From f53db356f53686cb0e4ddb25946b8cff9e82453d Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Timo=20Ter=C3=A4s?= Date: Fri, 22 Oct 2010 13:58:13 +0200 Subject: libm/x86: use call instead of jump for wrappers MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Signed-off-by: Denys Vlasenko --- libm/ldouble_wrappers.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) (limited to 'libm') diff --git a/libm/ldouble_wrappers.c b/libm/ldouble_wrappers.c index bf7ae15f0..f78a97a05 100644 --- a/libm/ldouble_wrappers.c +++ b/libm/ldouble_wrappers.c @@ -61,6 +61,10 @@ long long func##l(long double x) \ * 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... + * + * Update: we do need to use call (instead of tail jump) as gcc can create + * stack frame, and push/modify/pop ebx during PIC build. + * TODO: add conditionals to use tail jump if possible? */ # define WRAPPER1(func) \ long double func##l(long double x) \ @@ -69,7 +73,7 @@ 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 +86,7 @@ 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 +99,7 @@ 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 +112,7 @@ 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) \ ); \ -- cgit v1.2.3