diff mbox series

[v2,01/36] linux-user: Add infrastructure for a signal trampoline page

Message ID 20210706234932.356913-2-richard.henderson@linaro.org
State New
Headers show
Series linux-user: Signal trampolines and vdsos | expand

Commit Message

Richard Henderson July 6, 2021, 11:48 p.m. UTC 
Allocate a page to hold the signal trampoline(s).
Invoke a guest-specific hook to fill in the contents
of the page before marking it read-execute again.

Reviewed-by: Max Filippov <jcmvbkbc@gmail.com>

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

---
 linux-user/qemu.h    |  7 +++++++
 linux-user/elfload.c | 17 +++++++++++++++++
 linux-user/signal.c  |  3 +++
 3 files changed, 27 insertions(+)

-- 
2.25.1
diff mbox series

Patch

diff --git a/linux-user/qemu.h b/linux-user/qemu.h
index 3b0b6b75fe..9e5e2aa499 100644
--- a/linux-user/qemu.h
+++ b/linux-user/qemu.h
@@ -437,6 +437,13 @@  abi_long do_sigaltstack(abi_ulong uss_addr, abi_ulong uoss_addr,
 int do_sigprocmask(int how, const sigset_t *set, sigset_t *oldset);
 abi_long do_swapcontext(CPUArchState *env, abi_ulong uold_ctx,
                         abi_ulong unew_ctx, abi_long ctx_size);
+
+/* Fallback addresses into sigtramp page. */
+extern abi_ulong default_sigreturn;
+extern abi_ulong default_rt_sigreturn;
+
+void setup_sigtramp(abi_ulong tramp_page);
+
 /**
  * block_signals: block all signals while handling this guest syscall
  *
diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index 598ab8aa13..9bec6613a2 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -14,6 +14,7 @@ 
 #include "qemu/units.h"
 #include "qemu/selfmap.h"
 #include "qapi/error.h"
+#include "target_signal.h"
 
 #ifdef _ARCH_PPC64
 #undef ARCH_DLINFO
@@ -25,6 +26,10 @@ 
 #undef ELF_ARCH
 #endif
 
+#ifndef TARGET_ARCH_HAS_SIGTRAMP_PAGE
+#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 0
+#endif
+
 #define ELF_OSABI   ELFOSABI_SYSV
 
 /* from personality.h */
@@ -3233,6 +3238,18 @@  int load_elf_binary(struct linux_binprm *bprm, struct image_info *info)
 #endif
     }
 
+    /*
+     * TODO: load a vdso, which would also contain the signal trampolines.
+     * Otherwise, allocate a private page to hold them.
+     */
+    if (TARGET_ARCH_HAS_SIGTRAMP_PAGE) {
+        abi_ulong tramp_page = target_mmap(0, TARGET_PAGE_SIZE,
+                                           PROT_READ | PROT_WRITE,
+                                           MAP_PRIVATE | MAP_ANON, -1, 0);
+        setup_sigtramp(tramp_page);
+        target_mprotect(tramp_page, TARGET_PAGE_SIZE, PROT_READ | PROT_EXEC);
+    }
+
     bprm->p = create_elf_tables(bprm->p, bprm->argc, bprm->envc, &elf_ex,
                                 info, (elf_interpreter ? &interp_info : NULL));
     info->start_stack = bprm->p;
diff --git a/linux-user/signal.c b/linux-user/signal.c
index a8faea6f09..099374d456 100644
--- a/linux-user/signal.c
+++ b/linux-user/signal.c
@@ -30,6 +30,9 @@  static struct target_sigaction sigact_table[TARGET_NSIG];
 static void host_signal_handler(int host_signum, siginfo_t *info,
                                 void *puc);
 
+/* Fallback addresses into sigtramp page. */
+abi_ulong default_sigreturn;
+abi_ulong default_rt_sigreturn;
 
 /*
  * System includes define _NSIG as SIGRTMAX + 1,