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x86: Add sigreturn asm stub

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glibc no longer defines sigreturn, but we want to use it
when unwinding through signal stacks to resture the signal mask,
without forcing all uses of getcontext/setcontext to save and
restore the signal mask
This commit is contained in:
Dave Watson 2017-08-16 15:35:38 -07:00
parent 3d9a694de8
commit 7f1aebadbf
2 changed files with 26 additions and 2 deletions
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23
src/x86/Gos-linux.c
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@ -296,7 +296,7 @@ x86_local_resume (unw_addr_space_t as, unw_cursor_t *cursor, void *arg)
struct sigcontext *sc = (struct sigcontext *) c->sigcontext_addr;
Debug (8, "resuming at ip=%x via sigreturn(%p)\n", c->dwarf.ip, sc);
sigreturn (sc);
x86_sigreturn (sc);
}
else
{
@ -305,4 +305,25 @@ x86_local_resume (unw_addr_space_t as, unw_cursor_t *cursor, void *arg)
}
return -UNW_EINVAL;
}
/* sigreturn() is a no-op on x86 glibc. */
HIDDEN void
x86_sigreturn (unw_cursor_t *cursor)
{
struct cursor *c = (struct cursor *) cursor;
struct sigcontext *sc = (struct sigcontext *) c->sigcontext_addr;
mcontext_t *sc_mcontext = &((struct ucontext*)sc)->uc_mcontext;
/* Copy in saved uc - all preserved regs are at the start of sigcontext */
memcpy(sc_mcontext, &c->uc->uc_mcontext,
DWARF_NUM_PRESERVED_REGS * sizeof(unw_word_t));
Debug (8, "resuming at ip=%llx via sigreturn(%p)\n",
(unsigned long long) c->dwarf.ip, sc);
__asm__ __volatile__ ("mov %0, %%esp;"
"mov %1, %%eax;"
"syscall"
:: "r"(sc), "i"(SYS_rt_sigreturn)
: "memory");
abort();
}
#endif

3
src/x86/unwind_i.h
View file

@ -52,6 +52,7 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */
#define x86_scratch_loc UNW_OBJ(scratch_loc)
#define x86_get_scratch_loc UNW_OBJ(get_scratch_loc)
#define x86_r_uc_addr UNW_OBJ(r_uc_addr)
#define x86_sigreturn UNW_OBJ(sigreturn)
extern void x86_local_addr_space_init (void);
extern int x86_local_resume (unw_addr_space_t as, unw_cursor_t *cursor,
@ -60,4 +61,6 @@ extern dwarf_loc_t x86_scratch_loc (struct cursor *c, unw_regnum_t reg);
extern dwarf_loc_t x86_get_scratch_loc (struct cursor *c, unw_regnum_t reg);
extern void *x86_r_uc_addr (ucontext_t *uc, int reg);
extern void x86_sigreturn (unw_cursor_t *cursor);
#endif /* unwind_i_h */