Hello,
On Fri, May 12, 2023 at 10:12 PM Bruno Haible <br...@clisp.org> wrote:
> * glibc/sysdeps/mach/hurd/x86_64/bits/sigcontext.h lines 57..79
> * glibc/sysdeps/mach/hurd/x86/trampoline.c lines 239..247.
> This code copies the values from the stack into a 'struct sigcontext'.
> But here the order of the registers is
No: trampoline.c copies the values of registers from the Mach thread
state, as returned by thread_get_state (). There's no way that glibc
could, from the userland, directly get at the values on the kernel
stack.
thread_get_state () returns the i386_thread_state structure defined in
gnumach i386/include/mach/i386/thread_status.h:
struct i386_thread_state {
unsigned int gs;
unsigned int fs;
unsigned int es;
unsigned int ds;
#if defined(__x86_64__) && !defined(USER32)
uint64_t r8;
uint64_t r9;
uint64_t r10;
uint64_t r11;
uint64_t r12;
uint64_t r13;
uint64_t r14;
uint64_t r15;
uint64_t rdi;
uint64_t rsi;
uint64_t rbp;
uint64_t rsp;
uint64_t rbx;
uint64_t rdx;
uint64_t rcx;
uint64_t rax;
uint64_t rip;
..more..
So struct sigcontext is supposed to mirror that arrangement.
Mach fills in i386_thread_state from its internal struct
i386_saved_state (defined in i386/i386/thread.h), and *that one* is
arranged in the popa order:
struct i386_saved_state {
#ifdef __x86_64__
unsigned long fsbase;
unsigned long gsbase;
#endif
unsigned long gs;
unsigned long fs;
unsigned long es;
unsigned long ds;
#ifdef __x86_64__
unsigned long r15;
unsigned long r14;
unsigned long r13;
unsigned long r12;
unsigned long r11;
unsigned long r10;
unsigned long r9;
unsigned long r8;
The conversion between i386_saved_state and i386_thread_state is not a
direct memcpy, but a bunch of explicit assignments (see
i386_thread_state:thread_getstatus):
#if defined(__x86_64__) && !defined(USER32)
state->r8 = saved_state->r8;
state->r9 = saved_state->r9;
state->r10 = saved_state->r10;
state->r11 = saved_state->r11;
state->r12 = saved_state->r12;
state->r13 = saved_state->r13;
state->r14 = saved_state->r14;
state->r15 = saved_state->r15;
state->rdi = saved_state->edi;
state->rsi = saved_state->esi;
state->rbp = saved_state->ebp;
state->rbx = saved_state->ebx;
state->rdx = saved_state->edx;
state->rcx = saved_state->ecx;
state->rax = saved_state->eax;
state->rip = saved_state->eip;
state->ursp = saved_state->uesp;
state->rfl = saved_state->efl;
state->rsp = 0; /* unused */
So there's no bug here.
Sergey
