diff mbox series

[PULL,01/26] linux-user: Add infrastructure for a signal trampoline page

Message ID 20211004074421.3141222-2-laurent@vivier.eu
State Accepted
Commit db2af69d6ba836a264878dbf2cf676d3c1fc46b4
Headers show
Series [PULL,01/26] linux-user: Add infrastructure for a signal trampoline page | expand

Commit Message

Laurent Vivier Oct. 4, 2021, 7:43 a.m. UTC 
From: Richard Henderson <richard.henderson@linaro.org>


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>

Message-Id: <20210929130553.121567-2-richard.henderson@linaro.org>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>

---
 linux-user/elfload.c       | 18 ++++++++++++++++++
 linux-user/signal-common.h |  6 ++++++
 linux-user/signal.c        |  3 +++
 3 files changed, 27 insertions(+)

-- 
2.31.1

Comments

Peter Maydell Nov. 5, 2021, 4:09 p.m. UTC | #1 
On Mon, 4 Oct 2021 at 08:44, Laurent Vivier <laurent@vivier.eu> wrote:
>

> From: Richard Henderson <richard.henderson@linaro.org>

>

> 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.


Hi; Coverity complains here about a missing error check
(CID 1464101):

>

> +    /*

> +     * 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);


target_mmap() can fail and return -1, but we don't check for that and
instead assume it's always valid.

> +        setup_sigtramp(tramp_page);

> +        target_mprotect(tramp_page, TARGET_PAGE_SIZE, PROT_READ | PROT_EXEC);

> +    }

> +


thanks
-- PMM
diff mbox series

Patch

diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index 5f9e2141ad1e..459a26ef1d93 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -7,6 +7,7 @@ 
 
 #include "qemu.h"
 #include "user-internals.h"
+#include "signal-common.h"
 #include "loader.h"
 #include "user-mmap.h"
 #include "disas/disas.h"
@@ -17,6 +18,7 @@ 
 #include "qemu/units.h"
 #include "qemu/selfmap.h"
 #include "qapi/error.h"
+#include "target_signal.h"
 
 #ifdef _ARCH_PPC64
 #undef ARCH_DLINFO
@@ -28,6 +30,10 @@ 
 #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 */
@@ -3249,6 +3255,18 @@  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-common.h b/linux-user/signal-common.h
index 79511becb4e7..7457f8025c47 100644
--- a/linux-user/signal-common.h
+++ b/linux-user/signal-common.h
@@ -20,6 +20,12 @@ 
 #ifndef SIGNAL_COMMON_H
 #define SIGNAL_COMMON_H
 
+/* Fallback addresses into sigtramp page. */
+extern abi_ulong default_sigreturn;
+extern abi_ulong default_rt_sigreturn;
+
+void setup_sigtramp(abi_ulong tramp_page);
+
 int on_sig_stack(unsigned long sp);
 int sas_ss_flags(unsigned long sp);
 abi_ulong target_sigsp(abi_ulong sp, struct target_sigaction *ka);
diff --git a/linux-user/signal.c b/linux-user/signal.c
index 203821645509..14d8fdfde152 100644
--- a/linux-user/signal.c
+++ b/linux-user/signal.c
@@ -35,6 +35,9 @@  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,