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2000-04-30 Mark Kettenis <kettenis@gnu.org> 

Fix single-stepping out of signal trampolines.
	* config/i386/nm-linux.h (CHILD_RESUME): Define.
	* i386-linux-nat.c (child_resume): New function.
This commit is contained in:
Mark Kettenis 2000-04-30 09:34:13 +00:00
parent b4911a31c0
commit a6abb2c0e9
3 changed files with 94 additions and 0 deletions
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6
gdb/ChangeLog
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@ -1,3 +1,9 @@
2000-04-30 Mark Kettenis <kettenis@gnu.org>
Fix single-stepping out of signal trampolines.
* config/i386/nm-linux.h (CHILD_RESUME): Define.
* i386-linux-nat.c (child_resume): New function.
Fri Apr 28 16:22:34 2000 Andrew Cagney <cagney@b1.cygnus.com>
* blockframe.c (frameless_look_for_prologue): Use

3
gdb/config/i386/nm-linux.h
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@ -72,6 +72,9 @@ extern int kernel_u_size PARAMS ((void));
#define CANNOT_FETCH_REGISTER(regno) ((regno) >= NUM_GREGS)
#define CANNOT_STORE_REGISTER(regno) CANNOT_FETCH_REGISTER (regno)
/* Override child_resume in `infptrace.c'. */
#define CHILD_RESUME
extern CORE_ADDR
i386_stopped_by_watchpoint PARAMS ((int));
extern int

85
gdb/i386-linux-nat.c
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@ -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 <asm/sigcontext.h>. */
#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