From: "H.J. Lu" <hjl.tools@gmail.com>
To: Joe Simmons-Talbott <josimmon@redhat.com>
Cc: libc-alpha@sourceware.org
Subject: Re: [PATCH v3 1/2] x86_64: Set the syscall register right before doing the syscall.
Date: Mon, 17 Apr 2023 08:54:17 -0700 [thread overview]
Message-ID: <CAMe9rOozntb6jgqF7she82-56JxM=wyo3=d6VQGGO=jM69rYXA@mail.gmail.com> (raw)
In-Reply-To: <20230417153451.1450817-2-josimmon@redhat.com>
On Mon, Apr 17, 2023 at 8:35 AM Joe Simmons-Talbott via Libc-alpha
<libc-alpha@sourceware.org> wrote:
>
> To make identifying syscalls easier during call tree analysis load the
> syscall number just before performing the syscall.
>
> Compiler optimizations can place quite a few instructions between the
> setting of the syscall number and the syscall instruction. During call
> tree analysis the number of instructions between the two can lead to
> more difficulty for both tools and humans in properly identifying the
> syscall number. Having the syscall number set in the prior instruction
> to the syscall instruction makes this task easier and less error prone.
> Being able to reliably identify syscalls made by a given API will make
> it easier to understand and verify the safety and security of glibc.
> ---
> sysdeps/unix/sysv/linux/x86_64/sysdep.h | 33 +++++++++++++++++++++++++
> 1 file changed, 33 insertions(+)
>
> diff --git a/sysdeps/unix/sysv/linux/x86_64/sysdep.h b/sysdeps/unix/sysv/linux/x86_64/sysdep.h
> index cfb51be8c5..800a56723f 100644
> --- a/sysdeps/unix/sysv/linux/x86_64/sysdep.h
> +++ b/sysdeps/unix/sysv/linux/x86_64/sysdep.h
> @@ -250,12 +250,20 @@
> (long int) resultvar; \
> })
>
> +#define MSTR_HELPER(x) #x
> +#define MSTR(x) MSTR_HELPER(x)
> +
> #undef internal_syscall1
> #define internal_syscall1(number, arg1) \
> ({ \
> unsigned long int resultvar; \
> TYPEFY (arg1, __arg1) = ARGIFY (arg1); \
> register TYPEFY (arg1, _a1) asm ("rdi") = __arg1; \
> + if (__builtin_constant_p(number)) \
> + asm volatile ("movl $" MSTR(number) ", %%eax\n\t" \
> + : /* no outputs */ \
> + : "i" (number) \
> + : "eax"); \
> asm volatile ( \
> "syscall\n\t" \
> : "=a" (resultvar) \
> @@ -272,6 +280,11 @@
> TYPEFY (arg1, __arg1) = ARGIFY (arg1); \
> register TYPEFY (arg2, _a2) asm ("rsi") = __arg2; \
> register TYPEFY (arg1, _a1) asm ("rdi") = __arg1; \
> + if (__builtin_constant_p(number)) \
> + asm volatile ("movl $" MSTR(number) ", %%eax\n\t" \
> + : /* no outputs */ \
> + : "i" (number) \
> + : "eax"); \
> asm volatile ( \
> "syscall\n\t" \
> : "=a" (resultvar) \
> @@ -290,6 +303,11 @@
> register TYPEFY (arg3, _a3) asm ("rdx") = __arg3; \
> register TYPEFY (arg2, _a2) asm ("rsi") = __arg2; \
> register TYPEFY (arg1, _a1) asm ("rdi") = __arg1; \
> + if (__builtin_constant_p(number)) \
> + asm volatile ("movl $" MSTR(number) ", %%eax\n\t" \
> + : /* no outputs */ \
> + : "i" (number) \
> + : "eax"); \
> asm volatile ( \
> "syscall\n\t" \
> : "=a" (resultvar) \
> @@ -310,6 +328,11 @@
> register TYPEFY (arg3, _a3) asm ("rdx") = __arg3; \
> register TYPEFY (arg2, _a2) asm ("rsi") = __arg2; \
> register TYPEFY (arg1, _a1) asm ("rdi") = __arg1; \
> + if (__builtin_constant_p(number)) \
> + asm volatile ("movl $" MSTR(number) ", %%eax\n\t" \
> + : /* no outputs */ \
> + : "i" (number) \
> + : "eax"); \
> asm volatile ( \
> "syscall\n\t" \
> : "=a" (resultvar) \
> @@ -332,6 +355,11 @@
> register TYPEFY (arg3, _a3) asm ("rdx") = __arg3; \
> register TYPEFY (arg2, _a2) asm ("rsi") = __arg2; \
> register TYPEFY (arg1, _a1) asm ("rdi") = __arg1; \
> + if (__builtin_constant_p(number)) \
> + asm volatile ("movl $" MSTR(number) ", %%eax\n\t" \
> + : /* no outputs */ \
> + : "i" (number) \
> + : "eax"); \
> asm volatile ( \
> "syscall\n\t" \
> : "=a" (resultvar) \
> @@ -357,6 +385,11 @@
> register TYPEFY (arg3, _a3) asm ("rdx") = __arg3; \
> register TYPEFY (arg2, _a2) asm ("rsi") = __arg2; \
> register TYPEFY (arg1, _a1) asm ("rdi") = __arg1; \
> + if (__builtin_constant_p(number)) \
> + asm volatile ("movl $" MSTR(number) ", %%eax\n\t" \
> + : /* no outputs */ \
> + : "i" (number) \
> + : "eax"); \
> asm volatile ( \
> "syscall\n\t" \
> : "=a" (resultvar) \
> --
> 2.39.2
>
Won't the compiler load EAX twice when number is a constant?
--
H.J.
next prev parent reply other threads:[~2023-04-17 15:54 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-11 13:30 [PATCH 0/2] x86_64: aarch64: Set call number just before syscall Joe Simmons-Talbott
2023-04-11 13:30 ` [PATCH 1/2] x86_64: Set the syscall register right before doing the syscall Joe Simmons-Talbott
2023-04-17 22:35 ` Noah Goldstein
2023-04-17 22:36 ` Noah Goldstein
2023-04-11 13:30 ` [PATCH 2/2] aarch64: " Joe Simmons-Talbott
2023-04-11 13:50 ` Florian Weimer
2023-04-11 14:15 ` Adhemerval Zanella Netto
2023-04-11 15:43 ` Szabolcs Nagy
2023-04-11 16:03 ` Florian Weimer
2023-04-11 16:39 ` Adhemerval Zanella Netto
2023-04-12 15:27 ` Joe Simmons-Talbott
2023-04-12 21:11 ` [PATCH v2 0/2] x86_64: aarch64: Set call number just before syscall Joe Simmons-Talbott
2023-04-12 21:11 ` [PATCH v2 1/2] x86_64: Set the syscall register right before doing the syscall Joe Simmons-Talbott
2023-04-12 21:11 ` [PATCH v2 2/2] aarch64: " Joe Simmons-Talbott
2023-04-17 15:34 ` [PATCH v3 0/2] x86_64: aarch64: Set call number just before syscall Joe Simmons-Talbott
2023-04-17 15:34 ` [PATCH v3 1/2] x86_64: Set the syscall register right before doing the syscall Joe Simmons-Talbott
2023-04-17 15:54 ` H.J. Lu [this message]
2023-04-17 16:00 ` Joe Simmons-Talbott
2023-04-17 18:38 ` H.J. Lu
2023-04-17 15:34 ` [PATCH v3 2/2] aarch64: " Joe Simmons-Talbott
2023-04-17 21:20 ` [PATCH v4 0/2] x86_64: aarch64: Set call number just before syscall Joe Simmons-Talbott
2023-04-17 21:20 ` [PATCH v4 1/2] x86_64: Set the syscall register right before doing the syscall Joe Simmons-Talbott
2023-04-17 21:20 ` [PATCH v4 2/2] aarch64: " Joe Simmons-Talbott
2023-04-18 12:57 ` Szabolcs Nagy
2023-04-18 19:33 ` Joe Simmons-Talbott
2023-04-19 13:58 ` [PATCH v5 0/3] x86_64: aarch64: Set call number just before syscall Joe Simmons-Talbott
2023-04-19 13:58 ` [PATCH v5 1/3] x86_64: Set the syscall register right before doing the syscall Joe Simmons-Talbott
2023-04-19 15:35 ` H.J. Lu
2023-04-19 15:48 ` Joe Simmons-Talbott
2023-04-19 13:58 ` [PATCH v5 2/3] aarch64: " Joe Simmons-Talbott
2023-04-19 14:56 ` Szabolcs Nagy
2023-04-19 15:21 ` Joe Simmons-Talbott
2023-04-19 13:58 ` [PATCH v5 3/3] nptl: Use direct syscall numbers in setxid Joe Simmons-Talbott
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