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[PATCH 16/21] linux-user/riscv: Implement setup_sigtramp

Richard Henderson posted 21 patches 4 years, 7 months ago
Maintainers: Jiaxun Yang <jiaxun.yang@flygoat.com>, Laurent Vivier <laurent@vivier.eu>, Taylor Simpson <tsimpson@quicinc.com>, "Philippe Mathieu-Daudé" <f4bug@amsat.org>, Cornelia Huck <cohuck@redhat.com>, Aleksandar Rikalo <aleksandar.rikalo@syrmia.com>, Thomas Huth <thuth@redhat.com>, Aurelien Jarno <aurelien@aurel32.net>
There is a newer version of this series
[PATCH 16/21] linux-user/riscv: Implement setup_sigtramp
Posted by Richard Henderson 4 years, 7 months ago 
Create and record the rt signal trampoline.

This fixes a bug wrt libgcc fallback unwinding.  It expects
the stack pointer to point to the siginfo_t, whereas we had
inexplicably placed our private signal trampoline at the start
of the signal frame instead of the end.  Now moot because we
have removed it from the stack frame entirely.

Cc: qemu-riscv@nongnu.org
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/riscv/target_signal.h |  2 ++
 linux-user/riscv/signal.c        | 22 +++++++++++++---------
 2 files changed, 15 insertions(+), 9 deletions(-)

diff --git a/linux-user/riscv/target_signal.h b/linux-user/riscv/target_signal.h
index f113ba9a55..3e36fddc9d 100644
--- a/linux-user/riscv/target_signal.h
+++ b/linux-user/riscv/target_signal.h
@@ -15,4 +15,6 @@ typedef struct target_sigaltstack {
 
 #include "../generic/signal.h"
 
+#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 1
+
 #endif /* RISCV_TARGET_SIGNAL_H */
diff --git a/linux-user/riscv/signal.c b/linux-user/riscv/signal.c
index 9405c7fd9a..4086dfa5d5 100644
--- a/linux-user/riscv/signal.c
+++ b/linux-user/riscv/signal.c
@@ -46,7 +46,6 @@ struct target_ucontext {
 };
 
 struct target_rt_sigframe {
-    uint32_t tramp[2]; /* not in kernel, which uses VDSO instead */
     struct target_siginfo info;
     struct target_ucontext uc;
 };
@@ -104,12 +103,6 @@ static void setup_ucontext(struct target_ucontext *uc,
     setup_sigcontext(&uc->uc_mcontext, env);
 }
 
-static inline void install_sigtramp(uint32_t *tramp)
-{
-    __put_user(0x08b00893, tramp + 0);  /* li a7, 139 = __NR_rt_sigreturn */
-    __put_user(0x00000073, tramp + 1);  /* ecall */
-}
-
 void setup_rt_frame(int sig, struct target_sigaction *ka,
                     target_siginfo_t *info,
                     target_sigset_t *set, CPURISCVState *env)
@@ -126,14 +119,13 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
 
     setup_ucontext(&frame->uc, env, set);
     tswap_siginfo(&frame->info, info);
-    install_sigtramp(frame->tramp);
 
     env->pc = ka->_sa_handler;
     env->gpr[xSP] = frame_addr;
     env->gpr[xA0] = sig;
     env->gpr[xA1] = frame_addr + offsetof(struct target_rt_sigframe, info);
     env->gpr[xA2] = frame_addr + offsetof(struct target_rt_sigframe, uc);
-    env->gpr[xRA] = frame_addr + offsetof(struct target_rt_sigframe, tramp);
+    env->gpr[xRA] = default_rt_sigreturn;
 
     return;
 
@@ -202,3 +194,15 @@ badframe:
     force_sig(TARGET_SIGSEGV);
     return 0;
 }
+
+void setup_sigtramp(abi_ulong sigtramp_page)
+{
+    uint32_t *tramp = lock_user(VERIFY_WRITE, sigtramp_page, 8, 0);
+    assert(tramp != NULL);
+
+    __put_user(0x08b00893, tramp + 0);  /* li a7, 139 = __NR_rt_sigreturn */
+    __put_user(0x00000073, tramp + 1);  /* ecall */
+
+    default_rt_sigreturn = sigtramp_page;
+    unlock_user(tramp, sigtramp_page, 8);
+}
-- 
2.25.1
Re: [PATCH 16/21] linux-user/riscv: Implement setup_sigtramp
Posted by Philippe Mathieu-Daudé 4 years, 7 months ago 
On 6/16/21 3:12 AM, Richard Henderson wrote:
> Create and record the rt signal trampoline.
> 
> This fixes a bug wrt libgcc fallback unwinding.  It expects
> the stack pointer to point to the siginfo_t, whereas we had
> inexplicably placed our private signal trampoline at the start
> of the signal frame instead of the end.  Now moot because we
> have removed it from the stack frame entirely.
> 
> Cc: qemu-riscv@nongnu.org
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  linux-user/riscv/target_signal.h |  2 ++
>  linux-user/riscv/signal.c        | 22 +++++++++++++---------
>  2 files changed, 15 insertions(+), 9 deletions(-)

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Re: [PATCH 16/21] linux-user/riscv: Implement setup_sigtramp
Posted by Alistair Francis 4 years, 7 months ago 
On Wed, Jun 16, 2021 at 11:22 AM Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> Create and record the rt signal trampoline.
>
> This fixes a bug wrt libgcc fallback unwinding.  It expects
> the stack pointer to point to the siginfo_t, whereas we had
> inexplicably placed our private signal trampoline at the start
> of the signal frame instead of the end.  Now moot because we
> have removed it from the stack frame entirely.
>
> Cc: qemu-riscv@nongnu.org
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>

Alistair

> ---
>  linux-user/riscv/target_signal.h |  2 ++
>  linux-user/riscv/signal.c        | 22 +++++++++++++---------
>  2 files changed, 15 insertions(+), 9 deletions(-)
>
> diff --git a/linux-user/riscv/target_signal.h b/linux-user/riscv/target_signal.h
> index f113ba9a55..3e36fddc9d 100644
> --- a/linux-user/riscv/target_signal.h
> +++ b/linux-user/riscv/target_signal.h
> @@ -15,4 +15,6 @@ typedef struct target_sigaltstack {
>
>  #include "../generic/signal.h"
>
> +#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 1
> +
>  #endif /* RISCV_TARGET_SIGNAL_H */
> diff --git a/linux-user/riscv/signal.c b/linux-user/riscv/signal.c
> index 9405c7fd9a..4086dfa5d5 100644
> --- a/linux-user/riscv/signal.c
> +++ b/linux-user/riscv/signal.c
> @@ -46,7 +46,6 @@ struct target_ucontext {
>  };
>
>  struct target_rt_sigframe {
> -    uint32_t tramp[2]; /* not in kernel, which uses VDSO instead */
>      struct target_siginfo info;
>      struct target_ucontext uc;
>  };
> @@ -104,12 +103,6 @@ static void setup_ucontext(struct target_ucontext *uc,
>      setup_sigcontext(&uc->uc_mcontext, env);
>  }
>
> -static inline void install_sigtramp(uint32_t *tramp)
> -{
> -    __put_user(0x08b00893, tramp + 0);  /* li a7, 139 = __NR_rt_sigreturn */
> -    __put_user(0x00000073, tramp + 1);  /* ecall */
> -}
> -
>  void setup_rt_frame(int sig, struct target_sigaction *ka,
>                      target_siginfo_t *info,
>                      target_sigset_t *set, CPURISCVState *env)
> @@ -126,14 +119,13 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
>
>      setup_ucontext(&frame->uc, env, set);
>      tswap_siginfo(&frame->info, info);
> -    install_sigtramp(frame->tramp);
>
>      env->pc = ka->_sa_handler;
>      env->gpr[xSP] = frame_addr;
>      env->gpr[xA0] = sig;
>      env->gpr[xA1] = frame_addr + offsetof(struct target_rt_sigframe, info);
>      env->gpr[xA2] = frame_addr + offsetof(struct target_rt_sigframe, uc);
> -    env->gpr[xRA] = frame_addr + offsetof(struct target_rt_sigframe, tramp);
> +    env->gpr[xRA] = default_rt_sigreturn;
>
>      return;
>
> @@ -202,3 +194,15 @@ badframe:
>      force_sig(TARGET_SIGSEGV);
>      return 0;
>  }
> +
> +void setup_sigtramp(abi_ulong sigtramp_page)
> +{
> +    uint32_t *tramp = lock_user(VERIFY_WRITE, sigtramp_page, 8, 0);
> +    assert(tramp != NULL);
> +
> +    __put_user(0x08b00893, tramp + 0);  /* li a7, 139 = __NR_rt_sigreturn */
> +    __put_user(0x00000073, tramp + 1);  /* ecall */
> +
> +    default_rt_sigreturn = sigtramp_page;
> +    unlock_user(tramp, sigtramp_page, 8);
> +}
> --
> 2.25.1
>
>

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