diff options
| author | Soby Mathew <soby.mathew@arm.com> | 2018-10-12 16:40:28 +0100 |
|---|---|---|
| committer | Soby Mathew <soby.mathew@arm.com> | 2018-10-29 09:54:31 +0000 |
| commit | f1722b693d363cc6a2b624d59f0442bf845baf62 (patch) | |
| tree | 2b8a412e48830f66641cecdb308a152db268a60f /bl2 | |
| parent | 3bd17c0fef46a7cd894974ac4c996801458f6d09 (diff) | |
PIE: Use PC relative adrp/adr for symbol reference
This patch fixes up the AArch64 assembly code to use
adrp/adr instructions instead of ldr instruction for
reference to symbols. This allows these assembly
sequences to be Position Independant. Note that the
the reference to sizes have been replaced with
calculation of size at runtime. This is because size
is a constant value and does not depend on execution
address and using PC relative instructions for loading
them makes them relative to execution address. Also
we cannot use `ldr` instruction to load size as it
generates a dynamic relocation entry which must *not*
be fixed up and it is difficult for a dynamic loader
to differentiate which entries need to be skipped.
Change-Id: I8bf4ed5c58a9703629e5498a27624500ef40a836
Signed-off-by: Soby Mathew <soby.mathew@arm.com>
Diffstat (limited to 'bl2')
| -rw-r--r-- | bl2/aarch64/bl2_entrypoint.S | 14 |
1 files changed, 10 insertions, 4 deletions
diff --git a/bl2/aarch64/bl2_entrypoint.S b/bl2/aarch64/bl2_entrypoint.S index bc8cbfd6..30a5c599 100644 --- a/bl2/aarch64/bl2_entrypoint.S +++ b/bl2/aarch64/bl2_entrypoint.S @@ -70,13 +70,19 @@ func bl2_entrypoint * - the coherent memory section. * --------------------------------------------- */ - ldr x0, =__BSS_START__ - ldr x1, =__BSS_SIZE__ + adrp x0, __BSS_START__ + add x0, x0, :lo12:__BSS_START__ + adrp x1, __BSS_END__ + add x1, x1, :lo12:__BSS_END__ + sub x1, x1, x0 bl zeromem #if USE_COHERENT_MEM - ldr x0, =__COHERENT_RAM_START__ - ldr x1, =__COHERENT_RAM_UNALIGNED_SIZE__ + adrp x0, __COHERENT_RAM_START__ + add x0, x0, :lo12:__COHERENT_RAM_START__ + adrp x1, __COHERENT_RAM_END_UNALIGNED__ + add x1, x1, :lo12:__COHERENT_RAM_END_UNALIGNED__ + sub x1, x1, x0 bl zeromem #endif |