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sigsegv: Add tentative support for Hurd/x86_64.

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Based on explanations by Sergey Bugaev <bugaevc@gmail.com>.

* lib/sigsegv.c: Update from libsigsegv/src/fault-hurd-i386-old.h.
This commit is contained in:
Bruno Haible
2023-05-15 18:33:47 +02:00
parent 7357169317
commit f3059fb805
2 changed files with 52 additions and 12 deletions
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6
ChangeLog
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@@ -1,3 +1,9 @@
2023-05-15 Bruno Haible <bruno@clisp.org>
sigsegv: Add tentative support for Hurd/x86_64.
Based on explanations by Sergey Bugaev <bugaevc@gmail.com>.
* lib/sigsegv.c: Update from libsigsegv/src/fault-hurd-i386-old.h.
2023-05-15 Paul Eggert <eggert@cs.ucla.edu>
file-has-acl: improve port to Fedora 39

58
lib/sigsegv.c
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@@ -361,7 +361,7 @@ int libsigsegv_version = LIBSIGSEGV_VERSION;
#if defined __GNU__ /* Hurd */
# define SIGSEGV_FAULT_HANDLER_ARGLIST int sig, int code, struct sigcontext *scp
# define SIGSEGV_FAULT_HANDLER_ARGLIST int sig, long code, struct sigcontext *scp
# define SIGSEGV_FAULT_ADDRESS (unsigned long) code
# define SIGSEGV_FAULT_CONTEXT scp
@@ -370,11 +370,29 @@ int libsigsegv_version = LIBSIGSEGV_VERSION;
/* scp points to a 'struct sigcontext' (defined in
glibc/sysdeps/mach/hurd/x86_64/bits/sigcontext.h).
The registers, at the moment the signal occurred, get pushed on the stack
through gnumach/x86_64/locore.S:alltraps and then copied into the struct
through glibc/sysdeps/mach/hurd/x86/trampoline.c. */
/* sc_rsp is unused (not set by gnumach/x86_64/locore.S:alltraps). We need
to use sc_ursp. */
The registers, at the moment the signal occurred, get pushed on the kernel
stack through gnumach/x86_64/locore.S:alltraps. They are denoted by a
'struct i386_saved_state' (defined in gnumach/i386/i386/thread.h).
Upon invocation of the Mach interface function thread_get_state
<https://www.gnu.org/software/hurd/gnumach-doc/Thread-Execution.html>
(= __thread_get_state in glibc), defined in gnumach/kern/thread.c,
the function thread_getstatus, defined in gnumach/i386/i386/pcb.c, copies the
register values in a different arrangement into a 'struct i386_thread_state',
defined in gnumach/i386/include/mach/i386/thread_status.h. (Different
arrangement: trapno, err get dropped; different order of r8...r15; also rsp
gets set to 0.)
This 'struct i386_thread_state' is actually the 'basic' part of a
'struct machine_thread_all_state', defined in
glibc/sysdeps/mach/x86/thread_state.h.
From there, the function _hurd_setup_sighandler, defined in
glibc/sysdeps/mach/hurd/x86/trampoline.c,
1. sets rsp to the same value as ursp,
2. copies the 'struct i386_thread_state' into the appropriate part of a
'struct sigcontext', defined in
glibc/sysdeps/mach/hurd/x86_64/bits/sigcontext.h. */
/* Both sc_rsp and sc_ursp have the same value.
It appears more reliable to use sc_ursp because sc_rsp is marked as
"not used". */
# define SIGSEGV_FAULT_STACKPOINTER scp->sc_ursp
# elif defined __i386__
@@ -382,12 +400,28 @@ int libsigsegv_version = LIBSIGSEGV_VERSION;
/* scp points to a 'struct sigcontext' (defined in
glibc/sysdeps/mach/hurd/i386/bits/sigcontext.h).
The registers, at the moment the signal occurred, get pushed on the stack
through gnumach/i386/i386/locore.S:alltraps and then copied into the struct
through glibc/sysdeps/mach/hurd/x86/trampoline.c. */
/* Both sc_esp and sc_uesp appear to have the same value.
It appears more reliable to use sc_uesp because it is labelled as
"old esp, if trapped from user". */
The registers, at the moment the signal occurred, get pushed on the kernel
stack through gnumach/i386/i386/locore.S:alltraps. They are denoted by a
'struct i386_saved_state' (defined in gnumach/i386/i386/thread.h).
Upon invocation of the Mach interface function thread_get_state
<https://www.gnu.org/software/hurd/gnumach-doc/Thread-Execution.html>
(= __thread_get_state in glibc), defined in gnumach/kern/thread.c,
the function thread_getstatus, defined in gnumach/i386/i386/pcb.c, copies the
register values in a different arrangement into a 'struct i386_thread_state',
defined in gnumach/i386/include/mach/i386/thread_status.h. (Different
arrangement: trapno, err get dropped; also esp gets set to 0.)
This 'struct i386_thread_state' is actually the 'basic' part of a
'struct machine_thread_all_state', defined in
glibc/sysdeps/mach/x86/thread_state.h.
From there, the function _hurd_setup_sighandler, defined in
glibc/sysdeps/mach/hurd/x86/trampoline.c,
1. sets esp to the same value as uesp,
2. copies the 'struct i386_thread_state' into the appropriate part of a
'struct sigcontext', defined in
glibc/sysdeps/mach/hurd/i386/bits/sigcontext.h. */
/* Both sc_esp and sc_uesp have the same value.
It appears more reliable to use sc_uesp because sc_esp is marked as
"not used". */
# define SIGSEGV_FAULT_STACKPOINTER scp->sc_uesp
# endif