[PATCH] libm/x86: use call instead of jump for wrappers
Ed W
lists at wildgooses.com
Wed Oct 20 10:32:49 UTC 2010
I don't see this in the git master branch? Was it rejected? (Perhaps
just missed?)
Thanks
Ed W
On 11/05/2010 13:42, Timo Teräs wrote:
> GCC can emit prologue/epilogue code for the functions in various
> different cases:
> - frame pointers
> - PIC build (to load ebx for indirect calls/jumps)
> - forced stack smashing protection
>
> If we used jump in such cases, we'd corrupt the call stack and
> crash.
>
> Signed-off-by: Timo Teräs<timo.teras at iki.fi>
> ---
> libm/ldouble_wrappers.c | 12 +++++++-----
> 1 files changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/libm/ldouble_wrappers.c b/libm/ldouble_wrappers.c
> index 7d5af90..5b424dc 100644
> --- a/libm/ldouble_wrappers.c
> +++ b/libm/ldouble_wrappers.c
> @@ -60,7 +60,9 @@ long long func##l(long double x) \
> * The return value is returned in st(0) per ABI in both cases (returning
> * a long double or returning a double). So we can simply jump to func.
> * Using __GI_func in jump to make optimized intra-library jump.
> - * gcc will still generate a useless "ret" after asm. Oh well...
> + *
> + * We do need to use call (instead of tail jump) as gcc can create
> + * stack frame, and push/modify/pop ebx during PIC build.
> */
> # define WRAPPER1(func) \
> long double func##l(long double x) \
> @@ -69,7 +71,7 @@ long double func##l(long double x) \
> __asm ( \
> " fldt %1\n" \
> " fstpl %1\n" \
> - " jmp " __stringify(__GI_##func) "\n" \
> + " call " __stringify(__GI_##func) "\n" \
> : "=t" (st_top) \
> : "m" (x) \
> ); \
> @@ -82,7 +84,7 @@ int func##l(long double x) \
> __asm ( \
> " fldt %1\n" \
> " fstpl %1\n" \
> - " jmp " __stringify(__GI_##func) "\n" \
> + " call " __stringify(__GI_##func) "\n" \
> : "=a" (ret) \
> : "m" (x) \
> ); \
> @@ -95,7 +97,7 @@ long func##l(long double x) \
> __asm ( \
> " fldt %1\n" \
> " fstpl %1\n" \
> - " jmp " __stringify(__GI_##func) "\n" \
> + " call " __stringify(__GI_##func) "\n" \
> : "=a" (ret) \
> : "m" (x) \
> ); \
> @@ -108,7 +110,7 @@ long long func##l(long double x) \
> __asm ( \
> " fldt %1\n" \
> " fstpl %1\n" \
> - " jmp " __stringify(__GI_##func) "\n" \
> + " call " __stringify(__GI_##func) "\n" \
> : "=A" (ret) \
> : "m" (x) \
> ); \
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