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[PATCH v2 01/23] linux-user: Add infrastructure for a signal trampoline
From: |
Richard Henderson |
Subject: |
[PATCH v2 01/23] linux-user: Add infrastructure for a signal trampoline page |
Date: |
Fri, 18 Jun 2021 12:29:29 -0700 |
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>
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(+)
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 17ab06f612..7bc67ac9cb 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 */
@@ -3232,6 +3237,18 @@ 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 9016896dcd..2f19cc0bf6 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,
--
2.25.1