| Message ID | 1390815426-10792-1-git-send-email-will.newton@linaro.org |
|---|---|
| State | Superseded |
| Headers | show |
On 27 January 2014 18:22, Joseph S. Myers <joseph@codesourcery.com> wrote: > On Mon, 27 Jan 2014, Will Newton wrote: > >> + /* longjmp probe expects longjmp first argument (4@r0), second >> + argument (-4@r1), and target address (4@r14), respectively. */ >> + LIBC_PROBE (longjmp, 3, 4@r0, -4@r1, 4@r14) > > I don't know what 4@r0 etc. mean - where is this documented (I don't see > it in include/stap-probe.h)? Also, where are the semantics of these > probes documented (I don't see them in manual/probes.texi)? None of this seems particularly well-documented as far as I can tell. The SystemTap probe syntax is covered here: https://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation But there's no mention of ARM specifically, and the gdb source seems to be the place where the syntax is parsed so I wrote to match that. For example, lr does not seem to be a supported register name but r14 is. The semantics of the probes is not documented at all as far as I can tell. Again gdb is the consumer so I looked at the sources there as well as the comments in the powerpc port of glibc (thanks powerpc maintainers!). Only the third argument is used by gdb, which is the target pc. It would be great if someone who actually knew the details of this for sure added some docs (i.e. see discussion of longjmp_target probe that other architectures implement).
On 28 January 2014 21:35, Joseph S. Myers <joseph@codesourcery.com> wrote: > On Mon, 27 Jan 2014, Will Newton wrote: > >> @@ -50,6 +48,11 @@ ENTRY (__longjmp) >> ldr sp, [ip], #4 >> ldr lr, [ip], #4 >> #endif >> + /* longjmp probe expects longjmp first argument (4@r0), second >> + argument (-4@r1), and target address (4@r14), respectively. */ >> + LIBC_PROBE (longjmp, 3, 4@r0, -4@r1, 4@r14) > > The discussion on libc-alpha said this probe should be before unwinding; > shouldn't that mean before sp and lr are restored, so that at probe time > it's still possible to unwind through the caller of longjmp? Yep, I'm working on an updated patch.
diff --git a/ports/sysdeps/arm/__longjmp.S b/ports/sysdeps/arm/__longjmp.S index 27c57a1..ad5fa9f 100644 --- a/ports/sysdeps/arm/__longjmp.S +++ b/ports/sysdeps/arm/__longjmp.S @@ -17,6 +17,7 @@ <http://www.gnu.org/licenses/>. */ #include <sysdep.h> +#include <stap-probe.h> #include <bits/setjmp.h> #include <rtld-global-offsets.h> #include <arm-features.h> @@ -25,24 +26,21 @@ ENTRY (__longjmp) mov ip, r0 - movs r0, r1 /* get the return value in place */ - it eq - moveq r0, #1 /* can't let setjmp() return zero! */ #ifdef CHECK_SP sfi_breg ip, \ - ldr r4, [\B, #32] /* jmpbuf's sp */ + ldr r4, [\B] /* jmpbuf's sp */ cfi_undefined (r4) #ifdef PTR_DEMANGLE PTR_DEMANGLE (r4, r4, a3, a4) #endif CHECK_SP (r4) #endif - sfi_sp sfi_breg ip, \ - ldmia \B!, JMP_BUF_REGLIST + #ifdef PTR_DEMANGLE ldr a4, [ip], #4 - PTR_DEMANGLE (a4, a4, a3, a2) + PTR_DEMANGLE (a4, a4, a3, r4) + cfi_undefined (r4) mov sp, a4 ldr a4, [ip], #4 PTR_DEMANGLE2 (lr, a4, a3) @@ -50,6 +48,11 @@ ENTRY (__longjmp) ldr sp, [ip], #4 ldr lr, [ip], #4 #endif + /* longjmp probe expects longjmp first argument (4@r0), second + argument (-4@r1), and target address (4@r14), respectively. */ + LIBC_PROBE (longjmp, 3, 4@r0, -4@r1, 4@r14) + sfi_sp sfi_breg ip, \ + ldmia \B!, JMP_BUF_REGLIST cfi_restore (v1) cfi_restore (v2) cfi_restore (v3) @@ -61,6 +64,10 @@ ENTRY (__longjmp) cfi_restore (sp) cfi_restore (lr) + movs r0, r1 /* get the return value in place */ + it eq + moveq r0, #1 /* can't let setjmp() return zero! */ + #if !defined ARM_ASSUME_NO_IWMMXT || defined __SOFTFP__ # define NEED_HWCAP 1 #endif diff --git a/ports/sysdeps/arm/include/bits/setjmp.h b/ports/sysdeps/arm/include/bits/setjmp.h index 220dfe8..5877c1f 100644 --- a/ports/sysdeps/arm/include/bits/setjmp.h +++ b/ports/sysdeps/arm/include/bits/setjmp.h @@ -30,7 +30,7 @@ # define JMP_BUF_REGLIST {v1-v6, sl, fp} /* Index of __jmp_buf where the sp register resides. */ -# define __JMP_BUF_SP 8 +# define __JMP_BUF_SP 0 #endif #endif /* include/bits/setjmp.h */ diff --git a/ports/sysdeps/arm/setjmp.S b/ports/sysdeps/arm/setjmp.S index b0b45ed..5e55ca5 100644 --- a/ports/sysdeps/arm/setjmp.S +++ b/ports/sysdeps/arm/setjmp.S @@ -17,6 +17,7 @@ <http://www.gnu.org/licenses/>. */ #include <sysdep.h> +#include <stap-probe.h> #include <bits/setjmp.h> #include <rtld-global-offsets.h> #include <arm-features.h> @@ -27,9 +28,11 @@ ENTRY (__sigsetjmp) #endif mov ip, r0 - /* Save registers */ - sfi_breg ip, \ - stmia \B!, JMP_BUF_REGLIST + /* setjmp probe expects sigsetjmp first argument (4@r0), second + argument (-4@r1), and target address (4@r14), respectively. */ + LIBC_PROBE (setjmp, 3, 4@r0, -4@r1, 4@r14) + + /* Save sp and lr */ #ifdef PTR_MANGLE mov a4, sp PTR_MANGLE2 (a4, a4, a3) @@ -40,6 +43,9 @@ ENTRY (__sigsetjmp) str sp, [ip], #4 str lr, [ip], #4 #endif + /* Save registers */ + sfi_breg ip, \ + stmia \B!, JMP_BUF_REGLIST #if !defined ARM_ASSUME_NO_IWMMXT || defined __SOFTFP__ # define NEED_HWCAP 1