addr; - addr = i386_linux_sigcontext_addr (frame); - return read_memory_integer (addr + LINUX_SIGCONTEXT_SP_OFFSET, 4); -} - -/* Immediately after a function call, return the saved pc. */ - -CORE_ADDR -i386_linux_saved_pc_after_call (struct frame_info *frame) -{ - if (frame->signal_handler_caller) - return i386_linux_sigtramp_saved_pc (frame); - - return read_memory_integer (read_register (SP_REGNUM), 4); -} - /* Register that we are able to handle Linux ELF core file formats. */